AD7715 3V 5V, 450mA 16-Bit Sigma-Delta ADC Data Sheet Manual

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3 V/5 V, 450 m A 16-Bit, Sigma-Delta ADC AD7715* FEATURES FUNCTIONAL BLOCK DIAGRAM

Charge-Balancing ADC

REF IN(–) REF IN(+) AVDD DVDD

16 Bits No Missing Codes 0.0015% Nonlinearity

CHARGE BALANCING

Programmable Gain Front End

A/D CONVERTER

Gains of 1, 2, 32 and 128

SIGMA-DELTA DIGITAL

AIN(+)

Differential Input Capability MODULATOR FILTER

PGABUFFER

AIN(–)

Three-Wire Serial Interface

SPI™, QSPI™, MICROWIRE™ and DSP Compatible A = 1–128 CLOCK MCLK IN

GENERATION MCLK OUT

Ability to Buffer the Analog Input

SERIAL RESET

3 V (AD7715-3) or 5 V (AD7715-5) Operation

INTERFACE

Low Supply Current: 450␣ m A max @ 3␣ V Supplies SCLK

REGISTER BANK

Low-Pass Filter with Programmable Output Update

16-Lead SOIC/DIP/TSSOP

AD7715 DRDY

AGND DGND

GENERAL DESCRIPTION CMOS construction ensures very low power dissipation, and the The AD7715 is a complete analog front end for low frequency power-down mode reduces the standby power consumption to measurement applications. The part can accept low level input 50␣ µW typ. The part is available in a 16-lead, 0.3 inch-wide, signals directly from a transducer and outputs a serial digital plastic dual-in-line package (DIP) as well as a 16-lead 0.3 inch- word. It employs a sigma-delta conversion technique to realize wide small outline (SOIC) package and a 16-lead TSSOP package. up to 16 bits of no missing codes performance. The input signal

is applied to a proprietary programmable gain front end based PRODUCT HIGHLIGHTS around an analog modulator. The modulator output is pro- 1. The AD7715 consumes less than 450␣ µA in total supply cessed by an on-chip digital filter. The first notch of this digital current at 3 V supplies and 1␣ MHz master clock, making it filter can be programmed via the on-chip control register allow- ideal for use in low-power systems. Standby current is less ing adjustment of the filter cutoff and output update rate. than 10␣ µA. The AD7715 features a differential analog input as well as a dif- 2. The programmable gain input allows the AD7715 to accept ferential reference input. It operates from a single supply (+3␣ input signals directly from a strain gage or transducer remov- or +5␣ V). It can handle unipolar input signal ranges of 0 m V to ing a considerable amount of signal conditioning.

+20␣ m V, 0 m V to +80␣ m V, 0 V to +1.25␣ V and 0 V to +2.5␣ V.

3. The AD7715 is ideal for microcontroller or DSP processor

It can also handle bipolar input signal ranges of ±20␣ m V, ±80␣ m V,

applications with a three-wire serial interface reducing the

±1.25␣ V and ±2.5␣ V. These bipolar ranges are referenced to

number of interconnect lines and reducing the number of

the negative input of the differential analog input. The AD7715

opto-couplers required in isolated systems. The part con-

thus performs all signal conditioning and conversion for a single-

tains on-chip registers which allow software control over

channel system.

output update rate, input gain, signal polarity and calibration The AD7715 is ideal for use in smart, microcontroller or DSP modes.

based systems. It features a serial interface that can be config-

4. The part features excellent static performance specifications

ured for three-wire operation. Gain settings, signal polarity and

with 16-bits no missing codes, ±0.0015% accuracy and low

update rate selection can be configured in software using the

rms noise (<550␣ n V). Endpoint errors and the effects of

input serial port. The part contains self-calibration and system

temperature drift are eliminated by on-chip calibration op-

calibration options to eliminate gain and offset errors on the

tions, which remove zero-scale and full-scale errors.

part itself or in the system.

SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corporation. *Protected by U.S. Patent No: 5,134,401. See page 30 for data sheet index.

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