Rev.1.0_02
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM
CONTROL SWITCHING REGULATOR CONTROLLER S-8333 Series
Seiko Instruments Inc. 1
The S-8333 Series is a CMOS step-up switching regulator which mainly consists of a
reference voltage circuit, an oscillator, an error amplifier, a PWM controller, an under voltage
lockout circuit (UVLO), and a timer latch short-circuit protection circuit. Because its minimum
operating voltage is as low as 1.8 V, this switching regulator is ideal for the power supply of
an LCD or for portable systems that operate on a low voltage. The internal oscillation
frequency can be set up to 1.133 MHz, via the resistor connected to the ROSC pin.
The maximum duty ratio of PWM control can be controlled by the resistor connected to the
RDuty pin. The soft-start function at power application is accomplished by combining the
reference voltage control and maximum duty control methods. Even if the voltage of the FB
pin is retained lower than the reference voltage due to the factor outside the IC, the output
voltage is raised by controlling the maximum duty. The phase compensation and gain value
can be adjusted according to the values of the resistor and capacitor connected to the CC
pin. Therefore, the operation stability and transient response can be correctly set for each
application. The reference voltage accuracy is as high as 1.0 V ±1.5%, and any voltage can
be output by using an external output voltage setting resistor.
In addition, the delay time of the short-circuit protection circuit can be set by using the
capacitor connected to the CSP pin. If the maximum duty condition continues because of
short-circuiting, the capacitor externally connected to the CSP pin is charged, and oscillation
stops after a specific time. The short-circuit protection function is cancelled when the power
supply is raised to the UVLO release voltage after it has been lowered to the UVLO detection
voltage. A ceramic capacitor or a tantalum capacitor is used as the output capacitor,
depending on the setting. This controller IC allows various settings and selections and
employs a small package, making it very easy to use.
Features
• Low voltage operation: 1.8 V to 6.0 V
• Oscillation frequency: 286 kHz to 1.133 MHz (selectable by external resistor)
• Maximum duty: 47 to 88.5% (selectable by external resistor)
• Reference voltage: 1.0 V ±1.5%
• UVLO (under-voltage lockout) function:
Detection voltage can be selected from between 1.5 V and 2.3 V in 0.1 V steps.
Hysteresis width can be selected from between 0.1 V and 0.3 V in 0.1 V steps.
• Timer latch short-circuit protection circuit:
Delay time can be set using an external capacitor.
• Soft-start function: Soft-start time can be selected in three steps, 10 ms, 15 ms, and 20 ms.
Both reference voltage control and maximum duty control methods are applied
• Phase compensation external setting:
Control is possible via the resistor connected between the CC and GND pins and
capacitor
• Small package: SNT-8A, 8-Pin TSSOP
Applications
• Power supplies for LCDs and CCDs
• Power supplies for portable equipment
Packages
Drawing Code
Package Name Package Tape Reel
SNT-8A PH008-A PH008-A PH008-A
8-Pin TSSOP FT008-A FT008-E FT008-E
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
2
Block Diagram
PWM
comparator
VOUT
Timer latch
short-circuit
p
rotection circuit
RDuty
RFB2
VSS
RFB1
FB
SD
L
VIN
EXT
UVLO
CSP CC
RZ CZ
ROSC
M1
CFB
+
−
+
−
Oscillator
Maximum duty
soft-start circuit
Reference voltage
(1.0 V) soft-start
circuit
Error amplifier
CIN CL
Figure 1 Block Diagram
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 3
Product Code Structure
1. Product name
(1) SNT-8A package
S-8333 A x x x - I8T1 G
Fixed
Package name(abbreviation) and packing specifications
I8T1: SNT-8A, Tape
Soft-start time setting
A: 10 ms
B: 15 ms
C: 20 ms
UVLO setting
A: 2.3 V
B: 2.2 V
C: 2.1 V
D: 2.0 V
E: 1.9 V
F: 1.8 V
G: 1.7 V
H: 1.6 V
I: 1.5 V
UVLO hysteresis setting
A: 0.1 V
B: 0.2 V
C: 0.3 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
4
(2) 8-Pin TSSOP package
S-8333 A x x x - T8T1
Package name(abbreviation) and packing specifications
T8T1: 8-Pin TSSOP, Tape
Soft-start time setting
A: 10 ms
B: 15 ms
C: 20 ms
UVLO setting
A: 2.3 V
B: 2.2 V
C: 2.1 V
D: 2.0 V
E: 1.9 V
F: 1.8 V
G: 1.7 V
H: 1.6 V
I: 1.5 V
UVLO hysteresis setting
A: 0.1 V
B: 0.2 V
C: 0.3 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 5
Pin Assignment
Table 1
Pin No. Pin Name Functions
1 CC
Error amplifier circuit output phase
compensation pin
2 FB Output voltage feedback pin
3 CSP Short-circuit protection delay time setting pin
4 VIN Power supply input pin
5 EXT External transistor connection pin
6 VSS GND pin
1
2
3
4
SNT-8A
Top view
8
7
6
5
7 ROSC
Oscillation frequency setting resistor
connection pin
Figure 2 8 RDuty Maximum duty setting resistor connection pin
Table 2
Pin No. Pin Name Functions
1 CC
Error amplifier circuit output phase
compensation pin
2 FB Output voltage feedback pin
3 CSP Short-circuit protection delay time setting pin
4 VIN Power supply input pin
5 EXT External transistor connection pin
6 VSS GND pin
8-Pin TSSOP
Top view
1
3
2
4
8
6
7
5
7 ROSC
Oscillation frequency setting resistor
connection pin
Figure 3 8 RDuty Maximum duty setting resistor connection pin
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
6
Absolute Maximum Ratings
Table 3 Absolute Maximum Ratings
(Unless otherwise specified: Ta = 25°C, VSS = 0 V)
Parameter Symbol Ratings Unit
VIN pin voltage VIN V
SS − 0.3 to VSS + 6.5 V
FB pin voltage VFB V
SS − 0.3 to VSS + 6.5
EXT pin voltage VEXT V
SS − 0.3 to VIN + 0.3
CSP pin voltage VCSP V
SS − 0.3 to VIN + 0.3
CC pin voltage VCC V
SS − 0.3 to VIN + 0.3
CC pin current ICC ±10 mA
ROSC pin voltage VROSC V
SS − 0.3 to VIN + 0.3 V
ROSC pin current IROSC ±10 mA
RDuty pin voltage VRDuty V
SS − 0.3 to VIN + 0.3 V
RDuty pin current IRDuty ±10 mA
Operating temperature Topr −40 to +85 °C
Storage temperature Tstg −40 to +125
SNT-8A 450*1 mW
Power dissipation
8-Pin TSSOP PD 300
*1. When mounted on printed circuit board
[Mounted board]
(1) Board size: 114 mm × 76 mm × 1.6t mm
(2) Name: JEDEC STANDARD51-7
Caution The absolute maximum ratings are rated values exceeding which the product could suffer
physical damage. These values must therefore not be exceeded under any conditions.
