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LMH2110
SNWS022D – JANUARY 2010 – REVISED JUNE 2015
LMH2110 8-GHz Logarithmic RMS Power Detector with 45-dB Dynamic Range
1 Features
3 Description
•
•
•
•
•
•
•
•
•
•
The LMH2110 is a 45-dB Logarithmic RMS power
detector particularly suited for accurate power
measurement of modulated RF signals that exhibit
large peak-to-average ratios; that is, large variations
of the signal envelope. Such signals are encountered
in W-CDMA and LTE cell phones. The RMS
measurement topology inherently ensures a
modulation insensitive measurement.
1
Wide Supply Range from 2.7 V to 5 V
Logarithmic Root Mean Square Response
45-dB Linear-in-dB Power Detection Range
Multi-Band Operation from 50 MHz to 8 GHz
LOG Conformance Better than ±0.5 dB
Highly Temperature Insensitive, ±0.25 dB
Modulation Independent Response, 0.08 dB
Minimal Slope and Intercept Variation
Shutdown Functionality
Tiny 6-Bump DSBGA Package
2 Applications
•
•
Multi-Mode, Multi-Band RF Power Control
– GSM/EDGE
– CDMA/CDMA2000
– W-CDMA
– OFDMA
– LTE
Infrastructure RF Power Control
space
The device has an RF frequency range from 50 MHz
to 8 GHz. It provides an accurate, temperature and
supply insensitive output voltage that relates linearly
to the RF input power in dBm. The LMH2110 device
has excellent conformance to a logarithmic response,
enabling easy integration by using slope and intercept
only, reducing calibration effort significantly. The
device operates with a single supply from 2.7 V to
5 V. The LMH2110 has an RF power detection range
from –40 dBm to 5 dBm and is ideally suited for use
in combination with a directional coupler.
Alternatively, a resistive divider can be used.
The device is active for EN = High; otherwise, it is in
a low power-consumption shutdown mode. To save
power and prevent discharge of an external filter
capacitance, the output (OUT) is high-impedance
during shutdown.
Device Information(1)
PART NUMBER
LMH2110
PACKAGE
BODY SIZE (MAX)
DSBGA (6)
1.27 mm × 0.87 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Circuit
COUPLER
ANTENNA
PA
3
2.4
2
2.0
50 :
-40°C
1.6
VOUT (V)
VDD
A1
RFIN
OUT
B1
1
0
1.2
-1
0.8
A2
LMH2110
25°C
85°C
ADC
-2
0.4
EN
ERROR (dB)
RF
Output Voltage and Log Conformance Error vs.
RF Input Power at 1900 MHz
C2
B2, C1
GND
0.0
-40
-3
-30
-20
-10
0
10
RF INPUT POWER (dBm)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMH2110
SNWS022D – JANUARY 2010 – REVISED JUNE 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
4
4
4
4
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
2.7-V and 4.5-V DC and AC Electrical
Characteristics ...........................................................
6.6 Timing Requirements ................................................
6.7 Typical Characteristics ..............................................
7
5
8
9
Detailed Description ............................................ 16
7.1 Overview ................................................................. 16
7.2 Functional Block Diagram ....................................... 16
7.3 Feature Description................................................. 16
7.4 Device Functional Modes........................................ 20
8
Application and Implementation ........................ 21
8.1 Application Information............................................ 21
8.2 Typical Applications ................................................ 21
9 Power Supply Recommendations...................... 29
10 Layout................................................................... 29
10.1 Layout Guidelines ................................................. 29
10.2 Layout Example .................................................... 29
11 Device and Documentation Support ................. 30
11.1
11.2
11.3
11.4
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
30
30
30
30
12 Mechanical, Packaging, and Orderable
Information ........................................................... 30
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (March 2013) to Revision D
•
Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1
Changes from Revision B (October 2013) to Revision C
•
2
Page
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 29
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SNWS022D – JANUARY 2010 – REVISED JUNE 2015
5 Pin Configuration and Functions
YFQ Package
6-Bump DSBGA
Top View
VDD
A1
A2
OUT
RFIN
B1
B2
GND
GND
C1
C2
EN
Pin Functions
PIN
NUMBER
A1
NAME
VDD
TYPE
Power Supply
DESCRIPTION
Positive supply voltage.
A2
OUT
Output
B1
RFIN
Analog Input
Ground referenced detector output voltage.
RF input signal to the detector, internally terminated with 50 Ω.
B2
GND
Power Supply
Power Ground. May be left floating in case grounding is not feasible.
C1
GND
Power Supply
Power Ground.
C2
EN
Logic Input
The device is enabled for EN = High, and in shutdown mode for EN = Low. EN
must be < 2.5 V to have low IEN. For EN > 2.5 V, IEN increases slightly, while
device is still functional. Absolute maximum rating for EN = 3.6 V.
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SNWS022D – JANUARY 2010 – REVISED JUNE 2015
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
Supply voltage
MAX
UNIT
5.5
V
Input power
12
dBm
DC voltage
1
V
VBAT – GND
RF input
Enable input voltage
GND – 0.4 < VEN and VEN< Min (VDD – 0.4 V, 3.6 V)
Junction temperature (3)
150
°C
Maximum lead temperature (Soldering,10 sec)
260
°C
150
°C
−65
Storage temperature, Tstg
(1)
(2)
(3)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
The maximum power dissipation is a function of TJ(MAX), RθJA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(MAX) – TA)/RθJA. All numbers apply for packages soldered directly into a PC board.
6.2 ESD Ratings
VALUE
Electrostatic
discharge
V(ESD)
(1)
(2)
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1000
Machine Model
±200
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1)
Supply voltage
Operating temperature
RF frequency
RF input power
(1)
MIN
MAX
2.7
5
UNIT
V
−40
85
50
8000
MHz
−40
5
dBm
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
6.4 Thermal Information
LMH2110
THERMAL METRIC (1)
YFQ (DSBGA)
UNIT
6 PINS
RθJA
Junction-to-ambient thermal resistance
133.7
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
1.7
°C/W
RθJB
Junction-to-board thermal resistance
22.6
°C/W
ψJT
Junction-to-top characterization parameter
5.7
°C/W
ψJB
Junction-to-board characterization parameter
22.2
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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SNWS022D – JANUARY 2010 – REVISED JUNE 2015
6.5 2.7-V and 4.5-V DC and AC Electrical Characteristics
Unless otherwise specified: all limits are ensured to TA = 25°C, VBAT = 2.7 V and 4.5 V (worst of the 2 is specified),
RFIN = 1900 MHz CW (Continuous Wave, unmodulated). (1)
MIN (2)
TYP (3)
MAX (2)
Active mode: EN = HIGH, no signal present at RFIN
3.7
4.8
5.5
Active mode: EN = HIGH, no signal present at RFIN
Limits apply at temperature extremes.
