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TPS7B4255: Output below 2V

Bryan McLaughlin
Prodigy 20 points
Part Number: TPS7B4255


Tool/software:

Hello, 

I need to supply an adjustable voltage 1.7-2.7V to a PCB at end-of-line test, 10mA max, 3.6VAbs Max.  This will come from an offboard bench supply but I want to dummy-proof accidental setting to higher voltages than this. These are super expensive PCBs.

I'm considering using a tracking LDO to "buffer" the voltage. I want to power the tracking LDO from 3.3V so in no case can it drive to 3.6V.

The TPS7B4255 spec says is can output down to 2.0V, but Figure 6-8 shows it stays linear down to ~1.7V which would be perfect. Can you clarify the datasheet spec or suggest other ideas?

Considering Power Op-Amps as well but it's the same concept, but those seem less happy to drive capacitive loads.

Thanks!

  • 0
    TI__Expert 6610 points

    Hi Bryan,

    Thank you for asking us!

    This part will regulate as expected down to 1.65VADJ.

    The ADJ pin has dual function as an Enable pin, so below a certain threshold it will shut down as seen in the datasheet curve.

    However, the spec defines that limit as below 1.65V, so it must try to regulate to VADJ/VOUTs above that:

    The recommended operating condition range ends at 2V, so all that means is that you lose the min/max performance spec guarantee. It will still work like an LDO/voltage buffer, and typical values or characteristic curves will remain a good estimate of typical performance. 

    Best,

    Gregory Thompson