(1) SNT-8A (when mounted on printed
circuit board)
(2) 8-Pin TSSOP (when not mounted on
printed circuit board)
0
50 100
150
600
400
200
0
Power dissipation P
D
(mW)
SNT-8A
Ambient temperature Ta (°C)
500
300
100
050 100
150
600
400
200
0
Power dissipation P
D
(mW)
8-Pin TSSOP
Ambient temperature Ta (°C)
500
300
100
Figure 4 Power Dissipation of Package
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 7
Electrical Characteristics
Table 4 Electrical Characteristics
(Unless otherwise specified: VIN = 3.3 V, Ta = 25°C)
Parameter Symbol Conditions Min. Typ. Max. Unit
Test
Circuit
Operating input voltage VIN 1.8 6.0 2
FB voltage VFB 0.985 1.000 1.015 V 2
Current consumption ISS1 fosc = 700 kHz
VFB = 0.95 V 450 700 µA 1
IEXTH V
EXT = VIN − 0.4 V −100 −60 1
EXT pin output current IEXTL V
EXT = 0.4 V 100 160 mA 1
FB voltage temperature
coefficient
∆VFB
∆Ta Ta = −40 to +85°C ±100 ppm/°C2
FB pin input current IFB −0.1 +0.1 µA 1
Oscillation frequency*1 fosc
When fosc = 1133 kHz is set
(ROSC = 120 kΩ)
When fosc = 700 kHz is set
(ROSC = 200 kΩ)
When fosc = 286 kHz is set
(ROSC = 510 kΩ)
VFB = 0.9 V
Waveform on EXT pin is measured.
fosc
× 0.9 fosc fosc
× 1.1 kHz 1
Oscillation frequency
temperature coefficient
∆fosc
∆Ta
Ta = −40 to +85°C
fosc = 700 kHz 1000 ppm/°C1
fosc = 1133 kHz (ROSC = 120 kΩ)
MaxDuty = 88.5% (RDuty = 62 kΩ)
MaxDuty = 73% (RDuty = 180 kΩ)
MaxDuty = 47% (RDuty = 390 kΩ)
Max. duty*2 MaxDuty
fosc = 700 kHz (ROSC = 200 kΩ)
MaxDuty = 88.5% (RDuty = 100 kΩ)
MaxDuty
− 5 MaxDuty MaxDuty
+ 5 % 1
Soft-start time tSS tSS = 10 ms, 15 ms, 20 ms
Selected in three steps
tSS
× 0.75 tSS tSS
× 1.5 1
Short-circuit protection
delay time*3 tPRO tPRO = 50 ms
(CSP = 0.1 µF) 37.5 50 75
ms
1
UVLO detection voltage VUVLO VUVLO = 1.5 V to 2.3 V
Selected in 0.1 V steps
VUVLO
× 0.95 VUVLO VUVLO
× 1.05 V 1
UVLO hysteresis width VUVLOHYS VUVLOHYS = 0.1 V to 0.3 V
Selected in 0.1 V steps
VUVLOHYS
× 0.6 VUVLOHYS VUVLOHYS
× 1.4 V 1
ICCH V
FB = 2 V −75 −50 −37.5 1
CC pin output current ICCL V
FB = 0 V 37.5 50 75 µA 1
VRTLT1 Within short-circuit protection delay
time 0.7 1.0 1.3
Timer latch reset voltage
VRTLT2 After short-circuit protection circuit
operated
VUVLO
× 0.95 VUVLO VUVLO
× 1.05
V 1
*1. The recommended range of the resistance (Rosc) for setting the oscillation frequency is Rosc = 120 kΩ to 510 kΩ (fOSC =
286 kHz to 1.133 MHz). However, the oscillation frequency is in the range of typical values when an ideal resistor is
externally connected, so actually the fluctuation of the IC (±10%) must be considered.
*2. The recommended range of the resistance (RDuty / Rosc) for setting the maximum duty is RDuty / Rosc = 0.5 to 3.2 (MaxDuty
= 47 to 88.5%). However, the maximum duty is in the range of typical values when an ideal resistor is externally
connected, so actually the fluctuation of the IC (±5%) must be considered.
*3. The short-circuit protection time can be set by the external capacitor, and the maximum set value by the external
capacitor is unlimited when an ideal case is assumed. But, use CSP = approximately 0.47 µF as a target maximum value
due to the need to consider the discharge time of the capacitor.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
8
External Parts When Measuring Electrical Characteristics
Table 5 External Parts
Element Name Symbol Manufacturer Part Number
Inductor L TDK Corporation LDR655312T 10 µH
Diode SD Rohm Co., Ltd. RB491D
Output capacitor CL Ceramic 10 µF
Transistor M1 Sanyo Electric Co., Ltd. MCH3406
Oscillation frequency setting resistor ROSC 200 kΩ (when fOSC = 700 kHz)
Maximum duty ratio setting resistor RDuty 300 kΩ (when MaxDuty = 73%)
Short-circuit protection delay time
setting capacitor
CSP 0.1 µF (when tPRO = 50 ms)
Output voltage setting resistor 1 RFB1 8.2 kΩ (when VOUT = 9.2 V)
Output voltage setting resistor 2 RFB2 1.0 kΩ (when VOUT = 9.2 V)
FB pin capacitor CFB 180 pF
Phase compensation resistor RZ 200 kΩ
Phase compensation capacitor CZ 0.01 µF
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 9
Test Circuit Diagram
1. CC
EXT
VSS
FB
CSP
ROSC
VIN
A
Oscilloscope
RDuty
CIN
CSP
CZ
RZ
ROSC RDuty
Figure 5
2. CC
EXT
VSS
FB
CSP
ROSC
VIN
V
RDuty
CSP
CIN
M1
CL
RFB2
RFB1 CFB
RZ
CZ
L
SD ROSC RDuty
Figure 6
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
10
Operation
1. Switching control method
1. 1 PWM control
The S-8333 Series is a DC-DC converter using a pulse width modulation method (PWM).
The pulse width of the S-8333 Series varies from 0% to the maximum duty set by RDuty depending on the load
current, but its switching frequency does not change. Consequently, the ripple voltage generated from switching
can be removed easily via a filter.
2. Soft-start function
For this IC, the built-in soft-start circuit controls the rush current and overshoot of the output voltage when
powering on. Reference voltage adjustment and maximum duty control methods are adopted as the soft-start
methods. The following describes the soft-start function at power application.
In the circuit where the input voltage is not directly output at shutdown by inserting a switch (SW) between the
diode (SD) and VOUT output, the VOUT voltage when the VIN voltage is applied with the SW OFF stays 0 V.
Therefore, the voltage of the FB pin stays 0 V and the EXT output is in the step up status between the “H” and “L”
levels due to the maximum duty. The maximum duty at this time is approximately 7% and the rush current at
power application is controlled. The maximum duty soft start is accomplished by gradually increasing the duty
width up to the maximum duty set by the external resistor RDuty (refer to Figure 8).
The reference voltage of the error amplifier input also gradually increases from 0 V at the same time as the
maximum duty soft start. The increasing of the output voltage is controlled by turning the SW ON. The soft-start
function is realized by controlling the voltage of the FB pin so that it is the same potential as the reference voltage
that is slowly raised. A Rail-to-Rail amplifier is adopted as the error amplifier, which means that the voltage is
loop controlled so that it can be the same as the reference voltage.
Once the reference voltage rises, the voltage cannot be reset (the reference voltage is 0 V) unless making the
power supply voltage lower than the UVLO detection voltage. Conversely, when the power supply voltage rises
up to the reset voltage after it is lowered to the UVLO detection voltage or lower, the output voltage is stepped up
by the soft-start function.
PWM
Comparator
VOUT
RFB2
RFB1
FB
SD
L
V
IN
EXT
CC
RZ
CZ
M1 +
−CL
Error amplifier
Vref
0.5 V
0 V
+
−Error amplifier
reference voltage
SW
Figure 7
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 11
(VIN = 0 V→3.3 V, VOUT = 9.2 V, RFB1 = 8.2 kΩ, RFB2 = 1.0 kΩ)
0 V
Input voltage
(V
IN
)
3.3 V
0 V
Output voltage
(V
OUT
) SW : ON
0 V
Error amplifier
reference voltage
1.0 V
0 V
FB pin voltage
(V
FB
)
1.0 V
0 V
EXT pin voltage
(V
EXT
)
3.3 V
t (ms)
VOUT×0.95
Maximum duty
soft-start period
9.2 V
Reference voltage soft-start period
tSS
Figure 8
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
12
3. Timer latch short-circuit protection function
This IC has a timer latch short-circuit protection circuit that stops the switching operation when the output voltage
drops for a specific time due to output short-circuiting. A capacitor (CSP) that is used to set the delay time of this
short-circuit protection circuit can be connected to the CSP pin.
