TNY263-268
TinySwitch-II Family
Enhanced, Energy Efficient,
Low Power Off-line Switcher
Figure 1. Typical Standby Application.
Product Highlights
TinySwitch-II Features Reduce System Cost
Fully integrated auto-restart for short circuit and open
loop fault protection – saves external component costs
Built-in circuitry practically eliminates audible noise with
ordinary dip-varnished transformer
Programmable line under-voltage detect feature prevents
power on/off glitches – saves external components
Frequency jittering dramatically reduces EMI (~10 dB)
– minimizes EMI filter component costs
132 kHz operation reduces transformer size – allows use
of EF12.6 or EE13 cores for low cost and small size
Very tight tolerances and negligible temperature variation
on key parameters eases design and lowers cost
Lowest component count switcher solution
Expanded scalable device family for low system cost
Better Cost/Performance over RCC & Linears
Lower system cost than RCC, discrete PWM and other
integrated/hybrid solutions
Cost effective replacement for bulky regulated linears
Simple ON/OFF control – no loop compensation needed
No bias winding – simpler, lower cost transformer
Simple design practically eliminates rework in
manufacturing
EcoSmart®– Extremely Energy Efficient
No load consumption <50 mW with bias winding and
<250 mW without bias winding at 265 VAC input
Meets California Energy Commission (CEC), Energy
Star, and EU requirements
Ideal for cell-phone charger and PC standby applications
High Performance at Low Cost
High voltage powered – ideal for charger applications
High bandwidth provides fast turn on with no overshoot
Current limit operation rejects line frequency ripple
Built-in current limit and thermal protection improves
safety
Description
TinySwitch-II integrates a 700 V power MOSFET, oscillator,
high voltage switched current source, current limit and
thermal shutdown circuitry onto a monolithic device. The
start-up and operating power are derived directly from
the voltage on the DRAIN pin, eliminating the need for
a bias winding and associated circuitry. In addition, the
PI-2684-101700
Wide-Range
HV DC Input D
S
EN/UV
BP
+
-
+
-
DC Output
TinySwitch-II
Optional
UV Resistor
®
April 2005
Table 1. Notes: 1. Minimum continuous power in a typical
non-ventilated enclosed adapter measured at 50 °C ambient.
2. Minimum practical continuous power in an open frame
design with adequate heat sinking, measured at 50 °C
ambient (See Key Applications Considerations). 3. Packages:
P: DIP-8B, G: SMD-8B. For lead-free package options, see Part
Ordering Information.
TinySwitch-II devices incorporate auto-restart, line under-
voltage sense, and frequency jittering. An innovative design
minimizes audio frequency components in the simple ON/OFF
control scheme to practically eliminate audible noise with
standard taped/varnished transformer construction. The fully
integrated auto-restart circuit safely limits output power during
fault conditions such as output short circuit or open loop,
reducing component count and secondary feedback circuitry
cost. An optional line sense resistor externally programs a line
under-voltage threshold, which eliminates power down glitches
caused by the slow discharge of input storage capacitors present
in applications such as standby supplies. The operating frequency
of 132 kHz is jittered to significantly reduce both the quasi-peak
and average EMI, minimizing filtering cost.
OUTPUT POWER TABLE
PRODUCT3
230 VAC ±15% 85-265 VAC
Adapter1Open
Frame2Adapter1Open
Frame2
TNY263 P or G 5 W 7.5 W 3.7 W 4.7 W
TNY264 P or G 5.5 W 9 W 4 W 6 W
TNY265 P or G 8.5 W 11 W 5.5 W 7.5 W
TNY266 P or G 10 W 15 W 6 W 9.5 W
TNY267 P or G 13 W 19 W 8 W 12 W
TNY268 P or G 16 W 23 W 10 W 15 W
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TNY263-268
Figure 2. Functional Block Diagram.
Figure 3. Pin Configuration.
Pin Functional Description
DRAIN (D) Pin:
Power MOSFET drain connection. Provides internal operating
current for both start-up and steady-state operation.
BYPASS (BP) Pin:
Connection point for a 0.1 µF external bypass capacitor for the
internally generated 5.8 V supply.
ENABLE/UNDER-VOLTAGE (EN/UV) Pin:
This pin has dual functions: enable input and line under-voltage
sense. During normal operation, switching of the power
MOSFET is controlled by this pin. MOSFET switching is
terminated when a current greater than 240 µA is drawn from
this pin. This pin also senses line under-voltage conditions
through an external resistor connected to the DC line
voltage. If there is no external resistor connected to this pin,
TinySwitch-II detects its absence and disables the line under-
voltage function.
SOURCE (S) Pin:
Control circuit common, internally connected to output
MOSFET source.
SOURCE (HV RTN) Pin:
Output MOSFET source connection for high voltage return.
PI-2643-030701
CLOCK
OSCILLATOR
5.8 V
4.8 V
SOURCE
(S)
S
R
Q
DCMAX
BYPASS
(BP)
+
-
VILIMIT
FAULT
PRESENT
CURRENT LIMIT
COMPARATOR
ENABLE
LEADING
EDGE
BLANKING
THERMAL
SHUTDOWN
+
-
DRAIN
(D)
REGULATOR
5.8 V
BYPASS PIN
UNDER-VOLTAGE
1.0 V + VT
ENABLE/
UNDER-
VOLTAGE
(EN/UV)
Q
240 µA 50 µA
LINE UNDER-VOLTAGE
RESET
AUTO-
RESTART
COUNTER
JITTER
1.0 V
6.3 V
CURRENT
LIMIT STATE
MACHINE
PI-2685-101600
EN/UV D
S
S
S (HV RTN)
S (HV RTN)
BP
P Package (DIP-8B)
G Package (SMD-8B)
8
5
7
1
4
2
3
3
TNY263-268
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Figure 4. Frequency Jitter.