2.9
PARAMETER
TEST CONDITIONS
UNIT
SUPPLY INTERFACE
IBAT
Supply current
Shutdown: EN = LOW, no signal
present at RFIN.
VBAT = 2.7 V
3.7
4.7
VBAT = 4.5 V
4.6
5.7
Shutdown: EN = LOW, no signal
present at RFIN.
Limits apply at temperature extremes.
VBAT = 2.7 V
5
VBAT = 4.5 V
6.1
EN = Low, RFIN = 0 dBm, 1900 MHz
EN = Low, RFIN = 0 dBm, 1900 MHz
Limits apply at temperature extremes.
PSRR
Power Supply Rejection
Ratio (4)
VBAT = 2.7V
3.5
4.7
VBAT = 4.5 V
4.6
5.7
VBAT = 2.7 V
5
VBAT = 4.5 V
6.1
RFIN = −10 dBm, 1900 MHz, 2.7V < VBAT < 5 V
RFIN = −10 dBm, 1900 MHz, 2.7V < VBAT < 5 V
Limits apply at temperature extremes.
mA
5.9
μA
μA
μA
μA
56
dB
45
LOGIC ENABLE INTERFACE
VLOW
EN logic low input level
(Shutdown mode)
Limits apply at temperature extremes.
VHIGH
EN logic high input level
Limits apply at temperature extremes.
IEN
Current into EN pin
Limits apply at temperature extremes.
0.6
V
50
nA
56
Ω
1.1
V
INPUT/OUTPUT INTERFACE
RIN
Input resistance
VOUT
Minimum output voltage
(pedestal)
44
No input signal
No input signal, limits apply at temperature extremes
0
EN = High, RFIN = –10 dBm, 1900 MHz, ILOAD = 1
mA, DC measurement
ROUT
IOUT
Output impedance
Output short circuit
current
32
Sourcing, RFIN = –10 dBm, OUT connected to GND
40
Sourcing, RFIN = –10 dBm, OUT connected to GND
Limits apply at temperature extremes.
34
VN
Integrated output referred Integrated over frequency band
noise (4)
1 kHz – 6.5 kHz, RFIN = –10 dBm, 1900 MHz
(4)
Ω
Sinking, RFIN = –10 dBm, OUT connected to 2.5 V
Limits apply at temperature extremes.
Output referred noise (4)
RFIN = −10 dBm, 1900 MHz, output spectrum at 10
kHz
2
3
37
en
(2)
(3)
0.2
Sinking, RFIN = –10 dBm, OUT connected to 2.5 V
Output leakage current in EN = Low, OUT connected to 2 V
shutdown mode
Limits apply at temperature extremes.
mV
8
EN = High, RFIN = –10 dBm, 1900 MHz, ILOAD = 1
mA,
DC measurement, limits apply at temperature
extremes.
IOUT,SD
(1)
50
1.5
42
mA
46
50
nA
3
µV√Hz
210
µVRMS
2.7-V and 4.5-V DC and AC Electrical Characteristics 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. Parametric performance is not ensured in the
2.7-V and 4.5-V DC and AC Electrical Characteristics under conditions of internal self-heating where TJ > TA.
All limits are specified 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 depend on the application and configuration. The typical values are not tested and are not specified on shipped
production material.
This parameter is specified by design and/or characterization and is not tested in production.
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2.7-V and 4.5-V DC and AC Electrical Characteristics (continued)
Unless otherwise specified: all limits are ensured to TA = 25°C, VBAT = 2.7 V and 4.5 V (worst of the 2 is specified),
RFIN = 1900 MHz CW (Continuous Wave, unmodulated).(1)
PARAMETER
TEST CONDITIONS
MIN (2)
TYP (3)
MAX (2)
UNIT
RF DETECTOR TRANSFER
RFIN = 50 MHz (fit range –20 dBm to –10 dBm) (5)
PMIN
Minimum power level,
bottom end of dynamic
range
Log conformance error within ±1 dB
–39
dBm
PMAX
Maximum power level,
Log conformance error within ±1 dB
top end of dynamic range
7
dBm
VMIN
Minimum output voltage
At PMIN
3
mV
VMAX
Maximum output voltage
At PMAX
1.96
KSLOPE
Logarithmic slope
PINT
Logarithmic Intercept
Dynamic Range for
specified accuracy
DR
V
42.2
44.3
46.4
mV/dB
–38.6
–38.3
–38.0
dBm
±1-dB Log conformance error (ELC)
46
±1-dB Log conformance error (ELC)
Limits apply at temperature extremes.
45
±3-dB Log Conformance Error (ELC)
51
±3-dB Log conformance error (ELC)
Limits apply at temperature extremes.
50
±0.5-dB input referred variation over temperature
(EVOT), from PMIN
Limits apply at temperature extremes.
42
dB
RF DETECTOR TRANSFER
RFIN = 900 MHz (fit range –20 dBm to –10 dBm) (5)
PMIN
Minimum power level,
bottom end of dynamic
range
Log conformance error within ±1 dB
–38
dBm
PMAX
Maximum power level,
Log conformance error within ±1 dB
top end of dynamic range
0
dBm
VMIN
Minimum output voltage
At PMIN
3
mV
VMAX
Maximum output voltage
At PMAX
1.58
KSLOPE
Logarithmic slope
PINT
Logarithmic intercept
Dynamic range for
specified accuracy
DR
EMOD
(5)
6
Input-referred variation
due to modulation
V
41.8
43.9
46
–37.4
–37
–36.7
±1-dB Log conformance error (ELC)
38
±1-dB Log conformance error (ELC)
Limits apply at temperature extremes.
37
±3-dB Log conformance error (ELC)
45
±3-dB Log conformance error (ELC)
Limits apply at temperature extremes.
44
±0.5-dB Input referred variation over temperature
(EVOT), from PMIN
Limits apply at temperature extremes.
44
±0.3-dB Error for a 1dB Step (E1dB STEP)
41
±0.3-dB Error for a 1dB Step (E1dB STEP)
Limits apply at temperature extremes.
38
±1-dB Error for a 10dB Step (E10dB 30 STEP)
Limits apply at temperature extremes.
32
W-CDMA Release 6/7/8,
–38 dBm < RFIN < –5 dBm
0.08
LTE, –38 dBm < RFIN < –5 dBm
0.19
mV/dB
dBm
dB
dB
All limits are specified by design and measurements which are performed on a limited number of samples. Limits represent the mean
±3–sigma values. The typical value represents the statistical mean value.
