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.
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