TinySwitch-II Functional Description
TinySwitch-II combines a high voltage power MOSFET switch
with a power supply controller in one device. Unlike conventional
PWM (pulse width modulator) controllers, TinySwitch-II uses
a simple ON/OFF control to regulate the output voltage.
The TinySwitch-II controller consists of an oscillator,
enable circuit (sense and logic), current limit state machine,
5.8 V regulator, BYPASS pin under-voltage circuit, over-
temperature protection, current limit circuit, leading edge
blanking and a 700 V power MOSFET. TinySwitch-II
incorporates additional circuitry for line under-voltage sense,
auto-restart and frequency jitter. Figure 2 shows the functional
block diagram with the most important features.
Oscillator
The typical oscillator frequency is internally set to an average
of 132 kHz. Two signals are generated from the oscillator: the
maximum duty cycle signal (DCMAX) and the clock signal that
indicates the beginning of each cycle.
The TinySwitch-II oscillator incorporates circuitry that
introduces a small amount of frequency jitter, typically 8 kHz
peak-to-peak, to minimize EMI emission. The modulation rate
of the frequency jitter is set to 1 kHz to optimize EMI reduction
for both average and quasi-peak emissions. The frequency jitter
should be measured with the oscilloscope triggered at the falling
edge of the DRAIN waveform. The waveform in Figure 4
illustrates the frequency jitter of the TinySwitch-II.
Enable Input and Current Limit State Machine
The enable input circuit at the EN/UV pin consists of a low
impedance source follower output set at 1.0 V. The current
through the source follower is limited to 240 µA. When the
current out of this pin exceeds 240 µA, a low logic level
(disable) is generated at the output of the enable circuit. This
enable circuit output is sampled at the beginning of each
cycle on the rising edge of the clock signal. If high, the power
MOSFET is turned on for that cycle (enabled). If low, the power
MOSFET remains off (disabled). Since the sampling is done
only at the beginning of each cycle, subsequent changes in the
EN/UV pin voltage or current during the remainder of the
cycle are ignored.
The current limit state machine reduces the current limit by
discrete amounts at light loads when TinySwitch-II is likely to
switch in the audible frequency range. The lower current limit
raises the effective switching frequency above the audio range
and reduces the transformer flux density, including the associated
audible noise. The state machine monitors the sequence of
EN/UV pin voltage levels to determine the load condition and
adjusts the current limit level accordingly in discrete amounts.
Under most operating conditions (except when close to no-load),
the low impedance of the source follower keeps the voltage on
the EN/UV pin from going much below 1.0 V in the disabled
state. This improves the response time of the optocoupler that
is usually connected to this pin.
5.8 V Regulator and 6.3 V Shunt Voltage Clamp
The 5.8 V regulator charges the bypass capacitor connected to
the BYPASS pin to 5.8 V by drawing a current from the voltage
on the DRAIN pin whenever the MOSFET is off. The BYPASS
pin is the internal supply voltage node for the TinySwitch-II.
When the MOSFET is on, the TinySwitch-II operates from the
energy stored in the bypass capacitor. Extremely low power
consumption of the internal circuitry allows TinySwitch-II to
operate continuously from current it takes from the DRAIN
pin. A bypass capacitor value of 0.1 µF is sufficient for both
high frequency decoupling and energy storage.
In addition, there is a 6.3 V shunt regulator clamping the
BYPASS pin at 6.3 V when current is provided to the BYPASS
pin through an external resistor. This facilitates powering of
TinySwitch-II externally through a bias winding to decrease the
no-load consumption to about 50 mW.
BYPASS Pin Under-Voltage
The BYPASS pin under-voltage circuitry disables the power
MOSFET when the BYPASS pin voltage drops below 4.8 V.
Once the BYPASS pin voltage drops below 4.8 V, it must rise
back to 5.8 V to enable (turn-on) the power MOSFET.
Over Temperature Protection
The thermal shutdown circuitry senses the die temperature. The
threshold is typically set at 135 °C with 70 °C hysteresis. When
the die temperature rises above this threshold the power MOSFET
is disabled and remains disabled until the die temperature falls
by 70 °C, at which point it is re-enabled. A large hysteresis of
600
0 5 10
136 kHz
128 kHz
VDRAIN
Time (µs)
PI-2741-041901
500
400
300
200
100
0
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TNY263-268
Figure 5. TinySwitch-II Auto-Restart Operation.
PI-2699-030701
01000 2000
Time (ms)
0
5
0
10
100
200
300 VDRAIN
VDC-OUTPUT
70 °C (typical) is provided to prevent overheating of the PC
board due to a continuous fault condition.
Current Limit
The current limit circuit senses the current in the power MOSFET.
When this current exceeds the internal threshold (ILIMIT), the
power MOSFET is turned off for the remainder of that cycle. The
current limit state machine reduces the current limit threshold
by discrete amounts under medium and light loads.
The leading edge blanking circuit inhibits the current limit
comparator for a short time (tLEB) after the power MOSFET is
turned on. This leading edge blanking time has been set so that
current spikes caused by capacitance and secondary-side rectifier
reverse recovery time will not cause premature termination of
the switching pulse.
Auto-Restart
In the event of a fault condition such as output overload, output
short circuit, or an open loop condition, TinySwitch-II enters
into auto-restart operation. An internal counter clocked by the
oscillator gets reset every time the EN/UV pin is pulled low. If
the EN/UV pin is not pulled low for 50 ms, the power MOSFET
switching is normally disabled for 850 ms (except in the case of
line under-voltage condition, in which case it is disabled until
the condition is removed). The auto-restart alternately enables
and disables the switching of the power MOSFET until the fault
condition is removed. Figure 5 illustrates auto-restart circuit
operation in the presence of an output short circuit.
In the event of a line under-voltage condition, the switching
of the power MOSFET is disabled beyond its normal 850 ms
time until the line under-voltage condition ends.
