1 MHz to 10 GHz, 40 dB

Log Detector/Controller

AD8319

Rev. A

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FEATURES

Wide bandwidth: 1 MHz to 10 GHz

High accuracy: ±1.0 dB over temperature

>40 dB dynamic range up to 8 GHz

Stability over temperature ±0.5 dB

Low noise measurement/controller output VOUT

Pulse response time: 8 ns/10 ns (fall/rise)

Small footprint 2 mm × 3 mm LFCSP_VD

Supply operation: 3.0 V to 5.5 V @ 22 mA

Fabricated using high speed SiGe process

APPLICATIONS

RF transmitter PA setpoint controls and level monitoring

Power monitoring in radiolink 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 AD8319 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 AD8319 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 40 dB (re: 50 Ω) with error less than ±1 dB. The

AD8319 has 8 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 AD8319 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 was 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 amplifier’s output to a magnitude

output capability at the VOUT pin, suitable for controller

applications. As a measurement device, VOUT is externally

decreasing linear-in-dB function of the RF input signal amplitude.

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

interface. The intercept is 15 dBm (re: 50 Ω, CW input) using

the INHI input. These parameters are very stable against supply

and temperature variations.

The AD8319 is fabricated on a SiGe bipolar IC process and is

available in a 2 mm × 3 mm, 8-lead LFCSP_VD for an operating

temperature range of −40°C to +85°C.