LT3060 output capacitor 200uFx2

Question

Hello 
 Customer use LT3060 (10Vin/3.3Vout). If add 220uFx2 on LT3060 output to supply MCU, the waveform is below and MCU damaged. It looks related to stability issue. Could LT3060 or LT3010 output with 220uFx2? Has limitation of output capacitor? Thank you.

BR 
 Patrick

ACaldejon · Accepted Answer

Hi Partrick, 
 Based on experience, it is always recommended that the input cap be equal to the output cap. So if you are adding 220uF to the output. Input cap should be at least equal or greater than the output cap. That practice is for stability of the LDO at load point. 
 What I know is that cap value should be above the minimum required (at this case for LT3060 requires a minimum 2.2uF Cout). But if you failed to make Input and output cap equal, let's say your input cap is lower than the output cap. At fast load transient at the output, the load will get that energy from the output cap, that energy will then be regenerated by the LDO from its input. There will be not enough energy available from the input that is needed by the output, if input cap is lower than the output cap. It is possible that LDO input voltage may drop or oscillate which could propagate to the LDO output causing the instability. You can typically make the input cap bigger than the output cap, but not the other way around. 
 regards,

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LT3060 output capacitor 200uFx2

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