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SN74HC04: Die-shrink and date-code verification

Part Number: SN74HC04
Other Parts Discussed in Thread: SN74AHCU04, SN74LVC1GX04

We have run into a problem with the SN74HC04DR part.  Parts with the code: 07C2CFK work fine, but parts with code 25A3D9K do not.

Examining the parts via X-ray, we see that the die inside the 25A* parts is signifcantly smaller.  In the same circuit, the good parts will have a 32 MHz output signal, as expected.

The 25A* parts only have a 17kHz output.  The parts are used in a Pierce Oscilaltor design as described in

See the attached schematic.

 - Was there a die-shrink between those 2 lot/date codes?

 - Is there a reason this circuit is not working?

Thank you.

  • The new die of the HC04 has more hysteresis at its input buffers, which improves handling of digital signals. But a crystal does not output a digital signal.

    The application report tells you that a Pierce oscillator requires an unbuffered inverter, such as the SN74AHCU04.

    If you can change the board layout, consider the SN74LVC1GX04.