Datasheet

ADS8634

ADS8638

SBAS541A –MAY 2011– REVISED AUGUST 2011

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OVERVIEW

The ADS8634 and ADS8638 are 12-bit, 4- and 8-channel devices, respectively. The ADS8634/8 feature

software-selectable bipolar and unipolar ranges, an internal reference with an option to use an external

reference, and an internal temperature sensor. Independent power-down control for the internal reference and

temperature sensor blocks allows for optimal power based on application. The following sections describe the

individual blocks and operation.

MULTIPLEXER AND ANALOG INPUT

The ADS8634/8 feature single ended inputs with ground sense and a 4-/8-channel, single-pole multiplexer,

respectively. The ADC samples the difference voltage between analog input pins AINx and the ground sense pin

AINGND. The ADS8634/8 can scan these analog inputs in either manual or auto-scan mode. In manual mode,

the channel is selected for every sample via a register write; in auto-scan mode, the channel number is

incremented automatically on every CS falling edge after the present channel is sampled. It is possible to select

the analog inputs for an auto scan with register settings. The devices automatically scan only the selected analog

inputs in ascending order.

The ADS8634/8 offer multiple software-programmable ranges ±10V, ±5V, ±2.5V, 0V to 5V, and 0V to 10V with a

2.5V reference. Any of these ranges can be assigned to any analog input (for instance, ±10V can be assigned to

AIN1, ±2.5V to AIN2, 0V to 10V can be assigned to AIN3, and so on). During a scan (either auto or manual), the

programmed signal range is assigned to the selected channel. The range selection, however, can be temporarily

overridden using the DIN line for a particular scan. This feature is useful for zooming into a narrow range when

needed. Refer to Table 11 for configuration register settings.

Product Folder Link(s): ADS8634 ADS8638