LTC5508
1
5508fa
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
s
802.11a, 802.11b, 802.11g, 802.15
s
Multimode Mobile Phone Products
s
Optical Data Links
s
Wireless Data Modems
s
Wireless and Cable Infrastructure
s
RF Power Alarm
s
Envelope Detector
s
Temperature Compensated Internal Schottky
Diode RF Detector
s
Wide Input Frequency Range: 300MHz to 7GHz
s
Wide Input Power Range: 32dBm to 12dBm
s
Buffered Detector Output
s
Wide V
CC
Range of 2.7V to 6V
s
Low Operating Current: 550
A
s
Low Shutdown Current: <2
A
s
SC70
Package
300MHz to 7GHz RF Power
Detector with Buffered Output
in SC70 Package
The LTC
5508 is an RF power detector for RF applications
operating in the 300MHz to 7GHz range. A temperature
compensated Schottky diode peak detector and buffer
amplifier are combined in a small SC70 package. The
supply voltage range is optimized for operation from a
single lithium-ion cell or 3xNiMH.
The RF input voltage is peak detected using an on-chip
Schottky diode. The detected voltage is buffered and
supplied to the V
OUT
pin. A power saving shutdown mode
reduces supply current to less than 2
A.
The LTC5508 operates with input power levels from
32dBm to 12dBm.
, LTC and LT are registered trademarks of Linear Technology Corporation.
300MHz to 7GHz RF Power Detector
LTC5508
6
2
1
4
5
3
100pF
0.1
F
V
CC
V
OUT
V
CC
V
OUT
RF
IN
GND
SHDN
DISABLE ENABLE
33pF
5508 TA01
RF
INPUT
GND
Output Voltage vs RF Input Power
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 TA02
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 25
C
7GHz
1GHz
2GHz
6GHz
4GHz
LTC5508
2
5508fa
V
CC
, V
OUT
to GND .................................... 0.3V to 6.5V
RF
IN
Voltage ...................................... (V
CC
1.3V) to 7V
SHDN Voltage to GND ................ 0.3V to (V
CC
+ 0.3V)
I
VOUT
...................................................................... 5mA
Operating Temperature Range (Note 2) .. 40
C to 85
C
Maximum Junction Temperature ......................... 125
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
ORDER PART
NUMBER
SC6 PART
MARKING
T
JMAX
= 125
C,
JA
= 256
C/W
LAAD
LTC5508ESC6
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 3.6V, SHDN = V
CC
= HI, SHDN = 0V = LO, RF Input Signal is Off,
unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Operating Voltage
q
2.7
6
V
I
VCC
Shutdown Current
SHDN = LO
q
2
A
I
VCC
Operating Current
SHDN = HI, I
VOUT
= 0mA
q
0.55
0.85
mA
V
OUT
V
OL
(No RF Input)
R
LOAD
= 2k, SHDN = HI, Enabled
150
250
400
mV
SHDN = LOW, Disabled
1
mV
V
OUT
Output Current
V
OUT
= 1.75V, V
CC
= 2.7V,
V
OUT
= 10mV
q
1
2
mA
V
OUT
Enable Time
SHDN = HI, C
LOAD
= 33pF, R
LOAD
= 2k
q
8
20
s
V
OUT
Bandwidth
C
LOAD
= 33pF, R
LOAD
= 2k (Note 4)
2
MHz
V
OUT
Load Capacitance
(Note 6)
q
33
pF
V
OUT
Slew Rate
V
RFIN
= 2V Step, C
LOAD
= 33pF, R
LOAD
= 2k (Note 3)
5
V/
s
V
OUT
Noise
V
CC
= 3V, Noise BW = 1.5MHz, 50
RF Input Termination
2
mV
P-P
SHDN Voltage, Chip Disabled
V
CC
= 2.7V to 6V
q
0.35
V
SHDN Voltage, Chip Enabled
V
CC
= 2.7V to 6V
q
1.4
V
SHDN Input Current
SHDN = 3.6V
q
24
40
A
RF
IN
Input Frequency Range
300 to 7000
MHz
RF
IN
Input Power Range
RF Frequency = 300MHz to 7GHz (Note 5, 6) V
CC
= 2.7V to 6V
32 to 12
dBm
RF
IN
AC Input Resistance
F = 1000MHz, Pin = 25dBm
150
RF
IN
Input Shunt Capacitance
F = 1000MHz, Pin = 25dBm
0.6
pF
Consult LTC Marketing for parts specified with wider operating temperature ranges.