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2.7-V and 4.5-V DC and AC Electrical Characteristics (continued)
Unless otherwise specified: all limits are ensured to TA = 25°C, VBAT = 2.7 V and 4.5 V (worst of the 2 is specified),
RFIN = 1900 MHz CW (Continuous Wave, unmodulated).(1)
PARAMETER
TEST CONDITIONS
MIN (2)
TYP (3)
MAX (2)
UNIT
RF DETECTOR TRANSFER
RFIN = 1900 MHz (fit range –20 dBm to –10 dBm) (5)
PMIN
Minimum power level,
bottom end of dynamic
range
Log conformance error within ±1 dB
–36
dBm
PMAX
Maximum power level,
Log conformance error within ±1 dB
top end of dynamic range
0
dBm
VMIN
Minimum output voltage
At PMIN
3
mV
VMAX
maximum output voltage
At PMAX
1.5
KSLOPE
Logarithmic slope
PINT
Logarithmic Intercept
DR
EMOD
Dynamic range for
specified accuracy
Input-referred variation
due to modulation
V
41.8
43.9
46.1
mV/dB
–35.5
–35.1
–34.7
dBm
±1-dB Log conformance error (ELC)
Limits apply at temperature extremes.
36
±3-dB Log conformance Error (ELC)
45
±3-dB Log conformance error (ELC)
Limits apply at temperature extremes.
43
±0.5-dB Input referred variation over temperature
(EVOT), from PMIN
Limits apply at temperature extremes.
41
±0.3-dB error for a 1-dB Step (E1dB STEP)
40
±0.3-dB error for a 1-dB Step (E1dB STEP)
Limits apply at temperature extremes.
38
±1-dB error for a 10-dB Step (E10-dB 30 STEP)
Limits apply at temperature extremes.
30
W-CDMA Release 6/7/8,
–38 dBm < RFIN < –5 dBm
0.09
LTE, –38 dBm < RFIN < –5 dBm
0.18
dB
dB
RFIN = 3500 MHz, fit range –15 dBm to –5 dBm (5)
PMIN
Minimum power level,
bottom end of dynamic
range
Log conformance error within ±1 dB
–31
dBm
PMAX
Maximum power level,
Log conformance error within ±1 dB
top end of dynamic range
6
dBm
VMIN
Minimum output voltage
At PMIN
2
mV
VMAX
Maximum output voltage
At PMAX
1.52
KSLOPE
Logarithmic slope
PINT
Logarithmic Intercept
DR
Dynamic range for
specified accuracy
V
41.8
44
46.1
mV/dB
–30.5
–29.7
–28.8
dBm
±1-dB Log conformance error (ELC)
37
±1-dB Log conformance error (ELC)
Limits apply at temperature extremes.
36
±3-dB Log conformance error (ELC)
44
±3-dB Log conformance error (ELC)
Limits apply at temperature extremes.
42
±0.5-dB Input referred variation over temperature
(EVOT), from PMIN
Limits apply at temperature extremes.
39
dB
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2.7-V and 4.5-V DC and AC Electrical Characteristics (continued)
Unless otherwise specified: all limits are ensured to TA = 25°C, VBAT = 2.7 V and 4.5 V (worst of the 2 is specified),
RFIN = 1900 MHz CW (Continuous Wave, unmodulated).(1)
PARAMETER
MIN (2)
TEST CONDITIONS
RFIN = 5800 MHz, fit range –20 dBm to 3 dBm
TYP (3)
MAX (2)
UNIT
(5)
PMIN
Minimum power level,
bottom end of dynamic
range
Log conformance error within ±1 dB
–22
dBm
PMAX
Maximum power level,
Log conformance error within ±1 dB
top end of dynamic range
10
dBm
VMIN
Minimum output voltage
At PMIN
3
mV
VMAX
Maximum output voltage
At PMAX
KSLOPE
Logarithmic slope
PINT
Logarithmic Intercept
DR
Dynamic range for
specified accuracy
1.34
V
42.5
44.8
47.1
mV/dB
–22
–21
–19.9
dBm
±1-dB Log conformance error (ELC)
32
±1-dB Log conformance error (ELC)
Limits apply at temperature extremes.
31
±3-dB Log conformance error (ELC)
39
±3-dB Log conformance error (ELC)
Limits apply at temperature extremes.
37
±0.5-dB Input referred variation over temperature
(EVOT), from PMIN
Limits apply at temperature extremes.
33
dB
6.6 Timing Requirements
NOM
MAX
tON
Turnon time from shutdown
RFIN = –10 dBm, 1900 MHz, EN LOW-HIGH transition to OUT at 90%
MIN
UNIT
15
19
tR
Rise time (1)
Signal at RFIN from –20 dBm to 0 dBm, 10% to 90%, 1900 MHz
2.2
µs
31
µs
µs
(1)
tF
(1)
8
Fall time
Signal at RFIN from 0 dBm to –20 dBm, 90% to 10%, 1900 MHz
This parameter is specified by design and/or characterization and is not tested in production.
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6.7 Typical Characteristics
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
7
8
EN = HIGH
SUPPLY CURRENT (éA)
SUPPLY CURRENT (mA)
EN = LOW
5
4
3
-40°C
25°C
85°C
2
6
5
25°C
4
3
-40°C
2
1
1
0
0
1
2
3
4
5
0
0
6
1
SUPPLY VOLTAGE (V)
3
4
5
6
Figure 2. Supply Current vs. Supply Voltage (Shutdown)
8
7
7
SUPPLY CURRENT (mA)
6
SUPPLY CURRENT (mA)
2
SUPPLY VOLTAGE (V)
Figure 1. Supply Current vs. Supply Voltage (Active)
5
4
85°C
3
25°C
2
-40°C
1
6
5
4
3
-40°C
2
85°C
25°C
1
0
0.5
0.6
0.7
0.8
0.9
1.0
1.1
0
-40
1.2
-30
ENABLE VOLTAGE (V)
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 3. Supply Current vs. Enable Voltage (EN)
Figure 4. Supply Current vs. RF Input Power
60
60
-40°C
50
40
-40°C
25°C
30
85°C
20
10
0
-40
OUT = 0V
RFin = 1900 MHz
-30
-20
-10
0
SINKING OUTPUT CURRENT (mA)
SOURCING OUTPUT CURRENT (mA)
85°C
7
6
25°C
50
40
30
85°C
20
10
OUT = 2.5V
RFin = 1900 MHz
0
-40
10
RF INPUT POWER (dBm)
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 5. Sourcing Output Current vs. RF Input Power
Figure 6. Sinking Output Current vs. RF Input Power
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
100
70
75
100
50
75
50
25
25
0
-25
-25
-50
60
50
PSRR (dB)
RF INPUT IMPEDANCE (Ö)
R
40
30
X
-75
-50
-100
20
10
-75
MEASURED ON BUMP
-100
10M
100M
1G
0
10
10G
100
1k
FREQUENCY (Hz)
10k
100k
FREQUENCY (Hz)
Figure 7. RF Input Impedance vs. Frequency,
Resistance (R) and Reactance (X)
Figure 8. Power Supply Rejection Ratio vs. Frequency
48
LOG SLOPE (mV/dB)
46
-40°C
44
85°C
42
25°C
40
38
10M
100M
1G
10G
FREQUENCY (Hz)
Figure 9. Output Voltage Noise vs. Frequency
Figure 10. Log Slope vs. Frequency
25°C
1.6
-28
85°C
-32
1
0
1.2
ERROR (dB)
-40°C
VOUT (V)
LOG INTERCEPT (dBm)
2
2.0
-24
-1
0.8
85°C
25°C
-36
-40
10M
100M
-40°C
1G
-2
0.4
10G
0.0
-40
FREQUENCY (Hz)
-3
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 11. Log Intercept vs. Frequency
10
3
2.4
-20
Figure 12. Output Voltage and Log Conformance Error vs.