Line Under-Voltage Sense Circuit
The DC line voltage can be monitored by connecting an external
resistor from the DC line to the EN/UV pin. During power-up
or when the switching of the power MOSFET is disabled in
auto-restart, the current into the EN/UV pin must exceed 49 µA
to initiate switching of the power MOSFET. During power-up,
this is accomplished by holding the BYPASS pin to 4.8 V while
the line under-voltage condition exists. The BYPASS pin then
rises from 4.8 V to 5.8 V when the line under-voltage condition
goes away. When the switching of the power MOSFET is
disabled in auto-restart mode and a line under-voltage condition
exists, the auto-restart counter is stopped. This stretches the
disable time beyond its normal 850 ms until the line under-
voltage condition ends.
The line under-voltage circuit also detects when there is
no external resistor connected to the EN/UV pin (less than
~ 2 µA into the pin). In this case the line under-voltage function
is disabled.
TinySwitch-II Operation
TinySwitch-II devices operate in the current limit mode. When
enabled, the oscillator turns the power MOSFET on at the
beginning of each cycle. The MOSFET is turned off when the
current ramps up to the current limit or when the DCMAX limit is
reached. Since the highest current limit level and frequency of
a TinySwitch-II design are constant, the power delivered to the
load is proportional to the primary inductance of the transformer
and peak primary current squared. Hence, designing the supply
involves calculating the primary inductance of the transformer
for the maximum output power required. If the TinySwitch-II
is appropriately chosen for the power level, the current in the
calculated inductance will ramp up to current limit before the
DCMAX limit is reached.
Enable Function
TinySwitch-II senses the EN/UV pin to determine whether or not
to proceed with the next switching cycle as described earlier.
The sequence of cycles is used to determine the current limit.
Once a cycle is started, it always completes the cycle (even when
the EN/UV pin changes state half way through the cycle). This
operation results in a power supply in which the output voltage
ripple is determined by the output capacitor, amount of energy
per switch cycle and the delay of the feedback.
The EN/UV pin signal is generated on the secondary by
comparing the power supply output voltage with a reference
voltage. The EN/UV pin signal is high when the power supply
output voltage is less than the reference voltage.
In a typical implementation, the EN/UV pin is driven by an
optocoupler. The collector of the optocoupler transistor is
connected to the EN/UV pin and the emitter is connected to
5
TNY263-268
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V
DRAIN
V
EN
CLOCK
D
DRAIN
I
MAX
PI-2749-050301
Figure 6. TinySwitch-II Operation at Near Maximum Loading.
V
DRAIN
V
EN
CLOCK
D
DRAIN
I
MAX
PI-2667-090700
Figure 8. TinySwitch-II Operation at Medium Loading.
PI-2377-091100
V
DRAIN
V
EN
CLOCK
D
DRAIN
I
MAX
Figure 7. TinySwitch-II Operation at Moderately Heavy Loading.
the SOURCE pin. The optocoupler LED is connected in series
with a Zener diode across the DC output voltage to be regulated.
When the output voltage exceeds the target regulation voltage
level (optocoupler LED voltage drop plus Zener voltage), the
optocoupler LED will start to conduct, pulling the EN/UV pin
low. The Zener diode can be replaced by a TL431 reference
circuit for improved accuracy.
ON/OFF Operation with Current Limit State Machine
The internal clock of the TinySwitch-II runs all the time. At
the beginning of each clock cycle, it samples the EN/UV pin to
decide whether or not to implement a switch cycle, and based
on the sequence of samples over multiple cycles, it determines
the appropriate current limit. At high loads, when the EN/UV
pin is high (less than 240 µA out of the pin), a switching cycle
with the full current limit occurs. At lighter loads, when EN/UV
is high, a switching cycle with a reduced current limit occurs.
At near maximum load, TinySwitch-II will conduct during nearly
all of its clock cycles (Figure 6). At slightly lower load, it will
“skip” additional cycles in order to maintain voltage regulation
at the power supply output (Figure 7). At medium loads, cycles
will be skipped and the current limit will be reduced (Figure 8).
At very light loads, the current limit will be reduced even further
(Figure 9). Only a small percentage of cycles will occur to
satisfy the power consumption of the power supply.
The response time of the TinySwitch-II ON/OFF control scheme
is very fast compared to normal PWM control. This provides
tight regulation and excellent transient response.
Power Up/Down
The TinySwitch-II requires only a 0.1 µF capacitor on the
BYPASS pin. Because of its small size, the time to charge this
capacitor is kept to an absolute minimum, typically 0.6 ms. Due
to the fast nature of the ON/OFF feedback, there is no overshoot
at the power supply output. When an external resistor (2 M)
is connected from the positive DC input to the EN/UV pin, the
power MOSFET switching will be delayed during power-up until
the DC line voltage exceeds the threshold (100 V). Figures 10
and 11 show the power-up timing waveform of TinySwitch-II
in applications with and without an external resistor (2 M)
connected to the EN/UV pin.
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TNY263-268
Figure 12. Normal Power-down Timing (without UV).
Figure 13. Slow Power-down Timing with Optional External
(2 M) UV Resistor Connected to EN/UV Pin.
Figure 10. TinySwitch-II Power-up with Optional External UV
Resistor (2 M) Connected to EN/UV Pin.
Figure 11. TinySwitch-II Power-up without Optional External UV
Resistor Connected to EN/UV Pin.
PI-2661-072400
V
DRAIN
V
EN
CLOCK
D
DRAIN
I
MAX
Figure 9. TinySwitch-II Operation at Very Light Load.
During power-down, when an external resistor is used, the
power MOSFET will switch for 50 ms after the output loses
regulation. The power MOSFET will then remain off without
any glitches since the under-voltage function prohibits restart
when the line voltage is low.
Figure 12 illustrates a typical power-down timing waveform of
TinySwitch-II. Figure 13 illustrates a very slow power-down
timing waveform of TinySwitch-II as in standby applications.
