LTC5508 - 300MHz to 7GHz RF Power Detector with Buffered Output in SC70 Package

LTC5508
300MHz to 7GHz RF Power
Detector with Buffered Output
in SC70 Package
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DESCRIPTIO
FEATURES
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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 VCC Range of 2.7V to 6V
Low Operating Current: 550µA
Low Shutdown Current: <2µA
SC70 Package
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APPLICATIO S
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The RF input voltage is peak detected using an on-chip
Schottky diode. The detected voltage is buffered and
supplied to the VOUT pin. A power saving shutdown mode
reduces supply current to less than 2µA.
The LTC5508 operates with input power levels from
–32dBm to 12dBm.
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
, LTC and LT are registered trademarks of Linear Technology Corporation.
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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.
TYPICAL APPLICATIO
Output Voltage vs RF Input Power
300MHz to 7GHz RF Power Detector
RF
INPUT
33pF
6
2
DISABLE ENABLE
1
LTC5508
VCC 4
RFIN
5
GND
GND
SHDN
VOUT 3 VOUT
VCC
100pF
0.1µF
VOUT OUTPUT VOLTAGE (mV)
10000
VCC = 3.6V
TA = 25°C
1000
2GHz
7GHz
1GHz
4GHz
6GHz
5508 TA01
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 TA02
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LTC5508
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
VCC, VOUT to GND .................................... –0.3V to 6.5V
RFIN Voltage ......................................(VCC ± 1.3V) to 7V
SHDN Voltage to GND ................ –0.3V to (VCC + 0.3V)
IVOUT ...................................................................... 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
TOP VIEW
SHDN 1
6 RFIN
GND 2
5 GND
VOUT 3
4 VCC
LTC5508ESC6
SC6 PART
MARKING
SC6 PACKAGE
6-LEAD PLASTIC SC70
TJMAX = 125°C, θJA = 256°C/W
LAAD
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
VCC Operating Voltage
●
IVCC Shutdown Current
SHDN = LO
●
IVCC Operating Current
SHDN = HI, IVOUT = 0mA
●
VOUT VOL (No RF Input)
RLOAD = 2k, SHDN = HI, Enabled
SHDN = LOW, Disabled
TYP
2.7
150
MAX
UNITS
6
V
2
µA
0.55
0.85
mA
250
1
400
mV
mV
VOUT Output Current
VOUT = 1.75V, VCC = 2.7V, ∆VOUT = 10mV
●
VOUT Enable Time
SHDN = HI, CLOAD = 33pF, RLOAD = 2k
●
VOUT Bandwidth
CLOAD = 33pF, RLOAD = 2k (Note 4)
VOUT Load Capacitance
(Note 6)
VOUT Slew Rate
VRFIN = 2V Step, CLOAD = 33pF, RLOAD = 2k (Note 3)
5
V/µs
VOUT Noise
VCC = 3V, Noise BW = 1.5MHz, 50Ω RF Input Termination
2
mVP-P
SHDN Voltage, Chip Disabled
VCC = 2.7V to 6V
●
SHDN Voltage, Chip Enabled
VCC = 2.7V to 6V
●
SHDN Input Current
SHDN = 3.6V
●
1
2
8
mA
20
2
RFIN Input Frequency Range
MHz
33
●
µs
0.35
1.4
pF
V
V
24
40
µA
300 to 7000
MHz
–32 to 12
dBm
RFIN Input Power Range
RF Frequency = 300MHz to 7GHz (Note 5, 6) VCC = 2.7V to 6V
RFIN AC Input Resistance
F = 1000MHz, Pin = –25dBm
150
Ω
RFIN Input Shunt Capacitance
F = 1000MHz, Pin = –25dBm
0.6
pF
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 VOUT 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.
