ADS7881IPFBT datasheet(7/35 Pages) TI2

7 / 35 page

ADS7881

SLAS400B − SEPTEMBER 2003 − REVISED NOVEMBER 2005

www.ti.com

TERMINAL FUNCTIONS

NAME

NO. PFB

NO. RGZ

I/O

DESCRIPTION

DATA BUS

8-Bit Bus

16-Bit Bus

DATA BUS

BYTE = 0

BYTE = 1

BYTE = 0

DB11

D11 (MSB)

DB10

D10

DB9

DB8

D0 (LSB)

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

D0 (LSB)

CONTROL PINS

Chip select. Active low signal enables chip operation like acquisition start, conver-

sion start, bus release from 3-state. Refer to the timing diagrams for more details.

CONVST

Conversion start. The rising edge starts the acquisition. The falling edge of this input

ends the acquisition and starts the conversion. Refer to the timing diagrams for more

details.

Active low synchronization pulse for the parallel output. When CS is low, this serves

as the output enable and puts the previous conversion results on the bus.

A_PWD

Nap mode enable, active low

PWD/RST

Active low input, acts as device power down/device reset signal.

BYTE

Byte select input. Used for 8-bit bus reading.

0: No fold back

1: Lower byte D[3:0] is folded back to high byte so D3 is available in D11 place.

STATUS OUTPUT

BUSY

Status output. High when a conversion is in progress.

POWER SUPPLY

+VBD

24, 34

36, 46

−

Digital power supply for all digital inputs and outputs. Refer to Table 3 for layout

guidelines.

BDGND

25, 35

37, 47

−

Digital ground for all digital inputs and outputs. Short to analog ground plane below

the device.

+VA

4, 9, 10, 13,

43, 46

7, 10, 16,

21, 22, 25

−

Analog power supplies. Refer to Table 3 for layout guidelines.

AGND

5, 8, 11, 12,

14, 15, 44, 45

8, 9, 17,

20, 23, 24,

26, 27

−

Analog ground pins. Short to analog ground plane below the device.

ANALOG INPUT

+IN

Noninverting analog input channel

−IN

Inverting analog input channel

REFIN

Reference (positive) input. Needs to be decoupled with REFM pin using 0.1-

µF by-

pass capacitor and 1-

µF storage capacitor.

REFOUT

Internal reference output. To be shorted to REFIN pin when internal reference is used.

Do not connect to REFIN pin when external reference is used. Always needs to be

decoupled with AGND using 0.1-

µF bypass capacitor.

REFM

47, 48

11, 12

Reference ground. Connect to analog ground plane.

3, 30, 31, 32,

15, 42, 43,

44, 45

−

No connection

ADS7881IPFBT Datasheet(PDF) 7 Page - Texas Instruments

ADS7881IPFBT Datasheet(HTML) 7 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Datasheet Download

Link URL