PA ANTENNA
RFIN/EN OUT
RF
VDD
GND
R2
50:
ADC
COUPLER
LMH2121
C
100 pF
ENABLE
R1
1 k:
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
LMH2121 3 GHz Fast-Responding Linear Power Detector with 40 dB Dynamic Range
Check for Samples: LMH2121
1FEATURES DESCRIPTION
The LMH2121 is an accurate fast-responding power
2• Linear Response detector / RF envelope detector. Its response
• 40 dB Power Detection Range between an RF input signal and DC output signal is
• Very Low Supply Current of 3.4 mA linear. The typical response time of 165 ns makes the
device suitable for an accurate power setting in
• Short Response Time of 165 ns handsets during a rise time of RF transmission slots.
• Stable Conversion Gain of 3.6 V/VRMS It can be used in all popular communications
• Multi-Band Operation from 100 MHz to 3 GHz standards: 2G/3G/4G/WAP.
• Very Low Conformance Error The LMH2121 has an input range from −28 dBm to
• High Temperature Stability of ±0.5 dB +12 dBm. Over this input range the device has an
intrinsic high insensitivity for temperature, supply
• Shutdown Functionality voltage and loading. The bandwidth of the device is
• Supply Range from 2.6V to 3.3V from 100 MHz to 3 GHz, covering 2G/3G/4G/WiFi
• Package: wireless bands.
– 4-Bump DSBGA, 0.4mm Pitch As a result of the unique internal architecture, the
device shows an extremely low part-to-part variation
APPLICATIONS of the detection curve. This is demonstrated by its low
intercept and slope variation as well as a very good
• Multi Mode, Multi band RF power control linear conformance. Consequently the required
– GSM/EDGE characterization and calibration efforts are low.
– CDMA The device is active for EN = High; otherwise it is in a
– W-CDMA low power consumption shutdown mode. To save
– LTE power and allow for two detector outputs in parallel,
the output (OUT) is high impedance during shutdown.
– WAP
• Tablets The LMH2121 is offered in a tiny 4-bump DSBGA
package: 0.866 mm x 1.07 mm x 0.6 mm.
TYPICAL APPLICATION
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2012–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS (1)(2)
Supply Voltage
VDD - GND 3.6V
RFIN/EN
VRF_PEAK+ VDC 3.6V
ESD Tolerance (3)
Human Body Model 1500V
Machine Model 200V
Charge Device Model 1250V
Storage Temperature Range −65°C to 150°C
Junction Temperature (4) 150°C
For soldering specifications:
See http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=snoa549c
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(3) Human body model, applicable std. MIL-STD-883, Method 3015.7. Machine model, applicable std. JESD22–A115–A (ESD MM std of
JEDEC). Field-Induced Charge-Device Model, applicable std. JESD22–C101–C. (ESD FICDM std. of JEDEC)
(4) The maximum power dissipation is a function of TJ(MAX) ,θJA. The maximum allowable power dissipation at any ambient temperature is
PD= (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly into a PC board.
OPERATING RATINGS (1)
Supply Voltage 2.6V to 3.3V
Temperature Range −40°C to +85°C
RF Frequency Range 100 MHz to 3 GHz
RF Input Power Range −28 dBm to +12 dBm
Package Thermal Resistance θJA(2) 130.9°C/W
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics.
(2) The maximum power dissipation is a function of TJ(MAX) ,θJA. The maximum allowable power dissipation at any ambient temperature is
PD= (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly into a PC board.
2.7 V DC AND AC ELECTRICAL CHARACTERISTICS
Unless otherwise specified, all limits are ensured to TA= 25°C, VDD = 2.7V, RFIN= 1900 MHz CW (Continuous Wave,
unmodulated), EN = 2.7V. Boldface limits apply at the temperature extremes (1).
Symbol Parameter Condition Min Typ Max Units
(2) (3) (2)
Supply Interface
IDD Supply Current Active Mode. EN= High, no RF input 2.4 3.4 4.7 mA
Signal
Shutdown. EN= Low, no RF input 2µA
Signal
(1) Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device such that TJ= TA. No specification of parametric performance is indicated in the electrical tables under
conditions of internal self-heating where TJ> TA.
(2) All limits are ensured by test or statistical analysis.
(3) Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary
over time and will also depend on the application and configuration. The typical values are not tested and are not specified on shipped
production material.
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
2.7 V DC AND AC ELECTRICAL CHARACTERISTICS (continued)
Unless otherwise specified, all limits are ensured to TA= 25°C, VDD = 2.7V, RFIN= 1900 MHz CW (Continuous Wave,
unmodulated), EN = 2.7V. Boldface limits apply at the temperature extremes (1).
