AD8318-EP_15 Datasheet, PDF (1/12 Pages) Analog Devices – 1 MHz to 8 GHz, 70 dB Logarithmic Detector/Controller

Enhanced Product
1 MHz to 8 GHz, 70 dB
Logarithmic Detector/Controller
AD8318-EP
FEATURES
Wide bandwidth: 1 MHz to 8 GHz
High accuracy: ±1.0 dB over 55 dB range (f < 5.8 GHz)
Stability over temperature: ±0.5 dB
Low noise measurement/controller output (VOUT)
Pulse response time: 10 ns/12 ns (fall/rise)
Integrated temperature sensor
Small footprint LFCSP
Power-down feature: <1.5 mW at 5 V
Single-supply operation: 5 V @ 68 mA
Fabricated using high speed SiGe process
APPLICATIONS
RF transmitter PA setpoint control and level monitoring
RSSI measurement in base stations, WLAN, WiMAX, and
radars
GENERAL DESCRIPTION
The AD8318-EP is a demodulating logarithmic amplifier,
capable of accurately converting an RF input signal to a
corresponding decibel-scaled output voltage. It employs the
progressive compression technique over a cascaded amplifier
chain, each stage of which is equipped with a detector cell.
The device is used in measurement or controller mode. The
AD8318-EP maintains accurate log conformance for signals of
1 MHz to 6 GHz and provides useful operation to 8 GHz. The
input range is typically 60 dB (re: 50 Ω) with error less than
±1 dB. The AD8318-EP has a 10 ns response time that enables
RF burst detection to beyond 45 MHz. The device provides
unprecedented logarithmic intercept stability vs. ambient
temperature conditions. A 2 mV/°C slope temperature sensor
output is also provided for additional system monitoring.
A single supply of 5 V is required. Current consumption is
typically 68 mA. Power consumption decreases to <1.5 mW
when the device is disabled.
The AD8318-EP can be configured to provide a control voltage
to a VGA, such as a power amplifier or a measurement output,
from Pin VOUT. Because the output can be used for controller
applications, wideband noise is minimal.
In this mode, the setpoint control voltage is applied to VSET.
The feedback loop through an RF amplifier is closed via VOUT,
the output of which regulates the amplifier output to a magnitude
corresponding to VSET. The AD8318-EP provides 0 V to 4.9 V
output capability at the VOUT pin, suitable for controller
TEMP
FUNCTIONAL BLOCK DIAGRAM
VPSI
ENBL
TADJ
VPSO
TEMP
SENSOR
GAIN
BIAS
SLOPE
IV
VSET
INHI
INLO
DET
DET
DET DET
IV
VOUT
CLPF
CMIP
Figure 1.
CMOP
2.4
6
2.2
5
2.0
4
1.8
3
1.6
2
1.4
1
1.2
0
1.0
–1
0.8
–2
0.6
–3
0.4
–4
0.2
–5
0
–6
–65 –60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10 –5 0 5 10
P_IN (dBm)
Figure 2. Typical Logarithmic Response and Error vs. Input Amplitude at 5.8 GHz
applications. As a measurement device, Pin VOUT is externally
connected to VSET to produce an output voltage, V_OUT, which
is a decreasing linear-in-dB function of the RF input signal
amplitude.
The logarithmic slope is nominally −25 mV/dB but can be
adjusted by scaling the feedback voltage from VOUT to the
VSET interface. The intercept is 20 dBm (re: 50 Ω, CW input)
using the INHI input. These parameters are very stable against
supply and temperature variations.
The AD8318-EP is fabricated on a SiGe bipolar IC process and
is available in a 4 mm × 4 mm, 16-lead LFCSP. Performance is
specified over a temperature range of –55^oC to +105^oC.
Additional application and technical information can be found
in the AD8318 data sheet.
Rev. 0
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