LT5581
6GHz RMS Power Detector
with 40dB Dynamic Range
FEATURES
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DESCRIPTION
The LT
®
5581 is a 10MHz to 6GHz, low power monolithic
precision RMS power detector. The RMS detector uses
a proprietary technique to accurately measure the RF
power from –34dBm to +6dBm (at 2.14GHz) of modulated
signals with a crest factor as high as 12dB. It outputs a DC
voltage in linear scale proportional to an RF input signal
power in dBm. The LT5581 is suitable for precision power
measurement and control for a wide variety of RF standards,
including GSM/EDGE, CDMA, CDMA2000, W-CDMA, TD-
SCDMA, UMTS, LTE and WiMAX, etc. The final DC output
is connected in series with an on-chip 300Ω resistor, which
enables further filtering of the output modulation ripple
with just a single off-chip capacitor.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 7342431.
Frequency Range: 10MHz to 6GHz
Accurate Power Measurement of High Crest Factor
(Up to 12dB) Waveforms
40dB Log Linear Dynamic Range
Exceptional Accuracy Over Temperature
Fast Response Time: 1μs Rise, 8μs Fall
Low Power: 1.4mA at 3.3V
Log-Linear DC Output vs Input RF Power in dBm
Small 3mm
×
2mm 8-Pin DFN Package
Single-Ended RF Input
APPLICATIONS
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GSM/EDGE, CMDA, CDMA2000, W-CDMA, LTE,
WiMAX RF Power Control
Pico-Cells, Femto-Cells RF Power Control
Wireless Repeaters
CATV/DVB Transmitters
MIMO Wireless Access Points
Portable RMS Power Measurement Instrumentation
TYPICAL APPLICATION
10MHz to 6GHz Infrastructure Power
Amplifier Level Control
RF
IN
POWER
AMP
V
CC
2.7V
DC
TO 5.25V
DC
0.1μF
DIGITAL
POWER
CONTROL
1
2
ADC
C
FILT
0.01μF
3
4
V
CC
EN
V
OUT
GND
GND
9
5581 TA01a
Linearity Error vs RF Input Power,
2140MHz Modulated Waveforms
DIRECTIONAL
COUPLER
RF
OUT
2
LINEARITY ERROR (dB)
C
MATCH
1
0
–1
–2
CW
WCDMA, UL
WCDMA DL 1C
WCDMA DL 4C
LTE DL 1C
LTE DL 4C
3
T
A
= 25°C
LT5581
0.01μF
8
C
SQ
1000pF
7
RF
IN
GND
GND
6
5
L
MATCH
50Ω
68Ω
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 TA01b
5581f
1
LT5581
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
V
CC
1
EN 2
V
OUT
3
GND 4
9
8
7
6
5
C
SQ
RF
IN
GND
GND
Supply Voltage .........................................................5.5V
Maximum Input Signal Power—Average .............15dBm
Maximum Input Signal Power—Peak (Note 7) ....25dBm
DC Voltage at RF
IN
....................................... –0.3V to 2V
V
OUT
Voltage ....................................–0.3V to V
CC
+ 0.3V
Maximum Junction Temperature, T
JMAX
............... 150°C
Operating Temperature Range.................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
CAUTION: This part is sensitive to electrostatic discharge. It
is very important that proper ESD precautions be observed
when handling the LT5581.
