LT5538
40MHz to 3.8GHz
RF Power Detector with
75dB Dynamic Range
FEATURES
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DESCRIPTION
The LT
®
5538 is a 40MHz to 3800MHz monolithic logarith-
mic RF power detector, capable of measuring RF signals
over a wide dynamic range, from –75dBm to 10dBm. The
RF signal in an equivalent decibel-scaled value is precisely
converted into DC voltage on a linear scale. The wide linear
dynamic range is achieved by measuring the RF signal us-
ing cascaded RF limiters and RF detectors. Their outputs
are summed to generate an accurate linear DC voltage
proportional to the input RF signal in dBm. The LT5538
delivers superior temperature stable output (within ±1dB
over full temperature range) from 40MHz to 3.8GHz. The
output is buffered with a low impedance driver.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Frequency Range: 40MHz to 3.8GHz
75dB Log Linear Dynamic Range
Exceptional Accuracy over Temperature
Linear DC Output vs. Input Power in dBm
–72dBm Detection Sensitivity
Single-ended RF Input
Low Supply Current: 29mA
Supply Voltage: 3V to 5.25V
8-lead DFN 3mm × 3mm package
APPLICATIONS
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Received Signal Strength Indication (RSSI)
RF Power Measurement and Control
RF/IF Power Detection
Receiver RF/IF Gain Control
Envelope Detection
ASK Receiver
TYPICAL APPLICATION
40MHz - 3.8GHz Logarithmic RF Detector
2.0
EN
RF
INPUT
56
1nF
1nF
LT5538
ENBL
IN
+
IN
–
GND
9
OUT
CAP
+
Output Voltage and Linearity Error
vs Input Power
V
CC
= 5V AT 880 MHz
3
2
LINEARITY ERROR (dB)
1
0
–1
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
–5
5
5538 TA02
V
OUT
1.7
1.4
V
OUT
(V)
5V
0.1μF
1.1
0.8
0.5
CAP
–
V
CC
5538 TA01
100pF
–2
–3
0.2
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
5538f
1
LT5538
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
ENBL 1
IN
+
2
IN
–
3
GND 4
8
7
6
5
OUT
CAP
+
CAP
–
V
CC
Power Supply Voltage ..............................................5.5V
Enable Voltage .....................................–0.3V, V
CC
+ 0.3V
RF Input Power ....................................................15dBm
Operating Ambient Temperature ............ –40°C to +85°C
Storage Temperature Range................. –65°C to +125°C
Maximum Junction Temperature........................... 150°C
DD PACKAGE
8-LEAD (3mm
×
3mm) PLASTIC DFN
θ
JA
= 43°C/W
EXPOSED PAD (PIN 9) SHOULD BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT5538IDD#PBF
TAPE AND REEL
LT5538IDD#TRPBF
PART MARKING
LCVG
PACKAGE DESCRIPTION
8-Lead (3mm × 3mm) 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/
ELECTRICAL CHARACTERISTICS
SYMBOL
RF Input
Input Frequency Range
DC Common Mode Voltage
Input Resistance
f
RF
= 40 MHZ
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
Sensitivity
Output Variation vs Temperature
PARAMETER
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, ENBL = 5V. (Note 2)
CONDITIONS
MIN
TYP
40 to 3800
V
CC
–0.5
394
–75 to 10
±1dB Linearity Error (Note 3)
(Note 5)
Normalized to Output at 25°C
P
IN
= –50dBm; –40°C < T
A
< 85°C
P
IN
= –30dBm; –40°C < T
A
< 85°C
P
IN
= –10dBm; –40°C < T
A
< 85°C
76
19.9
–87.5
–72
●
●
●
MAX
UNITS
MHz
V
Ω
dBm
dB
mV/dB
dBm
dBm
dB
dB
dB
0.1/0.6
–0.1/0.6
–0.2/0.6
5538f
2
LT5538
