LMH2121
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SNVS876A – AUGUST 2012 – REVISED MARCH 2013
LMH2121 3 GHz Fast-Responding Linear Power Detector with 40 dB Dynamic Range
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FEATURES
DESCRIPTION
•
•
•
•
•
•
•
•
•
•
•
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.
1
2
Linear Response
40 dB Power Detection Range
Very Low Supply Current of 3.4 mA
Short Response Time of 165 ns
Stable Conversion Gain of 3.6 V/VRMS
Multi-Band Operation from 100 MHz to 3 GHz
Very Low Conformance Error
High Temperature Stability of ±0.5 dB
Shutdown Functionality
Supply Range from 2.6V to 3.3V
Package:
– 4-Bump DSBGA, 0.4mm Pitch
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.
As a result of the unique internal architecture, the
device shows an extremely low part-to-part variation
of the detection curve. This is demonstrated by its low
intercept and slope variation as well as a very good
linear conformance. Consequently the required
characterization and calibration efforts are low.
APPLICATIONS
•
•
Multi Mode, Multi band RF power control
– GSM/EDGE
– CDMA
– W-CDMA
– LTE
– WAP
Tablets
The device is active for EN = High; otherwise it is in a
low power consumption shutdown mode. To save
power and allow for two detector outputs in parallel,
the output (OUT) is high impedance during shutdown.
The LMH2121 is offered in a tiny 4-bump DSBGA
package: 0.866 mm x 1.07 mm x 0.6 mm.
TYPICAL APPLICATION
RF
COUPLER
ANTENNA
PA
R2
50:
VDD
C
100 pF
RFIN/EN
ENABLE
R1
1 k:
LMH2121
OUT
ADC
GND
1
2
Please 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.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2012–2013, Texas Instruments Incorporated
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
ESD Tolerance
3.6V
(3)
Human Body Model
1500V
Machine Model
200V
Charge Device Model
1250V
−65°C to 150°C
Storage Temperature Range
Junction Temperature
(4)
150°C
For soldering specifications:
See http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=snoa549c
(1)
(2)
(3)
(4)
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.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
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)
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
−40°C to +85°C
Temperature Range
RF Frequency Range
100 MHz to 3 GHz
−28 dBm to +12 dBm
RF Input Power Range
Package Thermal Resistance θJA
(1)
(2)
(2)
130.9°C/W
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.
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
2.4
3.4
4.7
mA
2
µA
(2)
(3)
(2)
Supply Interface
IDD
Supply Current
Active Mode. EN= High, no RF input
Signal
Shutdown. EN= Low, no RF input
Signal
(1)
(2)
(3)
2
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.
All limits are ensured by test or statistical analysis.
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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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
PSRR
Parameter
Condition
Typ
40
69
(2)
RFIN = −10 dBm, 1900 MHz, 2.6V <
VDD < 3.3V
Power Supply Rejection Ratio
Min
(3)
Max
(2)
Units
dB
Logic Enable Interface
VLOW
RFIN/EN logic LOW input level
(Shutdown)
VHIGH
RFIN/EN logic HIGH input level
(Active)
IRFIN/EN
Current into RFIN/EN pin
0.6
V
1.1
EN = 1.8V
1
µA
Input / Output Interface
ZIN
Input Impedance
Resistor and Capacitor in
series from RFIN/EN to GND
RIN
50
Ω
CIN
30
pF
VOUT
Minimum Output Voltage
(Pedestal)
No RF Input Signal
ROUT
Output Resistance
RFIN = −10 dBm, 1900 MHz, ILOAD = 1
mA, DC measurement
IOUT
Output Sinking Current
RFIN = −10 dBm, 1900 MHz, OUT
connected to 2.5V
17
16
20
Output Sourcing Current
RFIN = −10 dBm, 1900 MHz, OUT
connected to GND
1.30
1.28
1.86
IOUT, SD
Output Leakage Current in
Shutdown
VEN = Low, OUT is connected to 2V
en
Output Referred Noise
vn
Output Referred Noise Integrated
