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TPS40170 current in UVLO

David Paulsen
Prodigy 235 points

Other Parts Discussed in Thread: TPS40170

Does anyone know what the operating current of the TPS40170 is when enabled, but UVLO is low?  I have an application that needs the 3.3V LDO output to run while the switching regulator main output is turned off.  I would like to get under about 2 or 3 mA.

  • 0
    TI__Genius 13700 points

    Hello David,

    Looking at the top of Pg 4 of the datasheet the term Iqq which gives the operating current when the drivers are not switching is what I would think is the current consumption of the chip when the system in UVLO.

    My reasoning being that the chip itself is still running and sampling and therefore not shut down but the UVLO feature is causing the drivers to not switch the external FETs.

    The list value is a max of 4mA which might mean that after the initial disengaging of the drivers the power consumption of the device might dip to the desired level.

    Ryan May

  • 0 in reply to Ryan May
    TI__Mastermind 35675 points

    Ryan is right, the Iqq is the specification you're looking for. Since this is a max, it accounts for variations from unit to unit so it is an absolute worst case. A more realistic value for a typical unit with 12V input is 2.1mA.

  • 0 in reply to Anthony F
    TI__Mastermind 35675 points

    A little more information after some lab testing, the Iqq specification is actually for when the device is not switching but the internal control circuit is still powered. This is done by pulling the FB pin up to 0.9V.

    If UVLO is pulled low there is actually much less current consumed by the TPS40170. On the TPS40170 EVM the input current is reduced to 0.9mA. This includes current which flows through the EN resistors and UVLO resistors which is about 0.2mA.