5508fa
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LTC5508
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TYPICAL PERFOR A CE CHARACTERISTICS
Typical Detector Characteristics,
300MHz
1000
10000
VCC = 3.6V
1000
TA = –40°C
TA = 85°C
TA = 25°C
1000
TA = 85°C
TA = –40°C
TA = 25°C
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G01
1000
TA = 85°C
TA = 25°C
TA = –40°C
TA = 85°C
TA = 25°C
5508 G04
VCC = 3.6V
8 12
TA = –40°C
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G06
Typical Detector Characteristics,
7000MHz
10000
VOUT OUTPUT VOLTAGE (mV)
VCC = 3.6V
TA = 85°C
TA = 25°C
5508 G05
Typical Detector Characteristics,
6000MHz
VOUT OUTPUT VOLTAGE (mV)
Typical Detector Characteristics,
5000MHz
1000
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
8 12
5508 G03
10000
1000
10000
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
VCC = 3.6V
VOUT OUTPUT VOLTAGE (mV)
VOUT OUTPUT VOLTAGE (mV)
10000
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
TA = 25°C
Typical Detector Characteristics,
4000MHz
VCC = 3.6V
TA = –40°C
TA = 85°C
5508 G02
Typical Detector Characteristics,
3000MHz
10000
TA = –40°C
VOUT OUTPUT VOLTAGE (mV)
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
VCC = 3.6V
VOUT OUTPUT VOLTAGE (mV)
10000
VCC = 3.6V
VOUT OUTPUT VOLTAGE (mV)
VOUT OUTPUT VOLTAGE (mV)
10000
Typical Detector Characteristics,
2000MHz
Typical Detector Characteristics,
1000MHz
VCC = 3.6V
1000
1000
TA = –40°C
TA = 85°C
TA = 25°C
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G07
TA = –40°C
TA = 85°C
TA = 25°C
100
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G08
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LTC5508
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TYPICAL PERFOR A CE CHARACTERISTICS
VOUT Slope vs RF Input Power at
300MHz
1000
100
10 TA = –40°C
TA = 25°C
1000
VCC = 3.6V
VOUT SLOPE (mV/dB)
VCC = 3.6V
VOUT SLOPE (mV/dB)
VOUT SLOPE (mV/dB)
1000
100
TA = –40°C
10
TA = 25°C
TA = 85°C
100
TA = –40°C
10
TA = 25°C
TA = 85°C
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G09
TA = –40°C
10
TA = 25°C
1000
VCC = 3.6V
TA = –40°C
VCC = 3.6V
100
10
TA = –40°C
TA = 25°C
TA = 25°C
TA = 85°C
TA = 85°C
TA = 85°C
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
VOUT Slope vs RF Input Power at
6000MHz
1000
VCC = 3.6V
100
10
TA = –40°C
TA = 25°C
5508 G14
VCC = 3.6V
100
10
TA = –40°C
TA = 25°C
TA = 85°C
TA = 85°C
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
VOUT Slope vs RF Input Power at
7000MHz
VOUT SLOPE (mV/dB)
1000
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G13
5508 G12
VOUT SLOPE (mV/dB)
VOUT Slope vs RF Input Power at
5000MHz
100
10
8 12
5508 G11
VOUT SLOPE (mV/dB)
VOUT SLOPE (mV/dB)
100
8 12
VOUT Slope vs RF Input Power at
4000MHz
1000
VCC = 3.6V
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
5508 G10
VOUT Slope vs RF Input Power at
3000MHz
VOUT SLOPE (mV/dB)
VCC = 3.6V
TA = 85°C
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
1000
VOUT Slope vs RF Input Power at
2000MHz
VOUT Slope vs RF Input Power at
1000MHz
8 12
5508 G15
1
–32 –28 –24 –20 –16 –12 –8 –4 0 4
RF INPUT POWER (dBm)
8 12
5508 G16
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LTC5508
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TYPICAL PERFOR A CE CHARACTERISTICS
RFIN Input Impedance (Pin = 0dBm, VCC = 3.6V, TA = 25°C)
FREQUENCY
(GHz)
RESISTANCE
(Ω)
REACTANCE
(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
(GHz)
RESISTANCE
(Ω)
REACTANCE
(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
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
5508 TA03
S11 Forward Reflection
Impedance
1.000GHz-7.000GHz
5508 TA04
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LTC5508
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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.
VOUT (Pin 3): Detector Output.
VCC (Pin 4): Power Supply Voltage, 2.7V to 6V. VCC should
be bypassed appropriately with ceramic capacitors.
RFIN (Pin 6): RF Input Voltage. Referenced to VCC. 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.
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BLOCK DIAGRA
RFSOURCE
12pF TO 200pF
(DEPENDING ON
APPLICATION)
VCC
4
GAIN
COMPRESSION
+
BUFFER
3
VOUT
–
SHDN
30k
250Ω
RFIN
6
30k
20k
28pF
20k
60µA
100Ω
100Ω
+
RF DET
130mV
–
40k
60µA
BIAS
150k
GND 2
GND 5
1
5508 BD
SHDN
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LTC5508
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APPLICATIO S I FOR ATIO
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
VOUT when coming out of shutdown and a gain compression circuit to extend the detector dynamic range.
Buffer Amplifier
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 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
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
VCC
R3
22k
E4
SHDN
C1
18pF
ENABLE 1
2
DISABLE 3
JP1
VOUT
E2
E3
GND
R2
68Ω
(OPT)
C5
(OPT)
GND
GND
VOUT
VCC
RFIN
J1
SHDN
RF
LTC5508
R1
68Ω
(OPT)
VCC
E1
VCC
C2
0.1µF
C3
100pF
E5
GND
5508 AI01
5508fa
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LTC5508
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PACKAGE DESCRIPTIO
SC6 Package
6-Lead Plastic SC70
(Reference LTC DWG # 05-08-1638)
0.47
MAX
0.65
REF
1.80 – 2.20
(NOTE 4)
1.16 REF
INDEX AREA
(NOTE 6)
1.80 – 2.40 1.15 – 1.35
(NOTE 4)
0.96 MIN
3.26 MAX 2.1 REF
PIN 1
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.15 – 0.30
6 PLCS (NOTE 3)
0.65 BSC
0.10 – 0.40
0.80 – 1.00
0.00 – 0.10
REF
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
1.00 MAX
0.10 – 0.30
SC6 SC70 0802
0.10 – 0.18
(NOTE 3)
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5508fa
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Linear Technology Corporation
LT/TP REV A 0603 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2002