Forums

really nice little switcher

Started by John Larkin September 1, 2016
http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything

The data sheet doesn't say much about thermals, and it looks scary to
me to make a 15 watt switcher in a SOT23-6 without a power pad, so I
got the eval board and tried it.

It's unusual in that it accepts 28 volts input and has internal
soft-start and spread-spectrum. And it's cheap.


https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg


I think 3 amps is pushing this little guy pretty hard, but 2 amps,
maybe even 2.5, looks reasonable. I don't know where the heat comes
out... most likely pin 1, ground. I guess I'll put a lot of copper on
all the pins.




-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

On Thu, 01 Sep 2016 19:16:13 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything > >The data sheet doesn't say much about thermals, and it looks scary to >me to make a 15 watt switcher in a SOT23-6 without a power pad, so I >got the eval board and tried it. > >It's unusual in that it accepts 28 volts input and has internal >soft-start and spread-spectrum. And it's cheap. > > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg > > >I think 3 amps is pushing this little guy pretty hard, but 2 amps, >maybe even 2.5, looks reasonable. I don't know where the heat comes >out... most likely pin 1, ground. I guess I'll put a lot of copper on >all the pins.
Looks similar to their TPS6xxx inverting charge pumps. They work pretty good too. Not much noise. Cheers
"John Larkin"  wrote in message 
news:i9nhsbpqtama43neod5af7n5dt1g677n3k@4ax.com...

http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything

The data sheet doesn't say much about thermals, and it looks scary to
me to make a 15 watt switcher in a SOT23-6 without a power pad, so I
got the eval board and tried it.

It's unusual in that it accepts 28 volts input and has internal
soft-start and spread-spectrum. And it's cheap.


https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG

https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg


I think 3 amps is pushing this little guy pretty hard, but 2 amps,
maybe even 2.5, looks reasonable. I don't know where the heat comes
out... most likely pin 1, ground. I guess I'll put a lot of copper on
all the pins.
===============================================================================

Can't you just take a pic with your IR camera and see how hot each pin is 
where it enters the body?  If not on the eval board, do a proto with the 
same pad area at each pin and drive it just hard enough to make it warm up a 
little and see  which pin(s) get hottest.

-----
Regards,
Carl Ijames


On Thu, 1 Sep 2016 22:47:30 -0400, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

>"John Larkin" wrote in message >news:i9nhsbpqtama43neod5af7n5dt1g677n3k@4ax.com... > >http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything > >The data sheet doesn't say much about thermals, and it looks scary to >me to make a 15 watt switcher in a SOT23-6 without a power pad, so I >got the eval board and tried it. > >It's unusual in that it accepts 28 volts input and has internal >soft-start and spread-spectrum. And it's cheap. > > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG > >https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg > > >I think 3 amps is pushing this little guy pretty hard, but 2 amps, >maybe even 2.5, looks reasonable. I don't know where the heat comes >out... most likely pin 1, ground. I guess I'll put a lot of copper on >all the pins. >=============================================================================== > >Can't you just take a pic with your IR camera and see how hot each pin is >where it enters the body? If not on the eval board, do a proto with the >same pad area at each pin and drive it just hard enough to make it warm up a >little and see which pin(s) get hottest. > >----- >Regards, >Carl Ijames >
The pins themselves are shiny in the thermal IR, so their temperature display is very wrong. I didn't quite have enough resolution to image the epoxy around each pin. Maybe I'll paint the pins with something with high emissivity to try to resolve pin temps. I wish I could image the heat flow! I probably don't need over 2 amps on any supply, so I'll just lay out the real board. These are cheap enough that I can use a lot of them for the various supplies. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thu, 01 Sep 2016 22:23:41 -0400, Martin Riddle
<martin_ridd@verizon.net> wrote:

