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LM26480: LM26480, VINLDO12 leakage.

Abdusamad PS
Prodigy 55 points
Part Number: LM26480
Other Parts Discussed in Thread: TPS62400

Hi !

I am using LM26480 and TPS62400 power regulators.

TPS62400 buck 1 provides output  = 3.3V

LM26480 Bucks are powered by 5V and LDOs are powered by 3.3V (from TPS62400)

Various supply connections is as follows 

AVDD = 5V

VIN BUCK1 = VIN BUCK2 = 5V

VINLDO12, VINLDO1, VINLDO2 = 3.3V (powered from TPS62400)

So , when this setup is powered, TPS62400 voltage shows as 4.2V and its not switching 3.3V output.

When I removed, 3.3V connection from VINLDO12, the 4.2V is gone and TPS62400 starts switching 3.3V out.

Looks like there is a leakage between VIN (5V) to VINLDO12 ? Is it that we have to power VINLDO12 to the same supply as AVDD ? Could you please explain this ? 

The datasheets says VINLDO12 is used as a UVLO input. Also there are some versions of the chip with UVLO disabled ? Does this has any relation internally to the VINLDO12 leakage from 5V ? or it is mandatory to power it similar to AVDD or BUCK inputs.

Appreciate your quick reply

Thanks in advance

Regards

Abdu Samad

  • 0
    TI__Genius 11020 points

    Hello,

    Yes there is a parasitic diode between VDDA and VINLDO12 in LM26480, so you have to connect them to the same input voltage. Unfortunately the datasheet is not clear about it..

    VINLDO12 is analog power for internal functions (VREF, BIAS, Logic). VDDA is buck converters' analog power.

    Thanks.

    Best regards,

    Tomi Koskela