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
2nd Order Harmonic Distortion
3rd Order Harmonic Distortion
f
RF
= 450 MHz
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
Sensitivity
Output Variation vs Temperature
Normalized to Output at 25°C
P
IN
= –50dBm; –40°C < T
A
< 85°C
P
IN
= –30dBm; –40°C < T
A
< 85°C
P
IN
= –10dBm; –40°C < T
A
< 85°C
Pin = –10dBm; At RF Input
Pin = –10dBm; At RF Input
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, ENBL = 5V. (Note 2)
CONDITIONS
Pin = –10dBm; At RF Input
Pin = –10dBm; At RF Input
MIN
TYP
–62
–61
–75 to 10
±1 dB Linearity Error (Note 3)
(Note 5)
75
19.6
–87.3
–71.5
0.1/0.6
0.1/0.5
–0.1/0.5
–43
–44
–75 to 10
±1 dB Linearity Error (Note 3)
(Note 5)
Normalized to Output at 25°C
P
IN
= –50dBm; –40°C < T
A
< 85°C
P
IN
= –30dBm; –40°C < T
A
< 85°C
P
IN
= –10dBm; –40°C < T
A
< 85°C
Pin = –10dBm; At RF Input
Pin = –10dBm; At RF Input
75
19.0
–88.8
–71.5
●
●
●
MAX
UNITS
dBc
dBc
dBm
dB
mV/dB
dBm
dBm
dB
dB
dB
dBc
dBc
dBm
dB
mV/dB
dBm
dBm
dB
dB
dB
dBc
dBc
dBm
dB
mV/dB
dBm
dBm
dB
dB
dB
dBm
dB
mV/dB
dBm
2nd Order Harmonic Distortion
3rd Order Harmonic Distortion
f
RF
= 880 MHz
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
Sensitivity
Output Variation vs Temperature
0.1/0.7
0.1/0.4
0.1/0.4
–37
–40
–72 to 10
2nd Order Harmonic Distortion
3rd Order Harmonic Distortion
f
RF
= 2140 MHz
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
Sensitivity
Output Variation vs Temperature
±1 dB Linearity Error (Note 3)
(Note 5)
Normalized to Output at 25°C
P
IN
= –50dBm; –40°C < T
A
< 85°C
P
IN
= –30dBm; –40°C < T
A
< 85°C
P
IN
= –10dBm; –40°C < T
A
< 85°C
70
17.7
–89.0
–69.0
●
●
●
0.3/0.4
0.4/0.1
0.7/0.5
–72 to 10
f
RF
= 2700 MHz
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
(Note 5)
±1 dB Linearity Error (Note 3)
65
17.6
–87.5
5538f
3
LT5538
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Sensitivity
Output Variation vs Temperature
Normalized to Output at 25°C
P
IN
= –50dBm; –40°C < T
A
< 85°C
P
IN
= –30dBm; –40°C < T
A
< 85°C
P
IN
= –10dBm; –40°C < T
A
< 85°C
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, ENBL = 5V. (Note 2)
CONDITIONS
MIN
TYP
–69.5
0.3/0.3
0.7/–0.3
1.1/–0.9
–65 to 10
±1 dB Linearity Error (Note 3)
(Note 5)
Normalized to Output at 25°C
P
IN
= –45dBm; –40°C < T
A
< 85°C
P
IN
= –25dBm; –40°C < T
A
< 85°C
P
IN
= –5dBm; –40°C < T
A
< 85°C
No RF Signal Present
57
18
–81.4
–63
●
●
●
MAX
UNITS
dBm
dB
dB
dB
dBm
dB
mV/dB
dBm
dBm
dB
dB
dB
V
Ω
mA
μA
ns
ns
V
f
RF
= 3600 MHz
RF Input Power Range
Linear Dynamic Range
Output Slope
Logarithmic Intercept
Sensitivity
Output Variation vs Temperature
0.6/–0.3
0.9/–0.6
1.4/–1.2
0.350
150
10
200
Output Interface
Output DC Voltage
Output Impedance
Source Current
Sink Current
Rise Time
Fall Time
Power Up/Down
ENBL = High (On)
ENBL = Low (Off)
ENBL Input Current
Turn ON time
Turn OFF Time
Power Supply
Supply Voltage
Supply Current
Shutdown Current
ENBL = Low
3
29
1
5.25
36
100
V
mA
μA
VENBL = 5V
●
●
0.5V to 1.6V, 10% to 90%, f
RF
= 880 MHz
1.6V to 0.5V, 10% to 90%, f
RF
= 880 MHz
1
100
180
0.3
205
300
1
V
μA
ns
μs
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:
Specifications over the –40°C to 85°C temperature range are
assured by design, characterization and correlation with statistical process
control.
