Boost converter at low current

[ubbut]

Hi,

for a project I need to convert 12V to 15V at relatively low output current (10-50mA). Usually my go-to switching controller is the AP3012. Low cost, high frequency.
However as it turns out at such low currents, the AP3012 has far worse ripple as compared to higher currents. The reason seems to be, that the 3012 goes into "pulse skipping" mode, effectively lowering the frequency significantly and thus creating a large output ripple.
I also tested the LT1615 with basically the same results.

Looking for an alternative part designed for lower current I found the LT1615-1, but even before the supply shortage it could not be obtained.

I did have success with LT3460, it is however much too expensive for my application.

AP3015 seems to have a undefined, much lower operation frequency. Have not tested yet

So basically this results in my 2 questions:

(1) Are there alternative parts I could use? Something I am not aware of? Recommendations?

(2) Is it possible to somehow reduce the ripple of the AP3012? I tried altering the feedback network, reducing and increasing the inductance and output cap - all with little to no positive effect.

thank you!

[SiliconWizard]

I can suggest the TPS61099, or equivalent in the same series.

[harerod]

Hi ubbut, I think you are on the right track. The "pulse skipping" is to counter saturation of the inductor due to low load current. The minimum required load current depends on inductance and lowest duty cycle. AP3012 Figure 9 shows 20..90% duty cycle.
Caveat: Higher inductivity may result in a more sluggish response to changing load current.
Regarding a feasible component - just have a look at the distri sites, what's available today... Digikey has some LT1930 in stock.
I second EVB149's LDO recommendation. While supply ripple current is low for boost topology, output ripple is high. Depending on your application filter+LDO might be indicated.

[Weston]

I cant think of any specific boost converters that fit your application off-hand, but the feature you want is "forced-PWM" mode, which means that the converter will never enter pulse skipping mode, regardless of load current.

Often dc/dc converters will have part variants that are always in forced PWM mode, or they have a pin you can tie to the supply / ground to define the behavior.