LTC7149

Hello,

I guess your used input cap is undersized in terms of current ripple:

Please check the statement on page 12 in the datasheet. 'Unluckily' with 12V to -12V the ripple reaches its max value. IRMS=IOUT. What is the ripple rating of C7?

Markus

C7 is Panasonic brand EEHZA1J100P with ripple current 1A @ 100kHz  

C7 is Panasonic brand EEHZA1J100P with ripple current 1A @ 100kHz  

Hello,

a) you have configured the LTC7149 for a1MHz switching frequency -> factor of 10 more than specified for your capacitor

b) according to the formula on page 12 ripple current equals output current with your 12V -> -12V setup. 1.5A is 50% above your ripple rating spec.

Do you see the potential problem?

regards

Markus

Hello Markus,

thank you for information. I add parallel additional capacitor, tests running now and it looks good.