Symbol Parameter Condition Min Typ Max Units
(2) (3) (2)
PSRR Power Supply Rejection Ratio RFIN =−10 dBm, 1900 MHz, 2.6V < 40 69 dB
VDD < 3.3V
Logic Enable Interface
VLOW RFIN/EN logic LOW input level 0.6
(Shutdown) V
VHIGH RFIN/EN logic HIGH input level 1.1
(Active)
IRFIN/EN Current into RFIN/EN pin EN = 1.8V 1µA
Input / Output Interface
ZIN Input Impedance Resistor and Capacitor in RIN 50 Ω
series from RFIN/EN to GND CIN 30 pF
VOUT Minimum Output Voltage No RF Input Signal 30
18 mV
(Pedestal) 38
ROUT Output Resistance RFIN =−10 dBm, 1900 MHz, ILOAD = 1 117
100 Ω
mA, DC measurement 120
IOUT Output Sinking Current RFIN =−10 dBm, 1900 MHz, OUT 17 20
connected to 2.5V 16 mA
Output Sourcing Current RFIN =−10 dBm, 1900 MHz, OUT 1.30 1.86
connected to GND 1.28
IOUT, SD Output Leakage Current in VEN = Low, OUT is connected to 2V 80 nA
Shutdown
enOutput Referred Noise (4) RFIN =−23 dBm, 1900 MHz, output 18 µV/√Hz
spectrum at 10 kHz
vnOutput Referred Noise Integrated RFIN =−23 dBm, 1900 MHz, Integrated 2 mVRMS
(4) over frequency band 1 kHz -13 kHz
Timing Characteristics
tON Turn-on Time from Shutdown (4) RFIN =−10 dBm, 1900 MHz, VEN LOW- 1.3 µs
to-HIGH transition to OUT at 90%
tRRise Time (4) Signal at RFIN from −20 dBm to 5 dBm, 165 ns
10% to 90%, 1900 MHz
tFFall Time (4) Signal at RFIN from 5 dBm to −20 dBm, 285 ns
90% to 10%, 1900 MHz
RF Detector Transfer, fit range −15 dBm to −5 dBm for Linear Slope and Intercept
RFIN = 100 MHz(5)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB −33
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 12
Dynamic Range
VMIN Minimum Output Voltage At PMIN 20 mV
VMAX Maximum Output Voltage At PMAX 2.7 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 1.2 1.9 2.4 dBm
Gain Conversion Gain 3.4 3.6 3.9 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 34 45
Accuracy 25 32
±3 dB Lin Conformance Error (ELC) 47 49 dB
41 46
±1 dB Input Referred Variation over 26 31
Temperature (EVOT)
(4) This parameter is ensured by design and/or characterization and is not tested in production.
(5) Limits are ensured by design and measurements which are performed on a limited number of samples.
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2.7 V DC AND AC ELECTRICAL CHARACTERISTICS (continued)
Unless otherwise specified, all limits are ensured to TA= 25°C, VDD = 2.7V, RFIN= 1900 MHz CW (Continuous Wave,
unmodulated), EN = 2.7V. Boldface limits apply at the temperature extremes (1).
Symbol Parameter Condition Min Typ Max Units
(2) (3) (2)
RFIN = 700 MHz(5)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB -33
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 12
Dynamic Range
VMIN Minimum Output Voltage At PMIN 20 mV
VMAX Maximum Output Voltage At PMAX 2.65 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 1.3 1.9 2.2 dBm
Gain Conversion Gain 3.5 3.6 3.9 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 34 45
Accuracy 34 38
±3 dB Lin Conformance Error (ELC) 47 50 dB
39 47
±0.5 dB Input Referred Variation over 34 37
Temperature (EVOT)
RFIN = 900 MHz(5)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB -33
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 12
Dynamic Range
VMIN Minimum Output Voltage At PMIN 20 mV
VMAX Maximum Output Voltage At PMAX 2.68 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 1.7 2.1 2.5 dBm
Gain Conversion Gain 3.4 3.5 3.7 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 34 45
Accuracy 33 37
±3 dB Lin Conformance Error (ELC) 48 50 dB
40 47
±0.5 dB Input Referred Variation over 35 37
Temperature (EVOT)
RFIN = 1700 MHz(6)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB −24
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 7
Dynamic Range
VMIN Minimum Output Voltage At PMIN 37 mV
VMAX Maximum Output Voltage At PMAX 1.23 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 3.8 4.1 4.5 dBm
Gain Conversion Gain 2.6 2.8 2.9 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 27 31
Accuracy 24 28
±3 dB Lin Conformance Error (ELC) 44 47 dB
34 43
±0.5 dB Input Referred Variation over 26 31
Temperature (EVOT)
(6) Limits are ensured by design and measurements which are performed on a limited number of samples.
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OUT
RFIN/EN
VDD A2 B2
A1 B1
GND
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
2.7 V DC AND AC ELECTRICAL CHARACTERISTICS (continued)
Unless otherwise specified, all limits are ensured to TA= 25°C, VDD = 2.7V, RFIN= 1900 MHz CW (Continuous Wave,
unmodulated), EN = 2.7V. Boldface limits apply at the temperature extremes (1).
Symbol Parameter Condition Min Typ Max Units
(2) (3) (2)
RFIN = 1900 MHz(7)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB −24
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 7
Dynamic Range
VMIN Minimum Output Voltage At PMIN 33 mV
VMAX Maximum Output Voltage At PMAX 1.1 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 4.7 5 5.3 dBm
Gain Conversion Gain 2.4 2.5 2.6 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 26 31
Accuracy 23 27
±3 dB Lin Conformance Error (ELC) 43 45 dB
33 41
±0.5 dB Input Referred Variation over 26 29
Temperature (EVOT)
RFIN = 2600 MHz(7)
PMIN Minimum Power Level, bottom Lin Conformance Error within ±1 dB −22
end of Dynamic Range dBm
PMAX Maximum Power Level, top end of 6
Dynamic Range
VMIN Minimum Output Voltage At PMIN 35 mV
VMAX Maximum Output Voltage At PMAX 0.78 V
KSLOPE Linear Slope 1 dB/dB
PINT Linear Intercept VOUT = 0 dBV 6.3 6.7 7.1 dBm
Gain Conversion Gain 2.0 2.1 2.2 V/VRMS
DR Dynamic Range for specified ±1 dB Lin Conformance Error (ELC) 24 28
Accuracy 21 25
±3 dB Lin Conformance Error (ELC) 40 42 dB
30 38
±0.5 dB Input Referred Variation over 21 27
Temperature (EVOT)
(7) Limits are ensured by design and measurements which are performed on a limited number of samples.