The external resistor (2 M) is connected to the EN/UV pin
in this case to prevent unwanted restarts.
PI-2395-030801
02.5 5
Time (s)
0
100
200
400
300
0
100
200
VDC-INPUT
VDRAIN
01 2
Time (ms)
0
200
400
5
0
10
0
100
200
PI-2383-030801
VDC-INPUT
VBYPASS
VDRAIN
PI-2348-030801
0.5 1
Time (s)
0
100
200
300
0
100
200
400
VDC-INPUT
VDRAIN
7
TNY263-268
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Figure 14. 2.5 W Constant Voltage, Constant Current Battery Charger with Universal Input (85-265 VAC).
PI-2706-080404
+ 5 V
500 mA
RTN
D1
1N4005
C1
3.3 µF
400 V
Fusible
RF1
8.2
C3
0.1 µF
C7
10 µF
10 V
85-265
VAC
L1
2.2 mH
D2
1N4005
D3
1N4005
D4
1N4005
R2
200 k
U2
LTV817
D5
1N5819
Shield
L2
3.3 µH
C5
330 µF
16 V
C2
3.3 µF
400 V
C6
100 µF
35 V
R7
100
R4
1.2
1/2 W
Q1
2N3904
R8
270
VR1
BZX79-
B3V9
3.9 V
U1
TNY264
C3
2.2 nF
D6
1N4937
R6
1
1/2 W
T1
R1
1.2 k
1 8
4 5
R3
22
R9
47
C8 680 pF
Y1 Safety
TinySwitch-II
D
S
BP
EN/UV
The TinySwitch-II does not require a bias winding to provide
power to the chip, because it draws the power directly from
the DRAIN pin (see Functional Description above). This
has two main benefits. First, for a nominal application, this
eliminates the cost of a bias winding and associated components.
Secondly, for battery charger applications, the current-voltage
characteristic often allows the output voltage to fall close to
zero volts while still delivering power. This type of application
normally requires a forward-bias winding which has many
more associated components. With TinySwitch-II, neither are
necessary. For applications that require a very low no-load power
consumption (50 mW), a resistor from a bias winding to the
BYPASS pin can provide the power to the chip. The minimum
recommended current supplied is 750 µA. The BYPASS pin in
this case will be clamped at 6.3 V. This method will eliminate the
power draw from the DRAIN pin, thereby reducing the no-load
power consumption and improving full-load efficiency.
Current Limit Operation
Each switching cycle is terminated when the DRAIN current
reaches the current limit of the TinySwitch-II. Current limit
operation provides good line ripple rejection and relatively
constant power delivery independent of input voltage.
BYPASS Pin Capacitor
The BYPASS pin uses a small 0.1 µF ceramic capacitor for
decoupling the internal power supply of the TinySwitch-II.
Application Examples
The TinySwitch-II is ideal for low cost, high efficiency power
supplies in a wide range of applications such as cellular phone
chargers, PC standby, TV standby, AC adapters, motor control,
appliance control and ISDN or a DSL network termination.
The 132 kHz operation allows the use of a low cost EE13 or
EF12.6 core transformer while still providing good efficiency.
The frequency jitter in TinySwitch-II makes it possible to use a
single inductor (or two small resistors for under 3 W applications
if lower efficiency is acceptable) in conjunction with two input
capacitors for input EMI filtering. The auto-restart function
removes the need to oversize the output diode for short circuit
conditions allowing the design to be optimized for low cost
and maximum efficiency. In charger applications, it eliminates
the need for a second optocoupler and Zener diode for open
loop fault protection. Auto-restart also saves the cost of adding
a fuse or increasing the power rating of the current sense
resistors to survive reverse battery conditions. For applications
requiring under-voltage lock out (UVLO), such as PC standby,
the TinySwitch-II eliminates several components and saves
cost. TinySwitch-II is well suited for applications that require
constant voltage and constant current output. As
TinySwitch-II is always powered from the input high voltage, it
therefore does not rely on bias winding voltage. Consequently
this greatly simplifies designing chargers that must work down
to zero volts on the output.
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TNY263-268
line sense resistors R2 and R3 sense the DC input voltage
for line under-voltage. When the AC is turned off, the under-
voltage detect feature of the TinySwitch-II prevents auto-restart
glitches at the output caused by the slow discharge of large
storage capacitance in the main converter. This is achieved by
preventing the TinySwitch-II from switching when the input
voltage goes below a level needed to maintain output regulation,
and keeping it off until the input voltage goes above the under-
voltage threshold, when the AC is turned on again. With R2
and R3, giving a combined value of 2 M, the power up under-
voltage threshold is set at 200 VDC, slightly below the lowest
required operating DC input voltage, for start-up at 170 VAC,
with doubler. This feature saves several components needed to
implement the glitch-free turn-off compared with discrete or
TOPSwitch-II based designs. During turn-on the rectified DC
input voltage needs to exceed 200 V under-voltage threshold
for the power supply to start operation. But, once the power
supply is on it will continue to operate down to 140 V rectified
DC input voltage to provide the required hold up time for the
standby output.
The auxiliary primary side winding is rectified and filtered by
D2 and C2 to create a 12 V primary bias output voltage for the
main power supply primary controller. In addition, this voltage is
used to power the TinySwitch-II via R4. Although not necessary
for operation, supplying the TinySwitch-II externally reduces
the device quiescent dissipation by disabling the internal drain
derived current source normally used to keep the BYPASS pin
capacitor (C3) charged. An R4 value of 10 k provides 600 µA
into the BYPASS pin, which is slightly in excess of the current
consumption of TinySwitch-II. The excess current is safely
clamped by an on-chip active Zener diode to 6.3 V.
The secondary winding is rectified and filtered by D3 and C6.
