Datasheet

SAR

ADC

AVDD

AIN0P

AVDD

AIN0N

AVDD

AIN1P

AVDD

AIN1N

GND

ADS7947

ADS7948

ADS7949

SLAS708 –SEPTEMBER 2010

www.ti.com

OVERVIEW

The ADS7947 is 12-bit, miniature, dual-channel, low-power SAR ADC. The ADS7948 and ADS7949 are 10-bit

and 8-bit devices, respectively, from the same product family. These devices feature very low power

consumption at rated speed. The PDEN pin enables an auto power-down mode that further reduces power

consumption at lower speeds.

MULTIPLEXER AND ADC INPUT

The devices feature pseudo-differential inputs with a double-pole, double-throw multiplexer. The negative inputs

(AINxN) can accept swings of ±0.2V; the positive inputs (AINxP) allow signals in the range of 0V to V

REF

over the

negative input. The ADC converts the difference in voltage: V

AINxP

– V

AINxN

. This feature can be used in multiple

ways.

Two signals can be connected from different sensors with unequal ground potentials (within ±0.2V) to a single

ADC. The pseudo-differential ADC rejects common-mode offset and noise. This feature also allows the use of a

single-supply op amp. The signal and the AINxN input can be offset by +0.2V, which provides the ground

clearance needed for a single-supply op amp.

Figure 38 shows the electrostatic discharge (ESD) diodes to supply and ground at every analog input. Make sure

that these diodes do not turn on by keeping the supply voltage within the specified input range.

Figure 38. Analog Inputs

Product Folder Link(s): ADS7947 ADS7948 ADS7949