Tireless search for a small 5A H-Bridge

If this is for a stepper motor I imagine you would need a dual bridge. For a dual bridge I would recommend L6205 by ST. I have not used this chip but parameters seem nice and most importantly (for me) it is one of the smallest dual bridges in this category. For single bridge I have used mc33887 and that is a really good chip. It has varios protection and feedback mechanisms and comes in a reasonable package (can be prototyped by hand).

Tiit

L6025 runs 2.8A, full bridge. Amp output too low.
mc33887 runs 5A, half bridge. Output is right, could use two in concert.

Thanks, the mc33887 is my best bet right now.

Cabe

I know this post is old, but I too am looking to build a bi-polar stepper motor controller in the 5 AMP range...  Have you found anything yet?

What about using two TI DRV8843 chips in parallel, would something like that work?  Or should I be looking at a solution to perhaps use a TI 4988 to drive external MOSFET's?

I am not an electrical engineer by any means, but I do know enough to get myself in a lot of trouble...

Ok, 5A for a full bridge isn't going to be easy to find in a single chip. You're looking at i2r losses of 5W for .1 ohm fets and 500mW for .01 ohm fets That means you are looking at D9 packages at the minimum for discrete FETs (no SOT23's will carry that much current and not desolder themselves). The typical TO-220AB package will dissipate 2.5W in free air. I wrote up a tutorial on h-bridges here http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/index.html and will follow up with a FET version here now that I've got stuff worked out on the web site (new site will be http://robotics.mcmanis.com)

The way to look at this is what the Rds(on) value is for the FET, then square the current and multiply that by 2 (high side fet and low side fet) that is the power that has to be dissipated by the package. If the temperature goes up (which it will do without a heat sink) then Rds goes up too (which means more power gets dissipated) Good general rule of thumb is that Rds(on) doubles at max temperature. So if the data sheet says it has a 1 milliohm Rds(on) then at full temp that will be 2 milliohms. On steppers you probably want a good chopper drive anyway to get maximum torque out of them.

---Chuck

How about the Allegro STA6940M which is an 8 amp device?!

I must say I am not impressed by Newark compared to Farnell as a supplier even though they are both parts of Premeir Farnell. It shows up the significant diffference in the customer experience of British and US companies with the British model far more favourable, I know it must seem ridiculous to you as surface mounting afficionados, but to obtain decent thermal performance you need a device that can dissipate to metal like this one: http://uk.farnell.com/semikron/skd51-08/bridge-rectifier-50a-800v-3ph/dp/9287078

I cant see the required Vds for the MOSFETs but here are a few options from FSC that at least provide the full bridge set of FETs in one small package although Rds(on) might be a bit high on the 100Vds parts

Quad MOSFET package

FDMQ8203- 100Vds 2( Nch + Pch) MOSFET for full bridge

FD/FDMQ8403- 100Vds 4* Nch MOSFET

FDMQ86530L- 60Vds 4* Nch MOSFET (logic level switching)

LV Bridge Drivers

FAN3268 20V bridge driver

FAN3278- 30V bridge driver

This topic belongs in group Motion control.

I may supply you with transistors for 2A, 3A, 6A or 7A.

30V.

The smaller ones come in pairs per chip (2 not connected transistors), or full bridge on one chip (4 readily interconnected transistors).

The bigger ones - 2 per chip.

Size of a chip is about 3mm.

Why build your own controller? Why not use what is already manufactured?

I may provide a full controller on a PCB.