For a 15 W design an additional output capacitor, C7, is required
due to the larger secondary ripple currents compared to the 10 W
standby design. The auto-restart function limits output current
during short circuit conditions, removing the need to over rate
D3. Switching noise filtering is provided by L1 and C8. The
5 V output is sensed by U2 and VR1. R5 is used to ensure that
the Zener diode is biased at its test current and R6 centers the
output voltage at 5 V.
In many cases the Zener regulation method provides sufficient
accuracy (typically ± 6% over a 0 °C to 50 °C temperature
range). This is possible because TinySwitch-II limits the
dynamic range of the optocoupler LED current, allowing the
Zener diode to operate at near constant bias current. However,
if higher accuracy is required, a TL431 precision reference IC
may be used to replace VR1.
2.5 W CV/CC Cell-Phone Charger
As an example, Figure 14 shows a TNY264 based 5 V,
0.5 A, cellular phone charger operating over a universal input
range (85 VAC to 265 VAC). The inductor (L1) forms a
π-filter in conjunction with C1 and C2. The resistor R1 damps
resonances in the inductor L1. Frequency jittering operation
of TinySwitch-II allows the use of a simple π-filter described
above in combination with a single low value Y1-capacitor (C8)
to meet worldwide conducted EMI standards. The addition
of a shield winding in the transformer allows conducted EMI
to be met even with the output capacitively earthed (which is
the worst case condition for EMI). The diode D6, capacitor
C3 and resistor R2 comprise the clamp circuit, limiting the
leakage inductance turn-off voltage spike on the TinySwitch-II
DRAIN pin to a safe value. The output voltage is determined
by the sum of the optocoupler U2 LED forward drop (~1 V),
and Zener diode VR1 voltage. Resistor R8 maintains a bias
current through the Zener diode to ensure it is operated close
to the Zener test current.
A simple constant current circuit is implemented using the VBE
of transistor Q1 to sense the voltage across the current sense
resistor R4. When the drop across R4 exceeds the VBE of
transistor Q1, it turns on and takes over control of the loop by
driving the optocoupler LED. Resistor R6 assures sufficient
voltage to keep the control loop in operation down to zero volts
at the output. With the output shorted, the drop across R4 and
R6 (~1.2 V) is sufficient to keep the Q1 and LED circuit active.
Resistors R7 and R9 limit the forward current that could be
drawn through VR1 by Q1 under output short circuit conditions,
due to the voltage drop across R4 and R6.
10 and 15 W Standby Circuits
Figures 15 and 16 show examples of circuits for standby
applications. They both provide two outputs: an isolated 5 V and
a 12 V primary referenced output. The first, using TNY266P,
provides 10 W, and the second, using TNY267P, 15 W of
output power. Both operate from an input range of 140 VDC to
375 VDC, corresponding to a 230 VAC or 100/115 VAC with
doubler input. The designs take advantage of the line under-
voltage detect, auto-restart and higher switching frequency of
TinySwitch-II. Operation at 132 kHz allows the use of a smaller
and lower cost transformer core, EE16 for 10 W and EE22 for
15 W. The removal of pin 6 from the 8 pin DIP TinySwitch-II
packages provides a large creepage distance which improves
reliability in high pollution environments such as fan cooled
power supplies.
Capacitor C1 provides high frequency decoupling of the high
voltage DC supply, only necessary if there is a long trace
length from the DC bulk capacitors of the main supply. The
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TNY263-268
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C1
0.01 µF
1 kV
140-375
VDC
INPUT
L1
10 µH
2 A
R5
680
R6
59
1%
D3
1N5822
U1
TNY266P
C5
2.2 nF
1 kV
D1
1N4005GP
U2
TLP181Y
VR1
BZX79B3V9
5
4
2
110
8
TinySwitch-II
D
S
BP
+5 V
2 A
RTN
C2
82 µF
35 V
C8
470 µF
10 V
PI-2713-080404
C4
1 nF Y1
D2
1N4148
EN
+12 VDC
20 mA
0 V
C3
0.1 µF
50 V
R4
10 k
C6
1000 µF
10 V
R2
1 M
R3
1 M
R1
200 k
T1
PERFORMANCE SUMMARY
Continuous Output Power: 10.24 W
Efficiency: 75%
Figure 16. 15 W Standby Supply.
C1
0.01 µF
1 kV
140-375
VDC
INPUT
L1
10 µH
3 A
R5
680
D3
SB540
U1
TNY267P
C5
2.2 nF
1 kV
D1
1N4005GP
U2
TLP181Y
PERFORMANCE SUMMARY
Continuous Output Power: 15.24 W
Efficiency: 78%
5
4
2
110
8
TinySwitch-II
D
S
BP
+5 V
3 A
RTN
C2
82 µF
35 V
C8
470 µF
10 V
PI-2712-080404
C4
1 nF Y1
D2
1N4148
EN
+12 VDC
20 mA
0 V
C3
0.1 µF
50 V
R4
10 k
C7
1000 µF
10 V
C6
1000 µF
10 V
R2
1 M
R3
1 M
R1
100 k
T1
R6
59
1%
VR1
BZX79B3V9
Figure 15. 10 W Standby Supply.
10 G
4/05
TNY263-268
Key Application Considerations
TinySwitch-II vs. TinySwitch
Table 2 compares the features and performance differences
between the TNY254 device of the TinySwitch family with
the TinySwitch-II family of devices. Many of the new features
eliminate the need for or reduce the cost of circuit components.
Other features simplify the design and enhance performance.
Table 2. Comparison Between TinySwitch and TinySwitch-II.
*Not available. ** See typical performance curves.
Design
Output Power
Table 1 (front page) shows the practical continuous output power
levels that can be obtained under the following conditions:
1. The minimum DC input voltage is 90 V or higher for
85 VAC input, or 240 V or higher for 230 VAC input or
115 VAC input with a voltage doubler. This corresponds to
a filter capacitor of 3 µF/W for universal input and 1 µF/W
for 230 VAC or 115 VAC with doubler input.
