74F621 datasheet(6/10 Pages) PHILIPS

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Philips Semiconductors

Product specification

74F621

Octal bus transceiver, non-inverting (open collector)

1996 Jan 05

TYPICAL PROPAGATION DELAYS VERSUS LOAD FOR OPEN COLLECTOR OUTPUTS

100

200

300

400

500

600

Load Resistor (

Propagation

delay (ns)

tPLH

tPHL

SF01153

NOTE:

When using open-collector parts, the value of the pull-up resistor greatly affects the value of the tPLH. For example, changing the pull-up

resistor value from 500

W to 100W will improve the tPLH up to 50% with only slight increase in the tPHL. However, if the pull-up resistor is

changed, the user must take certain that the total IOL current through the resistor and the total IIL’s of the receivers do not exceed the IOL

maximum specification.

TEST CIRCUIT AND WAVEFORMS

90%

10%

90%

10%

90%

10%

90%

10%

NEGATIVE

PULSE

POSITIVE

PULSE

AMP (V)

tTHL (tf )

INPUT PULSE REQUIREMENTS

rep. rate

tTLH

tTHL

1MHz

500ns

2.5ns

Input Pulse Definition

VCC

family

74F

D.U.T.

PULSE

GENERATOR

VIN

VOUT

Test Circuit for Open Collector Outputs

DEFINITIONS:

RL = Load resistor;

see AC electrical characteristics for value.

CL = Load capacitance includes jig and probe capacitance;

see AC electrical characteristics for value.

RT = Termination resistance should be equal to ZOUT of

pulse generators.

tTHL (tf )

tTLH (tr )

AMP (V)

amplitude

3.0V

1.5V

7.0V

SF00027

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