This IC operates at the maximum duty ratio if the output voltage drops due to output short-circuiting. At the
maximum duty ratio, constant-current charging of CSP starts. If this status lasts for a short-circuit protection
delay time and the CSP pin voltage rises above the reference voltage, the latch mode is set. Note that the latch
mode is different from the shutdown status in that the switching operation is stopped but the internal circuitry
operates normally.
To reset the latch operation to protect the IC from short-circuiting, lower VIN than the UVLO detection voltage.
The latch mode within the short-circuit protection delay time is reset by decreasing VIN to 1.0 V (Typ.) or lower.
Note that the mode is not reset even if the VIN is lowered to the UVLO detection voltage (refer to Figure 9).
Input voltage
(V
IN
)
Output load
CSP pin voltage
(V
CSP
)
Latch mode
Short-circuit status
50 ms (CSP = 0.1
µ
F)
Normal
status
Short-circuit
protection time
Latch
period
Reset period
Reset period
Short-circuit
protection time
Short-circuit
protection time
UVLO release
UVLO detection
1.0 V
Reference
voltage
Figure 9
4. UVLO function
This IC includes a UVLO (under-voltage lockout) circuit to prevent the IC from malfunctioning due to a transient
status when power is applied or a momentary drop of the power supply voltage. When UVLO is in the detection
state, switching is stopped and the external FET is held in the off status. Once UVLO enters the detection state,
the soft-start function is reset.
Note that the other internal circuits operate normally and that the status is different from the power-off status.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 13
5. Error amplifier
The error amplifier outputs the PWM control signal so that the voltage of the FB pin is held at a specific value (1
V). By connecting a resistor (RZ) and capacitor (CZ) to the output pin (CC pin) of the error amplifier in series, an
optional loop gain can be set, enabling stabilized phase compensation.
6. Operation
The following are basic equations [(1) through (7)] of the step-up switching regulator (refer to Figure 10).
D
L
CL
M1 FB
CONT
VIN
EXT
VSS
VOUT
Figure 10 Step-up Switching Regulator Circuit for Basic Equations
Voltage at the CONT pin at the moment M1 is turned ON (current IL flowing through L is zero), VA:
VA = VS*1 .................................................................................................................................................(1)
*1. VS: Non-saturated voltage of M1
Change in IL over time:
L
VV
L
V
dt
dl SINLL −
==
................................................................................................................................(2)
Integration of the above equation:
t
L
VV
ISIN
L•
−
=
.....................................................................................................................................(3)
IL flows while M1 is ON (ton). This time is determined by the oscillation frequency of OSC.
Peak current (IPK) after tON:
ON
SIN
PK t
L
VV
I•
−
=
...............................................................................................................................(4)
The energy stored in L is represented by • L(IPK)2.
When M1 is turned OFF (tOFF), the energy stored in L is released via a diode, generating a reverse voltage (VL).
VL:
()
INDOUTL VVVV −+= *2
............................................................................................................................ (5)
*2. VD: Diode forward voltage
The voltage on the CONT pin rises only by VOUT + VD.
1
2
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
14
Change in current (IL) flowing through the diode into VOUT during tOFF:
L
VVV
L
V
dt
dl INDOUTLL −+
==
...................................................................................................................... (6)
Integration of the above equation is as follows:
t
L
VVV
II INDOUT
PKL •
−+
−=
.................................................................................................................. (7)
During tON, energy is stored in L and is not transmitted to VOUT. When receiving output current (IOUT) from VOUT,
the energy of the capacitor (CL) is used. As a result, the pin voltage of CL is reduced, and goes to the lowest level
after M1 is turned ON (tON). When M1 is turned OFF, the energy stored in L is transmitted via the diode to CL, and
the pin voltage of CL rises drastically. Because VOUT is a time function indicating the maximum value (ripple
voltage: Vp-p) when the current flowing through the diode into VOUT and the load current IOUT match.
Next, this ripple voltage is determined as follows.
IOUT vs t1 (time) from after tON, when VOUT reaches the maximum level:
1
INDOUT
PKOUT t
L
VVV
II •
−+
−=
............................................................................................................. (8)
()
−+
•−=∴
INDOUT
OUTPK1 VVV
L
IIt
......................................................................................................... (9)
When tOFF, IL = 0 (when the energy of the inductor is completely transmitted):
Based on equation (7),
PK
OFF
INDOUT I
t
VVV
L=
−+ ....................................................................................................................... (10)
When substituting equation (10) for equation (9):
OFF
PK
OUT
OFF1 t
I
I
tt •
−=
........................................................................................................................... (11)
Electrical charge ∆Q1 which is charged in CL during t1:
2
1
INDOUT
1PK
1t
0
INDOUT
1t
0
PKL
1t
0
1t
2
1
L
VVV
tItdt
L
VVV
dtIdtIQ •
−+
−•=∫•
−+
−∫•=∫=∆
.................................. (12)
When substituting equation (12) for equation (9):
()
1
OUTPK
1OUTPKPK1 t
2
II
tII
2
1
IQ •
+
=•−−=∆
.............................................................................................. (13)
A rise voltage (Vp-p) due to ∆Q1:
1
OUTPK
LL
1
pp t
2
II
C
1
C
Q
V•
+
•=
∆
=
−................................................................................................................. (14)
When taking into consideration IOUT consumed during t1 and ESR*1 (RESR) of CL:
L
1OUT
ESR
OUTPK
1
OUTPK
LL
1
pp C
tI
R
2
II
t
2
II
C
1
C
Q
V•
−•
+
+•
+
•=
∆
=
−........................................................... (15)
*1. Equivalent Series Resistance
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 15
When substituting equation (11) for equation (15):
()
ESR
OUTPK
L
OFF
PK
2
OUTPK
pp R
2
II
C
t
I2
II
V•
+
+•
−
=
−........................................................................................ (16)
Therefore to reduce the ripple voltage, it is important that the capacitor connected to the output pin has a large
capacity and a small ESR.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
16
External Parts Selection
1. Inductor
The inductance has a strong influence on the maximum output current (IOUT) and efficiency (η).
The peak current (IPK) increases by decreasing L and the stability of the circuit improves and IOUT increases. If L
is decreased further, the efficiency falls, and IOUT decreases if the current drive capability of the external
transistor is insufficient.
The loss of IPK by the switching transistor decreases by increasing L and the efficiency becomes maximum at a
certain L value. Further increasing L decrease the efficiency due to the loss of the DC resistance of the inductor.
IOUT also decreases.
If the oscillation frequency is higher, a smaller L value can be chosen, making the inductor smaller. In the S-8333
Series, the oscillation frequency can be varied within the range of 286 kHz to 1.133 MHz by the external resistor,
so select an L value best suited to the frequency. The recommended value is between 2.2 µH and 22 µH.
When selecting an inductor, note the allowable current of the inductor. If a current exceeding this allowable
current flows through the inductor, magnetic saturation occurs, substantially lowering the efficiency and
increasing the current, which results in damage to the IC.
Therefore, select an inductor so that IPK does not exceed the allowable current. IPK is expressed by the following
equations in the discontinuous mode and continuous mode.