RF Input Power at 50 MHz
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
2.0
3
1.5
2
-40°C
1.0
-40°C
ERROR (dB)
0
0.5
0.0
-0.5
-1
85°C
-2
-3
-40
85°C
-1.0
-1.5
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
10
-40°C
2.4
3
2.0
2
1.0
ERROR (dB)
0
RF INPUT POWER (dBm)
2.0
-40°C
25°C
1.6
VOUT (V)
0.5
0.0
-0.5
1
0
1.2
-1
0.8
-1.0
85°C
85°C
-30
-20
-2
0.4
-1.5
-2.0
-40
-10
Figure 14. Temperature Variation vs.
RF Input Power at 50 MHz
Figure 13. Log Conformance Error (50 Units) vs.
RF Input Power at 50 MHz
1.5
-20
ERROR (dB)
ERROR (dB)
1
-10
0
0.0
-40
10
RF INPUT POWER (dBm)
-3
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 15. Temperature Variation (50 Units) vs.
RF Input Power at 50 MHz
Figure 16. Output Voltage and Log Conformance Error vs.
RF Input Power at 900 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
-2
-3
-40
85°C
-1.0
85°C
-1.5
-30
-20
-10
0
10
RF INPUT POWER (dBm)
-2.0
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 17. Log Conformance Error (50 Units) vs.
RF Input Power at 900 MHz
Figure 18. Temperature Variation vs.
RF Input Power at 900 MHz
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
2.0
2.0
1.5
1.5
-40°C
85°C
ERROR (dB)
ERROR (dB)
25°C
1.0
1.0
0.5
0.0
-0.5
0.5
0.0
-0.5
-40°C
-1.0
-1.0
85°C
-1.5
-1.5
-2.0
-40
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 20. 1-dB Power Step Error vs.
RF Input Power at 900 MHz
Figure 19. Temperature Variation (50 Units) vs.
RF Input Power at 900 MHz
1.5
2.0
1.5
1.0
85°C
0.5
ERROR (dB)
ERROR (dB)
1.0
0.5
0.0
-0.5
W-CDMA, REL8
0.0
W-CDMA, REL6
-0.5
-40°C
W-CDMA, REL7
-1.0
-1.0
-1.5
-5
-1.5
-40
0
-30
RF INPUT POWER (dBm)
-10
0
10
Figure 22. W-CDMA Variation vs.
RF Input Power at 900 MHz
Figure 21. 10 dB Power Step Error vs.
RF Input Power at 900 MHz
1.5
3
2.4
20MHz, 100RB
1.0
2
2.0
-40°C
0.5
LTE, QPSK
0.0
-0.5
1.6
VOUT (V)
ERROR (dB)
-20
RF INPUT POWER (dBm)
25°C
1
0
1.2
-1
0.8
LTE, 16QAM
ERROR (dB)
-2.0
-40 -35 -30 -25 -20 -15 -10
85°C
-1.0
-2
0.4
LTE, 64QAM
-1.5
-40
-30
-20
-10
0
10
0.0
-40
RF INPUT POWER (dBm)
Figure 23. LTE Variation vs.
RF Input Power at 900 MHz
12
-3
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 24. Output Voltage and Log Conformance Error vs.
RF Input Power at 1900 MHz
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
2.0
3
1.5
2
1.0
ERROR (dB)
ERROR (dB)
-40°C
1
0
-40°C
0.5
0.0
-0.5
-1
85°C
-1.0
85°C
-2
-1.5
-3
-40
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
-10
10
2.0
2.0
1.5
1.5
-40°C
25°C
1.0
1.0
ERROR (dB)
85°C
0.5
0.0
-0.5
0.5
0.0
-0.5
-40°C
-1.0
-1.0
85°C
-1.5
-1.5
-2.0
-40
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 28. 1-dB Power Step Error vs.
RF Input Power at 1900 MHz
Figure 27. Temperature Variation (50 Units) vs.
RF Input Power at 1900 MHz
1.5
2.0
1.5
1.0
1.0
W-CDMA, REL8
85°C
ERROR (dB)
ERROR (dB)
0
Figure 26. Temperature Variation vs.
RF Input Power at 1900 MHz
Figure 25. Log Conformance Error (50 Units) vs.
RF Input Power at 1900 MHz
ERROR (dB)
-20
RF INPUT POWER (dBm)
0.5
0.0
-0.5
0.5
0.0
W-CDMA, REL6
-0.5
-40°C
-1.0
W-CDMA, REL7
-1.0
-1.5
-2.0
-40 -35 -30 -25 -20 -15 -10
-5
-1.5
-40
0
RF INPUT POWER (dBm)
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 29. 10-dB Power Step Error vs.
RF Input Power at 1900 MHz
Figure 30. W-CDMA Variation vs.
RF Input Power at 1900 MHz
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
1.5
20MHz, 100RB
1.0
2.4
3
2.0
2
-40°C
0.0
1.6
1
25°C
0
1.2
-0.5
-1
0.8
LTE, 16QAM
ERROR (dB)
LTE, QPSK
VOUT (V)
ERROR (dB)
0.5
85°C
-1.0
-2
0.4
LTE, 64QAM
-1.5
-40
-30
-20
-10
0
-3
0.0
-40
10
-30
RF INPUT POWER (dBm)
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 31. LTE Input referred Variation vs.
RF Input Power at 1900 MHz
Figure 32. Output Voltage and Log Conformance Error vs.
