CS5571

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DS768PP1

3/26/08

14:22

4. PIN DESCRIPTIONS

CS – Chip Select, Pin 1

The Chip Select pin allows an external device to access the serial port. When held high, the

SDO output will be held in a high-impedance output state.

TST – Factory Test, Pin 2

For factory use only. Connect to VLR.

SMODE – Serial Mode Select, Pin 3

The serial interface mode pin (SMODE) dictates whether the serial port behaves as a master or

slave interface. If SMODE is tied high (to VL), the port will operate in the Synchronous

Self-Clocking (SSC) mode. In SSC mode, the port acts as a master in which the converter out-

puts both the SDO and SCLK signals. If SMODE is tied low (to VLR), the port will operate in the

Synchronous External Clocking (SEC) mode. In SEC mode, the port acts as a slave in which

the external logic or microcontroller generates the SCLK used to output the conversion data

word from the SDO pin.

AIN – Analog Input, Pin 4

AIN is the single-ended input.

ACOM – Analog Return, Pin 5

ACOM is the analog return for the input signal.

V1- – Negative Power 1, Pin 6

The V1- and V2- pins provide a negative supply voltage to the core circuitry of the chip. These

two pins should be decoupled as shown in the application block diagrams. V1- and V2- should

be supplied from the same source voltage. For single-supply operation, these two voltages are

nominally 0 V (Ground). For dual-supply operation, they are nominally -2.5 V.

V1+ – Positive Power 1, Pin 7

The V1+ and V2+ pins provide a positive supply voltage to the core circuitry of the chip. These

two pins should be decoupled as shown in the application block diagrams. V1+ and V2+ should

be supplied from the same source voltage. For single supply-operation, these two voltages are

nominally +5 V. For dual-supply operation, they are nominally +2.5 V.

BUFEN – Buffer Enable, Pin 8

Buffers on input pins AIN and ACOM are enabled if BUFEN is connected to V1+ and disabled if

connected to V1-.

VREF+, VREF- – Voltage Reference Input, Pins 9, 10

A differential voltage reference input on these pins functions as the voltage reference for the

converter. The voltage between these pins can range between 2.4 volts and 4.2 volts, with

4.096 volts being the nominal reference voltage value.

RST

Reset

VLR2

Logic Interface Return

CONV

Convert

DCR

Digital Core Regulator

V2+

Positive Voltage 2

V2-

Negative Voltage 2

MCLK

Master Clock

VLR

Logic Interface Return

VL

Logic Interface Power

SDO

Serial Data Output

SCLK

Serial Clock Input/Output

RDY

Ready

DITHER

Dither Select

BP/UP

Bipolar/Unipolar Select

VREF-

Voltage Reference Input

VREF+

Voltage Reference Input

BUFEN

Buffer Enable

V1+

Positive Power 1

V1-

Negative Power 1

ACOM

Analog Return

AIN

Analog Input

CS

Chip Select

TST

Factory Test

SMODE

Serial Mode Select

12

11

10

9

8

7

6

5

4

3

2

1

13

14

15

16

17

18

19

20

21

22

23

24