) mode ousdiscontinu (
Lfosc
)VV(VI 2
IINDOUTOUT
PK •
−+
= ................................................................................. (17)
mode) s(continuou
Lfosc)V(V2
V)VV(V
I
V
VV
I
DOUT
ININDOUT
OUT
IN
DOUT
PK ••+•
•−+
+•
+
= .............................................................. (18)
fOSC = Oscillation frequency, VD ≅ 0.4 V.
2. Diode
Use an external diode that meets the following requirements.
• Low forward voltage
• High switching speed
• Reverse breakdown voltage: VOUT + [Spike voltage] or more
• Rated current: IPK or more
3. Capacitors (CIN, CL)
The capacitor on the input side (CIN) can lower the supply impedance and level the input current for better
efficiency. Select CIN according to the impedance of the power supply to be used.
The capacitor on the output side (CL) is used to smooth the output voltage. Select an appropriate capacitance
value based on the I/O conditions and load conditions. A capacitance of 10 µF or more is recommended.
By adjusting the phase compensation of the feedback loop using the external resistor (RZ) and capacitor (CZ), a
ceramic capacitor can be used as the capacitor on the output side. If a capacitor whose equivalent series
resistance is between 30 mΩ and 500 mΩ is used as the output capacitor, the adjustable range of the phase
compensation is wider; however, note that other characteristics may be affected by ripple voltage or other
conditions at this time. The optimal capacitor differs depending on the L value, capacitance value, wiring, and
application (output load), so select the capacitor after performing sufficient evaluation under the actual usage
conditions.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 17
4. External transistor
A bipolar (NPN) or enhancement (N-channel) MOS FET transistor can be used as the external capacitor.
4. 1 Bipolar (NPN) type
The driving capability when the output current is increased by using a bipolar transistor is determined by hFE
and Rb of the bipolar transistor. Figure 11 shows a peripheral circuit.
Nch
Pch
Rb
VIN
IPK
EXT
Cb
2200 pF
1 kΩ
Figure 11 External Transistor Periphery
1 kΩ is recommended for Rb. Actually, calculate the necessary base current (Ib) from hFE of the bipolar
transistor as follows and select an Rb value lower than this.
I
b
=
h
FE
I
PK
R
b
= I
b
V
IN
− 0.7 − I
EXTH
0.4
A small Rb increases the output current, but the efficiency decreases. Actually, a pulsating current flows and
a voltage drop occurs due to the wiring capacitance. Determine the optimum value by experiment.
A speed-up capacitor (Cb) connected in parallel with Rb resistance as shown in Figure 11 decreases the
switching loss and improves the efficiency.
Select Cb by observing the following equation.
C
b
≤
2π • R
b
• f
OSC
• 0.7
1
However, in practice, the optimum Cb value also varies depending on the characteristics of the bipolar
transistor employed. Therefore, determine the optimum value of Cb by experiment.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
18
4. 2 Enhancement MOS FET type
Use an Nch power MOS FET. For high efficiency, using a MOS FET with a low ON resistance (RON) and
small input capacitance (CISS) is ideal, however, ON resistance and input capacitance generally share a
trade-off relationship. The ON resistance is efficient in a range in which the output current is relatively great
during low-frequency switching, and the input capacitance is efficient in a range in which the output current
is middling during high-frequency switching. Select a MOS FET whose ON resistance and input
capacitance are optimal depending on the usage conditions.
The input voltage (VIN) is supplied for the gate voltage of the MOS FET, so select a MOS FET with a gate
withstanding voltage that is equal to the maximum usage value of the input voltage or higher and a drain
withstanding voltage that is equal to the amount of the output voltage (VOUT) and diode voltage (VD) or
higher.
If a MOS FET with a threshold that is near the UVLO detection voltage is used, a large current may flow,
stopping the output voltage from rising and possibly generating heat in the worst case. Select a MOS FET
with a threshold that is sufficiently lower than the UVLO detection voltage value.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 19
5. Oscillation frequency and maximum duty ratio setting resistors (ROSC, RDuty)
With the S-8333 Series, the oscillation frequency can be set in a range of 286 kHz to 1.133 MHz using external
resistance. Connect a resistor across the ROSC and VSS pins. Select the resistor by using the following
equation and referring to Figure 12. However, the following equation and figure assume that the resistance
value is the desired value and show the theoretical values when the IC is in the typical conditions. Note that
fluctuations of resistance and IC are not considered.
140 • 103
ROSC [kΩ] ≅ fOSC [kHz]
1400
1200
1000
800
600
400
200
0
0200 400 600
fOSC [kHz]
ROSC [kΩ]
Figure 12 ROSC vs. fOSC
With the S-8333 Series, the maximum duty ratio can be set in a range of 47% to 88.5% by an external resistor.
Connect the resistor across the RDuty and VSS pins. Select the resistance by using the following equation and
referring to Figure 13. The maximum duty ratio fluctuates according to the oscillation frequency. If the value of
ROSC is changed, therefore, be sure to change the value of RDuty so that it is always in proportion to RDuty /
ROSC. However, the following equation and figure assume that the resistance value is the desired value and
show the theoretical values when the IC is in the typical conditions. Note that fluctuations of resistance and IC
are not considered.
(95.5 − MaxDuty)
≅
ROSC
RDuty
15.0
100
90
80
70
60
50
40
02
4
MaxDuty [%]
R
Duty
/ R
OSC
1 3
Figure 13 RDuty / ROSC vs. MaxDuty
Connect resistors ROSC and RDuty as close to the IC as possible.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
20
6. Short-circuit protection delay time setting capacitor (CSP)
With the S-8333 Series, the short-circuit protection delay time can be set to any value by an external capacitor.
Connect the capacitor across the CSP and VSS pins. Select the capacitance by using the following equation and
referring to Figure 14. However, the following equation and figure assume that the capacitor value is the desired
value and show the theoretical values when the IC is in the typical conditions. Note that fluctuations of capacitor
and IC are not considered.
C
SP
[µF] ≅ 1.0
t
PRO
[ms] • 2 • 10
−3
120
100
80
60
40
20
0
00.10 0.20 0.25
tPRO [ms]
CSP [µF]
0.05 0.15
Figure 14 CSP vs. tPRO
7. Output voltage setting resistors (RFB1, RBF2)
With the S-8333 Series, the output voltage can be set to any value by external divider resistors.
Connect the divider resistors across the VOUT and VSS pins. Because VFB = 1 V, the output voltage can be
calculated by this equation.
=
V
OUT
R
FB2
(R
FB1
+ R
FB2
)
Connect divider resistors RFB1 and RFB2 as close to the IC to minimize effects from of noise. If noise does have
an effect, adjust the values of RFB1 and RFB2 so that RFB1 + RFB2 < 100 kΩ.
CFB connected in parallel with RFB1 is a capacitor for phase compensation. Select the optimum value of this
capacitor at which the stable operation can be ensured from the values of the inductor and output capacitor.
8. Phase compensation setting resistor and capacitor (RZ, CZ)
The S-8333 Series needs appropriate compensation for the voltage feedback loop to prevent excessive output
ripple and unstable operation from deteriorating the efficiency. This compensation is implemented by connecting
RZ and CZ in series across the CC and VSS pins. RZ sets the high-frequency gain for a high-speed transient
response. CZ sets the pole and zero of the error amplifier and keeps the loop stable. Adjust RZ and CZ, taking
into consideration conditions such as the inductor, output capacitor, and load current, so that the optimum
transient characteristics can be obtained.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 21
Standard Circuits
PWM
comparator
V
OUT
Timer latch
short-circuit
protection circuit
RDuty
RFB2
VSS
RFB1
FB
SD
L
VIN
EXT
UVLO
CSP CC
RZ
CZ
ROSC
M1
CFB
+
−
+
−
C
IN
Oscillator
Maximum duty
soft-start circuit
Reference voltage
(1.0 V)
soft-start circuit
Error amplifier
0.1 µF
ROSC RDuty
C
L
Ground point
Figure 15 Standard Circuit
Caution The above connection diagram and constant will not guarantee successful operation.
