SN74HC86: in someone batch, product can't work stably and the current increase continually.

Zhiyong Yang

Part Number: SN74HC86
Other Parts Discussed in Thread: SN74HCS86

Dears,

We purchase 80kpcs SN74HC86PWR in Jun,2021, which is used on our Industrial Sensor product. The TI order No. is T01506638.

In the production, we find there are two kinds of mark on the chip: HC86 08K & HC86 14K. Products with 14K are all working stably, but others with 08k are all test failure. That：After 3-4 mins system power on, the current increase continually and the chip become heat.

Now, more than 12kpcs 08k are system test failure and there are other 12k chips in our stock. This problem is making our production stagnation and we have to spend a lot of time to sift through the rest PCBA.

Please check is there any difference between HC86 08K &HC86 14K, and the cause of the failure.

Look forward to your reply early.

Thanks.

over 4 years ago

0 Emrys Maier over 4 years ago

TI__Guru* 97066 points

Hello,

The SN74HC86 has recently had a change in it's design which caused a decrease in thermal dissipation. This issue may be related to the thermals, or it may be related to how the device is being used.

Can you share details of the operation of the device?

We would like to see a schematic for the device and anything connected to it, as well as scope shots of the input/output signals to see exactly what's going on. It would be helpful to see results from both a good and bad device.

0 Zhiyong Yang over 4 years ago in reply to Emrys Maier

Prodigy 10 points

Hi Emrys,

I have sent the schemetic to your email address noreply-e2e@mail.ti.com, did you get it? Looking forwward to you early reply. Thanks.

0 Emrys Maier over 4 years ago in reply to Zhiyong Yang

TI__Guru* 97066 points

Hi Zhiyong,

That's not my email address. That is an automated email system -- the "noreply" indicates that you should not reply to it.

Is there a reason you cannot post the schematic here?

0 Zhiyong Yang over 4 years ago in reply to Emrys Maier

Prodigy 10 points

Hi Emrys,

Sorry I didn't notice Schematic is attached, please check it. Sheet1.pdf

0 Clemens Ladisch over 4 years ago in reply to Zhiyong Yang

Guru 318460 points

How have you connected the inputs of the fourth gate? They must never float.

What is the current through D2? Is the voltage at pin 1 ever between V_IL and V_IH?

C2 makes the signal edges quite slow. You should use a device with Schmitt-trigger inputs like the SN74HCS86.

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Logic forum

SN74HC86: in someone batch, product can't work stably and the current increase continually.