CONNECTION DIAGRAM
Figure 1. 4-bump DSBGA (Top View)
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RFIN/EN OUT
GND
V/I
V/I
V/I
V/I
A
VDD
K
LOGIC ENABLE
A1
A2
B1
B2
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
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PIN DESCRIPTIONS
Name DSBGA Description
VDD A2 Positive Supply Voltage.
GND B2 Ground
DC voltage determines the state of the device (HIGH = device is active, LOW =
RFIN/EN A1 device in shutdown). AC voltage is the RF input signal to the detector (beyond 100
MHz). The RFIN/EN pin is internally terminated with 50Ωin series with 30 pF.
OUT B1 Ground referenced detector output voltage.
BLOCK DIAGRAM
Figure 2. LMH2121
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FREQUENCY (Hz)
RF INPUT IMPEDANCE ()
100
75
50
25
0
-25
-50
-75
-100
10M 100M 1G 10G
R
X
MEASURED ON BUMP
|Z|
Z = R + jX
RF INPUT POWER (dBm)
OUTPUT SINKING CURRENT (mA)
100
10
1
0.1
-40 -30 -20 -10 0 10 20
85°C
25°C
-40°C
RFin = 1900 MHz
OUT = 2.5V
RF INPUT POWER (dBm)
SUPPLY CURRENT (mA)
6
5
4
3
2
1
0
-40 -30 -20 -10 0 10 20
85°C
25°C
-40°C
RF INPUT POWER (dBm)
OUTPUT SOURCING CURRENT (mA)
100
10
1
0.1
-40 -30 -20 -10 0 10 20
85°C25°C
-40°C
RFin = 1900 MHz
OUT = 0V
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
5
4
3
2
1
0
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
-40°C
85°C
25°C
EN = HIGH
0.5 0.6 0.7 0.8 0.9 1.0
5
4
3
2
1
0
ENABLE VOLTAGE (V)
SUPPLY CURRENT (mA)
-40°C
85°C
25°C
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
TYPICAL PERFORMANCE CHARACTERISTICS
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred.
Supply Current vs. Supply Voltage Supply Current vs. Enable Voltage
Figure 3. Figure 4.
Supply Current vs. RF Input Power Output Sourcing Current vs. RF Input Power
Figure 5. Figure 6.
RF Input Impedance
Output Sinking Current vs. RF Input Power vs. Frequency, Resistance (R) and Reactance (X)
Figure 7. Figure 8.
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FREQUENCY (Hz)
LIN INTERCEPT (dBm)
18
16
14
12
10
8
6
4
2
0
-2
10M 100M 1G 10G
85°C
25°C
-40°C
FREQUENCY (Hz)
LIN SLOPE (dB/dB)
1.3
1.2
1.1
1.0
0.9
0.8
0.7
10M 100M 1G 10G
85°C
25°C
-40°C
TIME (0.5 s/DIV)
OUTPUT VOLTAGE (V)
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0.00
+10 dBm
+5 dBm
0 dBm
-5 dBm
-10 dBm
PIN1 = -20 dBm
~
~~
~~
~~
~~
~~
~
PIN2 = Mentioned at curve
TIME (0.5 s/DIV)
OUTPUT VOLTAGE (0.5V/DIV)
+10 dBm
+5 dBm
0 dBm
-5 dBm
-10 dBm
~
~
EN-step (0 to 2.7V)
VOUT for various PIN levels
FREQUENCY (Hz)
OUTPUT VOLTAGE NOISE (V/¥+])
30
25
20
15
10
5
0
100 1k 10k 100k 1M 10M
PIN = -23 dBm
FREQUENCY (Hz)
PSRR (dB)
70
60
50
40
30
20
10
0
100 1k 10k 100k 1M 10M
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred. Power Supply Rejection Ratio
vs. Frequency (Small Signal) Output Voltage Noise vs. Frequency
Figure 9. Figure 10.
Turn-on time from EN-step Rise and Fall Time
Figure 11. Figure 12.
Slope vs. Frequency Intercept vs. Frequency
Figure 13. Figure 14.
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RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
25°C
85°C
-40°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
2.6 GHz
RF INPUT POWER (dBm)
VOUT (V)
1.7 GHz
1.9 GHz
100 MHz
700 MHz
900 MHz
FREQUENCY (Hz)
VOUT (V)
10
1
0.1
0.01
10M 100M 1G 10G
RFIN = -25 dBm
RFIN = -10 dBm
RFIN = -5 dBm
RFIN = 0 dBm
RFIN = -15 dBm
RFIN = -20 dBm
RFIN = -30 dBm
RFIN = 5 dBm
RFIN = 10 dBm
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred.
Output Voltage vs. RF Input power Output Voltage vs. Frequency
Figure 15. Figure 16.
