10-Bit, 4-Channel, 350 kSPS, Serial A/D Converter

The AD7811 and AD7812 are high speed, low power, 10-bit A/D converters that operate from a single 2.7 V to 5.5 V supply. The devices contain a 2.3 µs successive approximation A/D converter, an on-chip track/hold amplifier, a 2.5 V on-chip reference and a high speed serial interface that is compatible with the serial interfaces of most DSPs (Digital Signal Processors) and microcontrollers. The user also has the option of using an external reference by connecting it to the VREF pin and setting the EXTREF bit in the control register. The VREF pin may be tied to VDD. At slower throughput rates the power-down mode may be used to automatically power down between conversions.

The control registers of the AD7811 and AD7812 allow the input channels to be configured as single-ended or pseudo differential. The control register also features a software convert start and a software power-down. Two of these devices can share the same serial bus and may be individually addressed in a multipackage application by hardwiring the device address pin. The AD7811 is available in a small, 16-lead 0.3" wide, plastic dual-in-line package (mini-DIP), in a 16-lead 0.15" wide, small outline IC (SOIC) and in a 16-lead, Thin Shrink Small Outline Package (TSSOP). The AD7812 is available in a small, 20-lead 0.3" wide, plastic dual-in-line package (mini-DIP), in a 20-lead, small outline IC (SOIC) and in a 20-lead, Thin Shrink Small Outline Package (TSSOP).

PRODUCT HIGHLIGHTS

* Low Power, Single Supply Operation

Both the AD7811 and AD7812 operate from a single 2.7 V

to 5.5 V supply and typically consume only 10 mW of power.

The power dissipation can be significantly reduced at

lower throughput rates by using the automatic power-down mode e.g., 315 µW @ 10 kSPS, VDD = 3 V—see

Power vs. Throughput.

* 4-/8-Channel, 10-Bit ADC

The AD7811 and AD7812 have four and eight single-ended

input channels respectively. These inputs can be configured

as pseudo differential inputs by using the Control Register.

* On-chip 2.5 V (±2.5%) reference circuit that is powered

down when using an external reference.

* Hardware and Software Control

The AD7811 and AD7812 provide for both hardware and

software control of Convert Start and Power-Down.

* 10-Bit ADC with 2.3 µs Conversion Time

* Four Single-Ended Inputs to Configure as Three Pseudo Differential Inputs with Respect to a Common, or as Two Independent Pseudo Differential Channels

* Onboard Track and Hold

* Onboard Reference 2.5 V ± 2.5%

* Operating Supply Range: 2.7 V to 5.5 V

* Specifications at 2.7 V–3.6 V and 5 V ± 10%