(4)
(4)
18
30
38
mV
100
117
120
Ω
mA
80
nA
RFIN = −23 dBm, 1900 MHz, output
spectrum at 10 kHz
18
µV/√Hz
RFIN = −23 dBm, 1900 MHz, Integrated
over frequency band 1 kHz -13 kHz
2
mVRMS
RFIN = −10 dBm, 1900 MHz, VEN LOWto-HIGH transition to OUT at 90%
1.3
µs
Signal at RFIN from −20 dBm to 5 dBm,
10% to 90%, 1900 MHz
165
ns
Signal at RFIN from 5 dBm to −20 dBm,
90% to 10%, 1900 MHz
285
ns
Timing Characteristics
tON
Turn-on Time from Shutdown
tR
Rise Time
tF
Fall Time
(4)
(4)
(4)
RF Detector Transfer, fit range −15 dBm to −5 dBm for Linear Slope and Intercept
RFIN = 100 MHz (5)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
20
mV
VMAX
Maximum Output Voltage
At PMAX
2.7
V
KSLOPE
Linear Slope
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
(4)
(5)
Lin Conformance Error within ±1 dB
−33
dBm
12
1
VOUT = 0 dBV
dB/dB
1.2
1.9
2.4
dBm
3.4
3.6
3.9
V/VRMS
±1 dB Lin Conformance Error (ELC)
34
25
45
32
±3 dB Lin Conformance Error (ELC)
47
41
49
46
±1 dB Input Referred Variation over
Temperature (EVOT)
26
31
dB
This parameter is ensured by design and/or characterization and is not tested in production.
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
(2)
(3)
Max
(2)
Units
RFIN = 700 MHz (5)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
20
mV
VMAX
Maximum Output Voltage
At PMAX
2.65
V
KSLOPE
Linear Slope
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
RFIN = 900 MHz
Lin Conformance Error within ±1 dB
-33
dBm
12
1
VOUT = 0 dBV
dB/dB
1.3
1.9
2.2
dBm
3.5
3.6
3.9
V/VRMS
±1 dB Lin Conformance Error (ELC)
34
34
45
38
±3 dB Lin Conformance Error (ELC)
47
39
50
47
±0.5 dB Input Referred Variation over
Temperature (EVOT)
34
37
dB
(5)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
Lin Conformance Error within ±1 dB
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
20
VMAX
Maximum Output Voltage
At PMAX
2.68
V
KSLOPE
Linear Slope
1
dB/dB
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
-33
dBm
12
VOUT = 0 dBV
mV
1.7
2.1
2.5
dBm
3.7
V/VRMS
3.4
3.5
±1 dB Lin Conformance Error (ELC)
34
33
45
37
±3 dB Lin Conformance Error (ELC)
48
40
50
47
±0.5 dB Input Referred Variation over
Temperature (EVOT)
35
37
dB
RFIN = 1700 MHz (6)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
37
mV
VMAX
Maximum Output Voltage
At PMAX
1.23
V
KSLOPE
Linear Slope
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
(6)
4
Lin Conformance Error within ±1 dB
−24
dBm
7
1
VOUT = 0 dBV
dB/dB
3.8
4.1
4.5
dBm
2.6
2.8
2.9
V/VRMS
±1 dB Lin Conformance Error (ELC)
27
24
31
28
±3 dB Lin Conformance Error (ELC)
44
34
47
43
±0.5 dB Input Referred Variation over
Temperature (EVOT)
26
31
dB
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
(2)
(3)
Max
(2)
Units
RFIN = 1900 MHz (7)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
33
mV
VMAX
Maximum Output Voltage
At PMAX
1.1
V
KSLOPE
Linear Slope
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
RFIN = 2600 MHz
Lin Conformance Error within ±1 dB
−24
dBm
7
1
VOUT = 0 dBV
dB/dB
4.7
5
5.3
dBm
2.4
2.5
2.6
V/VRMS
±1 dB Lin Conformance Error (ELC)
26
23
31
27
±3 dB Lin Conformance Error (ELC)
43
33
45
41
±0.5 dB Input Referred Variation over
Temperature (EVOT)
26
29
dB
(7)
PMIN
Minimum Power Level, bottom
end of Dynamic Range
PMAX
Maximum Power Level, top end of
Dynamic Range
VMIN
Minimum Output Voltage
At PMIN
35
VMAX
Maximum Output Voltage
At PMAX
0.78
V
KSLOPE
Linear Slope
1
dB/dB
PINT
Linear Intercept
Gain
Conversion Gain
DR
Dynamic Range for specified
Accuracy
(7)
Lin Conformance Error within ±1 dB
−22
dBm
6
VOUT = 0 dBV
mV
6.3
6.7
7.1
dBm
2.2
V/VRMS
2.0
2.1
±1 dB Lin Conformance Error (ELC)
24
21
28
25
±3 dB Lin Conformance Error (ELC)
40
30
42
38
±0.5 dB Input Referred Variation over
Temperature (EVOT)
21
27
dB
Limits are ensured by design and measurements which are performed on a limited number of samples.