Lin Conformance
Output Voltage vs. RF Input Power at 100 MHz vs. RF Input Power at 100 MHz
Figure 17. Figure 18.
Lin Conformance (50 units) Temperature Variation
vs. RF Input Power at 100 MHz vs. RF Input Power at 100 MHz
Figure 19. Figure 20.
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RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
-40°C
25°C
85°C
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred. Temperature Variation (50 units)
vs. RF Input Power at 100 MHz Output Voltage vs. RF Input Power at 700 MHz
Figure 21. Figure 22.
Lin Conformance vs. RF Input Power at 700 MHz Lin Conformance (50 units) vs. RF Input Power at 700 MHz
Figure 23. Figure 24.
Temperature Variation (50 units)
Temperature Variation vs. RF Input Power at 700 MHz vs. RF Input Power at 700 MHz
Figure 25. Figure 26.
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RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
-40°C
25°C
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
-40°C
25°C
85°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred.
Output Voltage vs. RF Input Power at 900 MHz Lin Conformance vs. RF Input Power at 900 MHz
Figure 27. Figure 28.
Lin Conformance (50 units) vs. RF Input Power at 900 MHz Temperature Variation vs. RF Input Power at 900 MHz
Figure 29. Figure 30.
Temperature Variation (50 units)
vs. RF Input Power at 900 MHz Output Voltage vs. RF Input Power at 1700 MHz
Figure 31. Figure 32.
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-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
-40°C
25°C
85°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred.
Lin Conformance vs. RF Input Power at 1700 MHz Lin Conformance (50 units) vs. RF Input Power at 1700 MHz
Figure 33. Figure 34.
Temperature Variation (50 units)
Temperature Variation vs. RF Input Power at 1700 MHz vs. RF Input Power at 1700 MHz
Figure 35. Figure 36.
Output Voltage vs. RF Input Power at 1900 MHz Lin Conformance vs. RF Input Power at 1900 MHz
Figure 37. Figure 38.
12 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: LMH2121
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
RF INPUT POWER (dBm)
VOUT (V)
-40°C
25°C
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred.
Lin Conformance (50 units) vs. RF Input Power at 1900 MHz Temperature Variation vs. RF Input Power at 1900 MHz
Figure 39. Figure 40.
Temperature Variation (50 units)
vs. RF Input Power at 1900 MHz Output Voltage vs. RF Input Power at 2600 MHz
Figure 41. Figure 42.
Lin Conformance (50 units)
Lin Conformance vs. RF Input Power at 2600 MHz vs. RF Input Power at 2600 MHz
Figure 43. Figure 44.
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 13
Product Folder Links: LMH2121
RF INPUT POWER (dBm)
ERROR (dB)
85°C
-40°C
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified TA= 25°C, VDD = 2.7V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified errors
are input referred. Temperature Variation (50 units)
Temperature Variation vs. RF Input Power at 2600 MHz vs. RF Input Power at 2600 MHz
Figure 45. Figure 46.
14 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: LMH2121
PA ANTENNA
RF
50:
COUPLER
VGA
GAIN
ADC
EN
RFIN/EN
OUT
VDD
GND
A1
A2
B1
B2
LMH2121
C
R2
100 pF
ENABLE
R1
1 k:
BASE
BAND
or
RF IC
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
APPLICATION INFORMATION
The LMH2121 is an accurate fast-responding power detector / RF envelope detector. Its response between an
RF input signal and DC output signal is linear. The typical response time of 165 ns makes the device suitable for
an accurate power setting in handsets during a rise time of RF transmission slots. It can be used in all popular
communications standards: 2G/3G/4G/WAP.
The LMH2121 has an input range from −28 dBm to +12 dBm. Over this input range the device has an intrinsic
high insensitivity for temperature, supply voltage and loading. The bandwidth of the device is from 100 MHz to 3
GHz, covering 2G/3G/4G/WiFi wireless bands.
TYPICAL APPLICATION
The LMH2121 can be used in a wide variety of applications such as LTE, W-CDMA, CDMA and GSM. This
section discusses the LMH2121 in a typical transmit power control loop for such applications.
Transmit-power control-loop circuits make the transmit-power level insensitive to power amplifier (PA)
inaccuracy. This is desirable because power amplifiers are non-linear devices and temperature dependent,
making it hard to estimate the exact transmit power level. If a control loop is used, the inaccuracy of the PA is
eliminated from the overall accuracy of the transmit-power level. The accuracy of the transmit power level now
depends on the RF detector accuracy instead. The LMH2121 is especially suited for transmit-power control
applications, since it accurately measures transmit power and is insensitive to temperature and supply voltage
variations.
Figure 47 shows a simplified schematic of a typical transmit-power control system. The output power of the PA is
measured by the LMH2121 through a directional coupler. The measured output voltage of the LMH2121 is
digitized by the ADC inside the baseband chip. Accordingly, the baseband controls the PA output power level by
changing the gain control signal of the RF VGA.
Figure 47. Transmit-Power Control System
ACCURATE POWER MEASUREMENT
Detectors have evolved over the years along with the communication standards. Newer communication
standards like LTE and W-CDMA raise the need for more advanced accurate power detectors. To be able to
distinguish the various detector types it is important to understand what the ideal power measurement should
look like and how a power measurement is implemented.
Power is often used as a metric for the strength of a signal in communication applications. By definition it is not a
function of the signal shape over time. In other words, the power content of a 0 dBm sine wave is identical to the
power content of a 0 dBm square wave or a 0 dBm W-CDMA signal; all these signals have the same average
power content.
