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TLV707: output of LDO rising

Part Number: TLV707

Question from my customer:

I am using the TLV70718 and it works fine only I plug in a LTE module and then the output goes from 1.8 to 2.7 volts. There’s an interface signal that is being driven with a buffer that’s sourced by the 1.8V rail, but the module has a 10K (or maybe 5K) pullup to 3.5V which seems to be pulling the regulator out of regulation (its input is 3.3V). I’m surprised that such a high resistance (through a buffer) is having this effect and I want to understand why.


  • Hi Nick, 

    What you are describing will occur with almost every LDO if there is little or no load. This is because LDOs are not designed to sink current, they only source current. So when there is a pull up voltage like this which is higher than the LDO's regulated output voltage (even if the current is very small) then you will need the load on the 1.8V rail to be higher than that current from the pull-up otherwise the voltage will drift higher and all the LDO can do is turn off the pass device when it detects that the output voltage is too high.