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AD7485

1 MSPS, Serial 14-Bit SAR ADC

FEATURES

Fast Throughput Rate: 1 MSPS

Wide Input Bandwidth: 40 MHz

Excellent DC Accuracy Performance

Flexible Serial Interface

Low Power:

80 mW (Full Power) and 3 mW (NAP Mode)

STANDBY Mode: 2

A Max

Single 5 V Supply Operation

Internal 2.5 V Reference

Full-Scale Overrange Indication

FUNCTIONAL BLOCK DIAGRAM

2.5 V

REFERENCE

BUF

T/H

DGND

REFSEL

REFOUT

REFIN

VIN

14-BIT

ALGORITHMIC

SAR

NAP

STBY

RESET

CONVST

MCLK

TFS

SCO

CONTROL

LOGIC AND I/O

REGISTERS

SMODE

AD7485

SDO

GENERAL DESCRIPTION

The AD7485 is a 14-bit, high speed, low power, successive-

approximation ADC. The part features a serial interface with

throughput rates up to 1 MSPS. The part contains a low noise,

wide bandwidth track-and-hold that can handle input frequencies

in excess of 40 MHz.

The conversion process is a proprietary algorithmic successive-

approximation technique. The input signal is sampled and a

conversion is initiated on the falling edge of the

CONVST signal.

The conversion process is controlled by an external master

clock. Interfacing is via standard serial signal lines, making the

part directly compatible with microcontrollers and DSPs.

The AD7485 provides excellent ac and dc performance specifi-

cations. Factory trimming ensures high dc accuracy resulting in

very low INL, DNL, offset, and gain errors.

The part uses advanced design techniques to achieve very low

power dissipation at high throughput rates. Power consumption

in the normal mode of operation is 80 mW. There are two power-

saving modes: a NAP mode keeps reference circuitry alive for

quick power-up and consumes 3 mW, while a STANDBY mode

reduces power consumption to a mere 10

µW.

The AD7485 features an on-board 2.5 V reference, but the part can

also accommodate an externally provided 2.5 V reference source.

The nominal analog input range is 0 V to 2.5 V.

The AD7485 also provides the user with overrange indication via a

fifteenth bit. If the analog input range strays outside the 0 V to

2.5 V input range, the fifteenth data bit is set to a logic high.

The AD7485 is powered from a 4.75 V to 5.25 V supply. The

voltage levels for the digital interface lines. The range for this

48-lead LQFP package and is specified over a –40

°C to +85°C

temperature range.