CONNECTION DIAGRAM
VDD
A2
B2
GND
RFIN/EN
A1
B1
OUT
Figure 1. 4-bump DSBGA (Top View)
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PIN DESCRIPTIONS
Name
DSBGA
Description
VDD
A2
Positive Supply Voltage.
GND
B2
Ground
RFIN/EN
A1
DC voltage determines the state of the device (HIGH = device is active, LOW =
device in shutdown). AC voltage is the RF input signal to the detector (beyond 100
MHz). The RFIN/EN pin is internally terminated with 50Ω in series with 30 pF.
OUT
B1
Ground referenced detector output voltage.
BLOCK DIAGRAM
VDD
A2
LOGIC
ENABLE
V/I
RFIN/EN
V/I
A1
B1
V/I
OUT
K
A
V/I
B2
GND
Figure 2. LMH2121
6
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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
5
5
EN = HIGH
25°C
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
4
85°C
3
2
-40°C
1
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4
85°C
25°C
3
-40°C
2
1
0
0.5
3.5
0.6
SUPPLY VOLTAGE (V)
0.9
1.0
Figure 4.
Supply Current vs. RF Input Power
Output Sourcing Current vs. RF Input Power
100
OUTPUT SOURCING CURRENT (mA)
5
SUPPLY CURRENT (mA)
0.8
Figure 3.
6
4
3
2
-40°C 25°C
85°C
1
0
-40
-30
-20
-10
0
10
RFin = 1900 MHz
OUT = 0V
10
1
85°C
25°C
-40°C
0.1
-40
20
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 5.
Figure 6.
Output Sinking Current vs. RF Input Power
RF Input Impedance
vs. Frequency, Resistance (R) and Reactance (X)
100
100
Z = R + jX
75
-40°C
10
25°C
85°C
1
0.1
-40
RF INPUT IMPEDANCE ( )
OUTPUT SINKING CURRENT (mA)
0.7
ENABLE VOLTAGE (V)
-20
-10
0
10
50
25
R
0
-25
-50
X
-75
OUT = 2.5V
RFin = 1900 MHz
-30
|Z|
-100
10M
20
RF INPUT POWER (dBm)
MEASURED ON BUMP
100M
1G
10G
FREQUENCY (Hz)
Figure 7.
Figure 8.
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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
70
OUTPUT VOLTAGE NOISE ( V/¥+])
30
60
PSRR (dB)
50
40
30
20
10
0
100
1k
10k
100k
1M
PIN = -23 dBm
25
20
15
10
5
0
100
10M
1k
10k
FREQUENCY (Hz)
Figure 9.
1M
10M
Figure 10.
Turn-on time from EN-step
Rise and Fall Time
2.00
VOUT for various PIN levels
PIN1 = -20 dBm
1.75 PIN2 = Mentioned at curve
+5 dBm
0 dBm
~
~
+10 dBm
1.25
+5 dBm
1.00
~
~
+10 dBm
1.50
0.75
0 dBm
~
~
EN-step (0 to 2.7V)
~
~
OUTPUT VOLTAGE (V)
0.50
-5 dBm
-5 dBm
~
~ ~
~
OUTPUT VOLTAGE (0.5V/DIV)
100k
FREQUENCY (Hz)
0.25
-10 dBm
-10 dBm
~
~
0.00
TIME (0.5 s/DIV)
TIME (0.5 s/DIV)
Figure 11.
Figure 12.
Slope vs. Frequency
Intercept vs. Frequency
18
1.3
16
14
25°C
1.1
1.0
-40°C
85°C
0.9
LIN INTERCEPT (dBm)
LIN SLOPE (dB/dB)
1.2
12
10
8
0
100M
1G
10G
-2
10M
-40°C
100M
1G
10G
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 13.