>On Thu, 01 Sep 2016 19:16:13 -0700, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything >> >>The data sheet doesn't say much about thermals, and it looks scary to >>me to make a 15 watt switcher in a SOT23-6 without a power pad, so I >>got the eval board and tried it. >> >>It's unusual in that it accepts 28 volts input and has internal >>soft-start and spread-spectrum. And it's cheap. >> >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg >> >> >>I think 3 amps is pushing this little guy pretty hard, but 2 amps, >>maybe even 2.5, looks reasonable. I don't know where the heat comes >>out... most likely pin 1, ground. I guess I'll put a lot of copper on >>all the pins. > >Looks similar to their TPS6xxx inverting charge pumps. They work >pretty good too. Not much noise. > >Cheers
This one will work in the inverting configuration, but it can't quite do +24 to -5... that's one volt over its abs max rating. I can switch down to +5 with one of these, and flip it to -5 with one more. I need some +5 anyhow. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 02/09/16 13:02, John Larkin wrote:
> On Thu, 1 Sep 2016 22:47:30 -0400, "Carl Ijames" >> Can't you just take a pic with your IR camera and see how hot each pin is >> where it enters the body? If not on the eval board, do a proto with the >> same pad area at each pin and drive it just hard enough to make it warm up a >> little and see which pin(s) get hottest. > The pins themselves are shiny in the thermal IR, so their temperature > display is very wrong. I didn't quite have enough resolution to image > the epoxy around each pin. Maybe I'll paint the pins with something > with high emissivity to try to resolve pin temps.
The NXP RF PA's (see recent discussion) show some thermal photos after the entire reference design was sprayed with a uniform black. The actual paint used was unlike any black I've seen - I suspect because it was extremely thin and high-conductivity, to avoid changing the heat flow. Does anyone know what it is?
> I wish I could image the heat flow!
You know the approximate thermal conductivity, and the heat flow is just the temperature derivative multiplied by the conductivity. Even just convolving the raw image to produce the derivative would be enlightening. I think most image manipulation tools have such a thing. Clifford Heath.
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
news:6lqhsblkb991lk7l52nbsdce8staeljrfg@4ax.com...
> On Thu, 1 Sep 2016 22:47:30 -0400, "Carl Ijames" > <carl.ijamesXyZZy@ZZxyz.verizon.net> wrote: > >>"John Larkin" wrote in message >>news:i9nhsbpqtama43neod5af7n5dt1g677n3k@4ax.com... >> >>http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything >> >>The data sheet doesn't say much about thermals, and it looks scary to >>me to make a 15 watt switcher in a SOT23-6 without a power pad, so I >>got the eval board and tried it. >> >>It's unusual in that it accepts 28 volts input and has internal >>soft-start and spread-spectrum. And it's cheap. >> >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG >> >>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg >> >> >>I think 3 amps is pushing this little guy pretty hard, but 2 amps, >>maybe even 2.5, looks reasonable. I don't know where the heat comes >>out... most likely pin 1, ground. I guess I'll put a lot of copper on >>all the pins. >>=============================================================================== >> >>Can't you just take a pic with your IR camera and see how hot each pin is >>where it enters the body? If not on the eval board, do a proto with the >>same pad area at each pin and drive it just hard enough to make it warm up >>a >>little and see which pin(s) get hottest. >> >>----- >>Regards, >>Carl Ijames >> > > The pins themselves are shiny in the thermal IR, so their temperature > display is very wrong. I didn't quite have enough resolution to image > the epoxy around each pin. Maybe I'll paint the pins with something > with high emissivity to try to resolve pin temps. I wish I could image > the heat flow! > > I probably don't need over 2 amps on any supply, so I'll just lay out > the real board. These are cheap enough that I can use a lot of them > for the various supplies. > > > > > > > -- >
Stick some kapton tape on the leads. It is black to LWIR.
On Fri, 2 Sep 2016 14:44:38 +1000, Clifford Heath <no.spam@please.net>
wrote:

