I’m having trouble finding fully-integrated MOSFET h-bridge ICs. I have found the L9110 integrated h-bridge that looks from its VHout of about 7.6V from a Vcc of 9V to be a BJT h-bridge (though the sparse datasheet doesn’t even call it an h-bridge and is low on details). However, the MOSFET h-bridge chips I’ve found are all like DMHC3025LSD which is just a convenient packaging of 4 MOSFETs. Very flexible and widely useful but not what I had in mind.

The L9110 looks like it will work, and it’s what I’ll use if I can’t find something better. (And it’s cheap at about $1 each.) But I’m looking for as low power draw as possible, small parts count, and physically small parts. So a single IC that’s a complete h-bridge implementation in a MOSFET design would be nicer.

Odd requirement?

My use case is a little constrained, and rather contrived to make an excuse for trying something new. I’m tired of butter that’s almost melted all summer and too hard to spread all winter. (I know, #firstworldproblems … ) I bought a marble tile sliced in half (giving me two 6x12 inch pieces) and a peltier element. My goal is to sandwich the peltier element between the two halves of the marble tile, and use an attiny to control the peltier element to keep the upper tile the right temperature, and just keep the ceramic butter dish on top of the tile. But I want to put all the electronics between the two tile halves so that I don’t have to have an exposed project box. Thus I want to fit everything in between the two slabs with the peltier element. The peltier element has to be coupled to both slabs, because the bottom slab acts as the heat sink. The peltier element is about 4mm thick. This puts a premium on small components… I’ll be using silicone to hold free-soldered components in place. I can’t use any components thicker than 4mm and still have the element thermally coupled to both slabs. I’ll have to get a little creative to make this work, like bending out the pins on the attiny to solder wires to them. No room for a circuit board here! Thus the desire for fewer small components here to make things easier.

Eugene Crosser July 27, 2014 17:16

not what you asked, but what about

  • use something else for the lower heat sink, metal and with fins maybe?

or

  • put the electronics in the power brick and have two extra wires going to the thermistor. you’ll need an external power supply anyway, right?

(coming from an armchair diy-er, sorry)

Michael K Johnson July 27, 2014 17:45

Since you ask…

The lower heat sink thermally couples to the granite countertop. The conditioned plate will be within 4°C of ambient. No need for metal or fins. Power brick is an existing 9V 500mA wall wart; already bigger than I’d like without building an ugly project case around it. I’m planning to use the internal thermistor in the attiny anyway, which also kills that idea. :-)

It will work with the L9110; I’m just looking to see if there is something better out there.

Michael K Johnson July 27, 2014 19:21

I wonder if even more complete motor driver chips like http://www.mouser.com/new/Texas-Instruments/ti-drv8839-motor-driver/ have taken over the market segment that an integrated h-bridge would have previously served. I looks like “dual half bridge” would be the magic words I was looking for. $1.62 in onesies isn’t bad.

Michael K Johnson September 27, 2014 16:23

Burned out one peltier element testing. It looks like at 5V it draws about 300-400mA and there is enough thermal mass that I don’t need to use PWM; I can just cycle it. I can’t measure the temperature accurately enough to do better anyway… That’s my guess so far.

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