8
25°C
4
2
0.8
0.7
10M
85°C
6
Figure 14.
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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.
Output Voltage vs. RF Input power
Output Voltage vs. Frequency
10
10
1.7 GHz
RFIN = 10 dBm
900 MHz
1
RFIN = 5 dBm
2.6 GHz
100 MHz
1.9 GHz
0.1
RFIN = 0 dBm
VOUT (V)
VOUT (V)
1
700 MHz
RFIN = -5 dBm
RFIN = -10 dBm
RFIN = -15 dBm
0.1
RFIN = -20 dBm
RFIN = -25 dBm
RFIN = -30 dBm
0.01
-40
-30
-20
-10
0
10
0.01
10M
20
100M
1G
10G
FREQUENCY (Hz)
RF INPUT POWER (dBm)
Figure 15.
Figure 16.
Lin Conformance
vs. RF Input Power at 100 MHz
Output Voltage vs. RF Input Power at 100 MHz
10
3
2
-40°C
ERROR (dB)
VOUT (V)
1
-40°C
0.1
1
0
-1
25°C
25°C
85°C
-2
0.01
-40
85°C
-30
-20
-10
0
10
-3
-30
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 17.
Figure 18.
Lin Conformance (50 units)
vs. RF Input Power at 100 MHz
Temperature Variation
vs. RF Input Power at 100 MHz
2.0
3
1.5
2
-40°C
1.0
1
ERROR (dB)
ERROR (dB)
-40°C
0
0.5
0.0
-0.5
-1
-1.0
85°C
85°C
-2
-3
-30
-1.5
-20
-10
0
10
-2.0
-30
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 19.
Figure 20.
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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
10
2.0
1.5
-40°C
1
0.5
VOUT (V)
ERROR (dB)
1.0
0.0
-0.5
85°C
0.1
-1.0
25°C
85°C
-1.5
-2.0
-30
-20
-10
0
10
0.01
-40
20
-40°C
-30
RF INPUT POWER (dBm)
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 21.
Figure 22.
Lin Conformance vs. RF Input Power at 700 MHz
Lin Conformance (50 units) vs. RF Input Power at 700 MHz
3
3
2
2
1
1
ERROR (dB)
ERROR (dB)
85°C
85°C
0
25°C
-1
0
-1
-40°C
-40°C
-2
-3
-30
-2
-20
-10
0
10
-3
-30
20
RF INPUT POWER (dBm)
-20
0
10
20
Figure 23.
Figure 24.
Temperature Variation vs. RF Input Power at 700 MHz
Temperature Variation (50 units)
vs. RF Input Power at 700 MHz
2.0
2.0
1.5
1.5
1.0
1.0
-40°C
0.5
ERROR (dB)
ERROR (dB)
-40°C
0.0
-0.5
0.5
0.0
-0.5
85°C
85°C
-1.0
-1.0
-1.5
-1.5
-2.0
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
-2.0
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 25.
10
-10
RF INPUT POWER (dBm)
Figure 26.
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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.
Output Voltage vs. RF Input Power at 900 MHz
Lin Conformance vs. RF Input Power at 900 MHz
3
10
2
ERROR (dB)
VOUT (V)
1
85°C
1
85°C
0
25°C
-1
0.1
-40°C
25°C
-2
0.01
-40
-40°C
-30
-20
-10
0
10
-3
-30
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 27.
Figure 28.
Lin Conformance (50 units) vs. RF Input Power at 900 MHz
Temperature Variation vs. RF Input Power at 900 MHz
2.0
3
1.5
2
1.0
85°C
ERROR (dB)
ERROR (dB)
85°C
1
0
0.5
0.0
-0.5
-1
-40°C
-1.0
-40°C
-2
-3
-30
-1.5
-20
-10
0
10
-2.0
-30
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 29.
Figure 30.
Temperature Variation (50 units)
vs. RF Input Power at 900 MHz
Output Voltage vs. RF Input Power at 1700 MHz
10
2.0
1.5
1.0
1
VOUT (V)
ERROR (dB)
85°C
0.5
0.0
-0.5
85°C
0.1
-40°C
-1.0
25°C
-1.5
-2.0
-30
-20
-10
0
10
0.01
-40
20
RF INPUT POWER (dBm)
-40°C
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 31.