The average power can be described by the following formula:
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 15
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ENVELOPE
CARRIER
RMS
INTEGRATION TIME (T)
ENVELOPE
CARRIER
RMS
INTEGRATION TIME (T)
³T
0
T
1
Pv(t)2
vdt
dt
RT
1T
0
³
P(T) = v(t)2
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
(1)
where T is the time interval over which is averaged, v(t) is the instantaneous voltage at time t, and R is the
resistance in which the power is dissipated.
When the resistor is constant (assume a 50Ωsystem), the average power is proportional to average of the
square of the instantaneous voltage:
(2)
For RF applications in which modulated signals are used, for instance, the instantaneous voltage can be
described by:
v(t) = [ 1 + a(t) ] sin (ωCt) (3)
where a(t) is the amplitude modulation and ωcthe carrier frequency. The frequency of a(t) is typically on the
order of a couple of MHz (up to 20 MHz) depending on the modulation standard. This is relatively low with
respect to the carrier frequency, i.e., several hundreds of MHz up to a few GHz.
For determining the average power of an RF modulated signal it is important how long the detector integrates
(averages) the RF signal relative to the speed of the modulation variation. On one hand, detectors with a
relatively high integration time will produce a constant output since the modulation is averaged-out (Figure 48-a).
An example of such a detector is an RMS detector. On the other hand, when the integration time is relatively
short, the detector output will track the envelope of the RF signal (Figure 48-b). These RF detectors are typically
called envelope detectors.
a. RF detector has a constant output b. RF detector tracks envelope
Figure 48. Modulation Bandwidth vs. Integration Time of RF detector
The most suitable detector for a particular application is mainly determined by the modulation standard and its
characteristics. 2G, for instance, works with time-division multiplex. As a result the detector must be able to track
the ramp-up and ramp-down of the RF signal in case of PA loop control. The detector should have a short
response time to handle this.
3G standards like W-CDMA have a constant modulation bandwidth of 5 MHz and a code-division multiplex
approach, i.e., continuous transmission. RMS detectors are tailored towards these signal characteristics because
they integrate long enough to obtain the actual RMS voltage, i.e., T >> 1/(5 MHz).
4G standards like LTE can vary in modulation bandwidth. An example of a signal with low modulation bandwidth
is LTE with 1 resource block (RB). It has a modulation bandwidth of 200 kHz. An RMS detector would need to
average over T >> 1/(200 kHz), which is on the order of tens of micro seconds. In contrast a 100 RB signal has a
20 MHz bandwidth which needs an averaging time T>> 1/(20 MHz). Depending on the modulation bandwidth a
different detector would be appropriate. For low modulation bandwidths (low RBs), the integration time of the
RMS detector would be long. This is usually too long, and therefore an envelope detector is used instead. For
high RBs an RMS detector would work.
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Product Folder Links: LMH2121
CARRIER
PEAK
ENVELOPE
P
T
1T
0
³
VRMS = v(t)2dt v
LMH2121
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SNVS876A –AUGUST 2012–REVISED MARCH 2013
TYPES OF RF DETECTORS
This section provides an overview of detectors based on their detection principle. Detectors that will be discussed
are:
•LOG AMP DETECTORS
•RMS DETECTORS
•ENVELOPE DETECTORS
LOG AMP DETECTORS
LOG Amp detectors are widely used RF power detectors for GSM and the early W-CDMA systems. The transfer
function of a LOG amp detector is linear-in-dB, which means that the output in volts changes linearly with the RF
power in dBm. This is convenient since most communication standards specify transmit power levels in dBm as
well. LOG amp detectors implement the logarithmic function by a piecewise linear approximation. Consequently,
the LOG amp detector does not implement an exact power measurement, which implies a dependency on the
signal shape. In systems using various modulation schemes calibration and lookup tables might be required.
RMS DETECTORS
An RMS detector has a response (VRMS) that is insensitive to the signal shape and modulation form. This is
because its operation is based on the definition of the average power, i.e., it implements:
(4)
RMS detectors are particularly suited for newer communication standards like W-CDMA and LTE that exhibit
large peak-to-average ratios and different modulation schemes (signal shapes). This is a key advantage
compared to other types of detectors in applications that employ signals with high peak-to-average power
variations or different modulation schemes. For example, the RMS detector response to a 0 dBm modulated W-
CDMA signal and a 0 dBm unmodulated carrier is essentially equal. This eliminates the need for long calibration
procedures and large calibration tables in the application due to different applied modulation schemes.
ENVELOPE DETECTORS
An envelope detector is a fast-responding detector capable of following the envelope of a modulated RF carrier.
This in contrast to other detectors that give the peak, average or RMS voltage. Envelope detectors are
particularly useful in communication systems where a fast control of the PA output power is desired, such as
LTE. A fast responding power detector enables a power measurement during the 50 µs power transition time at
the beginning of a transmission slot. As a result the transmit power level can be set accurately before
transmission starts.
A commonly used fast-responding RF power detector is a diode detector. A diode detector is typically used with
a relatively long holding time when compared to the carrier frequency and a relatively short holding time with
respect to the envelope frequency. In this way a diode detector is used as AM demodulator or envelope tracker
(Figure 49).
