Alpha & Omega AOZ1282 buck regulator--experiences?

No experience yet but if it's any comfort I just placed its higher speed brother AOZ1280 into a sensitive x-ray system. I like small inductors.

In the past I mostly used Richtek and never had any issues. Of course, whenever I can get away with it I take the old 34063 which is hard to beat in price.

Regarding noise use an inductor with the least amount of leakage and in the layout keep the loop through which switching power flows small.

For good pricing on the inductor contact these folks:

Den mandag den 11. januar 2016 kl. 22.25.54 UTC+1 skrev Phil Hobbs:

how about mp1584 ? I think they can do 100k-1.5M

you can get a whole board with everything for less than $1 so they must to be dirt cheap

-Lasse

Thanks. With a 1.8 MHz maximum frequency, the AOZ1280's 100-ns minimum on-time is a bit sporty for a 24 V -> 5 V converter, so I'll stick with the AOZ1282, which is 150 ns min and 540 kHz max.

Cheers

Phil Hobbs

Stock's pretty thin over here--Octopart finds only 141 parts at Mouser, for $2 each.

Cheers

Phil Hobbs

In the efficiency graphs on page 6 they even have a 24V -> 3.3V case. That would be a real white-knuckle ride unless the chip enters skip mode if it can't get down far enough without.

FWIW, I've been impressed with their MOSFET offerings, which seem to turn up often, in terms of being that little edge above the competition on the whole Qg(tot) * $ / Rds(on) figure of merit. Haven't used any of their PMIC stuff yet.

If you're more comfortable with TI, I'm sure they have something TPS54xxx-ey that would fit..? Guessing anything newer and fancier probably blows the bill, if LM2594's marginal already though.

Tim

Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

Hi, all,

I'm doing the back end for that cotton spark detector system. Each integrator box (Pi Zero based) digitizes the output of up to 8 sensors and talks via multimaster RS485 or maybe industrial CANbus to a control panel, which sends data to the outside world. (Getting the SCADA security right is the client's job--I bowed out of that bit because I'm not a crypto guy.)

I need a 24V->5V switcher with a quiet output, so I'm using my fave topology: a buck with a cap multiplier inside the regulation loop.

I only need a couple of watts, so I'd normally use an LM2594. The customer sells a lot of stuff into Bangladesh and Pakistan and places like that, though, so it's a bit more price-sensitive than usual--$2 matters a fair amount. Also the power feed is +24V, so I'll need a decent sized inductor if I stay with the 150 kHz ones.

So I'm looking at the 450-kHz AOD1282CI from the oddly named Alpha & Omega Semiconductor. MOSFET with bootstrap, 1.2A switch, decent specs. Seems like only Digikey has them, but they've got a metric buttload (90k pieces), and they're only 30 cents each. Plus I can use a 670 uH inductor instead of 2 mH (!).

I don't really want to deal with the EMI issues of a much faster converter, so this seems like a good compromise.

Anybody used them? Good? Bad? Ugly?

Thanks

Phil Hobbs

Just a warning about Richtek:

The RT8258 part has funny startup behavior, can draw a lot of current during voltage ramping of the input from 0 to whatever

Cheers

Klaus

They have SuperJunction designs, like most others. A nice line of MOSFETs, but not much distributor choice (at Digi-Key). I've placed an order to give some of their 650V parts a try. I guess Alpha & Omega is another fabless semi company.

It doesn't have a soft-start but if it would violate its cycle-to-cycle current limit that would be really bad.

Not just HV parts, but the same thing in lower voltages too.

Distributor choice is a downer, true.

Tim