RF Input Power at 3500 MHz
2.0
3
1.5
2
1.0
ERROR (dB)
0
-40°C
0.5
0.0
-0.5
-1
-2
-3
-40
85°C
-1.0
85°C
-1.5
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
-20
0
10
RF INPUT POWER (dBm)
Figure 34. Temperature Variation vs.
RF Input Power at 3500 MHz
Figure 33. Log Conformance Error (50 Units) vs.
RF Input Power at 3500 MHz
2.0
1.5
-40°C
2.4
3
2.0
2
1.0
-40°C
0.5
VOUT (V)
ERROR (dB)
-10
0.0
-0.5
25°C
1.6
1
1.2
0
0.8
-1
ERROR (dB)
ERROR (dB)
-40°C
1
-1.0
85°C
0.4
-1.5
-2.0
-40
-30
-20
-10
0
10
0.0
-40
RF INPUT POWER (dBm)
-3
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 35. Temperature Variation (50 Units) vs.
RF Input Power at 3500 MHz
14
-2
85°C
Figure 36. Output Voltage and Log Conformance Error vs.
RF Input Power at 5800 MHz
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Typical Characteristics (continued)
Unless otherwise specified: TA = 25°C, VBAT = 2.7 V, RFIN = 1900 MHz CW (Continuous Wave, unmodulated). Specified
errors are input referred.
2.0
3
1.5
-40°C
-40°C
1.0
1
ERROR (dB)
0
0.5
0.0
-0.5
-1
-1.0
85°C
-2
-3
-40
85°C
-1.5
-30
-20
-10
0
-2.0
-40
10
-30
RF INPUT POWER (dBm)
-40°C
3
2.0
2
-40°C
0.5
VOUT (V)
ERROR (dB)
10
2.4
1.0
0.0
-0.5
25°C
1.6
1
1.2
0
0.8
-1
-1.0
-2.0
-40
0
RF INPUT POWER (dBm)
2.0
-1.5
-10
Figure 38. Temperature Variation vs.
RF Input Power at 5800 MHz
Figure 37. Log Conformance Error (50 Units) vs.
RF Input Power at 5800 MHz
1.5
-20
85°C
-2
0.4
85°C
-30
-20
-10
0
RF INPUT POWER (dBm)
-3
0.0
-40
10
ERROR (dB)
ERROR (dB)
2
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 39. Temperature Variation (50 Units) vs.
RF Input Power at 5800 MHz
Figure 40. Output Voltage and Log Conformance Error vs.
RF Input Power at 8000 MHz
2.0
1.5
ERROR (dB)
1.0
-40°C
0.5
0.0
-0.5
-1.0
85°C
-1.5
-2.0
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 41. Temperature Variation vs.
RF Input Power at 8000 MHz
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7 Detailed Description
7.1 Overview
The LMH2110 is a high-performance logarithmic root mean square (RMS) power detector which measures the
actual power content of a signal. The device has a RF input power detection range from –40 dBm to 5 dBm and
provides accurate output voltage that relates linearly to the RF input power in dBm. This output voltage exhibits
high temperature insensitivity ranging ±0.25 dB.
The device has an internal low dropout linear regulator (LDO) making the device insensitive to input supply
variation and allowing operation from a wide input supply range from 2.7 V to 5 V. Additional features include
multi-band operation from 50 MHz to 8 GHz, shutdown functionality to save power, and minimal slope and
intercept variation.
7.2 Functional Block Diagram
A1
VDD
LDO
EXP
V/I
B1
Internal
Supply
RFIN
OUT
A2
A
C2
EN
EXP
V/I
GND
B2,
C1
7.3 Feature Description
7.3.1 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 the ideal power measurement and how a
power measurement is implemented.
Power is a metric for the average energy content of a signal. 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.
16
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Feature Description (continued)
The average power can be described by Equation 1:
1
P=
T
T
³0
2
VRMS
v(t)
dt =
R
R
2
where
•
•
•
•
T is the time interval over which is averaged
v(t) is the instantaneous voltage at time t
R is the resistance in which the power is dissipated
VRMS is the equivalent RMS voltage
(1)
According to aforementioned formula for power, an exact power measurement can be done via measuring the
RMS voltage (VRMS) of a signal. The RMS voltage is described by:
VRMS =
2
1
v(t) dt
T³
(2)
Implementing the exact formula for RMS can be challenging. A simplification can be made in determining the
average power when information about the waveform is available. If the signal shape is known, the relationship
between RMS value and, for instance, the peak value of the RF signal is also known. It thus enables a
measurement based on measuring peak voltage rather than measuring the RMS voltage. To calculate the RMS
value (and therewith the average power), the measured peak voltage is translated into an RMS voltage based on
the waveform characteristics. A few examples:
• Sine wave: VRMS = VPEAK / √2
• Square wave: VRMS = VPEAK
• Saw-tooth wave: VRMS = VPEAK / √3
For more complex waveforms it is not always easy to determine the exact relationship between RMS value and
peak value. A peak measurement can then become impractical. An approximation can be used for the VRMS to
VPEAK relationship but it can result in a less-accurate average power estimate.
Depending on the detection mechanism, power detectors may produce a slightly different output signal in
response to more complex waveforms, even though the average power level of these signals are the same. This
error is due to the fact that not all power detectors strictly implement the definition for signal power, being the
RMS of the signal. To cover for the systematic error in the output response of a detector, calibration can be
used. After calibration a look-up table corrects for the error. Multiple look-up tables can be created for different
modulation schemes.
7.3.2 Types of RF Detectors
The following is an overview of detectors based on their detection principle. Detectors discussed in detail are:
• Peak Detectors
• LOG Amp Detectors
• RMS Detectors
7.3.2.1 Peak Detectors
A peak detector is one of the simplest types of detectors. According to the naming, the peak detector stores the
highest value arising in a certain time window. However, usually a peak detector is used with a relative long
holding time when compared to the carrier frequency and a relative short holding time with respect to the
envelope frequency. In this way a peak detector is used as AM demodulator or envelope tracker (Figure 42).
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Feature Description (continued)
PEAK
ENVELOPE
CARRIER
Figure 42. Peak Detection vs. Envelope Tracking
A peak detector usually has a linear response. An example of this is a diode detector (Figure 43). The diode
rectifies the RF input voltage and 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. A
configuration with a relatively large time constant can be used for supply regulation of the power amplifier (PA).
Controlling the supply voltage of the PA can reduce power consumption significantly. The optimal mode of
operation is to set the supply voltage such that it is just above the maximum output voltage of the PA. A diode
detector with relative large RC time constant measures this maximum (peak) voltage.