Figure 32.
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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.
Lin Conformance vs. RF Input Power at 1700 MHz
Lin Conformance (50 units) vs. RF Input Power at 1700 MHz
3
3
2
2
1
1
ERROR (dB)
ERROR (dB)
85°C
85°C
0
25°C
-1
0
-1
-40°C
-40°C
-2
-2
-3
-30
-20
-10
0
10
-3
-30
20
-20
RF INPUT POWER (dBm)
-10
0
10
20
RF INPUT POWER (dBm)
Figure 33.
Figure 34.
Temperature Variation vs. RF Input Power at 1700 MHz
Temperature Variation (50 units)
vs. RF Input Power at 1700 MHz
2.0
2.0
1.5
1.5
1.0
1.0
85°C
ERROR (dB)
ERROR (dB)
85°C
0.5
0.0
-0.5
0.5
0.0
-0.5
-40°C
-40°C
-1.0
-1.0
-1.5
-1.5
-2.0
-30
-20
-10
0
10
20
-2.0
-30
-20
RF INPUT POWER (dBm)
-10
0
10
20
RF INPUT POWER (dBm)
Figure 35.
Figure 36.
Output Voltage vs. RF Input Power at 1900 MHz
Lin Conformance vs. RF Input Power at 1900 MHz
3
10
2
VOUT (V)
ERROR (dB)
1
85°C
0.1
1
85°C
0
25°C
-1
-40°C
25°C
-2
-40°C
0.01
-40
-30
-20
-10
0
10
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 37.
12
-3
-30
Figure 38.
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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.
Lin Conformance (50 units) vs. RF Input Power at 1900 MHz
Temperature Variation vs. RF Input Power at 1900 MHz
2.0
3
1.5
2
1.0
85°C
85°C
ERROR (dB)
ERROR (dB)
1
0
0.5
0.0
-0.5
-1
-40°C
-1.0
-40°C
-2
-1.5
-3
-30
-20
-10
0
10
-2.0
-30
20
-20
-10
0
10
20
RF INPUT POWER (dBm)
RF INPUT POWER (dBm)
Figure 39.
Figure 40.
Temperature Variation (50 units)
vs. RF Input Power at 1900 MHz
Output Voltage vs. RF Input Power at 2600 MHz
10
2.0
1.5
1.0
1
VOUT (V)
ERROR (dB)
85°C
0.5
0.0
85°C
-0.5
0.1
-40°C
-1.0
25°C
-1.5
-40°C
-2.0
-30
-20
-10
0
10
0.01
-40
20
-30
RF INPUT POWER (dBm)
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 41.
Figure 42.
Lin Conformance vs. RF Input Power at 2600 MHz
Lin Conformance (50 units)
vs. RF Input Power at 2600 MHz
3
3
2
2
1
1
ERROR (dB)
ERROR (dB)
85°C
85°C
0
25°C
-1
0
-1
-40°C
-2
-2
-40°C
-3
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
-3
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 43.
Figure 44.
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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 2600 MHz
Temperature Variation vs. RF Input Power at 2600 MHz
2.0
2.0
1.5
1.5
1.0
1.0
85°C
ERROR (dB)
ERROR (dB)
85°C
0.5
0.0
-0.5
0.5
0.0
-0.5
-40°C
-40°C
-1.0
-1.0
-1.5
-1.5
-2.0
-30
-20
-10
0
10
20
-2.0
-30
RF INPUT POWER (dBm)
-10
0
10
20
RF INPUT POWER (dBm)
Figure 45.
14
-20
Figure 46.
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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.
COUPLER
RF
PA
VGA
ANTENNA
R1
50:
VDD
GAIN
ADC
A2
OUT
A1
B1
RFIN/EN
LMH2121
BASE
BAND
or
RF IC
C
100 pF
R2
1 k:
B2
GND
ENABLE
EN
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:
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P(T) =
1
T
T
³0
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2
v(t)
dt
R
(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 50Ω system), the average power is proportional to average of the
square of the instantaneous voltage:
Pv
1
T
T
³0 v(t)
2
dt
(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 (ωC t)
(3)
where a(t) is the amplitude modulation and ωc the 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.