6 RF
IN
5 GND
4 V
CC
SHDN 1
TOP VIEW
SC6 PACKAGE
6-LEAD PLASTIC SC70
GND 2
V
OUT
3
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Specifications over the 40
C to 85
C operating temperature
range are assured by design, characterization and correlation with
statistical process controls.
Note 3: The rise time at V
OUT
is measured between 0.5V and 1.5V.
Note 4: Bandwidth is calculated using the 10% to 90% rise time equation:
BW = 0.35/rise time.
Note 5: RF performance is tested at 1800MHz
Note 6: Guaranteed by design.
LTC5508
3
5508fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Typical Detector Characteristics,
300MHz
Typical Detector Characteristics,
1000MHz
Typical Detector Characteristics,
2000MHz
Typical Detector Characteristics,
3000MHz
Typical Detector Characteristics,
4000MHz
Typical Detector Characteristics,
5000MHz
Typical Detector Characteristics,
6000MHz
Typical Detector Characteristics,
7000MHz
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G01
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G02
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G03
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G04
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G05
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G06
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G07
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
OUTPUT VOLTAGE (mV)
10000
5508 G08
100
1000
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
LTC5508
4
5508fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
OUT
Slope vs RF Input Power at
300MHz
V
OUT
Slope vs RF Input Power at
1000MHz
V
OUT
Slope vs RF Input Power at
2000MHz
V
OUT
Slope vs RF Input Power at
3000MHz
V
OUT
Slope vs RF Input Power at
4000MHz
V
OUT
Slope vs RF Input Power at
5000MHz
V
OUT
Slope vs RF Input Power at
6000MHz
V
OUT
Slope vs RF Input Power at
7000MHz
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G09
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G10
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 40
C
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
T
A
= 85
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G11
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 25
C
T
A
= 40
C
T
A
= 85
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G12
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 25
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G13
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 25
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G14
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G15
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
RF INPUT POWER (dBm)
V
OUT
SLOPE (mV/dB)
1000
5508 G16
1
10
100
32 28 24 20 16 12 8 4 0
8
4
12
V
CC
= 3.6V
T
A
= 25
C
T
A
= 85
C
T
A
= 40
C
LTC5508
5
5508fa
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
RF
IN
Input Impedance (Pin = 0dBm, V
CC
= 3.6V, T
A
= 25
C)
FREQUENCY
RESISTANCE
REACTANCE
(GHz)
(
)
(
)
1.000
129.136
86.960
1.375
100.771
92.142
1.750
73.844
81.141
2.125
60.159
68.796
2.500
50.135
58.139
2.875
43.042
48.927
3.250
37.570
41.033
3.625
33.924
33.346
4.000
30.923
26.405
4.375
28.793
20.012
4.750
26.992
14.080
5.125
25.717
8.323
5.500
24.920
3.228
5.875
24.318
2.177
6.250
24.549
7.535
6.625
25.273
12.197
7.000
26.337
16.503
RF
IN
Input Impedance (Pin = 25dBm, V
CC
= 3.6V, T
A
= 25
C)
FREQUENCY
RESISTANCE
REACTANCE
(GHz)
(
)
(
)
1.000
114.531
63.267
1.375
95.061
71.669
1.750
71.491
64.607
2.125
59.563
54.798
2.500
51.714
46.844
2.875
44.940
39.753
3.250
39.708
32.738
3.625
36.151
26.385
4.000
33.227
20.478
4.375
31.108
15.107
4.750
29.514
9.941
5.125
27.899
4.793
5.500
27.047
0.266
5.875
26.627
5.250
6.250
26.760
10.267
6.625
27.619
14.616
7.000
28.241
18.523
5508 TA03
5508 TA04
LTC5508
6
5508fa
BLOCK DIAGRA
W
U
U
U
PI FU CTIO S
SHDN (Pin 1): Shutdown Input. A logic low on the SHDN
pin places the part in shutdown mode. A logic high enables
the part. SHDN has an internal 150k pull down resistor to
ensure that the part is in shutdown when no input is
applied.
GND (Pin 2, 5): Ground.
V
OUT
(Pin 3): Detector Output.
V
CC
(Pin 4): Power Supply Voltage, 2.7V to 6V. V
CC
should
be bypassed appropriately with ceramic capacitors.