Z0
D
VREF
C
R
VOUT
Figure 43. Diode Detector
Because peak detectors measure a peak voltage, their response is inherently depended on the signal shape or
modulation form as discussed in the previous section. Knowledge about the signal shape is required to
determine an RMS value. For complex systems having various modulation schemes, the amount of calibration
and look-up tables can become unmanageable.
7.3.2.2 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 has a linear-in-dB response, which means that the output in volts changes
linearly with the RF power in dBm. This is convenient because 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.
7.3.2.3 RMS Detectors
An RMS detector has a response that is insensitive to the signal shape and modulation form. This is because its
operation is based on exact determination of the average power, that is, it implements:
VRMS =
18
2
1
v(t) dt
T³
(3)
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Feature Description (continued)
RMS detectors are in particular suited for the 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 baseband due to different applied modulation schemes.
7.3.3 LMH2110 RF Power Detector
For optimal performance of the LMH2110, the device must to be configured correctly in the application (see
Functional Block Diagram).
For measuring the RMS (power) level of a signal, the time average of the squared signal needs to be measured
as described in Accurate Power Measurement. This is implemented in the LMH2110 by means of a multiplier and
a low-pass filter in a negative-feedback loop. A simplified block diagram of the LMH2110 is depicted in Functional
Block Diagram. 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
(4)
where
•
•
iLF is a current depending on the DC output voltage of the RF detector, and
iRF is a current depending on the RF input signal.
(5)
The output of the multiplier (iOUT) is the product of these two current and equals:
2
2
iout =
iLF iRF
I0
where
•
I0 is a normalizing current.
(6)
By a low-pass filter at the output of the multiplier the DC term of this current is isolated and integrated. The input
of the amplifier A acts as the nulling point of the negative feedback loop, yielding:
³ iLF dt = ³ iRF dt
2
2
(7)
which implies that the average power content of the current related to the output voltage of the LMH2110 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 logarithmic transfer for this RF detector, the feedback network implements an exponential
function resulting in an overall transfer function for the LMH2110 of:
§ 1 V 2dt ·
³ RF ¸
© Vx
¹
Vout = V0 log ¨
where
•
V0 and VX are normalizing voltages.
(8)
As a result of the feedback loop a square-root is also implemented, yielding the RMS function.
Given this architecture for the RF detector, the high-performance of the LMH2110 can be understood. In theory
the accuracy of the logarithmic transfer is set by:
• The exponential feedback network, which basically needs to process a DC signal only.
• A high loop gain for the feedback loop, which is specified by the amplifier gain A.
The RMS functionality is inherent to the feedback loop and the use of a multiplier; thus, a very accurate LOGRMS RF power detector is obtained.
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Feature Description (continued)
To ensure a low dependency on the supply voltage, the internal detector circuitry is supplied via a low drop-out
(LDO) regulator. This enables the usage of a wide range of supply voltage (2.7 V to 5 V) in combination with a
low sensitivity of the output signal for the external supply voltage.
7.3.3.1 RF Input
Refer to Application With Resistive Divider for more details and applications.
7.3.3.2 Enable
To save power, the LMH2110 can be brought into a low-power shutdown mode by means of the enable pin (EN).
The device is active for EN = HIGH (VEN>1.1 V) and in the low-power shutdown mode for EN = LOW
(VEN < 0.6 V). In this state the output of the LMH2110 is switched to a high impedance mode. This high
impedance mode prevents the discharge of the optional low-pass filter which is good for the power efficiency.
Using the shutdown function, care must be taken not to exceed the absolute maximum ratings. Because the
device has an internal operating voltage of 2.5 V, the voltage level on the enable must not be higher than 3 V to
prevent damage to the device. Also enable voltage levels lower than 400 mV below GND must be prevented. In
both cases the ESD devices start to conduct when the enable voltage range is exceeded, and excessive current
is drawn. A correct operation is not ensured then. The absolute maximum ratings are also exceeded when the
enable (EN) is switched to HIGH (from shutdown to active mode) while the supply voltage is switched off. This
situation must be prevented at all times. A possible solution to protect the device is to add a resistor of 1 kΩ in
series with the enable input to limit the current.
7.3.3.3 Output
Refer to Application With Low-Pass Output Filter for Residual Ripple Reduction for more details and applications.
7.3.3.4 Supply
The LMH2110 has an internal LDO to handle supply voltages between 2.7 V to 5 V. This enables a direct
connection to the battery in cell-phone applications. The high PSRR of the LMH2110 ensures that the
performance is constant over its power supply range.
7.4 Device Functional Modes
To save power, the LMH2120 has an Enable/Disable feature that can bring the device in low-power shutdown
mode. For implementation details, refer to Enable.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers must
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LMH2110 is a 45-dB Logarithmic RMS power detector particularly suited for accurate power measurements
of modulated RF signals that exhibit large peak-to-average ratios (PARs). The RMS detector implements the
exact definition of power resulting in a power measurement insensitive to high PARs. Such signals are
encountered, for exampe, in LTE and W-CDMA applications. The LMH2110 has an RF frequency range from
50 MHz to 8 GHz. It provides an output voltage that relates linearly to the RF input power in dBm. Its output
voltage is highly insensitive to temperature and supply variations.
8.2 Typical Applications
8.2.1 Application With Transmit Power Control
The LMH2110 can be used in a wide variety of applications such as LTE, W-CDMA, CDMA, and GSM. Transmitpower-control-loop circuits make the transmit power level insensitive to 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 LMH2110 is especially suited for transmit power control applications, because it accurately
measures transmit power and is insensitive to temperature, supply voltage and modulation variations.
Figure 44 shows a simplified schematic of a typical transmit power control system. The output power of the PA is
measured by the LMH2110 through a directional coupler. The measured output voltage of the LMH2110 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. Although the output ripple of the LMH2110 is typically low
enough, an optional low-pass filter can be placed in between the LMH2110 and the ADC to further reduce the
ripple.
COUPLER
RF
PA
VGA
ANTENNA
B
A
S
E
B
A
N
D
50:
GAIN
VDD
OPTIONAL
RS
ADC
A2
CS
EN
A1
OUT
RFIN
B1
LMH2110
EN
C2
B2, C1
GND
Figure 44. Transmit Power Control System
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Typical Applications (continued)
8.2.1.1 Design Requirements
Some of the design requirements for this logarithmic RMS power detector include:
Table 1. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Supply voltage
2.7 V
RF input frequency (unmodulated continuous wave)
1900 MHz
Minimum power level
–36 dBm
Maximum power level
0 dBm
Maximum output voltage
1.5 V
8.2.1.2 Detailed Design Procedure
8.2.1.2.1 Specifying Detector Performance
The performance of the LMH2110 can be expressed by a variety of parameters.