Note 3:
The linearity error is calculated by the difference between the
incremental slope of the output and the average slope from –50dBm
to –20dBm. The dynamic range is defined as the range over which the
linearity error is within ±1dB.
Note 4:
Sensitivity is defined as the minimum input power required for the
linearity error within 3dB of the ideal log-linear transfer curve.
Note 5:
Logarithmic Intercept is an extrapolated input power level from the
best-fitted log-linear straight line, where the output voltage is 0V.
5538f
4
LT5538
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
40
35
SUPPLY CURRENT I
CC
(mA)
30
V
OUT
(V)
25
20
15
10
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
2.5
3
5
3.5
4
4.5
SUPPLY VOLTAGE V
CC
(V)
5.5
5538 G01
(Test Circuit shown in Figure 5)
V
OUT
Variation vs Input Power at
40MHz
3
2
LINEARITY ERROR (dB)
1
0
–1
V
OUT
VARIATION (dB)
3
2
1
0
–1
–2
–3
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
T
A
= –40°C
T
A
= 85°C
V
CC
= 5V
NORMALIZED AT 25°C
Output Voltage, Linearity Error vs
Input Power at 40MHz
2.0
1.7
1.4
1.1
0.8
0.5
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
–5
5
5538 G02
V
CC
= 5V
–2
–3
0.2
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
–5
5
5538 G03
Output Voltage, Linearity Error vs
Input Power at 450MHz
2.0
1.7
1.4
V
OUT
(V)
1.1
0.8
0.5
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
–5
5
5538 G04
V
OUT
Variation vs Input Power at
450MHz
3
2
LINEARITY ERROR (dB)
V
OUT
VARIATION (dB)
1
0
–1
–2
–3
3
2
1
0
–1
–2
–3
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
T
A
= –40°C
T
A
= 85°C
V
OUT
(V)
V
CC
= 5V
NORMALIZED AT 25°C
2.0
1.7
1.4
1.1
0.8
0.5
Output Voltage, Linearity Error vs
Input Power at 880MHz
V
CC
= 5V
3
2
LINEARITY ERROR (dB)
1
0
–1
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
5
5538 G06
V
CC
= 5V
–2
–3
0.2
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
–5
5
5538 G05
0.2
–75 –65 –55 –45 –35 –25 –15 –5
INPUT POWER (dBm)
V
OUT
Variation vs Input Power at
880MHz
3
2
V
OUT
VARIATION (dB)
1
V
OUT
(V)
0
–1
–2
–3
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
T
A
= –40°C
T
A
= 85°C
2.0
V
CC
= 5V
NORMALIZED AT 25°C
1.7
1.4
1.1
0.8
0.5
Output Voltage, Linearity Error vs
Input Power at 2.14GHz
V
CC
= 5V
3
2
LINEARITY ERROR (dB)
1
0
–1
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
–5
5
5538 G08
V
OUT
Variation vs Input Power at
2.14GHz
3
2
V
OUT
VARIATION (dB)
1
0
–1
–2
–3
–75 –65 –55 –45 –35 –25 –15 –5
INPUT POWER (dBm)
T
A
= –40°C
T
A
= 85°C
V
CC
= 5V
NORMALIZED AT 25°C
–2
–3
–5
5
5538 G07
0.2
–75 –65 –55 –45 –35 –25 –15
INPUT POWER (dBm)
5
5538 G09
5538f
5
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