RF
IN
(Pin 6): RF Input Voltage. Referenced to V
CC
. A
coupling capacitor must be used to connect to the RF
signal source. The frequency range is 300MHz to 7GHz.
This pin has an internal 250
termination, an internal
Schottky diode detector and a peak detector capacitor.
+
+
5508 BD
GAIN
COMPRESSION
SHDN
28pF
V
OUT
SHDN
GND
GND
12pF TO 200pF
(DEPENDING ON
APPLICATION)
2
5
1
3
4
BUFFER
250
RF DET
30k
30k
60
A
60
A
150k
40k
130mV
BIAS
100
100
RF
SOURCE
RF
IN
V
CC
6
20k
20k
LTC5508
7
5508fa
APPLICATIO S I FOR ATIO
W
U
U
U
Operation
The LTC5508 RF detector integrates several functions to
provide RF power detection over frequencies ranging from
300MHz to 7GHz. These functions include an internally
compensated buffer amplifier, an RF Schottky diode peak
detector and level shift amplifier to convert the RF input
signal to DC, a delay circuit to avoid voltage transients at
V
OUT
when coming out of shutdown and a gain compres-
sion circuit to extend the detector dynamic range.
Buffer Amplifier
The buffer amplifier has a gain of two and is capable of
driving a 2mA load. The buffer amplifier typically has an
output voltage range of 0.25V to 1.75V.
RF Detector
The internal RF Schottky diode peak detector and level
shift amplifier converts the RF input signal to a low
frequency signal. The detector demonstrates excellent
efficiency and linearity over a wide range of input power.
The Schottky detector is biased at about 60
A and drives
a peak detector capacitor of 28pF.
Gain Compression
The gain compression circuit changes the feedback ratio
as the RF peak-detected input voltage increases above
60mV. Below 60mV, the voltage gain from the peak
detector to the buffer output is 4. Above 120mV, the
voltage gain is reduced to 0.85. The compression expands
the low power detector range due to higher gain.
Modes of Operation
MODE
SHDN
OPERATION
Shutdown
Low
Disabled
Enable
High
Power Detect
Applications
The LTC5508 can be used as a self-standing signal strength
measuring receiver for a wide range of input signals from
32dBm to 12dBm for frequencies from 300MHz to 7GHz.
The LTC5508 can be used as a demodulator for AM and
ASK modulated signals with data rates up to 2MHz.
Depending on specific application needs, the RSSI output
can be split into two branches, providing AC-coupled data
(or audio) output and DC-coupled, RSSI output for signal
strength measurements and AGC.
The LTC5508 can be used for RF power detection and
control. Refer to Application Note 91, "Low Cost Coupling
Methods for RF Power Detectors Replace Directional
Couplers."
Demo Board Schematic
SHDN
GND
V
OUT
RF
GND
V
CC
LTC5508
1
2
3
JP1
V
CC
V
CC
V
CC
R2
68
(OPT)
R1
68
(OPT)
C5
(OPT)
C2
0.1
F
C3
100pF
C1
18pF
RF
IN
J1
E1
E5
E2
E4
E3
GND
V
OUT
GND
SHDN
R3
22k
ENABLE
DISABLE
5508 AI01
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC5508
8
5508fa
LT/TP REV A 0603 1K PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
q
FAX: (408) 434-0507
q
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2002
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LT5500
1.8GHz to 2.7GHz RF Front End
Dual LNA gain Setting +13.5dB/14dB at 2.5GHz, Double-Balanced Mixer,
1.8V
V
SUPPLY
5.25V
LT5502
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LT5503
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PACKAGE DESCRIPTIO
U
1.15 1.35
(NOTE 4)
1.80 2.40
0.15 0.30
6 PLCS (NOTE 3)
0.10 0.18
(NOTE 3)
SC6 SC70 0802
1.80 2.20
(NOTE 4)
0.65 BSC
PIN 1
0.80 1.00
1.00 MAX
0.00 0.10
REF
0.10 0.40
0.10 0.30
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. DETAILS OF THE PIN 1 INDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE INDEX AREA
7. EIAJ PACKAGE REFERENCE IS EIAJ SC-70
3.26 MAX
0.47
MAX
0.65
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.96 MIN
2.1 REF
1.16 REF
INDEX AREA
(NOTE 6)
SC6 Package
6-Lead Plastic SC70
(Reference LTC DWG # 05-08-1638)
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