Figure 49. Peak Detection vs. Envelope Tracking
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Product Folder Links: LMH2121
RFIN/EN OUT
GND
V/I
V/I
V/I
V/I
A
VDD
K
LOGIC ENABLE
i1
i2
IOUT VOUT
CRVOUT
Z0D
VREF
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
An example of a diode detector is depicted in Figure 50. The diode rectifies the RF input voltage; subsequently,
the RC filter determines the averaging (holding) time. The selection of the holding time configures the diode
detector for its particular application. For envelope tracking a relatively small RC time constant is chosen such
that the output voltage tracks the envelope nicely. In contrast, a configuration with a relatively large time constant
for RC measures the maximum (peak) voltage of a signal, see Figure 49.
Figure 50. Diode Detector
A limitation of the diode detector is its relative small dynamic range. The LMH2121 is an envelope detector with
high dynamic range and will be discussed next.
LMH2121 RF POWER DETECTOR
For optimal performance, the LMH2121 should to be configured correctly in the application. The detector will be
discussed by means of its block diagram (Figure 51). Details of the electrical interfacing are separately discussed
for each pin below.
Figure 51. Block Diagram of LMH2121
For measuring the power level of a signal, the time average of the squared signal needs to be measured as
described in section ACCURATE POWER MEASUREMENT. This is implemented in the LMH2121 by means of a
multiplier and a low-pass filter in a negative-feedback loop. A simplified block diagram of the LMH2121 is
depicted in Figure 51. The core of the loop is a multiplier. The two inputs of the multiplier are fed by (i1, i2):
i1= iLF + iRF (5)
i2= iLF - iRF (6)
in which iLF is a current depending on the DC output voltage of the RF detector (made by the V/I converter) and
iRF is a current depending on the RF input signal (made by a V/I converter as well). The output of the multiplier
(iOUT) is the product of these two currents and equals:
18 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: LMH2121
³
VOUT = k vRF2dt
iLF2dt =
³iRF2dt
³
iOUT =I0
iLF2 - iRF2
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
(7)
in which I0is a normalizing current. By using a low-pass filter at the output of the multiplier the DC term of this
current is isolated and integrated. The input of amplifier A acts as the nulling point of the negative feedback loop,
yielding:
(8)
which implies that the average power content of the current related to the output voltage of the LMH2121 is
made equal to the average power content of the current related to the RF input signal.
For a negative-feedback system, the transfer function is given by the inverse function of the feedback block.
Therefore, to have a linear conversion gain for this RF detector, the feedback network implements a linear
function as well resulting in an overall transfer function for the LMH2121 of:
(9)
in which k is the conversion gain. Note that as a result of the feedback loop the square root is implemented.
The envelope response time of this fast-responding RF detector is given by the gain-bandwidth product of the
feedback loop.
Given this architecture for the RF detector, the high performance of the LMH2121 can be understood. In theory
the accuracy of the linear transfer function is set by:
• The linear feedback network, which basically needs to process a DC signal only.
• A high loop gain for the feedback loop, which is ensured by the high amplifier gain A.
The square-root functionality is inherent to the feedback loop and the use of a multiplier. Therefore, a very
accurate relation between the power content of the input signal and the output is obtained.
RF Input and Enable
To minimize pin-count, in this case. only 4, the RF input and the enable functionality are combined into one pin.
The RF signal is supplied to the RFIN/EN pin via an external capacitor, while the Enable signal is connected via a
resistor to the RFIN/EN pin (see TYPICAL APPLICATION on the front page). Internally there is an AC path for the
RF signal and a DC path for the enable voltage. Care should be taken with the selection of capacitor C. The turn-
on time of the RF detector will increase when a large capacitor value is chosen. This is because the capacitor
forms a time constant together with resistor R2. A capacitor value of 100 pF and resistor value of 1 kΩis
recommended which hardly impacts the turn-on time for those values. The turn-on time is mainly determined by
the device itself.
RF systems typically use a characteristic impedance of 50Ω; the LMH2121 is no exception to this. The 50Ωinput
impedance enables an easy, direct connection to a directional coupler without the need for impedance
adjustments. Please note that as a result of the internal AC coupling the 50ohm is not obtained for the complete
DC to HF range. However, the input impedance does approximate 50Ωat the usual transmit bands.
The LMH2121 can be brought into a low power consumption shutdown mode by means of the DC enable level
which is supplied via a resistor to the RFIN/EN pin. The device is active for Enable = HIGH (VEN > 1.1V), and in
the low-power shutdown mode for Enable = LOW (VEN < 0.6V). In shutdown the output of the LMH2121 is
switched to high impedance.
Output
The output of the LMH2121 provides a DC voltage that is a measure for the applied RF power to the input pin. It
tracks the input RF envelope with a 3 dB bandwidth around 2 MHz. The output voltage has a linear-in-V
response for an applied RF signal. In active mode the output impedance is 100Ωsuch that with an external
capacitor some filtering can be obtained if necessary. The output impedance of the LMH2121 is high impedance
in shutdown. This enables a parallel connection of multiple detector outputs where one of the detectors is
enabled at a time.
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LMH2121
R2 = 10 - 1
AdB
20 RIN
AdB = 20 LOG 1 + RIN
R2
PA ANTENNA
RF
ADC
B1 A1
A2
B2
R2
RFIN/EN OUT
VDD
GND
LMH2121
C
100 pF
ENABLE
R1
1 k:
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
Supply
The LMH2121 can handle supply voltages between 2.6V to 3.3V. The high PSRR of the LMH2121 ensures a
constant performance over its power supply range.
