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SN74ALS245A: output high level issue

Intellectual 1250 points

Replies: 5

Views: 46

Part Number: SN74ALS245A

Hi team,

When applying SN74ALS245ANSR in buffer, sometimes there would occur output all high level issue and such issue goes with the IC during ABA swap test. See below schematic, see if any advice to better improve.

Best Regards

  • Hi Gene,

    I don't see any issue with your schematic.

    It sounds like there's been some damage to the device. How many failures like this have you seen?  Can you give me more details regarding the failures?


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  • In reply to Emrys Maier:

    Hi Emrys

    Appreciate for your help.

    Just several pcs from customer's end customer failed products,  failure rate is not high like 1/10000. then locate such issue on SN74ALS245A for the abnormal output with all high level, which should be PWM output normally. Just want your help to see whether from application point of view any suggestion for the customer circuit design?   any possibility leads to such abnormal behavior for all output high ?

    I checked with power supply and Enable signal, it is normal.

    Best Regards

  • In reply to Gene Qiu:

    The most common reason to see a failure like this is an ESD strike, but there are also other possibilities - excessive heat can damage a device, or a short on the board - for example, two outputs being shorted together could cause a failure.

    It's extremely strange to see a device with 8 channels that all fail high at the same time. Usually if one channel is damaged due to an ESD strike you might see that -- but only for a single output, not all.

    What is connected beyond the 100 ohm series output resistors to UU, UD, VU, VD, WU, and WD?


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.

  • In reply to Emrys Maier:

    Hi Emrys

    Thank you for the hint. For the ESD point of view, do we have other higher ESD level P2P device? 

    can SN74LV245A P2P replace  SN74ALS245A?

    The 100ohm series output resistors to UU, UD, VU, VD, WU, and WD are connected to Isolator , and then gate driver to drive the IPM of BLDC.

    Best Regards

    Gene

  • In reply to Gene Qiu:

    Hey Gene,

    Logic devices all have relatively low ESD protection levels - these are only intended for protection of the device during manufacturing and assume that the manufacturing site uses ESD protection measures.

    In a final system, system-level ESD protection should be added externally to protect the device. There's an application report with additional details here: https://www.ti.com/lit/an/slyt492/slyt492.pdf 


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.