Perform thorough evaluation using the actual application to set the constant.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
22
Precaution
• Mount external capacitors, diodes, and inductor as close as possible to the IC.
• Characteristics ripple voltage and spike noise occur in IC containing switching regulators. Moreover rush current
flows at the time of a power supply injection. Because these largely depend on the inductor, the capacitor and
impedance of power supply used, fully check them using an actually mounted model.
• Make sure the dissipation of the switching transistor (especially at a high temperature) does not exceed the
allowable power dissipation of the package.
• The performance of a switching regulator varies depending on the design of the PCB patterns, peripheral circuits,
and external parts. Thoroughly test all settings with your device.
• This IC builds in soft start function, starts reference voltage gradually, and it is controlled so that FB pin voltage and
reference voltage become this potential. Therefore, keep in mind that it will be in a maximum duty state according
to the factor of IC exterior if FB pin voltage is held less than reference voltage.
• Although the IC contains a static electricity protection circuit, static electricity or voltage that exceeds the limit of the
protection circuit should not be applied.
• Seiko Instruments Inc. assumes no responsibility for the way in which this IC is used on products created using this
IC or for the specifications of that product, nor does Seiko Instruments Inc. assume any responsibility for any
infringement of patents or copyrights by products that include this IC either in Japan or in other countries.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 23
Characteristics (Typical Data)
1. Example of Major Temperature Characteristics (Ta = −40 to 85°C)
ISS1 vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
800
700
600
500
400
300
200
100
0
I
SS1
[µA]
Ta [°C]
f
OSC
= 1133 kHz (R
OSC
= 120 kΩ)
−20 100
f
OSC
= 700 kHz (R
OSC
= 200 kΩ)
f
OSC
= 286 kHz (R
OSC
= 510 kΩ)
IEXTH vs. Ta (VIN = 3.3 V) IEXTL vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
−200
−180
−160
−140
−120
−100
−80
−60
−40
−20
0
I
EXTH
[mA]
Ta [°C]
−20 100
f
OSC
= 700 kHz, MaxDuty = 73%
(R
OSC
= 200 kΩ, R
Duty
= 300 kΩ)
−40 0 20 40 60 80
200
180
160
140
120
100
80
60
40
20
0
I
EXTL
[mA]
Ta [°C]
−20 100
f
OSC
= 700 kHz, MaxDuty = 73%
(R
OSC
= 200 kΩ, R
Duty
= 300 kΩ)
IFB vs. Ta (VIN = 3.3 V) fOSC vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
0.10
0.08
0.06
0.04
0.02
0
−0.02
−0.04
−0.06
−0.08
−0.10
I
FB
[µA]
Ta [°C]
−20 100
−40 0 20 40 60 80
1400
1200
1000
800
600
400
200
0
f
OSC
[kHz]
Ta [°C]
−20 100
f
OSC
= 1133 kHz (R
OSC
= 120 kΩ)
f
OSC
= 700 kHz (R
OSC
= 200 kΩ)
f
OSC
= 286 kHz (R
OSC
= 510 kΩ)
MaxDuty vs. Ta (VIN = 3.3 V) tSS vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
100
90
80
70
60
50
40
30
20
10
0
MaxDuty [%]
Ta [°C]
−20 100
MaxDuty = 88.5%
(ROSC = 200 kΩ, RDuty = 100 kΩ)
MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
MaxDuty = 47%
(ROSC = 200 kΩ, RDuty = 640 kΩ)
−40 0 20 40 60 80
25.0
20.0
15.0
10.0
5.0
0
t
SS
[ms]
Ta [°C]
−20 100
t
SS
= 20 ms
t
SS
= 10 ms
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
24
tPRO vs. Ta (VIN = 3.3 V) VUVLO vs. Ta
−40 0 20 40 60 80
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0
t
PRO
[ms]
Ta [°C]
−20 100
tPRO = 50 ms (CSP = 0.1 µF)
−40 0 20 40 60 80
2.5
2.0
1.5
1.0
0.5
0
V
UVLO
[V]
Ta [°C]
−20 100
V
UVLO
= 2.3 V
V
UVLO
= 1.5 V
VUVLOHYS vs. Ta ICCH vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
V
UVLOHYS
[V]
Ta [°C]
−20 100
V
UVLOHYS
= 0.3 V
V
UVLOHYS
= 0.1 V
−40 0 20 40 60 80
−100
−90
−80
−70
−60
−50
−40
−30
−20
−10
0
I
CCH
[µA]
Ta [°C]
−20 100
ICCL vs. Ta (VIN = 3.3 V) VRTLT1 vs. Ta (VIN = 3.3 V)
−40 0 20 40 60 80
100
90
80
70
60
50
40
30
20
10
0
ICCL [µA]
Ta [°C]
−20 100
−40 0 20 40 60 80
1.2
1.0
0.8
0.6
0.4
0.2
0
V
RTLT1
[V]
Ta [°C]
−20 100
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 25
2. Example of Major Power Supply Dependence Characteristics (Ta = 25°C)
ISS vs. VIN
023456
1400
1200
1000
800
600
400
200
0
I
SS1
[µA]
V
IN
[V]
17
f
OSC
= 1133 kHz
(R
OSC
= 120 kΩ)
f
OSC
= 700 kHz
(R
OSC
= 200 kΩ)
f
OSC
= 286 kHz
(R
OSC
= 510 kΩ)
IEXTH vs. VIN I
EXTL vs. VIN
023456
−200
−180
−160
−140
−120
−100
−80
−60
−40
−20
0
IEXTH [mA]
V
IN
[V]
17
fOSC = 700 kHz, MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
023456
200
180
160
140
120
100
80
60
40
20
0
IEXTL [mA]
V
IN
[V]
17
fOSC = 700 kHz, MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
IFB vs. VIN fOSC vs. VIN
023456
0.10
0.08
0.06
0.04
0.02
0
−0.02
−0.04
−0.06
−0.08
−0.10
I
FB
[µA]
VIN [V]
17
023456
1400
1200
1000
800
600
400
200
0
f
OSC
[kHz]
V
IN
[V]
17
f
OSC
= 1133 kHz (R
OSC
= 120 kΩ)
f
OSC
= 700 kHz (R
OSC
= 200 kΩ)
f
OSC
= 286 kHz (R
OSC
= 510 kΩ)
MaxDuty vs. VIN tSS vs. VIN
023456
100
90
80
70
60
50
40
30
20
10
0
MaxDuty [%]
VIN [V]
17
MaxDuty = 88.5%
(R
OSC
= 200 kΩ, R
Duty
= 100 kΩ)
MaxDuty = 73%
(R
OSC
= 200 kΩ, R
Duty
= 300 kΩ)
MaxDuty = 47%
(R
OSC
= 200 kΩ, R
Duty
= 640 kΩ)
023456
25.0
20.0
15.0
10.0
5.0
0
t
SS
[ms]
V
IN
[V]
17
t
SS
= 20 ms
t
SS
= 10 ms
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
26
tPRO vs. VIN ICCH vs. VIN
023456
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0
t
PRO
[ms]
VIN [V]
17
t
PRO
=50 ms (CSP = 0.1 µF)
023456
−100
−90
−80
−70
−60
−50
−40
−30
−20
−10
0
I
CCH
[µA]
V
IN
[V]
17
ICCL vs. VIN
023456
100
90
80
70
60
50
40
30
20
10
0
I
CCL
[µA]
V
IN
[V]
17
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 27
3. Example of External Parts Dependence Characteristics
fOSC vs. ROSC (VIN = 3.3 V)
0 200 300 400 500 600
1600
1400
1200
1000
800
600
400
200
0
f
OSC
[kHz]
R
OSC
[kΩ]
100
Ta = 25°C
Ta = −40°C
Ta = 85°C
MaxDuty vs. RDuty / ROSC (ROSC = 200 kΩ, VIN = 3.3 V)
0 1 1.5 2 2.5 3
100
90
80
70
60
50
40
30
20
10
0
MaxDuty [%]
RDuty / ROSC
0.5 3.5 4.54
Ta = 25°C
Ta = −40°C
Ta = 85°C
tPRO vs. CSP (VIN = 3.3 V)
0 0.2 0.3 0.4 0.5
350
300
250
200
150
100
50
0
tPRO [ms]
CSP [µF]
0.1
Ta = 25°C
Ta = −40°C
Ta = 85°C
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
28
4. Examples of Transient Response Characteristics
4.1 Powering ON (VOUT = 9.2 V, VIN = 0 V → 3.3 V, Ta = 25°C)
Remark The switch (SW) is inserted between the diode (SD) and VOUT output.
