REV. 0

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a

AD8314

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 1999

100 MHz–2500 MHz 45 dB

RF Detector/Controller

FEATURES

Complete RF Detector/Controller Function

Typical Range –58 dBV to –13 dBV

–45 dBm to 0 dBm re 50

Frequency Response from 100 MHz to 2.5 GHz

Temperature-Stable Linear-in-dB Response

Accurate to 2.5 GHz

Rapid Response: 70 ns to a 10 dB Step

Low Power: 12 mW at 2.7 V

Power-Down to 20

A

APPLICATIONS

Cellular Handsets (TDMA, CDMA, GSM)

RSSI and TSSI for Wireless Terminal Devices

Transmitter Power Measurement and Control

PRODUCT DESCRIPTION

The AD8314 is a complete low-cost subsystem for the mea-

surement and control of RF signals in the frequency range

0.1 GHz–2.5 GHz, with a typical dynamic range of 45 dB,

intended for use in a wide variety of cellular handsets and other

wireless devices. It provides a wider dynamic range and better

accuracy than possible using discrete diode detectors. In particular,

its temperature stability is excellent over the full operating range of

–30

°C to +85°C.

Its high sensitivity allows control at low power levels, thus

reducing the amount of power that needs to be coupled to the

detector. It is essentially a voltage-responding device, with a

typical signal range of 1.25 mV to 224 mV rms or –58 dBV to

–13 dBV. This is equivalent to –45 dBm to 0 dBm re 50

Ω.

For convenience, the signal is internally ac-coupled, using a 5 pF

capacitor to a load of 3 k

Ω in shunt with 2 pF. This high-pass

coupling, with a corner at 16 MHz, determines the lowest oper-

ating frequency. Thus, the source may be dc-grounded.

The AD8314 provides two voltage outputs. The first, called

V_UP, increases from close to ground to about 1.2 V as the

input signal level increases from 1.25 mV to 224 mV. This output

is intended for use in measurement mode. Consult the Appli-

cations section of this data sheet for information on use in this

mode. A capacitor may be connected between the V_UP and

FLTR pins when it is desirable to increase the time interval over

which averaging of the input waveform occurs.

The second output, V_DN, is an inversion of V_UP, but with

twice the slope and offset by a fixed amount. This output starts

at about 2.25 V (provided the supply voltage is

≥3.3 V) for

the minimum input and falls to a value close to ground at the

maximum input. This output is intended for analog control

loop applications. A setpoint voltage is applied to VSET and

V_DN is then used to control a VGA or power amplifier. Here

again, an external filter capacitor may be added to extend the

averaging time. Consult the Applications section of this data

sheet for information on use in this mode.

The AD8314 is available in a micro_SOIC package and con-

sumes 4.5 mA from a 2.7 V to 5.5 V supply. When powered

down, the typical sleep current is 20

µA.

FUNCTIONAL BLOCK DIAGRAM

10dB

OFFSET

COMP'N

V-I

I-V

RFIN

COMM

(PADDLE)

VPOS

X2

ENBL

V DN

V UP

VSET

FLTR

AD8314

10dB

10dB

10dB

BAND-GAP

REFERENCE

DET

DET

DET

DET

DET