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TPS5401 UVLO

Gerry Kurz
Intellectual 685 points
Other Parts Discussed in Thread: TPS5401

In the TPS5401 datasheet on page 15 in the Undervoltage Lockout section, the following statement is made:

Though it is not necessary to use the UVLO adjust resistors, for operation it is highly recommended to provide consistent power-up behavior.

I would like to know what sort of inconsistent power-up behavior to expect if I choose not to use this feature. My interest is to create a software controlled enable/disable for this part that minimizes shutdown current.

  • 0
    TI__Guru**** 191445 points

    There is no hysteresis on the internal UVLO.  So when powering up (or down) load change on the input can cause the local input voltage at the UVLO comparator to transistion back across the threshold voltage, momentarily shuting down (or restarting during shutdown, the device.  This is primarily an issue with slowly rising or falling input voltage.  The external UVL has some hysteresis in teh form of the I1 and I2 current.  You can control EN externally with logic rather than the UVLO resistors if you desire.

  • 0 in reply to JohnTucker
    Intellectual 685 points

    OK thanks. That should not be an issue in my application as the device will be continuously powered by batteries except during final assembly or some extreme fault condition.

  • 0 in reply to Gerry Kurz
    Intellectual 685 points

    One more question..... does the 1.3 uA (typical) shutdown supply current include the 0.9 uA current sourced by the enable pin (enable pin held low by external logic)?

  • 0 in reply to Gerry Kurz
    TI__Guru**** 191445 points

    Yes.  If EN is held low, the EN source current is typically close to 1.3 uA (it is spec'd at 0.9 uA at Vth - 50 mV).  So the shutdown current is essentially, EN current plus leakagecurrents elsewhere.