Controlled externally to turn SW on a few ms later after the VIN voltage is applied.
(1) fOSC = 1133 kHz, IOUT = 0 mA, tSS = 10 ms (2) fOSC = 1133 kHz, IOUT = 100 mA, tSS = 10 ms
−5 5 10 15 20
4
2
0
VIN [V]
time [ms]
0
12
8
4
0
VOUT [V]
−5 5 10 15 20
4
2
0
V
IN
[V]
time [ms]
0
12
8
4
0
V
OUT
[V]
(3) fOSC = 700 kHz, IOUT = 0 mA, tSS = 10 ms (4) fOSC = 700 kHz, IOUT = 100 mA, tSS = 10 ms
−5 5 10 15 20
4
2
0
V
IN
[V]
time [ms]
0
12
8
4
0
V
OUT
[V]
−5 5 10 15 20
4
2
0
V
IN
[V]
time [ms]
0
12
8
4
0
V
OUT
[V]
(5) fOSC = 286 kHz, IOUT = 0 mA, tSS = 10 ms (6) fOSC = 286 kHz, IOUT = 100 mA, tSS = 10 ms
−5 5 10 15 20
4
2
0
VIN [V]
time [ms]
0
12
8
4
0
VOUT [V]
−5 5 10 15 20
4
2
0
V
IN
[V]
time [ms]
0
12
8
4
0
V
OUT
[V]
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 29
4.2 Load fluctuations (VOUT = 9.2 V, VIN = 3.3 V, Ta = 25°C, RZ = 200 kΩ, CZ = 0.01 µF)
(1) fOSC = 1133 kHz, IOUT = 0.1 mA→100 mA (2) fOSC = 1133 kHz, IOUT = 100 mA→0.1 mA
−20 0 10 20
time [ms]
−10
I
OUT
100 mA
0.1 mA
V
OUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
−20 0 10 20
time [ms]
−10
I
OUT
100 mA
0.1 mA
V
OUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
(3) fOSC = 700 kHz, IOUT = 0.1 mA→100 mA (4) fOSC = 700 kHz, IOUT = 100 mA→0.1 mA
−20 0 10 20
time [ms]
−10
IOUT
100 mA
0.1 mA
VOUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
−20 0 10 20
time [ms]
−10
I
OUT
100 mA
0.1 mA
V
OUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
(5) fOSC = 286 kHz, IOUT = 0.1 mA→100 mA (6) fOSC = 286 kHz, IOUT = 100 mA→0.1 mA
−20 0 10 20
time [ms]
−10
I
OUT
100 mA
0.1 mA
V
OUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
−20 0 10 20
time [ms]
−10
I
OUT
100 mA
0.1 mA
V
OUT
[0.2 V/div]
10.0
9.8
9.6
9.4
9.2
9.0
8.8
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
30
4.3 Input voltage fluctuations (VOUT = 9.2 V, IOUT = 100 mA, RZ = 200 kΩ, CZ = 0.01 µF)
(1) fOSC = 1133 kHz, VIN = 2.8 V→3.8 V (2) fOSC = 1133 kHz, VIN = 3.8 V→2.8 V
−20 0 10 20
time [ms]
−10
VIN
[V]
4.0
3.5
3.0
2.5
VOUT
[V]
9.40
9.30
9.20
9.10
−20 0 10 20
time [ms]
−10
VIN
[V]
4.0
3.5
3.0
2.5
VOUT
[V]
9.40
9.30
9.20
9.10
(3) fOSC = 700 kHz, VIN = 2.8 V→3.8 V (4) fOSC = 700 kHz, VIN = 3.8 V→2.8 V
−20 0 10 20
time [ms]
−10
V
IN
[V]
4.0
3.5
3.0
2.5
V
OUT
[V]
9.40
9.30
9.20
9.10
−20 0 10 20
time [ms]
−10
V
IN
[V]
4.0
3.5
3.0
2.5
V
OUT
[V]
9.40
9.30
9.20
9.10
(5) fOSC = 286 kHz, VIN = 2.8 V→3.8 V (6) fOSC = 286 kHz, VIN = 3.8 V→2.8 V
−20 0 10 20
time [ms]
−10
VIN
[V]
4.0
3.5
3.0
2.5
VOUT
[V]
9.40
9.30
9.20
9.10
−20 0 10 20
time [ms]
−10
VIN
[V]
4.0
3.5
3.0
2.5
VOUT
[V]
9.40
9.30
9.20
9.10
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 31
Reference Data
1. Reference data for external parts
Table 6 Properties of External Parts
Element Name Product Name Manufacture Characteristics
Inductor LDR655312T
TDK Corporation 10 µH, DCR*1 = 307 mΩ, IMAX*2 = 0.7 A,
Height = 1.2 mm
Diode RB491D
Rohm Co., Ltd. VF*3 = 0.45 V, IF*4 = 1.0 A
Output capacitor
(ceramic) 16 V, 10 µF
Transistor MCH3406
Sanyo Electric Co., Ltd. VDSS*5 = 20 V, VGSS*6 = ±10 V, Ciss*7 = 280 pF,
RDS(ON)*8 = 82 mΩ max. (VGS*9 = 2.5 V, ID*10 = 1 A)
*1. DCR : DC resistance
*2. IMAX : Maximum allowable current
*3. VF : Forward voltage
*4. IF : Forward current
*5. VDSS : Drain to source voltage (when short circuited between the gate and source)
*6. VGSS : Gate to source voltage (when short circuited between the drain and source)
*7. Ciss : Input capacitance
*8. RDS(ON) : Drain to source on resistance
*9. VGS : Gate to source voltage
*10. ID : Drain current
Caution The values shown in the characteristics column of Table 6 above are based on the materials
provided by each manufacturer. However, consider the characteristics of the original materials
when using the above products.
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
32
2. Reference data (1)
The data of (a) output current (IOUT) vs. efficiency (η) characteristics and (b) output current (IOUT) vs. output voltage
(VOUT) characteristics is shown below.