DDB PACKAGE
8-LEAD (3mm 2mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT5581IDDB#PBF
TAPE AND REEL
LT5581IDDB#TRPBF
PART MARKING
LDKM
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
PARAMETER
AC Input
Input Frequency Range (Note 4)
Input Impedance
f
RF
= 450MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Linear Dynamic Range, CDMA (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Output Variation vs Temperature
Deviation from CW Response;
P
IN
= –34dBm to 0dBm
Normalized to Output at 25˚C, –40°C < T
A
< 85°C;
P
IN
= –34 to +6dBm
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –27 to –10dBm
TETRA π/4 DQPSK
CDMA 4-Carrier 64-Channel Fwd 1.23Mcps
Externally Matched to 50Ω Source
±1dB Linearity Error
±1dB Linearity Error; CDMA 4-Carrier
–34 to 6
40
40
31
–42
±1
±0.5
±0.1
±0.5
dBm
dB
dB
mV/dB
dBm
dB
dB
dB
dB
5581f
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
10-6000
205||1.6
MAX
UNITS
MHz
Ω||pF
2
LT5581
ELECTRICAL CHARACTERISTICS
PARAMETER
2nd Order Harmonic Distortion
3rd Order Harmonic Distortion
f
RF
= 880MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Linear Dynamic Range, EDGE (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Output Variation vs Temperature
Deviation from CW Response, Pin = –34 to +6dBm
f
RF
= 2140MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Linear Dynamic Range, WCDMA (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Output Variation vs Temperature
Maximum Deviation from CW Response
P
IN
= –34 to –4dBm
f
RF
= 2600MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Output Variation vs Temperature
Maximum Deviation from CW Response
P
IN
= –34 to 2dBm
f
RF
= 3500MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –30 to +6dBm
Externally Matched to 50Ω Source
±1dB Linearity Error
–30 to 6
36
31
–41
±1
dBm
dB
mV/dB
dBm
dB
5581f
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
CONDITIONS
At RF Input; CW Input; P
IN
= 0dBm
At RF Input; CW Input; P
IN
= 0dBm
Externally Matched to 50Ω Source
±1dB Linearity Error
±1dB Linearity Error; EDGE 3π/8-Shifted 8PSK
MIN
TYP
–57
–52
–34 to 6
40
40
31
–42
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –34 to +6dBm
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –27 to –10dBm
EDGE 3π/8 Shifted 8PSK
Externally Matched to 50Ω Source
±1dB Linearity Error
±1dB Linearity Error; 4-Carrier WCDMA
±1
±0.5
±0.1
–34 to 6
43
37
31
–42
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –34 to 6dBm
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –27 to –10dBm
WCDMA 1-Carrier Uplink
WCDMA 64-Channel 4-Carrier Downlink
Externally Matched to 50Ω Source
±1dB Linearity Error
±1
±0.5
±0.1
±0.5
–34 to 6
40
31
–42
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –34 to +6dBm
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –27 to –10dBm
WiMAX OFDMA Preamble
WiMAX OFDM Burst
±1
±0.5
±0.1
±0.5
MAX
UNITS
dBc
dBc
dBm
dB
dB
mV/dB
dBm
dB
dB
dB
dBm
dB
dB
mV/dB
dBm
dB
dB
dB
dB
dBm
dB
mV/dB
dBm
dB
dB
dB
dB
3
LT5581
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Variation vs Temperature
Deviation from CW Response
P
IN
= –34 to –4dBm
f
RF
= 5800MHz
RF Input Power Range
Linear Dynamic Range, CW (Note 3)
Output Slope
Logarithmic Intercept (Note 5)
Output Variation vs Temperature
Output Variation vs Temperature
Deviation from CW Response
Output
Output DC Voltage
Output Impedance
Output Current Sourcing/Sinking
Rise Time
Fall Time
Power Supply Rejection Ratio (Note 6)
Integrated Output Voltage Noise
Enable (EN) Low = Off, High = On
EN Input High Voltage (On)
EN Input Low Voltage (Off)
Enable Pin Input Current
Turn-On Time; CW RF input
Settling Time; RF Pulse
Power Supply
Supply Voltage
Supply Current
Shutdown Current
No RF Input Signal
EN = 0.3V, V
CC
= 3.3V
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The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
CONDITIONS
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –27 to –10dBm
WiMAX OFDMA Preamble
WiMAX OFDM Burst
Externally Matched to 50Ω Source
±1dB Linearity Error
MIN
TYP
±0.5
±0.1
±0.5
–25 to 6
31
31
–33
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –25 to +6dBm
Normalized to Output at 25°C, –40°C < T
A
< 85°C;
P
IN
= –20 to +6dBm
WiMAX OFDM Burst; P
IN
= –25 to 6dBm
No Signal Applied to RF Input
Internal Series Resistor Allows for Off-Chip Filter Cap
0.2V to 1.6V, 10% to 90%, f
RF
= 2140MHz
1.6V to 0.2V, 10% to 90%, f
RF
= 2140MHz
For Over Operating Input Power Range
1kHz to 6.5kHz Integration BW, P
IN
= 0dBm CW
2
0.3
20
1
1
2.7
3.3
1.4
0.2
6
5.25
±1
±0.5
±0.2
180
300
5/5
1
8
49
150
MAX
UNITS
dB
dB
dB
dBm
dB
mV/dB
dBm
dB
dB
dB
mV
Ω
mA
μs
μs
dB
μV
RMS
V
V
μA
μs
μs
V
mA
μA
EN = 3.3V
V
OUT
Within 10% of Final Value; P
IN
= 0dBm
V
OUT
Within 10% of Final Value; P
IN
= 0dBm
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LT5581 is guaranteed to meet specified performance from
–40°C to 85°C.
