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Alpha & Omega AOZ1282 buck regulator--experiences?

Started by Phil Hobbs January 11, 2016
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

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
On 2016-01-11 13:25, Phil Hobbs wrote:
> 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? >
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: http://xfmrs.com/ -- Regards, Joerg http://www.analogconsultants.com/
Den mandag den 11. januar 2016 kl. 22.25.54 UTC+1 skrev Phil Hobbs:
> 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? >
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
On 01/11/2016 04:42 PM, Joerg wrote:
> On 2016-01-11 13:25, Phil Hobbs wrote: >> 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? >> > > 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: > > http://xfmrs.com/ >
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 -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On 01/11/2016 05:05 PM, Lasse Langwadt Christensen wrote:
> Den mandag den 11. januar 2016 kl. 22.25.54 UTC+1 skrev Phil Hobbs: >> 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? >> > > > 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
Stock's pretty thin over here--Octopart finds only 141 parts at Mouser, for $2 each. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On 2016-01-11 14:18, Phil Hobbs wrote:
> On 01/11/2016 04:42 PM, Joerg wrote: >> On 2016-01-11 13:25, Phil Hobbs wrote: >>> 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? >>> >> >> 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: >> >> http://xfmrs.com/ >> > > 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. >
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. http://aosmd.com/res/data_sheets/AOZ1280CI.pdf -- Regards, Joerg http://www.analogconsultants.com/
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: http://seventransistorlabs.com


"Phil Hobbs"  wrote in message 
news:7-WdnSTbPNpBgAnLnZ2dnUU7-TudnZ2d@supernews.com...

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

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net 


On Monday, January 11, 2016 at 10:42:22 PM UTC+1, Joerg wrote:
> On 2016-01-11 13:25, Phil Hobbs wrote: > > 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? > > > > 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. >
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
Tim Williams wrote...
> > 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.
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. -- Thanks, - Win
On 2016-01-12 02:22, Klaus Kragelund wrote:
> On Monday, January 11, 2016 at 10:42:22 PM UTC+1, Joerg wrote: >> On 2016-01-11 13:25, Phil Hobbs wrote: >>> 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? >>> >> >> 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. >> > 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 >
It doesn't have a soft-start but if it would violate its cycle-to-cycle current limit that would be really bad. -- Regards, Joerg http://www.analogconsultants.com/