2. 1 VOUT = 13.1 V (RFB1 = 7.5 kΩ, RFB2 = 620 Ω)
(1) fOSC = 1133 kHz, MaxDuty = 73% (ROSC = 120 kΩ, RDuty = 180 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
0.01 1 10 100 1000
13.20
13.15
13.10
13.05
13.00
12.95
12.90
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
(2) fOSC = 700 kHz, MaxDuty = 73% (ROSC = 200 kΩ, RDuty = 300 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
0.01 1 10 100 1000
13.20
13.15
13.10
13.05
13.00
12.95
12.90
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
(3) fOSC = 286 kHz, MaxDuty = 73% (ROSC = 510 kΩ, RDuty = 750 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
0.01 1 10 100 1000
13.20
13.15
13.10
13.05
13.00
12.95
12.90
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 33
2. 2 VOUT = 9.2 V (RFB1 = 8.2 kΩ, RFB2 = 1.0 kΩ)
(1) fOSC = 1133 kHz, MaxDuty = 73% (ROSC = 120 kΩ, RDuty = 180 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
0.01 1 10 100 1000
9.30
9.25
9.20
9.15
9.10
9.05
9.00
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
(2) fOSC = 700 kHz, MaxDuty = 73% (ROSC = 200 kΩ, RDuty = 300 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
0.01 1 10 100 1000
9.30
9.25
9.20
9.15
9.10
9.05
9.00
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
(3) fOSC = 286 kHz, MaxDuty = 73% (ROSC = 510 kΩ, RDuty = 750 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
0.01 1 10 100 1000
9.30
9.25
9.20
9.15
9.10
9.05
9.00
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
34
2. 3 VOUT = 6.1 V (RFB1 = 5.1 kΩ, RFB2 = 1.0 kΩ)
(1) fOSC = 1133 kHz, MaxDuty = 73% (ROSC = 120 kΩ, RDuty = 180 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
0.01 1 10 100 1000
6.20
6.15
6.10
6.05
6.00
5.95
5.90
V
OUT
[V]
I
OUT
[mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
(2) fOSC = 700 kHz, MaxDuty = 73% (ROSC = 200 kΩ, RDuty = 300 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
0.01 1 10 100 1000
6.20
6.15
6.10
6.05
6.00
5.95
5.90
V
OUT
[V]
I
OUT
[mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
(3) fOSC = 286 kHz, MaxDuty = 73% (ROSC = 510 kΩ, RDuty = 750 kΩ)
(a) IOUT vs. η (b) IOUT vs. VOUT
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
η [%]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
0.01 1 10 100 1000
6.20
6.15
6.10
6.05
6.00
5.95
5.90
V
OUT
[V]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 35
3. Reference data (2)
The data of output current (IOUT) vs. ripple voltage (Vr) characteristics is shown below.
3. 1 VOUT = 13.1 V (RFB1 = 7.5 kΩ, RFB2 = 620 Ω)
(1) fOSC = 1133 kHz, MaxDuty = 73 %
(ROSC = 120 kΩ, RDuty = 180 kΩ)
(2) fOSC = 700 kHz, MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
I
OUT
[mA]
0.1
VIN = 5.0 V
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
I
OUT
[mA]
0.1
VIN = 5.0 V
(3) fOSC = 286 kHz, MaxDuty = 73%
(ROSC = 510 kΩ, RDuty = 750 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 5.0 V
3. 2 VOUT = 9.2 V (RFB1 = 8.2 kΩ, RFB2 = 1.0 kΩ)
(1) fOSC = 1133 kHz, MaxDuty = 73%
(ROSC = 120 kΩ, RDuty = 180 kΩ)
(2) fOSC = 700 kHz, MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
(3) fOSC = 286 kHz, MaxDuty = 73%
(ROSC = 510 kΩ, RDuty = 750 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 5.0 V
V
IN
= 3.3 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
36
3. 3 VOUT = 6.1 V (RFB1 = 5.1 kΩ, RFB2 = 1.0 kΩ)
(1) fOSC = 1133 kHz, MaxDuty = 73%
(ROSC = 120 kΩ, RDuty = 180 kΩ)
(2) fOSC = 700 kHz, MaxDuty = 73%
(ROSC = 200 kΩ, RDuty = 300 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
IOUT [mA]
0.1
V
IN
= 3.3 V
V
IN
= 2.5 V
(3) fOSC = 286 kHz, MaxDuty = 73%
(ROSC = 510 kΩ, RDuty = 750 kΩ)
0.01 1 10 100 1000
100
90
80
70
60
50
40
30
20
10
0
Vr [mV]
I
OUT
[mA]
0.1
VIN = 3.3 V
VIN = 2.5 V
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.1.0_02 S-8333 Series
Seiko Instruments Inc. 37
Marking Specification
(1) SNT-8A
(1) to (3) Product code (Refer to Product name vs. Product code)
(4) to (9) Lot number
SNT-8A
Top view
1
4
8
5
(7)
(4)
(1)
(8)
(5)
(2)
(9)
(6)
(3)
Product name vs. Product code
Product code Product code
Product name (1) (2) (3) Product name (1) (2) (3)
S-8333AAAA-I8T1G O F A S-8333ABEC-I8T1G O G O
S-8333AAAB-I8T1G O F B S-8333ABFA-I8T1G O G P
S-8333AAAC-I8T1G O F C S-8333ABFB-I8T1G O G Q
S-8333AABA-I8T1G O F D S-8333ABFC-I8T1G O G R
S-8333AABB-I8T1G O F E S-8333ABGA-I8T1G O G S
S-8333AABC-I8T1G O F F S-8333ABGB-I8T1G O G T
S-8333AACA-I8T1G O F G S-8333ABGC-I8T1G O G U
S-8333AACB-I8T1G O F H S-8333ABHA-I8T1G O G V
S-8333AACC-I8T1G O F I S-8333ABHB-I8T1G O G W
S-8333AADA-I8T1G O F J S-8333ABHC-I8T1G O G X
S-8333AADB-I8T1G O F K S-8333ABIA-I8T1G O G Y
S-8333AADC-I8T1G O F L S-8333ABIB-I8T1G O G Z
S-8333AAEA-I8T1G O F M S-8333ABIC-I8T1G O G 3
S-8333AAEB-I8T1G O F N S-8333ACAA-I8T1G O H A
S-8333AAEC-I8T1G O F O S-8333ACAB-I8T1G O H B
S-8333AAFA-I8T1G O F P S-8333ACAC-I8T1G O H C
S-8333AAFB-I8T1G O F Q S-8333ACBA-I8T1G O H D
S-8333AAFC-I8T1G O F R S-8333ACBB-I8T1G O H E
S-8333AAGA-I8T1G O F S S-8333ACBC-I8T1G O H F
S-8333AAGB-I8T1G O F T S-8333ACCA-I8T1G O H G
S-8333AAGC-I8T1G O F U S-8333ACCB-I8T1G O H H
S-8333AAHA-I8T1G O F V S-8333ACCC-I8T1G O H I
S-8333AAHB-I8T1G O F W S-8333ACDA-I8T1G O H J
S-8333AAHC-I8T1G O F X S-8333ACDB-I8T1G O H K
S-8333AAIA-I8T1G O F Y S-8333ACDC-I8T1G O H L
S-8333AAIB-I8T1G O F Z S-8333ACEA-I8T1G O H M
S-8333AAIC-I8T1G O F 3 S-8333ACEB-I8T1G O H N
S-8333ABAA-I8T1G O G A S-8333ACEC-I8T1G O H O
S-8333ABAB-I8T1G O G B S-8333ACFA-I8T1G O H P
S-8333ABAC-I8T1G O G C S-8333ACFB-I8T1G O H Q
S-8333ABBA-I8T1G O G D S-8333ACFC-I8T1G O H R
S-8333ABBB-I8T1G O G E S-8333ACGA-I8T1G O H S
S-8333ABBC-I8T1G O G F S-8333ACGB-I8T1G O H T
S-8333ABCA-I8T1G O G G S-8333ACGC-I8T1G O H U
S-8333ABCB-I8T1G O G H S-8333ACHA-I8T1G O H V
S-8333ABCC-I8T1G O G I S-8333ACHB-I8T1G O H W
S-8333ABDA-I8T1G O G J S-8333ACHC-I8T1G O H X
S-8333ABDB-I8T1G O G K S-8333ACIA-I8T1G O H Y
S-8333ABDC-I8T1G O G L S-8333ACIB-I8T1G O H Z
S-8333ABEA-I8T1G O G M S-8333ACIC-I8T1G O H 3
S-8333ABEB-I8T1G O G N
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
S-8333 Series Rev.1.0_02
Seiko Instruments Inc.