Note 3:
The linearity error is calculated by the difference between the
incremental slope of the output and the average output slope from
–20dBm to 0dBm. The dynamic range is defined as the range over which
the linearity error is within ± 1dB.
Note 4:
An external capacitor at the C
SQ
pin should be used for input
frequencies below 250MHz. Lower frequency operation results in
excessive RF ripple in the output voltage.
Note 5:
Logarithmic intercept is an extrapolated input power level from the
best fitted log-linear straight line, where the output voltage is 0V.
Note 6:
PSRR is determined as the dB value of the change in V
OUT
voltage
over the change in V
CC
supply voltage.
Note 7:
Not production tested. Guaranteed by design and correlation to
production tested parameters.
5581f
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LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
EN = 3.3V and T
A
= 25°C, unless otherwise noted. (Test circuit shown in Figure 1)
Output Voltage vs Frequency
2.0
1.8
1.6
1.4
V
OUT
(V)
1.2
1.0
0.8
0.6
0.4
0.2
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
T
A
= 25°C
10MHz
450MHz
880MHz
2.14GHz
2.6GHz
3.5GHz
5.8GHz
2.0
1.8
1.6
1.4
V
OUT
(V)
1.2
1.0
0.8
0.6
0.4
0.2
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
Performance characteristics taken at V
CC
= 3.3V,
Output Voltage vs Frequency
T
A
= 25°C
880MHz
2.14GHz
2.6GHz
3.5GHz
3
2
LINEARITY ERROR (dB)
1
0
–1
–2
Linearity Error vs Frequency
T
A
= 25°C
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10MHz
450MHz
880MHz
2.14GHz
2.6GHz
3.5GHz
5.8GHz
5
10
5581 G01
5581 G02
5581 G03
Output Voltage and Linearity Error
at 450MHz
2.0
1.8
1.6
1.4
V
OUT
(V)
1.2
1.0
0.8
0.6
0.4
0.2
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
25°C
85°C
– 40°C
2.5
2.0
1.5
LINEARITY ERROR (dB)
VARIATION (dB)
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
10
2
1
0
–1
–2
3
Linearity Error Temperature
Variation from 25°C at 450MHz
3
2
85°C
LINEARITY ERROR(dB)
1
0
–1
–2
Linearity Error vs RF Input Power,
450MHz Modulated Waveforms
T
A
= 25°C
CW
TETRA
CDMA 4C
–40°C
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G04
5581 G05
5581 G06
Output Voltage and Linearity Error
at 880MHz
2.0
1.8
1.6
1.4
V
OUT
(V)
1.2
1.0
0.8
0.6
0.4
0.2
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
25°C
85°C
– 40°C
2.5
2.0
1.5
LINEARITY ERROR (dB)
VARIATION (dB)
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
10
2
1
0
–1
–2
3
Linearity Error Temperature
Variation from 25°C at 880MHz
3
2
85°C
LINEARITY ERROR(dB)
1
0
–1
–2
Linearity Error vs RF Input Power,
880MHz Modulated Waveforms
T
A
= 25°C
CW
EDGE
–40°C
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G07
5581 G08
5581 G09
5581f
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