SN74HC04: Some lot codes working, others don't

Greg Aspland

Part Number: SN74HC04
Other Parts Discussed in Thread: CD74HCU04, SN74AHCU04, SN74HCU04

Tool/software:

I have a product which has been in production for around 30 years. With my most recent batch of boards, I have found that the SN74HC04N with date codes 3CA4T9M and 3CA4SEM do not work, but 25ASN5M does work. This hex inverter has only one gate used in the design, and it is in a crystal oscillator circuit. The clock runs at 8MHz, but on the parts that don't work, the output is around 5kHz.

Has there been a change to SN74HC04N that could account for this?

Any other help you can give?

1 month ago

0 Owen Westfall 1 month ago

TI__Expert 6931 points

Hi Greg,

You can see in this PCN we qualified a new fab for this device https://www.mouser.com/PCN/Texas_Instruments_PCN20210628000_20210629182107229.pdf

We have seen many devices have had their VIH and VIL value change slightly. These device are still operating within datasheet limits, so that's why it was not mentioned in the PCN from that time.

If this device is operating outside datasheet values please let us know, but if it is still within datasheet specs there is not much we can assist with here.

Regards,

Owen

0 Clemens Ladisch 1 month ago

Guru 272400 points

The SN74HC04 is a digital logic gate. But that circuit tries to use it as an analog amplifier, which has never been guaranteed to work.

You have to use an unbuffered inverter, i.e., SN74HCU04, CD74HCU04, or SN74AHCU04.

Logic

Logic forum

SN74HC04: Some lot codes working, others don't