TPS54302 is a wonderful little synchronous switcher chip. 3 amp switcher in SOT-23, under a dollar. It does radical spread-spectrum pwm but the dc output is quiet. We're designing a small box that contains about 400 power relays. To reduce coil power, we'll run the relay coils at 12 volts and bump them up to 24 briefly when we change setups. One issue is whether the switcher can switch 24 to 24, full on, without its bootstrap cap discharging. The TPS makes a tiny blip once in a while to recharge the cap. It seems to do everything right. They do get pretty warm at 3 amps. We've done a lot of testing on the eval board. https://www.dropbox.com/s/jban5vjybbb2g77/TPS54302_PWM.JPG?raw=1 https://www.dropbox.com/s/etctkh2rzesockj/TPS54302_spectrum.JPG?raw=1 -- I yam what I yam - Popeye
TPS54302 again
Started by ●January 13, 2022
Reply by ●January 13, 20222022-01-13
jlarkin@highlandsniptechnology.com wrote:> TPS54302 is a wonderful little synchronous switcher chip. > > 3 amp switcher in SOT-23, under a dollar. It does radical > spread-spectrum pwm but the dc output is quiet. > > We're designing a small box that contains about 400 power relays. To > reduce coil power, we'll run the relay coils at 12 volts and bump them > up to 24 briefly when we change setups. One issue is whether the > switcher can switch 24 to 24, full on, without its bootstrap cap > discharging. The TPS makes a tiny blip once in a while to recharge the > cap. It seems to do everything right. > > They do get pretty warm at 3 amps. > > We've done a lot of testing on the eval board. > > https://www.dropbox.com/s/jban5vjybbb2g77/TPS54302_PWM.JPG?raw=1 > > https://www.dropbox.com/s/etctkh2rzesockj/TPS54302_spectrum.JPG?raw=1 > > > >Nice. When running from a lowish input rail, I sometimes use a 10k resistor from the bootstrap pin to some higher supply to reduce the ON resistance. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●January 13, 20222022-01-13
On Thu, 13 Jan 2022 11:47:03 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>jlarkin@highlandsniptechnology.com wrote: >> TPS54302 is a wonderful little synchronous switcher chip. >> >> 3 amp switcher in SOT-23, under a dollar. It does radical >> spread-spectrum pwm but the dc output is quiet. >> >> We're designing a small box that contains about 400 power relays. To >> reduce coil power, we'll run the relay coils at 12 volts and bump them >> up to 24 briefly when we change setups. One issue is whether the >> switcher can switch 24 to 24, full on, without its bootstrap cap >> discharging. The TPS makes a tiny blip once in a while to recharge the >> cap. It seems to do everything right. >> >> They do get pretty warm at 3 amps. >> >> We've done a lot of testing on the eval board. >> >> https://www.dropbox.com/s/jban5vjybbb2g77/TPS54302_PWM.JPG?raw=1 >> >> https://www.dropbox.com/s/etctkh2rzesockj/TPS54302_spectrum.JPG?raw=1 >> >> >> >> >Nice. When running from a lowish input rail, I sometimes use a 10k >resistor from the bootstrap pin to some higher supply to reduce the ON >resistance. > >Cheers > >Phil HobbsThat's another way to keep the highside fet on forever. In our case, we have no higher voltage available. -- I yam what I yam - Popeye
Reply by ●January 13, 20222022-01-13
jlarkin@highlandsniptechnology.com Wrote in message:r> TPS54302 is a wonderful little synchronous switcher chip.3 amp switcher in SOT-23, under a dollar. It does radicalspread-spectrum pwm but the dc output is quiet.We're designing a small box that contains about 400 power relays. Toreduce coil power, we'll run the relay coils at 12 volts and bump themup to 24 briefly when we change setups. One issue is whether theswitcher can switch 24 to 24, full on, without its bootstrap capdischarging. The TPS makes a tiny blip once in a while to recharge thecap. It seems to do everything right.They do get pretty warm at 3 amps.We've done a lot of testing on the eval board.https://www.dropbox.com/s/jban5vjybbb2g77/TPS54302_PWM.JPG?raw=1https://www.dropbox.com/s/etctkh2rzesockj/TPS54302_spectrum.JPG?raw=1-- I yam what I yam - PopeyeI use the tps69xxx, nice little part. Lots of current for a small part. Cheers -- ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html