DYNAMIC RANGE ALIGNMENT
For an accurate power measurement the signal power range needs to be aligned with the input power range of
the LMH2121. When a directional couple is used, the dynamic range of the power amplifier (PA) and RF detector
can be aligned by choosing a coupler with the appropriate coupling factor.
Since the LMH2121 has an input impedance that approximates 50Ωfor the useful frequency range, a resistive
divider can also be used instead of a directional coupler (Figure 52).
Figure 52. Dynamic Range Alignment with Resistive Divider
Resistor R2implements an attenuator, together with the detector input impedance. The attenuator can be used to
match the signal range with the input range of the LMH2121. The attenuation (AdB) realized by R2and the
effective input resistance (RIN) of the LMH2121 equals:
(10)
Solving this expression for R2yields:
(11)
Suppose the desired attenuation is 30 dB with a given LMH2121 input impedance of 50Ω, the resistor R2needs
to be 1531Ω. A practical value is 1.5 kΩ. Although this is a cheaper solution than the application with directional
coupler, it has a disadvantage. After calculating the resistor value it is possible that the realized attenuation is
less than expected. This is because of the parasitic capacitance of resistor R2which results in a lower actual
realized attenuation. Whether the attenuation will be reduced depends on the frequency of the RF signal and the
parasitic capacitance of resistor R2. Since the parasitic capacitance varies from resistor to resistor, exact
determination of the realized attenuation can be difficult. A way to reduce the parasitic capacitance of resistor R2
is to realize it as a series connection of several separate resistors.
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Product Folder Links: LMH2121
FREQUENCY (Hz)
OUTPUT (dB)
3
0
-3
-6
-9
-12
-15
-18
-21
10k 100k 1M 10M
RFin = 0 dBm
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
RESPONSE BANDWIDTH
Modulation standards available today have a wide variety of modulation bandwidths. LTE, for instance, has
modulation bandwidths varying from 200 kHz (1RB) up to 20 MHz (100RB). Whether the RF detector can track
the envelope of these modulated RF signals depends on its response bandwidth. Figure 53 depicts the response
bandwidth of the LMH2121. The plot shows the output as a function of a varying amplitude modulation frequency
where the output is normalized to 0 dB at low modulation frequency.
Figure 53. Response Bandwidth
The response bandwidth of the LMH2121 is about 2 MHz for 0 dBm input power level.
SPECIFYING DETECTOR PERFORMANCE
The performance of the LMH2121 can be expressed by a variety of parameters. This section discusses the key
parameters.
Dynamic Range
The LMH2121 is designed to have a predictable and accurate response over a certain input power range. This is
called the dynamic range (DR) of a detector. For determining the dynamic range a couple of different criteria can
be used. The most commonly used ones are:
• Linear conformance error, ELC
• Variation over temperature error, EVOT
The specified dynamic range is the range over which the specified error metric is within a predefined window. An
explanation of these errors is given in the following sections.
Linear Conformance error
The LMH2121 implements a linear detection function. In order to describe how close the transfer is to an ideal
linear function the linear conformance error is used. To calculate the linear conformance error the detector
transfer function can be modeled as a linear function between input power in dBm and output voltage in dBV.
The ideal linear transfer is modeled by 2 parameters:
• Slope, KSLOPE
• Intercept, PINT
and is described by:
VOUT = KSLOPE (PIN - PINT) (12)
where VOUT is the output voltage in dBV, KSLOPE is the slope of the function in dB/dB, PIN the input power level in
dBm and PINT is the power level in dBm at which the function intersects VOUT = 0 dBV = 1V (See Figure 54).
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 21
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-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
85°C
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
25°C
ELC (T) = KSLOPE (25°C)
VOUT (T) - KSLOPE (25°C) [PIN - PINT (25°C)]
RF INPUT POWER (dBm)
VOUT (V)
10
1
0.1
0.01
-50 -40 -30 -20 -10 0 10
PINT
Detector
response KSLOPE
PINT = RFIN at VOUT is 0 dBV (1V)
Ideal LIN function
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
Figure 54. Comparing Actual Transfer with an Ideal Linear Transfer
To determine the linear conformance error two steps are required:
1. Determine the best fitted ideal transfer at 25°C.
2. Determine the difference between the actual data and the best fitted ideal transfer.
The best fit can be determined by standard routines. A careful selection of the fit range is important. The fit range
should be within the normal range of operation of the device. Outcome of the fit is KSLOPE and PINT.
Subsequently, the difference between the actual data and the best fitted ideal transfer is determined. The linear
conformance is specified as an input referred error. The output referred error is therefore divided by the KSLOPE to
obtain the input referred error. The linear conformance error is calculated by the following equation:
(13)
where VOUT(T) is the measured output voltage at temperature T, for a power level PIN. KSLOPE25°C (dB/dB) and
PINT25°C (dBm) are the parameters of the best fitted ideal transfer for the actual transfer at 25°C.
Figure 55 shows that both the error with respect to the ideal linear response as well as the error due to
temperature variation are included in this error metric. This is because the measured data for all temperatures is
compared to the fitted line at 25°C. The measurement result of a typical LMH2121 in Figure 55 shows a dynamic
range of 27 dB for ELC= ±1dB over the operating temperature range.
