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TLV743P: Input and output voltage is dropping if I apply input to TLV743P from TP4056-4.2

Baranidaran Panneer Selvam
Prodigy 50 points
Part Number: TLV743P

Part number: TLV74333PDBVR

We have developed a battery-powered board with TLV743P LDO.

The input of the LDO is supplied by the battery, and when the battery is not inserted, it is directly connected to the battery charger IC TP4056-4.2. The enable pin of the LDO is shorted with the input voltage, and 1uF of capacitance is placed at the input and output of the LDO.

When there is no battery inserted in the board, the output of the LDO drops below a certain level. I have also checked the input and the input of TP4056-4.2 and observed this behavior reflecting at those points as well. However, when the battery is inserted, there are no issues, and the voltages are stable.

When the LDO is removed, the input and output voltage of TP4056-4.2 is stable.

Please help me to identify the cause of the issue and solution.

  • 0
    TI__Guru 50025 points

    Hi Baranidaran,

    This sounds like an issue with the TP4056-4.2 and not the TLV743P because the TLV743P cannot control what its input does. Can you capture a scope shot showing the input to the TP4056-4.2, output of the TP4056-4.2 (i.e. the input to the TLV743P), and the output of the TLV743P on the same plot?

    Can you share a schematic of the circuit? 

    What is the load on the TLV743P? Does the issue persist if the TLV743P is still populated but not loaded?

    Thanks,

    Nick