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LMZM33603: Maximum Output Capacitance

Part Number: LMZM33603
Other Parts Discussed in Thread: LMZM33606, LMR33630

I am using LMZM33603 to generate a 9V DC rail from a 12V-24V input.  Table 1 says the required Cout max for a 9V Vout is 110 uF.  My 9V rail provides power to a processor board that has over 800 uF of capacitance on that rail.  What will the effect be on the LMZM33603 if the output capacitance is way more than the recommended max from table 1?

What are my options for providing a 9V rail to this processor board?  Should I consider a different DC/DC converter?

  • Hi Howard,

    I would recommend switching to a different power module. The issue with capacitance over 110uF for your application is during a power cycle/startup condition. During startup, the output voltage will ramp to final value of 9V. Too much output capacitance may result in the device tripping output short fault condition because the output capacitance may take too long of a time to ramp to final value.

    The LMZM33606 may be considered if you can reduce the output capacitance to around around 650uF just to be slighly below the maximum output capacitance spec based on the datasheet recommended operation conditions (Section 6.3)

    Otherwise I would recommend designing with a DC/DC converter (external inductor required). The LMR33630 should be able to go up to 1000uF (Section