Figure 55. ELC vs. RF input Power at 1900 MHz
22 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: LMH2121
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C
Typical 25°C ELC
RF INPUT POWER (dBm)
ERROR (dB)
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
-40°C
85°C Typical 25°C ELC
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-40°C
85°C
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
Variation over Temperature Error
In contrast to the linear conformance error, the variation over temperature error (EVOT) purely measures the error
due to temperature variation. The measured output voltage at 25°C is subtracted from the output voltage at
another temperature for the same power level. Subsequently, the difference is translated into an input referred
error by dividing it by KSLOPE at 25°C. The equation for variation over temperature is given by:
EVOT(T) = [ VOUT(T) - VOUT(25°C) ] / KSLOPE(25°C) (14)
The variation over temperature is shown in Figure 56, where a dynamic range of 29 dB is obtained for EVOT =
±0.5 dB.
Figure 56. EVOT vs. RF Input Power at 1900 MHz
Dynamic Range Improvement
The LMH2121 has a very low part-to-part variation. This implies that compensation for systematic imperfection
would be beneficial. One example is to compensate with the typical ELC for 25°C of the LMH2121. This would
correct for systematic bending at the lower- and top ends of the curve. As a result a significant improvement of
the dynamic range can be achieved. Figure 57 shows the ELC before and after compensation. The figure after
compensation shows the resulting ELC of 50 units when the typical ELC curve is subtracted from each of the 50
ELC curves.
Before Compensation After Compensation
Figure 57. ELC vs. RF Input Power
With this technique a dynamic range improvement of 10 dB is obtained. Likewise EVOT compensation can be
done to move a larger portion of the error band within the ±0.5 dB, for instance.
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 23
Product Folder Links: LMH2121
-30 -20 -10 0 10 20
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
RF INPUT POWER (dBm)
ERROR (dB)
-50°C
0°C
-25°C
50°C
75°C
100°C
125°C
-30 -20 -10 0 10 20
3
2
1
0
-1
-2
-3
RF INPUT POWER (dBm)
ERROR (dB)
125°C
-50°C
In Steps of 25°C
-40 -30 -20 -10 0 10 20
10
1
0.1
0.01
125°C
RF INPUT POWER (dBm)
VOUT (V)
-50°C
125°C
-50°C
In Steps of 25°C
LMH2121
SNVS876A –AUGUST 2012–REVISED MARCH 2013
www.ti.com
Temperature Behavior
The specified temperature range of the LMH2121 is from −40°C to 85°C. The RF detector is, to a certain extent
however, still functional outside these temperature limits. Figure 58 and Figure 59 show the detector behavior for
temperatures from −50°C up to 125°C in steps of 25°C. The LMH2121 is still very accurate within a dynamic
range from −28 dBm to +12 dBm. On the upper and lower ends the curves deviate in a gradual way, the lowest
temperature at the bottom side and the highest temperature at top side.
Figure 58. VOUT vs. RF Input Power at 1900 MHz for Extended Temperature Range
Linear Conformance Error vs. RF Input Power Temperature Variation vs. RF Input Power
Figure 59. Linear Conformance and Temperature Variation vs. RF Input Power at 1900 MHz for Extended
Temperature Range
Layout Recommendations
As with any other RF device, careful attention must be paid to the board layout. If the board layout isn’t properly
designed, performance might be less than can be expected for the application.
The LMH2121 is designed to be used in RF applications having a characteristic impedance of 50Ω. To achieve
this impedance, the input of the LMH2121 needs to be connected via a 50Ωtransmission line. Transmission lines
can be created on PCBs using microstrip or (grounded) coplanar waveguide (GCPW) configurations.
In order to minimize injection of RF interference into the LMH2121 through the supply lines, the PCB traces for
VDD and GND should be minimized for RF signals. This can be done by placing a decoupling capacitor between
the VDD and GND. It should be placed as close as possible to the VDD and GND pins of the LMH2121.
24 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: LMH2121
LMH2121
www.ti.com
SNVS876A –AUGUST 2012–REVISED MARCH 2013
REVISION HISTORY
Changes from Original (March 2013) to Revision A Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 24
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Links: LMH2121
PACKAGE OPTION ADDENDUM
www.ti.com 19-Oct-2017
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LMH2121TME/NOPB NRND DSBGA YFQ 4 250 Green (RoHS
& no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85
LMH2121TMX/NOPB NRND DSBGA YFQ 4 3000 Green (RoHS
& no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
PACKAGE OPTION ADDENDUM
www.ti.com 19-Oct-2017
Addendum-Page 2
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LMH2121TME/NOPB DSBGA YFQ 4 250 178.0 8.4 0.94 1.14 0.71 4.0 8.0 Q1
LMH2121TMX/NOPB DSBGA YFQ 4 3000 178.0 8.4 0.94 1.14 0.71 4.0 8.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 26-Mar-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LMH2121TME/NOPB DSBGA YFQ 4 250 210.0 185.0 35.0
LMH2121TMX/NOPB DSBGA YFQ 4 3000 210.0 185.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 26-Mar-2013
Pack Materials-Page 2
MECHANICAL DATA
YFQ0004xxx
www.ti.com
TMD04XXX (Rev A)
0.600±0.075
E
D
A
. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
NOTES:
4215073/A 12/12
D: Max =
E: Max =
1.088 mm, Min =
0.888 mm, Min =
1.028 mm
0.828 mm
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