LT3463 stability

Hi,

Stability can be checked by using the FRA tool. If you attach your .asc file to the EZ post, we can take a look.

Thanks!

Hi,

It appears that your design is actually stable. The ripple comes from the fact that the part is operating in DCM. If you look at the datasheet, on page 8, it shows typical waveforms for the positive and negative output (LT3463/LT3463A - Dual Micropower DC/DC Converters with Schottky Diodes):

As shown here, the output voltage ripple matches what you see in LTSpice. Basically, the way that this chip works is that it has a continuous off time of 300ns. Because of this, the chip will switch with that off time until the voltage reaches the value set by the FB pins. However, since the load is so small, the chip keeps switching with an off time of 300ns, and the capacitor continues to charge to a more negative voltage than your set point of -13V. Eventually, this negative voltage reaches a value large enough that in order to maintain regulation, the chip stops switching and skips a cycle to let the output capacitor to discharge back down to an acceptable level. Then, switching resumes, and the cycle repeats.

Because of this excess ripple, it is good that you included a linear regulator after the LT3463.

Thanks!