REV. 0

–6–

AD7927

PIN FUNCTION DESCRIPTIONS

Pin No.

Mnemonic

Function

1

SCLK

Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part. This clock

input is also used as the clock source for the AD7927s conversion process.

2DIN

Data In. Logic input. Data to be written to the AD7927s Control Register is provided on this input

and is clocked into the register on the falling edge of SCLK (see the Control Register section).

3

CS

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

the AD7927 and framing the serial data transfer.

4, 8, 17, 20

AGND

Analog Ground. Ground reference point for all analog circuitry on the AD7927. All analog input

signals and any external reference signal should be referred to this AGND voltage. All AGND pins

should be connected together.

5, 6

0V to 2

7

Reference Input for the AD7927. An external reference must be applied to this input. The voltage

range for the external reference is 2.5 V

± 1% for specified performance.

into the on-chip track-and-hold. The analog input channel to be converted is selected by using the

address bits ADD2 through ADD0 of the Control Register. The address bits in conjunction with the

SEQ and SHADOW bits allow the sequencer to be programmed. The input range for all input channels

Any unused input channels should be connected to AGND to avoid noise pickup.

18

DOUT

Data Out. Logic output. The conversion result from the AD7927 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 from the

AD7927 consists of two leading zeros, two address bits indicating which channel the conversion result

corresponds to, followed by the 12 bits of conversion data, MSB first. The output coding may be

selected as straight binary or twos complement via the CODING bit in the Control Register.

19

Logic Power Supply Input. The voltage supplied at this pin determines at what voltage the serial interface

of the AD7927 will operate.

PIN CONFIGURATION

20-Lead TSSOP

1

AD7927

SCLK

AGND

20

TOP VIEW

(Not to Scale)

2

DIN

19

3

CS

DOUT

18

4

AGND

AGND

17

5

16

6

15

7

14

8

AGND

13

9

12

10

11