Function TinySwitch
TNY254
TinySwitch-II
TNY263-268
TinySwitch-II
Advantages
Switching Frequency
and Tolerance
Temperature Variation
(0-100 °C)**
44 kHz ±10% (at 25 °C)
+8%
132 kHz ±6% (at 25 °C)
+2%
Smaller transformer for low cost
Ease of design
Manufacturability
Optimum design for lower cost
Active Frequency Jitter N/A* ±4 kHz Lower EMI minimizing filter
component costs
Transformer Audible
Noise Reduction
N/A* Yes–built into controller Practically eliminates audible
noise with ordinary dip varnished
transformer – no special
construction or gluing required
Line UV Detect N/A* Single resistor
programmable
Prevents power on/off glitches
Current Limit Tolerance
Temperature Variation
(0-100 °C)**
±11% (at 25 °C)
-8%
±7% (at 25 °C)
0%
Increases power capability and
simplifies design for high volume
manufacturing
Auto-Restart N/A* 6% effective on-time Limits output short-circuit current
to less than full load current
- No output diode size penalty
Protects load in open loop fault
conditions
- No additional components
required
BYPASS Pin Zener
Clamp
N/A* Internally clamped to
6.3 V
Allows
TinySwitch-II
to be
powered from a low voltage bias
winding to improve efficiency and
to reduce on-chip power
dissipation
DRAIN Creepage at
Package
0.037 in. / 0.94 mm 0.137 in. / 3.48 mm • Greater immunity to arcing as a
result of dust, debris or other
contaminants build-up
11
TNY263-268
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4/05
2. A secondary output of 5 V with a Schottky rectifier diode.
3. Assumed efficiency of 77% (TNY267 & TNY268),
75% (TNY265 & TNY266) and 73% (TNY263 & TNY264).
4. The parts are board mounted with SOURCE pins soldered
to sufficient area of copper to keep the die temperature at
or below 100 °C.
In addition to the thermal environment (sealed enclosure,
ventilated, open frame, etc.), the maximum power capability
of TinySwitch-II in a given application depends on transformer
core size and design (continuous or discontinuous), efficiency,
minimum specified input voltage, input storage capacitance,
output voltage, output diode forward drop, etc., and can be
different from the values shown in Table 1.
Audible Noise
The TinySwitch-II practically eliminates any transformer audio
noise using simple ordinary varnished transformer construction.
No gluing of the cores is needed. The audio noise reduction
is accomplished by the TinySwitch-II controller reducing the
current limit in discrete steps as the load is reduced. This
minimizes the flux density in the transformer when switching
at audio frequencies.
Worst Case EMI & Efficiency Measurement
Since identical TinySwitch-II supplies may operate at several
different frequencies under the same load and line conditions,
care must be taken to ensure that measurements are made under
worst case conditions. When measuring efficiency or EMI verify
that the TinySwitch-II is operating at maximum frequency and
that measurements are made at both low and high line input
voltages to ensure the worst case result is obtained.
Layout
Single Point Grounding
Use a single point ground connection at the SOURCE pin for
the BYPASS pin capacitor and the Input Filter Capacitor
(see Figure 17).
Primary Loop Area
The area of the primary loop that connects the input filter
capacitor, transformer primary and TinySwitch-II together
should be kept as small as possible.
Primary Clamp Circuit
A clamp is used to limit peak voltage on the DRAIN pin at
turn-off. This can be achieved by using an RCD clamp (as
shown in Figure 14). A Zener and diode clamp (200 V) across
the primary or a single 550 V Zener clamp from DRAIN to
SOURCE can also be used. In all cases care should be taken
to minimize the circuit path from the clamp components to the
transformer and TinySwitch-II.
Thermal Considerations
Copper underneath the TinySwitch-II acts not only as a single
point ground, but also as a heatsink. The hatched areas shown
in Figure 17 should be maximized for good heat sinking of
TinySwitch-II and the same applies to the output diode.
EN/UV pin
If a line under-voltage detect resistor is used then the resistor
should be mounted as close as possible to the EN/UV pin to
minimize noise pick up.
The voltage rating of a resistor should be considered for the under-
voltage detect (Figure 15: R2, R3) resistors. For 1/4 W resistors,
the voltage rating is typically 200 V continuous, whereas for
1/2 W resistors the rating is typically 400 V continuous.
Y-Capacitor
The placement of the Y-capacitor should be directly from the
primary bulk capacitor positive rail to the common/return
terminal on the secondary side. Such placement will maximize
the EMI benefit of the Y-capacitor and avoid problems in
common-mode surge testing.
Optocoupler
It is important to maintain the minimum circuit path from
the optocoupler transistor to the TinySwitch-II EN/UV and
SOURCE pins to minimize noise coupling.
The EN/UV pin connection to the optocoupler should be kept
to an absolute minimum (less than 12.7 mm or 0.5 in.), and
this connection should be kept away from the DRAIN pin
(minimum of 5.1 mm or 0.2 in.).
Output Diode
For best performance, the area of the loop connecting the secondary
winding, the output diode and the output filter capacitor, should
be minimized. See Figure 17 for optimized layout. In addition,
sufficient copper area should be provided at the anode and
cathode terminals of the diode for adequate heatsinking.
Input and Output Filter Capacitors
There are constrictions in the traces connected to the input and
output filter capacitors. These constrictions are present for two
reasons. The first is to force all the high frequency currents
to flow through the capacitor (if the trace were wide then it
could flow around the capacitor). Secondly, the constrictions
minimize the heat transferred from the TinySwitch-II to the input
filter capacitor and from the secondary diode to the output filter
capacitor. The common/return (the negative output terminal
in Figure 17) terminal of the output filter capacitor should be
connected with a short, low impedance path to the secondary
winding. In addition, the common/return output connection
should be taken directly from the secondary winding pin and
not from the Y-capacitor connection point.
