®

PCM78

3

PIN

NAME

I/O

DESCRIPTION

1

Analog In

I

Analog Signal Input (1.5k

Ω impedance).

I

Analog power supply (–5V to –15V).

3

MSB Adjust

I

Internal adjustment point to allow adjustment of MSB major carry.

I

Power connection for comparator (+5V).

5

No Connection

—

No internal connection.

6

Comparator Common

I

Comparator common connection. Connect to ground.

7

MSB

O

Parallel output of bit 1 (MSB) inverted.

8

BTC/BOB Select

I

Two’s complement (open) or straight binary (grounded) data output format selection.

9

Status

O

Output signal held high until conversion is complete.

10

Clock Out

O

Internal clock output generated from RC network on pins 11 and 12 (also present when external clock is used lagging

external clock by ~24ns and same duty cycle).

11

I

RC connection point used to generate internal clock. Sets clock high time. See text for details.

12

I

RC connection point used to generate internal clock. Sets clock low time. See text for details.

13

O

Internal shift register containing the previous conversion result. (Alternate latched data output mode).

14

I

Power connection for +5V logic supply.

15

O

Primary real-time data output synchronized to clock out.

16

External Clock

I

External clock input point (internal clock must be disabled).

17

Int/Ext Clock Select

I

Selects either internal or external clock mode (low = internal; open = external).

18

Short Cycle

I

Terminates conversion at less than 16 bits (open for 16-bit mode). See text for details.

19

Convert Command

I

Starts conversion process (can optionally be generated internally).

20

I

command).

21

I

Used to read out internally latched data from previous conversion.

22

Digital Common

I

Digital grounding pin.

23

I

Analog supply connection (+5V to +15V).

24

O

Voltage output (~2.5V) for optional adjustment of MSB transition.

25

Reference Decouple

I

Reference decoupling point.

26

Analog Common

I

Analog grounding pin.

27

Reference Out

O

2V reference out. Should not be used except as shown in connection diagram.

28

Speed Up

I

Connection point for a capacitor to speed reference settling. See text for details.

NOTE: Analog and digital commons are connected internally.

PIN ASSIGNMENTS

ABSOLUTE MAXIMUM RATINGS

Analog Common to Digital Common .................................................

±0.5V

Analog Inputs to Analog Common ..................................................

±16.5V

Lead Temperature (soldering, 10s) ................................................ +300

°C

Stresses above these ratings may permanently damage the device.

DIGITAL OUTPUT

ANALOG INPUT

CONDITION

BTC

BOB

+2.999908V

+ Full Scale

7FFF Hex

FFFF Hex

–3.000000V

–Full Scale

8000 Hex

0000 Hex

0.000000V

Bipolar Zero

0000 Hex

8000 Hex

–0.000092V

Zero-1 LSB

FFFF Hex

7FFF Hex

INPUT/OUTPUT RELATIONSHIPS

PACKAGE INFORMATION

PACKAGE DRAWING

MODEL

PACKAGE

PCM78P

28-Pin Plastic DIP

215

NOTE: (1) For detailed drawing and dimension table, please see end of data

sheet, or Appendix D of Burr-Brown IC Data Book.

The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes

no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change

without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant

any BURR-BROWN product for use in life support devices and/or systems.