ANALOG DEVICES AD8370 Data Sheet

LF to 750 MHz, Digitally Controlled VGA

AD8370 FEATURES FUNCTIONAL BLOCK DIAGRAM

Programmable low and high gain (<2 d B resolution) VCCI VCCO VCCO

Low range: −11 d B to +17 d B High range: 6 d B to 34 d B

BIAS CELL VOCMPWUP

Differential input and output

ICOM OCOM

200 Ω differential input 100 Ω differential output INHI OPHI

PRE OUTPUT

7 d B noise figure @ maximum gain TRANSCONDUCTANCE

AMP AMP

INLO OPLO

Two-tone IP3 of 35 d Bm @ 70 MHz −3 d B bandwidth of 750 MHz

ICOM OCOM

40 d B precision gain range SHIFT REGISTER AND LATCHES

Serial 8-bit digital interface

AD8370

Wide input dynamic range

Power-down feature DATA CLCK LTCH

Single 3 V to 5 V supply Figure 1.

APPLICATIONS CODE = LAST 7 BITS OF GAIN CODE VO LT IN (V /V (NO MSB)

Differential ADC drivers

HIGH GAIN MODE

IF sampling receivers RF/IF gain stages

Cable and video applications LOW GAIN MODE

Δ GAIN

SAW filter interfacing ≅ 0.409 www.BDTIC.com/ DI Δ CODE

HIGH GAIN MODE

Single-ended-to-differential conversion

GENERAL DESCRIPTION

Δ GAIN

The AD8370 is a low cost, digitally controlled, variable gain Δ CODE

LOW GAIN MODE

amplifier (VGA) that provides precision gain control, high IP3,

and low noise figure. The excellent distortion performance and

GAIN CODE

wide bandwidth make the AD8370 a suitable gain control

device for modern receiver designs. Figure 2. Gain vs. Gain Code at 70 MHz

For wide input, dynamic range applications, the AD8370 Gain control of the AD8370 is through a serial 8-bit gain control provides two input ranges: high gain mode and low gain mode. word. The MSB selects between the two gain ranges, and the A vernier, 7-bit, transconductance (gm) stage provides 28 d B of remaining 7 bits adjust the overall gain in precise linear gain steps. 2- VO LT IN (d

gain range at better than 2 d B resolution and 22 d B of gain 2-

Fabricated on the ADI high speed XFCB process, the high

range at better than 1 d B resolution. A second gain range, 17 d B

bandwidth of the AD8370 provides high frequency and low

higher than the first, can be selected to provide improved noise

distortion. The quiescent current of the AD8370 is 78 m A

performance.

typically. The AD8370 amplifier comes in a compact, thermally The AD8370 is powered on by applying the appropriate logic enhanced 16-lead TSSOP package and operates over the level to the PWUP pin. When powered down, the AD8370 temperature range of −40°C to +85°C.

consumes less than 4 m A and offers excellent input to output isolation. The gain setting is preserved when operating in a power-down mode.

Rev. A 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

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

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. Tel: 781.329.4700 www.analog.com Trademarks and registered trademarks are the property of their respective owners. Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.