REV. B

AD7887

–5–

PIN FUNCTION DESCRIPTIONS

Pin

Pin

No.

Mnemonic

Function

1

CS

Chip Select. Active low logic input. This input provides the dual function of initiating conversions on the

AD7887 and also frames the serial data transfer. When the AD7887 operates in its default mode, the CS pin

also acts as the shutdown pin such that with the CS pin high, the AD7887 is in its power-down mode.

figured for two-channel operation, this pin also provides the reference source for the part.

3

GND

Ground Pin. This pin is the ground reference point for all circuitry on the AD7887. In systems with separate

AGND and DGND planes, these planes should be tied together as close as possible to this GND pin. Where

this is not possible, this GND pin should connect to the AGND plane.

4

Analog Input 1/Voltage Reference Input. In single-channel mode, this pin becomes the reference input/

output. In this case, the user can either access the internal +2.5 V reference or overdrive the internal refer-

ence with the voltage applied to this pin. The reference voltage range for an externally-applied reference is

5

AIN0

6

DIN

Data In. Logic Input. Data to be written to the AD7887’s Control Register is provided on this input and is

clocked into the register on the rising edge of SCLK (see Control Register section). The AD7887 can be

operated as a single-channel read-only ADC by tying the DIN line permanently to GND.

7

DOUT

Data Out. Logic Output. The conversion result from the AD7887 is provided on this output as a serial data

stream. The bits are clocked out on the falling edge of the SCLK input. The data stream consists of four

leading zeros followed by the 12 bits of conversion data, which is provided MSB first.

8

SCLK

Serial Clock. Logic Input. SCLK provides the serial clock for accessing data from the part and writing serial

data to the Control Register. This clock input is also used as the clock source for the AD7887’s conversion

process.

PIN CONFIGURATION

TOP VIEW

(Not to Scale)

8

7

6

5

1

2

3

4

CS

SCLK

AD7887

GND

DOUT

DIN

AIN0