LTC5508
1
5508fa
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
■
802.11a, 802.11b, 802.11g, 802.15
■
Multimode Mobile Phone Products
■
Optical Data Links
■
Wireless Data Modems
■
Wireless and Cable Infrastructure
■
RF Power Alarm
■
Envelope Detector
■
Temperature Compensated Internal Schottky
Diode RF Detector
■
Wide Input Frequency Range: 300MHz to 7GHz
■
Wide Input Power Range: –32dBm to 12dBm
■
Buffered Detector Output
■
Wide V
CC
Range of 2.7V to 6V
■
Low Operating Current: 550µA
■
Low Shutdown Current: <2µA
■
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 2µA.
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 0.1µF
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 84 12
V
CC
= 3.6V
T
A
= 25°C
7GHz
1GHz
2GHz
6GHz
4GHz
LTC5508
2
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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, θ
JA
= 256°C/W LAAD
LTC5508ESC6
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.6V, SHDN = VCC = HI, SHDN = 0V = LO, RF Input Signal is Off,
unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Operating Voltage ●2.7 6 V
I
VCC
Shutdown Current SHDN = LO ●2µA
I
VCC
Operating Current SHDN = HI, I
VOUT
= 0mA ●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 ●12 mA
V
OUT
Enable Time SHDN = HI, C
LOAD
= 33pF, R
LOAD
= 2k ●820 µs
V
OUT
Bandwidth C
LOAD
= 33pF, R
LOAD
= 2k (Note 4) 2 MHz
V
OUT
Load Capacitance (Note 6) ●33 pF
V
OUT
Slew Rate V
RFIN
= 2V Step, C
LOAD
= 33pF, R
LOAD
= 2k (Note 3) 5 V/µs
V
OUT
Noise V
CC
= 3V, Noise BW = 1.5MHz, 50Ω RF Input Termination 2 mV
P-P
SHDN Voltage, Chip Disabled V
CC
= 2.7V to 6V ●0.35 V
SHDN Voltage, Chip Enabled V
CC
= 2.7V to 6V ●1.4 V
SHDN Input Current SHDN = 3.6V ●24 40 µA
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 Ω
RF
IN
Input Shunt Capacitance F = 1000MHz, Pin = –25dBm 0.6 pF
Consult LTC Marketing for parts specified with wider operating temperature ranges.
6 RFIN
5 GND
4 VCC
SHDN 1
TOP VIEW
SC6 PACKAGE
6-LEAD PLASTIC SC70
GND 2
VOUT 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
UW
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)
VOUT OUTPUT VOLTAGE (mV)
10000
5508 G01
100
1000
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 85°C
TA = 25°C
TA = –40°C
RF INPUT POWER (dBm)
VOUT OUTPUT VOLTAGE (mV)
10000
5508 G02
100
1000
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 85°C
TA = 25°C
TA = –40°C
RF INPUT POWER (dBm)
VOUT OUTPUT VOLTAGE (mV)
10000
5508 G03
100
1000
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 85°C
TA = –40°C
TA = 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 84 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 84 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 84 12
V
CC
= 3.6V
T
A
= 85°C
T
A
= 25°C
T
A
= –40°C
RF INPUT POWER (dBm)
VOUT OUTPUT VOLTAGE (mV)
10000
5508 G07
100
1000
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 85°C
TA = 25°C
TA = –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 84 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
UW
V
OUT Slope vs RF Input Power at
300MHz
VOUT Slope vs RF Input Power at
1000MHz
VOUT Slope vs RF Input Power at
2000MHz
VOUT Slope vs RF Input Power at
3000MHz
VOUT Slope vs RF Input Power at
4000MHz
VOUT Slope vs RF Input Power at
5000MHz
VOUT Slope vs RF Input Power at
6000MHz
VOUT Slope vs RF Input Power at
7000MHz
RF INPUT POWER (dBm)
VOUT SLOPE (mV/dB)
1000
5508 G09
1
10
100
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 85°C
TA = 25°C
TA = –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 84 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 84 12
V
CC
= 3.6V
T
A
= 25°C
TA = –40°C
TA = 85°C
RF INPUT POWER (dBm)
VOUT SLOPE (mV/dB)
1000
5508 G12
1
10
100
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 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 84 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 84 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 84 12
V
CC
= 3.6V
T
A
= 85°C
T
A
= –40°C
T
A
= 25°C
RF INPUT POWER (dBm)
VOUT SLOPE (mV/dB)
1000
5508 G16
1
10
100
–32 –28 –24 –20 –16–12 –8 –4 0 84 12
VCC = 3.6V
TA = 25°C
TA = 85°C
TA = –40°C
LTC5508
5
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TYPICAL PERFOR A CE CHARACTERISTICS
UW
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
RFIN Input Impedance (Pin = 0dBm, VCC = 3.6V, TA = 25°C)
FREQUENCY RESISTANCE REACTANCE
(GHz) (Ω)(Ω)
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
RFIN Input Impedance (Pin = –25dBm, VCC = 3.6V, TA = 25°C)
FREQUENCY RESISTANCE REACTANCE
(GHz) (Ω)(Ω)
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
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BLOCK DIAGRA
W
UU
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 250Ω 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
250Ω
RF DET
30k
30k
60µA60µA
150k
40k
130mV
BIAS
100Ω
100Ω
RF
SOURCE
RF
IN
V
CC
6
20k
20k
LTC5508
7
5508fa
APPLICATIO S I FOR ATIO
WUU 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 60µA 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
VOUT
RF
GND
VCC
LTC5508
1
2
3
JP1
VCC
VCC
VCC
R2
68Ω
(OPT)
R1
68Ω
(OPT)
C5
(OPT)
C2
0.1µF
C3
100pF
C1
18pF RFIN
J1
E1
E5
E2
E4
E3
GND
VOUT
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
●
FAX: (408) 434-0507
●
www.linear.com
LINEAR TE CHNO LOGY CORP O R ATION 2002
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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)