ENVELOPE
ENVELOPE
RMS
RMS
CARRIER
CARRIER
INTEGRATION TIME (T)
INTEGRATION TIME (T)
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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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:
VRMS =
1 T
2
v(t) dt v P
T ³0
(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 WCDMA 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).
PEAK
ENVELOPE
CARRIER
Figure 49. Peak Detection vs. Envelope Tracking
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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.
Z0
D
VREF
C
R
VOUT
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.
VDD
LOGIC
ENABLE
V/I
V/I
i1
IOUT
VOUT
RFIN/EN
OUT
K
A
i2
V/I
V/I
GND
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
i2 = iLF - iRF
(5)
(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:
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2
iOUT =
2
iLF - iRF
I0
(7)
in which I0 is 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:
³ iLF dt = ³ iRF dt
2
2
(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:
VOUT = k
2
³ vRF dt
(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 turnon 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 kΩ is
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 50Ω input
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 50Ω at 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 100Ω such 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.
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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 50Ω for the useful frequency range, a resistive
divider can also be used instead of a directional coupler (Figure 52).
RF
ANTENNA
PA
R2
VDD
C
100 pF
A2
ADC
LMH2121
RFIN/EN
ENABLE
R1
1 k:
OUT
B1
A1
B2
GND
Figure 52. Dynamic Range Alignment with Resistive Divider
Resistor R2 implements 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 R2 and the
effective input resistance (RIN) of the LMH2121 equals:
AdB = 20 LOG 1 +
R2
RIN
(10)
Solving this expression for R2 yields:
AdB
20
R2 = 10
- 1 RIN
(11)
Suppose the desired attenuation is 30 dB with a given LMH2121 input impedance of 50Ω, the resistor R2 needs
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 R2 which 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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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.
3
RFin = 0 dBm
0
OUTPUT (dB)
-3
-6
-9
-12
-15
-18
-21
10k
100k
1M
10M
FREQUENCY (Hz)
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).
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10
PINT = RFIN at VOUT is 0 dBV (1V)
PINT
VOUT (V)
1
Detector
response
0.1
KSLOPE
Ideal LIN function
0.01
-50
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
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:
ELC (T) =
VOUT (T) - KSLOPE (25°C) [PIN - PINT (25°C) ]
KSLOPE (25°C)
(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.
3
ERROR (dB)
2
1
85°C
0
25°C
-1
-40°C
-2
-3
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 55. ELC vs. RF input Power at 1900 MHz
22
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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.
2.0
1.5
1.0
ERROR (dB)
85°C
0.5
0.0
-0.5
-40°C
-1.0
-1.5
-2.0
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
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.
3
3
2
2
ERROR (dB)
ERROR (dB)
1
Typical 25°C E LC
0
-1
1
0
-1
-40°C
-40°C
-2
-3
-30
Typical 25°C E LC
85°C
85°C
-2
-20
-10
0
10
20
-3
-30
-20
RF INPUT POWER (dBm)
Before Compensation
-10
0
10
20
RF INPUT POWER (dBm)
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.
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LMH2121
SNVS876A – AUGUST 2012 – REVISED MARCH 2013
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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.
10
In Steps of 25°C
125°C
1
VOUT (V)
-50°C
0.1
125°C
0.01
-40
-50°C
-30
-20
-10
0
10
20
RF INPUT POWER (dBm)
Figure 58. VOUT vs. RF Input Power at 1900 MHz for Extended Temperature Range
3
2.0
In Steps of 25°C
125°C
1.5
1
100°C
125°C
ERROR (dB)
ERROR (dB)
2
0
-1
1.0
75°C
0.5
50°C
0.0
-0.5
0°C
-1.0
-2
-50°C
-25°C
-1.5
-50°C
-3
-30
-20
-10
0
10
20
-2.0
-30
RF INPUT POWER (dBm)
Linear Conformance Error vs. RF Input Power
-20
-10
0
10
20
RF INPUT POWER (dBm)
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 50Ω transmission 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
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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
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
(3)
Device Marking
(4/5)
(6)
LMH2121TME/NOPB
ACTIVE
DSBGA
YFQ
4
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
LMH2121TMX/NOPB
ACTIVE
DSBGA
YFQ
4
3000
RoHS & Green
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
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