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How can I automatically shut down the TPS92512 when IADJ = 0 mV?

Jason Work
Genius 10830 points
Other Parts Discussed in Thread: TPS92512, LM211, TPS3839

How can I automatically shut down the TPS92512 when IADJ = 0 mV?

Assume I do not have the luxury of more than one output pin from my microcontroller, so I cannot use one pin for PWM and another pin dedicated for either UVLO or PDIM.  The input to the IADJ pin must shut off the LEDs when the voltage is close to 0 mV.

Would a circuit like this work?

When IADJ is well above 0 V, the voltage at UVLO will be well above the threshold to keep the LED driver on.  As IADJ approaches to 0 V then the voltage at UVLO will drop below the threshold voltage and the output will be shut off.

A more precise way to do this would be to use a comparator like the LM211 but this would add cost and space which would be worth it only if the tolerance on the shutdown threshold is tight.

  • 0
    TI__Mastermind 46140 points
    Hi Josh,

    Have you thought about just using a reset IC like the TPS3839? You can pick the threshold where you want to to drive the UVLO pin low or high. Let me know what you think.

    Regards,
  • 0 in reply to JCHK
    TI__Genius 10830 points
    Thanks. Good suggestion. I made a mistake on the above circuit. I thought the UVLO threshold was 2.9 V. It is not. It's 1.22 V, so I'd have to modifiy the circuit for that to make sense. Zener diodes don't go down that low, but a few regular diodes in series could add to 1.3 V for example.

    Your suggestion of a reset IC is a good one too. I wonder what the lowest cost option will be.