28 Lead Package Block and PIN Diagrams

Pin

Pin Name

Description

1

VDD

5V Digital Supply2

2

RNC

Read/Not Convert Input – A high-to-low transition initiates an A-to-D conversion.

When held low, the outputs are in a high impedance mode.

3

NCS

Not Chip Select Input – A low input will select the chip and enable the outputs.

A high input will de-select the chip and place the outputs in a high impedance state.

4

CE

Chip Enable Input – A high input will enable the chip and enable the outputs.

A low input will disable the chip and place the outputs in a high impedance state.

5

VDDA

5V Analog Supply2

6

VREFOUT

VREF Buffered Output. Nominally 2.5V buffered output of on-chip voltage reference.

May be connected to VREFIN on the board.

7

VSSA

Analog Ground

8

VREFIN

Voltage Reference Input. May be connected to VREFOUT or to an external voltage reference.

9

AIN1

Analog Input – Input to buffer amplifier

10

AIN2

Analog Input – Input to buffer amplifier

11

BUFFIN

Analog Input – Input to negative terminal of the buffer amplifier

12

BUFFOUT

Analog Buffer Output

13

VIN

ADC Signal Input – Analog input signal

14

VSS

Digital Ground

15

DO

Data Output. D0 is the LSB. This is a tri-state output driver.1

16-26 D1 – D11

Data Output. D1 – D11. These are tri-state output drivers.1

27

AO

Output Data Byte Select Input – The digital data can be output as a standard 12 bit parallel output or

can be presented in two 8-bit bytes for use with 8 bit microprocessors.

The 8 bit bus will be aligned with D4 – D11.

When A0 is low, the digital data is output in a standard 12 bit format (D0 = LSB).

This will also represent the first byte (bits D4 – D11) for an 8 bit system.

When A0 is high, the second byte will be available at the output. D11 through D8 now contain the

4 LSB’s of the 12-bit parallel data (D0 – D3).

28

STS

Status Output – A low signal indicates the conversion is complete and the data is available at the outputs.

A high signal indicates a conversion is in process.

(1) The data outputs may be put into a high impedance state according to truth table.

(2) These power supplies are required to be the same supply on the board. They cannot be independent supplies.

3

Pin Description