8-Channel, 1.5 MSPS, 10-Bit Parallel ADCs with a Sequencer

The AD7938/AD7939 are 12-bit and 10-bit, high speed, low power, successive approximation (SAR) analog-to-digital converters (ADCs). The parts operate from a single 2.7 V to 5.25 V power supply and feature throughput rates up to 1.5 MSPS. The parts contain a low noise, wide bandwidth, differential track-and-hold amplifier that can handle input frequencies up to 50 MHz.

The AD7938/AD7939 feature eight analog input channels with a channel sequencer that allows a preprogrammed selection of channels to be converted sequentially. These parts can operate with either single-ended, fully differential, or pseudo differential analog inputs.

The conversion process and data acquisition are controlled using standard control inputs that allow easy interfacing with microprocessors and DSPs. The input signal is sampled on the falling edge of CONVST and the conversion is also initiated at this point.

The AD7938/AD7939 have an accurate on-chip 2.5 V reference that can be used as the reference source for the analog-to-digital conversion. Alternatively, this pin can be overdriven to provide an external reference.

These parts use advanced design techniques to achieve very low power dissipation at high throughput rates. They also feature flexible power management options. An on-chip control register allows the user to set up different operating conditions, including analog input range and configuration, output coding, power management, and channel sequencing.

Product Highlights

* High throughput with low power consumption.

* Eight analog inputs with a channel sequencer.

* Accurate on-chip 2.5 V reference.

* Single-ended, pseudo differential, or fully differential

analog inputs that are software selectable.

* Single-supply operation with VDRIVE function. The VDRIVE

function allows the parallel interface to connect directly to

3 V or 5 V processor systems independent of VDD.

* No pipeline delay.

* Accurate control of the sampling instant via a CONVST

input and once-off conversion control.

* Throughput rate: 1.5 MSPS

* Specified for VDD of 2.7 V to 5.25 V

* 8 analog input channels with a sequencer

* Software-configurable analog inputs

* 8-channel single-ended inputs

* 4-channel fully differential inputs

* 4-channel pseudo differential inputs

* 7-channel pseudo differential inputs

* Accurate on-chip 2.5 V reference

* ±0.2% maximum at 25°C, 25 ppm/°C maximum