>On 02/09/16 13:02, John Larkin wrote: >> On Thu, 1 Sep 2016 22:47:30 -0400, "Carl Ijames" >>> Can't you just take a pic with your IR camera and see how hot each pin is >>> where it enters the body? If not on the eval board, do a proto with the >>> same pad area at each pin and drive it just hard enough to make it warm up a >>> little and see which pin(s) get hottest. >> The pins themselves are shiny in the thermal IR, so their temperature >> display is very wrong. I didn't quite have enough resolution to image >> the epoxy around each pin. Maybe I'll paint the pins with something >> with high emissivity to try to resolve pin temps. > >The NXP RF PA's (see recent discussion) show some thermal photos >after the entire reference design was sprayed with a uniform black. >The actual paint used was unlike any black I've seen - I suspect >because it was extremely thin and high-conductivity, to avoid >changing the heat flow. Does anyone know what it is?
Black whiteboard marker seems to have high emissivity, and it wipes or washes off easily without making a mess. I have a Testor model paint set, and I suspect that's high e, so I could paint the pins and just leave it that way. Most paints are high e.
> >> I wish I could image the heat flow! > >You know the approximate thermal conductivity, and the heat flow >is just the temperature derivative multiplied by the conductivity. >Even just convolving the raw image to produce the derivative would >be enlightening. I think most image manipulation tools have such a >thing.
I'd need pretty high imaging resolution to see the temp gradient along a pin. The FLIR could probably manage that, but not handheld! Maybe I could hack up a tripod sort of thing to hold it steady. It would be interesting to compara the temp gradients on all six pins. But the heat flow will still depend on the board layout. TI should better discuss heat flow on a SOT23 part that can switch 30 watts. Oh well, playing with parts like this is fun, a break from being a grownup. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Fri, 2 Sep 2016 01:08:28 -0400, "tom" <tmiller11147@verizon.net>
wrote:

> >"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message >news:6lqhsblkb991lk7l52nbsdce8staeljrfg@4ax.com... >> On Thu, 1 Sep 2016 22:47:30 -0400, "Carl Ijames" >> <carl.ijamesXyZZy@ZZxyz.verizon.net> wrote: >> >>>"John Larkin" wrote in message >>>news:i9nhsbpqtama43neod5af7n5dt1g677n3k@4ax.com... >>> >>>http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything >>> >>>The data sheet doesn't say much about thermals, and it looks scary to >>>me to make a 15 watt switcher in a SOT23-6 without a power pad, so I >>>got the eval board and tried it. >>> >>>It's unusual in that it accepts 28 volts input and has internal >>>soft-start and spread-spectrum. And it's cheap. >>> >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG >>> >>>https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg >>> >>> >>>I think 3 amps is pushing this little guy pretty hard, but 2 amps, >>>maybe even 2.5, looks reasonable. I don't know where the heat comes >>>out... most likely pin 1, ground. I guess I'll put a lot of copper on >>>all the pins. >>>=============================================================================== >>> >>>Can't you just take a pic with your IR camera and see how hot each pin is >>>where it enters the body? If not on the eval board, do a proto with the >>>same pad area at each pin and drive it just hard enough to make it warm up >>>a >>>little and see which pin(s) get hottest. >>> >>>----- >>>Regards, >>>Carl Ijames >>> >> >> The pins themselves are shiny in the thermal IR, so their temperature >> display is very wrong. I didn't quite have enough resolution to image >> the epoxy around each pin. Maybe I'll paint the pins with something >> with high emissivity to try to resolve pin temps. I wish I could image >> the heat flow! >> >> I probably don't need over 2 amps on any supply, so I'll just lay out >> the real board. These are cheap enough that I can use a lot of them >> for the various supplies. >> >> >> >> >> >> >> -- >> > >Stick some kapton tape on the leads. It is black to LWIR. >
I do that sometimes. These pins are really tiny, but it could be done. Here's a piece of Kapton on copperclad FR4: https://dl.dropboxusercontent.com/u/53724080/Thermal/Cool1.JPG https://dl.dropboxusercontent.com/u/53724080/Thermal/Cool2.jpg -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thursday, September 1, 2016 at 10:16:21 PM UTC-4, John Larkin wrote:
> http://www.ti.com/product/tps54302?keyMatch=TPS54302&tisearch=Search-EN-Everything > > The data sheet doesn't say much about thermals, and it looks scary to > me to make a 15 watt switcher in a SOT23-6 without a power pad, so I > got the eval board and tried it. > > It's unusual in that it accepts 28 volts input and has internal > soft-start and spread-spectrum. And it's cheap. > > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06829.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06826.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06825.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/DSC06828.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302EVB_WB.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/TPS54302_rise.JPG > > https://dl.dropboxusercontent.com/u/53724080/Parts/VREGS/TPS54302/IR_0057_3A.jpg >
Nice, thanks for the data. Did you try stressing it to the thermal limit shutdown? I always like to do that... let it thermal cycle on and off for a few hours and make sure it still runs after that. George H.
> > I think 3 amps is pushing this little guy pretty hard, but 2 amps, > maybe even 2.5, looks reasonable. I don't know where the heat comes > out... most likely pin 1, ground. I guess I'll put a lot of copper on > all the pins. > > > > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics