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CD74HC04: There is hysteresis in the chip of a specific lot.

Conor
Mastermind 9800 points
Part Number: CD74HC04

Hi, 

We are using CD74HC04. There was no significant difference in the threshold values for both Lo→Hi and Hi→Lo for the normal products that had been used until now.

However, all newly delivered chips have a hysteresis of about 700mV. The input voltage when the output voltage changes from Lo to Hi is -549mV. Also, the input voltage when the output voltage changes from Hi to Lo is 138mV.

* Since the power supply to the product is ±2.5V, the Hi level is 2.5V and the Lo level is -2.5V.

Is this a spec according to the datasheet?

[The normal products]

[Chip with hysteresis]

Thanks,

Eevee

  • +1
    TI__Guru* 96842 points

    Hi Eevee,

    Conor said:

    We are using CD74HC04. There was no significant difference in the threshold values for both Lo→Hi and Hi→Lo for the normal products that had been used until now.

    However, all newly delivered chips have a hysteresis of about 700mV. The input voltage when the output voltage changes from Lo to Hi is -549mV. Also, the input voltage when the output voltage changes from Hi to Lo is 138mV.

    Yes, the device does have some hysteresis on the inputs with the new version as you have shown - this is expected behavior.

    Conor said:
    Is this a spec according to the datasheet?

    No, the datasheet does not include a threshold specification. It only includes the V_IL and V_IH levels that are required for the device, which the new device continues to meet.

    I understand that this is not always the desired behavior for our customers with this type of device. We still make many logic families that do not include hysteresis on the inputs if you want to switch to a device that has behavior similar to the older HC devices. For example, the CD74AC04 would be one option.