Switching regulators.
ke4pjw
Posts: 1,240
in Propeller 2
Anyone use the SD8942 or MT2492 as either the 1.8V or 3.3V regulator for the P2? Looking at these for my first P2 board.
Comments
Beware of the "PFM" regulators. One of Ray's earlier boards had one and it put a cool ~9 kHz ripple onto the VIO rail.
Looking it up, PFM looks similar to PDM in terms of pure modulation. So I suspect there's a technical difference in the circumstances of use since PDM produces a less noisy filter compared to PWM. But it does so at worse efficiency. Just the opposite of PFM.
I guess I should build a circuit for it and determine at what current draw forces PWM mode. Maybe I could use this as a step down to feed linear regulators at 3.3V. I don't think running one of these for the 1.8v core would cause too much of an issue.
I have 100 of the SD8942 laying around.
The datasheet should give that information... at what load it switches down from PWM to low current mode / PFM/etc..?
Often switchers have a couple stock code variants- one with fixed PWM and the other having "eco" specs.
But having 100 parts laying around surely trumps that anyway!!!!
And probably the PWM-only variant is footprint compatible, so you might choose to swap out the 3.3V regulator later without board changes. I tend to agree on your 1.8V assumption. Just the consistency for the VIO's can be important for sensitive applications. The digital core is a hardy fellow.