Read-Only, Pin-Configured, 24-bit Sigma-Delta ADC with Excitation Current Sources

The AD7783 is a complete analog front end for low frequency measurement applications. The 24-bit sigma-delta ADC contains one fully differential input channel that can be configured with a gain of 1 or 16 allowing full-scale input signal ranges of ±2.56 V or ±160 mV from a +2.5 V differential reference input. It also contains two 200 mA integrated current sources.

The AD7783 has an extremely simple, read-only digital interface that can be operated in master mode or slave mode. There are no on-chip registers to be programmed. The input signal range and current source selection are configured using two external pins.

The device operates from a 32.768 kHz crystal with an on-chip PLL generating the required internal operating frequency. The output data rate from the part is fixed via the master clock at 19.79 Hz and provides simultaneous 50 Hz and 60 Hz rejection at this update rate. At this update rate, 18-bit p-p resolution can be obtained.

The part operates from a single 3 V or 5 V supply. When operating from 3 V supplies, the power dissipation for the part is 3.9 mW. The AD7783 is available in a 16-lead TSSOP.

Another part in the AD778x family is the AD7782. It is similar to the AD7783 except it has no integrated current sources and two differential input channels.

APPLICATIONS

* Sensor Measurement

* Industrial Process Control

* Temperature Measurement

* Pressure Measurement

* Weigh Scales

* Portable Instrumentation

ON-CHIP FUNCTIONS

* Rail-to-Rail Input Buffer and PGA

INTERFACE

* Master or Slave Mode of Operation

* Slave Mode

3-Wire Serial

SPI®, QSPI™, MICROWIRE™, and DSP-Compatible

Schmitt Trigger on SCLK

POWER

* Specified for Single 3 V and 5 V Operation

* Normal: 1.3 mA @ 3 V

* Power-Down: 9 µA