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LP5907-Q1: maximum output capacitor

Part Number: LP5907-Q1
Other Parts Discussed in Thread: TLV702, TLV700

Hi team,

why there is maximum capacitor limited for LP5907-Q1? if the maximum capacitor is larger than 10uF, what will happen?  It seems there is no such limit in other parts.

thanks!

  • Hi Terry,

    Many, but certainly not all, LDOs have a maximum output capacitance that they can support. There are design trade-offs that are made in order to support very large capacitances and so some LDO designs have tighter or wider capacitor ranges. Specifically LP5907-Q1 can become unstable if more than 10uF is used. 

  • Hi Kyle,

    thanks!

    what 'trade-offs' do you mean? stable capacitor range and what?

    So for LDO, there is similar capacitor range to ensure loop stable like DCDC?

  • Hi Terry,

    Yes like a DC/DC the output cap usually has a range of values that can be used to keep the control loop stable. The range of output capacitor a device supports can effect many things such as the compensation of the LDO, the die size, the Iq current, and the transient response. 

  • thanks Kyle,

    So why there are many LDO didn't specify the maximum output capacitance in the datasheet, like TLV700, TLV702? Is there any limits for them?

  • Hey Terry,

    We try to give as much flexibility as possible to our customers so many devices do not have a max limit for Cout (this depends on the design decision/trades needed when a product is defined).

    For those specific devices they are low current devices and so in rush current can become a concern during startup. Generally I'd recommend keeping Cout below 47uF for those devices, if you need something close to that (or higher) let me know the cap value and the output voltage and we can assess it more specifically.