8.2.1.2.1.1 Dynamic Range
The LMH2110 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:
• Log conformance error, ELC
• Variation over temperature error, EVOT
• 1-dB step error, E1 dB
• 10-dB step error, E10 dB
• Variation due to modulation, EMOD
The specified dynamic range is the range in which the specified error metric is within a predefined window. See
Log Conformance Error, Variation Over Temperature Error, Variation Over Temperature Error, 1-dB Step Error,
10-dB Step Error, and Variation Due to Modulation for an explanation of these errors.
8.2.1.2.1.2 Log Conformance Error
The LMH2110 implements a logarithmic function. In order to describe how close the transfer is to an ideal
logarithmic function the log conformance error is used. To calculate the log conformance error the detector
transfer function is modeled as a linear-in-dB relationship between the input power and the output voltage.
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The ideal linear-in-dB transfer is modeled by 2 parameters:
• Slope
• Intercept
and is described by Equation 9:
VOUT = KSLOPE (PIN – PINT)
where
•
•
•
KSLOPE is the slope of the line in mV/dB
PIN the input power level
PINT is the power level in dBm at which the line intercepts VOUT = 0 V (see Figure 45).
(9)
2.4
Ideal
LOG function
2.0
VOUT (V)
1.6
Detector
response
1.2
0.8
KSLOPE
PINT
0.4
0.0
-50
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 45. Ideal Logarithmic Response
To determine the log conformance error two steps are required:
1. Determine the best fitted line at 25°C.
2. Determine the difference between the actual data and the best fitted line.
The best fit can be determined by standard routines. A careful selection of the fit range is important. The fit range
must 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 line is determined. The log 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 log conformance error is calculated by Equation 10:
ELC =
VOUT KSLOPE 25qC (PIN PINT 25qC)
KSLOPE 25qC
where
•
•
VOUT is the measured output voltage at a power level at PIN at a temperature. KSLOPE 25°C (mV/dB).
PINT 25°C (dBm) are the parameters of the best fitted line of the 25°C transfer.
(10)
In Figure 46 both the error with respect to the ideal LOG 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 LMH2110 in Figure 46 shows a dynamic range of
36 dB for ELC = ±1 dB.
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2.4
3
2.0
2
VOUT (V)
25°C
1
ERROR (dB)
-40°C
1.6
1.2
0
0.8
-1
85°C
-2
0.4
-3
0.0
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 46. VOUT and ELC vs. RF input Power at 1900 MHz
8.2.1.2.1.3 Variation Over Temperature Error
In contrast to the log 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. Subsequently, it is translated into an input referred error by dividing it by KSLOPE at 25°C.
Variation over temperature is given by Equation 11:
EVOT = (VOUT_TEMP – VOUT 25°C) / KSLOPE 25°C
(11)
The variation over temperature is shown in Figure 47, where a dynamic range of 41 dB is obtained
(from PMIN = –36 dBm) for EVOT = ±0.5 dB.
2.0
1.5
ERROR (dB)
1.0
-40°C
0.5
0.0
-0.5
85°C
-1.0
-1.5
-2.0
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 47. EVOT vs. RF Input Power at 1900 MHz
8.2.1.2.1.4 1-dB Step Error
This parameter is a measure for the error for a 1-dB power step. According to a 3GPP specification, the error
must be less than ±0.3 dB. Often, this condition is used to define a useful dynamic range of the detector.
The 1-dB step error is calculated in 3 steps:
1. Determine the maximum sensitivity.
2. Determine average sensitivity.
3. Calculate the 1-dB step error.
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First the maximum sensitivity (SMAX) is calculated per temperature by determining the maximum difference
between two output voltages for a 1-dB step within the power range:
SMAX = VOUT P+1 – VOUT P
(12)
To calculate the 1-dB step error an average sensitivity (SAVG) is used which is the average of the maximum
sensitivity and an allowed minimum sensitivity (SMIN). The allowed minimum sensitivity is determined by the
application. In this datasheet SMIN = 30 mV/dB is used. Subsequently, the average sensitivity can be calculated
by:
SAVG = (SMAX + SMIN) / 2
(13)
The 1-dB error is than calculated by:
E1
dB
= (SACTUAL - SAVG) / SAVG
where
•
SACTUAL (actual sensitivity) is the difference between two output voltages for a 1-dB step at a given power
level.
(14)
Figure 48 shows the typical 1-dB step error at 1900 MHz, where a dynamic range of 38 dB over temperature is
obtained for E1dB = ±0.3 dB.
2.0
1.5
25°C
1.0
ERROR (dB)
85°C
0.5
0.0
-0.5
-40°C
-1.0
-1.5
-2.0
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 48. 1-dB Step Error vs. RF Input Power at 1900 MHz
8.2.1.2.1.5 10-dB Step Error
This error is defined in a different manner than the 1-dB step error. This parameter shows the input power error
over temperature when a 10-dB power step is made. The 10-dB step at 25°C is taken as a reference.
VOUT (V)
To determine the 10-dB step error, first the output voltage levels (V1 and V2) for power levels P and P+10 dB” at
the 25°C are determined (Figure 49). Subsequently these 2 output voltages are used to determine the
corresponding power levels at temperature T (PT and PT + X). The difference between those two power levels
minus 10 results in the 10-dB step error.
25°C response
V2
Temp (T)
response
V1
RFIN (dBm)
P
PT
P+10 dB
PT+X
Figure 49. Graphical Representation of 10-dB Step Calculations
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Figure 50 shows the typical 10-dB step error at 1900 MHz, where a dynamic range of 30 dB is obtained for
E10dB = ±1 dB.
2.0
1.5
ERROR (dB)
1.0
85°C
0.5
0.0
-0.5
-40°C
-1.0
-1.5
-2.0
-40 -35 -30 -25 -20 -15 -10
-5
0
RF INPUT POWER (dBm)
Figure 50. 10 dB Step Error vs. RF Input Power at 1900 MHz
8.2.1.2.1.6 Variation Due to Modulation
The response of an RF detector may vary due to different modulation schemes. How much it varies depends on
the modulation form and the type of detector. Modulation forms with high peak-to-average ratios (PAR) can
cause significant variation, especially with traditional RF detectors. This is because the measurement is not an
actual RMS measurement and is therefore waveform dependent.
To calculate the variation due to modulation (EMOD), the measurement result for an un-modulated RF carrier is
subtracted from the measurement result of a modulated RF carrier. The calculations are similar to those for
variation over temperature. The variation due to modulation can be calculated by:
EMOD = (VOUT_MOD – VOUT_CW) / KSLOPE
where
•
•
VOUT_MOD is the measured output voltage for an applied power level of a modulated signal.
