5

HS-3374RH

Functional Block Diagram

1 OF 8 IDENTICAL CIRCUITS

NOTES:

1. Enable and disable are TTL type inputs

2. D and E outputs are common to all 8 channels

GND

2 (3, 4, 5, 6, 7, 8, 9)

A1 CMOS

INPUT (OUTPUT)

VDD

D

E

VCC

VDD

LEVEL

SHIFTER

GND

VCC

B1 TTL

OUTPUT

(INPUT)

21 (20, 19,

18, 17, 16,

15, 14)

ENABLE

DISABLE

13

10

GND

GND

VDD

VDD

D

E

LEVEL

SHIFTER

LEVEL

SHIFTER

INPUT (OUTPUT)

OUTPUT (INPUT)

DATA

TERMINAL

NUMBER

DATA

TERMINAL

NUMBER

A0

2

B0

21

A1

3

B1

20

A2

4

B2

19

A3

5

B3

18

A4

6

B4

17

A5

7

B5

16

A6

8

B6

15

A7

9

B7

14

TRUTH TABLE

ENABLE

DISABLE

FUNCTION

X

0

Convert CMOS Level to TTL Level

1

1

Convert TTL Level to CMOS Level

0

1

High Impedance (Z)

0 = Low Level

1 = High Level

X = Don’t Care

Z = High Impedance on Both CMOS and TTL sides.

NOTE: An important caveat that is applicable to CMOS devices in

general is that unused inputs should never be left floating. This rule

applies to inputs connected to a three-state bus. The need for

external pull-up resistors during three-state bus conditions is

eliminated by the presence of regenerative latches on the following

HS-3374RH pins: A0 - 7.

The functional block diagram depicts one of these pins with the

regenerative latch. When the CMOS driver assumes the high

impedance state, the latch holds the bus in whatever logic state

(high or low) it was before the three-state condition. A transient

drive current of

±1.5mA at VDD/2 ±0.5V for 10ns is required to

switch the latch. Thus, CMOS device inputs connected to the bus

are not allowed to float during three-state conditions.

* WARNING: Do not activate the Disable input by hardwiring to any

TTL input pins. This is an incorrect mode of operation.

Spec Number

518052