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UC3525A: 3k at the shut down PIN?

Andres Miguel Machara Chomiak
Prodigy 50 points
Part Number: UC3525A

Hello all,

I'm just curious about the series resistor in the 10 input pin. Why in some parts of the datasheet of the UC3525 is shower a 3K, and in others you can see a 5K resistor? Could be a mistake?

Thanks!

  • 0
    TI__Mastermind 26215 points

    Andres,

    I see two examples in the UCC3525A data sheet block diagrams that are showing 3 kΩ internally connected to pin 10 (shutdown) and one example showing 5 kΩ (Fig 5). You are correct that this is most likely a typo in the Fig 5 example. In either case, the internal resistor is simply limiting the base current to the internal NPN shutdown transistor. The internal value of this resistor will have no impact on external component selection since it is recommended to pull pin 10 high (~1V<V<5V) for shutdown. Thanks for connecting through E2E and bringing this to our attention.

    Regards,

    Steve M