SN74F112: One circuit didn't work.

Takashi Matsumura

Intellectual 725 points

Part Number: SN74F112

Hi TI Team,

Thank you for your support.

One of our customer has trouble with SN74F112N.

Our understanding is this Logic IC has 2 elements.

These working individually.

But One output applied to one circuit, It didn't work normally.

It's typical way for Asynchronous counter circuit.

1. At what point in the production process was a failure detected?

When testing Asynchronous counter circuit

2. Has this part been used in your design or production process before?

The customer used CD74HC112E and that was no problem. But SN74F112N is not.

9. Testing equipment and method

This is video for Testing

https://datadeliver.net/receiver/file_boxes/6113a8cb385b400fb385d3a1e0001d9f/rc/924d785458e64c27a56c87fe994790d9

PW：kogakuin0110

Defective IC：SN74F112N

IC which working correct：CD74H112E

Details

Input rate
Vcc	+5V
GND	0V
PRE	H
CLR	setup: L, Operation:H
J	H
K	H
1CLK	Input by push switch
2CLK	Connected to 1Q output

10. If applicable what is the operating current and voltage the parts are being supplied?

Connected to 4 x 1.5V batteries for series and testing as 5V. Batteries are new.

Can you give some advice?

Thank you so much for your patience.

Kind Regards,

Takashi

T4639702

6 months ago

0 Clemens Ladisch 6 months ago

Guru 258710 points

In theory, connecting 1Q to 2CLK should work.

The SN74F112 is an old bipolar device with TTL outputs. A high output cannot source more than 1 mA, and can drop down to 2.7 V. I suspect that the additional LED connected to 1Q tries to draw too much current, i.e., it acts like a pull-down resistor that is too strong.

Why are you using the SN74F112? Nowadays, there should be no reason to use it in a new design.

Logic

Logic forum

SN74F112: One circuit didn't work.