VOUT_CW is the output voltage as a result of an applied un-modulated signal having the same power level.
(15)
Figure 51 shows the variation due to modulation for W-CDMA, where a EMOD of 0.09 dB in obtained for a
dynamic range from –38 dBm to –5 dBm.
1.5
1.0
ERROR (dB)
W-CDMA, REL8
0.5
0.0
-0.5
W-CDMA, REL6
W-CDMA, REL7
-1.0
-1.5
-40
-30
-20
-10
0
10
RF INPUT POWER (dBm)
Figure 51. Variation Due to Modulation for W-CDMA
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8.2.1.3 Application Curves
2.4
2.00
1.75
2.0
5.8 GHz
900 MHz
50 MHz
0.8
0.4
-30
-20
-10
0
1.25
1.00
RFIN = -10 dBm
RFIN = -15 dBm
0.75
RFIN = -20 dBm
0.50
RFIN = -25 dBm
0.25
8 GHz
0.0
-40
RFIN = 0 dBm
RFIN = -5 dBm
1.9 GHz
VOUT (V)
VOUT (V)
1.6
1.2
1.50
3.5 GHz
0.00
10M
10
100M
RF INPUT POWER (dBm)
1G
10G
FREQUENCY (Hz)
Figure 52. Output Voltage vs. RF Input Power
Figure 53. Output Voltage vs. Frequency
8.2.2 Application With Resistive Divider
RF systems typically use a characteristic impedance of 50 Ω. The LMH2110 is no exception to this. The RF input
pin of the LMH2110 has an input impedance of 50 Ω. It enables an easy, direct connection to a directional
coupler without the need for additional components (Figure 44). For an accurate power measurement the input
power range of the LMH2110 needs to be aligned with the output power range of the power amplifier. This can
be done by selecting a directional coupler with the correct coupling factor.
Because the LMH2110 has a constant input impedance, a resistive divider can also be used instead of a
directional coupler (Figure 54).
RF
ANTENNA
PA
R1
VDD
A1
RFIN
B1
A2
OUT
LMH2110
EN
ADC
C2
B2, C1
GND
Figure 54. Application With Resistive Divider
Resistor R1 implements an attenuator together with the detector input impedance to match the output range of
the PA to the input range of the LMH2110. The attenuation (AdB) realized by R1 and the effective input
impedance of the LMH2110 equals:
R1 º
ª
AdB = 20LOG «1 +
»
RIN ¼
¬
(16)
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Solving Equation 16 for R1 yields:
A
ª dB º
20
R1 = «¬10
- 1»¼ RIN
(17)
Suppose the desired attenuation is 30 dB with a given LMH2110 input impedance of 50 Ω, the resistor R1 needs
to be 1531 Ω. A practical value is 1.5 kΩ. Although this is a cheaper solution than the application with directional
coupler, it also comes with a disadvantage. After calculating the resistor value it is possible that the realized
attenuation is less then expected. This is because of the parasitic capacitance of resistor R1 which results in a
lower actual realized attenuation. Whether the attenuation is reduced depends on the frequency of the RF signal
and the parasitic capacitance of resistor R1. Because 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 R1 is to realize it as a series connection of several separate resistors.
8.2.3 Application With Low-Pass Output Filter for Residual Ripple Reduction
The output of the LMH2110 provides a DC voltage that is a measure for the applied RF power to the input pin.
The output voltage has a linear-in-dB response for an applied RF signal.
RF power detectors can have some residual ripple on the output due to the modulation of the applied RF signal.
The residual ripple on the output of the LMH2110 device is small though and, therefore, additional filtering is
usually not needed. This is because its internal averaging mechanism reduces the ripple significantly. For some
modulation types however, having very high peak-to-average ratios, additional filtering might be useful.
Filtering can be applied by an external low-pass filter. Filtering reduces not only the ripple, but also increases the
response time. In other words, it takes longer before the output reaches its final value. A trade-off must be made
between allowed ripple and allowed response time. The filtering technique is depicted in Figure 55. The filtering
of the low pass output filter is realized by resistor RS and capacitor CS. The –3-dB bandwidth of this filter can be
calculated by:
f−3
dB
= 1 / (2πRSCS)
(18)
VDD
RFIN
B1
A1
A2
OUT
LMH2110
EN
RS
+
CS
C2
B2,C1
ADC
GND
Figure 55. Low-Pass Output Filter for Residual Ripple Reduction
The output impedance of the LMH2110 is HIGH in shutdown. This is especially beneficial in pulsed mode
systems. It ensures a fast settling time when the device returns from shutdown into active mode and reduces
power consumption.
In pulse mode systems, the device is active only during a fraction of the time. During the remaining time the
device is in low-power shutdown. Pulsed mode system applications usually require that the output value is
available at all times. This can be realized by a capacitor connected between the output and GND that “stores”
the output voltage level. To apply this principle, capacitor discharging must be minimized in shutdown mode. The
connected ADC input must therefore have a high input impedance to prevent a possible discharge path through
the ADC. When an additional filter is applied at the output, the capacitor of the RC-filter can be used to store the
output value. An LMH2110 with a high impedance shutdown mode saves power in pulse mode systems. This is
because the capacitor CS does not need to be fully re-charged each cycle.
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9 Power Supply Recommendations
The LMH2110 is designed to operate from an input voltage supply range between 2.7 V to 5 V. This input
voltage must be well regulated. Enable voltage levels lower than 400 mV below GND could lead to incorrect
operation of the device. Also, the resistance of the input supply rail must be low enough to ensure correct
operation of the device.
10 Layout
10.1 Layout Guidelines
As with any other RF device, pay close careful attention to the board layout. If the board layout is not properly
designed, performance might be less then can be expected for the application.
The LMH2110 is designed to be used in RF applications, having a characteristic impedance of 50 Ω. To achieve
this impedance, the input of the LMH2110 needs to be connected via a 50-Ω 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 LMH2110 through the supply lines, the PCB traces for
VDD and GND must be minimized for RF signals. This can be done by placing a small decoupling capacitor
between the VDD and GND. It must be placed as close as possible to the VDD and GND pins of the LMH2110.
10.2 Layout Example
Figure 56. LMH2110 Layout
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11 Device and Documentation Support
11.1 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.2 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
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.
11.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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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)
Device Marking
(3)
(4/5)
(6)
LMH2110TM/NOPB
ACTIVE
DSBGA
YFQ
6
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
P
LMH2110TMX/NOPB
ACTIVE
DSBGA
YFQ
6
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
P
(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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