1 MHz to 10 GHz, 55 dB

Log Detector/Controller

Data Sheet

AD8317

Rev. C

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FEATURES

Wide bandwidth: 1 MHz to 10 GHz

High accuracy: ±1.0 dB over temperature

55 dB dynamic range up to 8 GHz ± 3 dB error

Stability over temperature: ±0.5 dB

Low noise measurement/controller output, VOUT

Pulse response time: 6 ns/10 ns (fall/rise)

Small footprint, 2 mm × 3 mm LFCSP

Supply operation: 3.0 V to 5.5 V at 22 mA

Fabricated using high speed SiGe process

APPLICATIONS

RF transmitter PA setpoint control and level monitoring

Power monitoring in radio link transmitters

RSSI measurement in base stations, WLANs, WiMAX, and radars

FUNCTIONAL BLOCK DIAGRAM

GAIN

BIAS

SLOPE

DET

DET

DET

DET

INHI

INLO

IV

VOUT

IV

VSET

CLPF

TADJ

VPOS

COMM

Figure 1.

GENERAL DESCRIPTION

The AD8317 is a demodulating logarithmic amplifier, capable of

accurately converting an RF input signal to a corresponding

decibel-scaled output. It employs the progressive compression

technique over a cascaded amplifier chain, each stage of which

is equipped with a detector cell. The device can be used in either

measurement or controller modes. The AD8317 maintains

accurate log conformance for signals of 1 MHz to 8 GHz and

provides useful operation to 10 GHz. The input dynamic range

is typically 55 dB (referenced to 50 Ω) with less than ±3 dB

error. The AD8317 has 6 ns/10 ns response time (fall time/rise

time) that enables RF burst detection to a pulse rate of beyond

50 MHz. The device provides unprecedented logarithmic intercept

stability vs. ambient temperature conditions. A supply of 3.0 V

to 5.5 V is required to power the device. Current consumption is

typically 22 mA, and it decreases to 200 μA when the device is

disabled.

The AD8317 can be configured to provide a control voltage to a

power amplifier or a measurement output from the VOUT pin.

Because the output can be used for controller applications, special

attention has been paid to minimize wideband noise. In this

mode, the setpoint control voltage is applied to the VSET pin.

The feedback loop through an RF amplifier is closed via VOUT,

the output of which regulates the output of the amplifier to a

controller applications. As a measurement device, VOUT is

externally connected to VSET to produce an output voltage,

signal amplitude.

The logarithmic slope is 22 mV/dB, determined by the VSET

interface. The intercept is 15 dBm (referenced to 50 Ω, CW

input) using the INHI input. These parameters are very stable

against supply and temperature variations.

The AD8317 is fabricated on a SiGe bipolar IC process and is

available in a 2 mm × 3 mm, 8-lead LFCSP with an operating

temperature range of −40°C to +85°C.