12 G
4/05
TNY263-268
TOP VIEW
PI-2707-012901
Y1-
Capacitor
Opto-
coupler
D
EN/UV
BP
+
HV
+ DC
Out
Input Filter Capacitor
Output Filter Capacitor
Safety Spacing
Maximize hatched copper
areas ( ) for optimum
heat sinking
S
S
SEC
CBP
TinySwitch-II
PRI
T
r
a
n
s
f
o
r
m
e
r
Figure 17. Recommended Circuit Board Layout for TinySwitch-II with Under-Voltage Lock Out Resistor.
PC Board Cleaning
Power Integrations does not recommend the use of “no clean”
flux.
For the most up-to-date information visit the
PI website at: www.powerint.com.
13
TNY263-268
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4/05
Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 18
(Unless Otherwise Specified)
Min Typ Max Units
CONTROL FUNCTIONS
Output Frequency fOSC
TJ = 25 °C
See Figure 4
Average 124 132 140
kHz
Peak-Peak Jitter 8
Maximum Duty
Cycle DCMAX S1 Open 62 65 68 %
EN/UV Pin Turnoff
Threshold Current IDIS TJ = -40 °C to 125 °C -300 -240 -170 µA
EN/UV Pin
Voltage VEN
IEN/UV = -125 µA 0.4 1.0 1.5
V
IEN/UV = 25 µA 1.3 2.3 2.7
DRAIN Supply
Current
IS1 VEN/UV = 0 V 430 500 µA
IS2
EN/UV Open
(MOSFET
Switching)
See Note A, B
TNY263 200 250
µA
TNY264 225 270
TNY265 245 295
TNY266 265 320
TNY267 315 380
TNY268 380 460
BYPASS Pin
Charge Current
ICH1
VBP = 0 V,
TJ = 25 °C
See Note C, D
TNY263-264 -5.5 -3.3 -1.8
mA
TNY265-268 -7.5 -4.6 -2.5
ICH2
VBP = 4 V,
TJ = 25 °C
See Note C, D
TNY263-264 -3.8 -2.0 -1.0
TNY265-268 -4.5 -3.0 -1.5
ABSOLUTE MAXIMUM RATINGS(1,4)
DRAIN Voltage .................................. ................ -0.3 V to 700 V
DRAIN Peak Current: TNY263......................................400 mA
TNY264......................................400 mA
TNY265......................................440 mA
TNY266......................................560 mA
TNY267......................................720 mA
TNY268......................................880 mA
EN/UV Voltage ................................................ -0.3 V to 9 V
EN/UV Current .................................................... 100 mA
BYPASS Voltage .................................................. -0.3 V to 9 V
Storage Temperature ......................................-65 °C to 150 °C
Operating Junction Temperature(2) .................-40 °C to 150 °C
Lead Temperature(3) ....................................................... 260 °C
Notes:
1. All voltages referenced to SOURCE, TA = 25 °C.
2. Normally limited by internal circuitry.
3. 1/16 in. from case for 5 seconds.
4. Maximum ratings specified may be applied one at a time,
without causing permanent damage to the product.
Exposure to Absolute Maximum Rating conditions for
extended periods of time may affect product reliability.
THERMAL IMPEDANCE
Thermal Impedance: P or G Package:
(θJA) ........................... 70 °C/W(2); 60 °C/W(3)
(θJC)(1) ............................................... 11 °C/W
Notes:
1. Measured on the SOURCE pin close to plastic interface.
2. Soldered to 0.36 sq. in. (232 mm2), 2 oz. (610 g/m2) copper clad.
3. Soldered to 1 sq. in. (645 mm2), 2 oz. (610 g/m2) copper clad.
14 G
4/05
TNY263-268
Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 18
(Unless Otherwise Specified)
Min Typ Max Units
CONTROL FUNCTIONS (cont.)
BYPASS Pin
Voltage VBP See Note C 5.6 5.85 6.15 V
BYPASS Pin
Voltage Hysteresis VBPH 0.80 0.95 1.20 V
EN/UV Pin Line
Under-Voltage
Threshold
ILUV TJ = 25 °C 44 49 54 µA
CIRCUIT PROTECTION
Current Limit ILIMIT
TNY263
TJ = 25 °C
di/dt = 42 mA/µs
See Note E 195 210 225
mA
TNY264
TJ = 25 °C
di/dt = 50 mA/µs
See Note E 233 250 267
TNY265
TJ = 25 °C
di/dt = 55 mA/µs
See Note E 255 275 295
TNY266
TJ = 25 °C
di/dt = 70 mA/µs
See Note E 325 350 375
TNY267
TJ = 25 °C
di/dt = 90 mA/µs
See Note E 419 450 481
TNY268
TJ = 25 °C
di/dt = 110 mA/µs
See Note E 512 550 588
Initial Current Limit IINIT
See Figure 21
TJ = 25 °C
0.65 x
ILIMIT(MIN)
mA
Leading Edge
Blanking Time tLEB
TJ = 25 °C
See Note F 170 215 ns
Current Limit
Delay tILD
TJ = 25 °C
See Note F, G 150 ns
Thermal Shutdown
Temperature 125 135 150 °C
Thermal Shutdown
Hysteresis 70 °C
15
TNY263-268
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4/05
Parameter Symbol
Conditions
SOURCE = 0 V; TJ = -40 to 125 °C
See Figure 18
(Unless Otherwise Specified)
Min Typ Max Units
OUTPUT
ON-State
Resistance RDS(ON)
TNY263
ID = 21 mA
TJ = 25 °C 33 38
TJ = 100 °C 50 57
TNY264
ID = 25 mA
TJ = 25 °C 28 32
TJ = 100 °C 42 48
TNY265
ID = 28 mA
TJ = 25 °C 19 22
TJ = 100 °C 29 33
TNY266
ID = 35 mA
TJ = 25 °C 14 16
TJ = 100 °C 21 24
TNY267
ID = 45 mA
TJ = 25 °C 7.8 9.0
TJ = 100 °C 11.7 13.5
TNY268
ID = 55 mA
TJ = 25 °C 5.2 6.0
TJ = 100 °C 7.8 9.0
OFF-State Drain
Leakage Current IDSS
VBP = 6.2 V,
VEN/UV = 0 V,
VDS = 560 V,
TJ = 125 °C
TNY263-266 50
µA
TNY267-268 100
Breakdown
Voltage BVDSS
VBP = 6.2 V, VEN/UV = 0 V,
See Note H, TJ = 25 °C700 V
Rise Time tRMeasured in a Typical Flyback
Converter Application
50 ns
Fall Time tF50 ns
Drain Supply
Voltage 50 V
Output EN/UV
Delay tEN/UV See Figure 20 10 µs
Output Disable
Setup Time tDST 0.5 µs
Auto-Restart
ON-Time tAR
TJ = 25 °C
See Note I 50 ms
Auto-Restart
Duty Cycle DCAR 5.6 %
16 G
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TNY263-268
NOTES:
A. Total current consumption is the sum of IS1 and IDSS when EN/UV pin is shorted to ground (MOSFET not
switching) and the sum of IS2 and IDSS when EN/UV pin is open (MOSFET switching).