38
(2) 8-Pin TSSOP
(1) to (4) Product name: 8333 (Fixed)
(5) to (8) Function code (Refer to Product name vs. Function code)
(9) to (14) Lot number
8-Pin TSSOP
Top view
(
1
)
(
2
)
(
3
)
(
4
)
(
5
)
(
6
)
(
7
)
(
8
)
(
11
)
(
12
)
(
13
)
(
14
)
(
9
)
(
10
)
1
4
8
5
Product name vs. Function code
Function code Function code
Product name (5) (6) (7) (8) Product name (5) (6) (7) (8)
S-8333AAAA-T8T1 A A A A S-8333ABEC-T8T1 A B E C
S-8333AAAB-T8T1 A A A B S-8333ABFA-T8T1 A B F A
S-8333AAAC-T8T1 A A A C S-8333ABFB-T8T1 A B F B
S-8333AABA-T8T1 A A B A S-8333ABFC-T8T1 A B F C
S-8333AABB-T8T1 A A B B S-8333ABGA-T8T1 A B G A
S-8333AABC-T8T1 A A B C S-8333ABGB-T8T1 A B G B
S-8333AACA-T8T1 A A C A S-8333ABGC-T8T1 A B G C
S-8333AACB-T8T1 A A C B S-8333ABHA-T8T1 A B H A
S-8333AACC-T8T1 A A C C S-8333ABHB-T8T1 A B H B
S-8333AADA-T8T1 A A D A S-8333ABHC-T8T1 A B H C
S-8333AADB-T8T1 A A D B S-8333ABIA-T8T1 A B I A
S-8333AADC-T8T1 A A D C S-8333ABIB-T8T1 A B I B
S-8333AAEA-T8T1 A A E A S-8333ABIC-T8T1 A B I C
S-8333AAEB-T8T1 A A E B S-8333ACAA-T8T1 A C A A
S-8333AAEC-T8T1 A A E C S-8333ACAB-T8T1 A C A B
S-8333AAFA-T8T1 A A F A S-8333ACAC-T8T1 A C A C
S-8333AAFB-T8T1 A A F B S-8333ACBA-T8T1 A C B A
S-8333AAFC-T8T1 A A F C S-8333ACBB-T8T1 A C B B
S-8333AAGA-T8T1 A A G A S-8333ACBC-T8T1 A C B C
S-8333AAGB-T8T1 A A G B S-8333ACCA-T8T1 A C C A
S-8333AAGC-T8T1 A A G C S-8333ACCB-T8T1 A C C B
S-8333AAHA-T8T1 A A H A S-8333ACCC-T8T1 A C C C
S-8333AAHB-T8T1 A A H B S-8333ACDA-T8T1 A C D A
S-8333AAHC-T8T1 A A H C S-8333ACDB-T8T1 A C D B
S-8333AAIA-T8T1 A A I A S-8333ACDC-T8T1 A C D C
S-8333AAIB-T8T1 A A I B S-8333ACEA-T8T1 A C E A
S-8333AAIC-T8T1 A A I C S-8333ACEB-T8T1 A C E B
S-8333ABAA-T8T1 A B A A S-8333ACEC-T8T1 A C E C
S-8333ABAB-T8T1 A B A B S-8333ACFA-T8T1 A C F A
S-8333ABAC-T8T1 A B A C S-8333ACFB-T8T1 A C F B
S-8333ABBA-T8T1 A B B A S-8333ACFC-T8T1 A C F C
S-8333ABBB-T8T1 A B B B S-8333ACGA-T8T1 A C G A
S-8333ABBC-T8T1 A B B C S-8333ACGB-T8T1 A C G B
S-8333ABCA-T8T1 A B C A S-8333ACGC-T8T1 A C G C
S-8333ABCB-T8T1 A B C B S-8333ACHA-T8T1 A C H A
S-8333ABCC-T8T1 A B C C S-8333ACHB-T8T1 A C H B
S-8333ABDA-T8T1 A B D A S-8333ACHC-T8T1 A C H C
S-8333ABDB-T8T1 A B D B S-8333ACIA-T8T1 A C I A
S-8333ABDC-T8T1 A B D C S-8333ACIB-T8T1 A C I B
S-8333ABEA-T8T1 A B E A S-8333ACIC-T8T1 A C I C
S-8333ABEB-T8T1 A B E B
1.97±0.03
0.2±0.05
0.48±0.02
0.08
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
SNT-8A-A-PKG Dimensions
PH008-A-P-SD-1.0
No. PH008-A-P-SD-1.0
0.5
+0.05
-0.02
123 4
56
78
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
PH008-A-C-SD-1.0
SNT-8A-A-Carrier Tape
No. PH008-A-C-SD-1.0
Feed direction
4.0±0.1
2.0±0.05
4.0±0.1
ø1.5 +0.1
-0
ø0.5±0.1
2.25±0.05
0.65±0.05
0.25±0.05
2134
7865
5°
12.5max.
9.0±0.3
ø13±0.2
(60°) (60°)
Enlarged drawing in the central part
QTY.
PH008-A-R-SD-1.0
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
SNT-8A-A-Reel
No. PH008-A-R-SD-1.0
5,000
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
TSSOP8-E-PKG Dimensions
No. FT008-A-P-SD-1.1
FT008-A-P-SD-1.1
0.17±0.05
3.00 +0.3
-0.2
0.65
0.2±0.1
14
5
8
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
ø1.55±0.05
2.0±0.05
8.0±0.1 ø1.55 +0.1
-0.05
(4.4)
0.3±0.05
1
45
8
4.0±0.1
Feed direction
TSSOP8-E-Carrier Tape
No. FT008-E-C-SD-1.0
FT008-E-C-SD-1.0
+0.4
-0.2
6.6
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
Enlarged drawing in the central part
No. FT008-E-R-SD-1.0
2±0.5
ø13±0.5
ø21±0.8
13.4±1.0
17.5±1.0
3,000
QTY.
TSSOP8-E-Reel
FT008-E-R-SD-1.0
•
The information described herein is subject to change without notice.
• Seiko Instruments Inc. is not responsible for any problems caused by circuits or diagrams described herein
whose related industrial properties, patents, or other rights belong to third parties. The application circuit
examples explain typical applications of the products, and do not guarantee the success of any specific
mass-production design.
• When the products described herein are regulated products subject to the Wassenaar Arrangement or other
agreements, they may not be exported without authorization from the appropriate governmental authority.
• Use of the information described herein for other purposes and/or reproduction or copying without the
express permission of Seiko Instruments Inc. is strictly prohibited.
• The products described herein cannot be used as part of any device or equipment affecting the human
body, such as exercise equipment, medical equipment, security systems, gas equipment, or any apparatus
installed in airplanes and other vehicles, without prior written permission of Seiko Instruments Inc.
• Although Seiko Instruments Inc. exerts the greatest possible effort to ensure high quality and reliability, the
failure or malfunction of semiconductor products may occur. The user of these products should therefore
give thorough consideration to safety design, including redundancy, fire-prevention measures, and
malfunction prevention, to prevent any accidents, fires, or community damage that may ensue.
