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AD608_15 Datasheet, PDF (1/16 Pages) Analog Devices – Low Power Mixer/Limiter/RSSI 3 V Receiver IF Subsystem | |||
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Low Power Mixer/Limiter/RSSI
3 V Receiver IF Subsystem
AD608
FEATURES
Mixer
â15 dBm, 1 dB compression point
â5 dBm IP3
24 dB conversion gain
>500 MHz input bandwidth
Logarithmic/limiting amplifier
80 dB RSSI range
±3° phase stability over 80 dB range
Low power
21 mW at 3 V power consumption
CMOS-compatible power-down to 300 μW typical
200 ns enable/disable time
APPLICATIONS
PHS, GSM, TDMA, FM, or PM receivers
Battery-powered instrumentation
Base station RSSI measurements
GENERAL DESCRIPTION
The AD608 provides a low power, low distortion, low noise mixer
as well as a complete, monolithic logarithmic/limiting amplifier
that uses a successive-detection technique. In addition, the AD608
provides both a high speed received signal strength indicator
(RSSI) output with 80 dB dynamic range and a hard-limited
output. The RSSI output is from a two-pole postdemodulation
low-pass filter and provides a loadable output voltage of 0.2 V to
1.8 V. The AD608 operates from a single 2.7 V to 5.5 V supply
at a typical power level of 21 mW at 3 V.
The RF and local oscillator (LO) bandwidths both exceed
500 MHz. In a typical IF application, the AD608 can accept the
output of a 240 MHz surface acoustic wave (SAW) filter and down-
convert it to a nominal 10.7 MHz IF with a conversion gain of
24 dB (ZIF = 165 Ω). The AD608 logarithmic/limiting amplifier
section handles any IF from low frequency (LF) up to 30 MHz.
The mixer is a doubly balanced gilbert-cell mixer and operates
linearly for RF inputs spanning â95 dBm to â15 dBm. It has a
nominal â5 dBm third-order intercept. An on-board LO pre-
amplifier requires only â16 dBm of LO drive. The current output
of the mixer drives a reverse-terminated, industry-standard
10.7 MHz, 330 Ω filter.
The nominal logarithmic scaling is such that the output is +0.2 V
for a sinusoidal input to the IF amplifier of â75 dBm and +1.8 V
at an input of +5 dBm; over this range, the logarithmic confor-
mance is typically ±1 dB. The logarithmic slope is proportional
to the supply voltage. A feedback loop automatically nulls the
input offset of the first stage down to the submicrovolt level.
The AD608 limiter output provides a hard-limited signal output
at 400 mV p-p. The voltage gain of the limiting amplifier to this
output is more than 100 dB. Transition times are 11 ns and the
phase is stable to within ±3° at 10.7 MHz for signals from â75 dBm
to +5 dBm.
The AD608 is enabled by a CMOS logic-level voltage input,
with a response time of 200 ns. When disabled, the standby
power is reduced to 300 μW within 400 ns.
The AD608 is specified for the industrial temperature range of
â25°C to +85°C for 2.7 V to 5.5 V supplies and â40°C to +85°C for
3.0 V to 5.5 V supplies. This device comes in a 16-lead plastic SOIC.
24dB MIXER GAIN
FUNCTIONAL BLOCK DIAGRAM
3dB NOMINAL
INSERTION LOSS
110dB LIMITER GAIN
90dB RSSI
RFHI 5
RF INPUT
â95dBm TO
â15dBm1
RFLO 6
±6mA MAX OUTPUT
(±890mV INTO 165â¦)
MIXER
LO
PREAMP
MXOP
7
BPF
DRIVER
VMID
8
MIDSUPPLY
IF BIAS
BIAS
IF INPUT
â75dBm TO
+15dBm2
10.7MHz
BAND-PASS
FILTER
IFHI
9
330â¦
100nF
330â¦
10nF
+
100â¦
10
IFLO
18nF
13
FDBK
VPS1 COM1 LOHI COM2
PRUP
1
2
3
4
16
2.7V TO
5.5V
LO INPUT
â16dBm
CMOS LOGIC
INPUT
1â15dBm = ±56mV MAXIMUM FOR LINEAR OPERATION.
239.76µV RMS TO 397.6mV RMS FOR ±1dB RSSI ACCURACY.
Figure 1.
7 FULL-WAVE
RECTIFIER CELLS
5-STAGE IF AMPLIFIER
(16dB PER STAGE)
2MHz
LPF
RSSI
RSSI OUTPUT
11 20mV/dB
0.2V TO 1.8V
COM3 12
VPS2 14 +2.7V TO 5.5V
LMOP
15 LIMITER
OUTPUT
FINAL
400mV p-p
LIMITER
AD608
±50µA
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©1996â2009 Analog Devices, Inc. All rights reserved.
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