B Since the output MOSFET is switching, it is difficult to isolate the switching current from the supply current at the
DRAIN. An alternative is to measure the BYPASS pin current at 6.1 V.
C. BYPASS pin is not intended for sourcing supply current to external circuitry.
D. See Typical Performance Characteristics section for BYPASS pin start-up charging waveform.
E. For current limit at other di/dt values, refer to Figure 25.
F. This parameter is derived from characterization.
G. This parameter is derived from the change in current limit measured at 1X and 4X of the di/dt shown in the ILIMIT
specification.
H. Breakdown voltage may be checked against minimum BVDSS specification by ramping the DRAIN pin voltage up
to but not exceeding minimum BVDSS.
I. Auto-restart on time has the same temperature characteristics as the oscillator (inversely proportional to
frequency).
17
TNY263-268
G
4/05
Figure 19. TinySwitch-II Duty Cycle Measurement. Figure 20. TinySwitch-II Output Enable Timing.
Figure 18. TinySwitch-II General Test Circuit.
PI-2686-101700
0.1 µF
10 V
50 V
470
5 W S2
470
NOTE: This test circuit is not applicable for current limit or output characteristic measurements.
DEN/UV
BPS
SS
S
150 V
S1
2 M
PI-2364-012699
EN/UV
tP
tEN/UV
DCMAX
tP = 1
fOSC
VDRAIN
(internal signal)
0.8
Figure 21. Current Limit Envelope.
18 G
4/05
TNY263-268
Typical Performance Characteristics
Figure 22. Breakdown vs. Temperature.
1.1
1.0
0.9
-50 -25 0 25 50 75 100 125 150
Junction Temperature (°C)
Breakdown Voltage
(Normalized to 25 °C)
PI-2213-012301
1.2
1.0
0.8
0.6
0.4
0.2
0
-50 -25 0 25 50 75 100 125
Junction Temperature (°C)
PI-2680-012301
Output Frequency
(Normalized to 25 °C)
6
5
4
3
2
1
0
0 0.2 0.4 0.6 0.8 1.0
Time (ms)
PI-2240-012301
BYPASS Pin Voltage (V)
7
Drain Voltage (V)
Drain Current (mA)
300
250
200
100
50
150
0
0 2 4 6 8 10
T
CASE = 25 °C
TCASE = 100 °C
PI-2221-032504
TNY263 0.85
TNY264 1.0
TNY265 1.5
TNY266 2.0
TNY267 3.5
TNY268 5.5
Scaling Factors:
Figure 23. Frequency vs. Temperature.
Figure 24. Current Limit vs. Temperature.
Figure 25. Current Limit vs. di/dt.
Figure 26. BYPASS Pin Start-up Waveform.
Figure 27. Output Characteristic.
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1 2 3 4
Normalized di/dt
PI-2697-033104
Normalized Current Limit
TNY263 42 mA/µs 210 mA
TNY264 50 mA/µs 250 mA
TNY265 55 mA/µs 275 mA
TNY266 70 mA/µs 350 mA
TNY267 90 mA/µs 450 mA
TNY268 110 mA/µs 550 mA
Normalized
di/dt = 1
Normalized
Current
Limit = 1
1
0.8
0.6
0.4
0.2
0
-50 0 50 100 150
Temperature (°C)
PI-2714-040704
1.2
Current Limit
(Normalized to 25 °C)
TNY263
TNY264-266
TNY267
TNY268
19
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4/05
Typical Performance Characteristics (cont.)
Drain Voltage (V)
Drain Capacitance (pF)
PI-2683-033104
0 100 200 300 400 500 600
1
10
100
1000
TNY263 1.0
TNY264 1.0
TNY265 1.5
TNY266 2.0
TNY267 3.5
TNY268 5.5
Scaling Factors:
35
20
25
30
5
10
15
0
0 200 400 600
Drain Voltage (V)
Power (mW)
PI-2225-033104
TNY263 1.0
TNY264 1.0
TNY265 1.5
TNY266 2.0
TNY267 3.5
TNY268 5.5
Scaling Factors:
1.2
1.0
0.8
0.6
0.4
0.2
0
-50 -25 0 25 50 75 100 125
Junction Temperature (°C)
PI-2698-012301
Under-Voltage Threshold
(Normalized to 25 °C)
Figure 28. COSS vs. Drain Voltage.
Figure 29. Drain Capacitance Power.
Figure 30. Under-voltage Threshold vs. Temperature.