Multiple H-Bridge Chip

[AndrewM]

I'm trying to find an IC containing multiple H-Bridges.  I've seen a few with up to 4 H-Bridges on chip, but I was hoping to find a single IC with lots more (I would not be opposed to 128+ on chip).  I figured before I get too deep into trying to find a product I should ask here and see if anyone has seen one already.  I would prefer something that can handle a decent amount of amps (over 16A) per H-Bridge, but I can find work arounds for lower amperage if need be.

Anyone used or heard of such a chip?

[airman00]

nope
but sounds like you need to custom make H bridges with high power mosfets

[izua]

a h-bridge that handles around 16 amps is a pretty big thing. a chip with 128 chips is usually called a pcb and is probably done with discrete transistors.

beeing back ontopic, allegro has some diversity in hbridge chips (they even have some dip stuff). some are stepper optimised (and they also know ustepping), some are pwm optimised. but the biggest one i've seen had only 4 hbridges per chip. oh, and i also got some samples from 'em

[Asellith]

your going to have to go with something smaller just a quick calculation at 12 volts with 16 amp is 192 watts of power time 128 is over 24 KW of power. The heat sink would be the size of most peoples robots. Do you want variable speed or is just forwards and reverse? Relays would work with a Digital I/O chip with 128 outputs that could control the relays then you could get away with it. Still going to cost you a lot of cash.

[AndrewM]

I don't need variable speed, although it would be helpful (pwm optimized).  And I only need forward, so a bunch of half H-Bridges.  I'm trying to get control down to as small as possible, preferrably under 1 sq in.

Asellith, could you give me more info on what you are thinking with relays and I/O chips?

[airman00]

I don't need variable speed, although it would be helpful (pwm optimized).  And I only need forward, so a bunch of half H-Bridges.  I'm trying to get control down to as small as possible, preferrably under 1 sq in.

Asellith, could you give me more info on what you are thinking with relays and I/O chips?

Get some 12V automotive relays from a surplus place ( like allelectronics.com). Then use a MOSFET to trigger the relays

[Asellith]

Get some 12V automotive relays from a surplus place ( like allelectronics.com). Then use a MOSFET to trigger the relays
[/quote]

basically what airman said. I'm assuming that what your controlling it with does not have 128 outputs. Then you will need a microcontroller with a uart or spi interface that will allow you to control a digital output chip. If I get time tomorrow I'll look some up for you. Its getting late here. Then hook the outputs from that chip to a bunch of small mosfets and configure the mosfets to sink the current from the coil of the relays. Then you have the ability to turn the motors on and off electronically without an H-bridge. Another option is not to use a standard automotive or general purpose relay but a solid state relay. This will increase cost a lot but gives you the ability to use PWM on the motors. These are generally used in AC motor applications and high current DC stuff. The last one I worked on was in a blower motor controller for HVAC equipment. Lots of options. Now the controller fitting in 1 square inch is possible if you do not include the size of the relays. With that many relays solid state or otherwise your going to need a lot of room. These can be mounted close to the motors and away from the control equipment then run signal lines and you will not even need to run the bigger power lines to the controller unit and with that many motors you'll need BIG wires depending on your voltages.

[AndrewM]

Thanks for the info.     I'll start digging around for digital output chips to see if I can find something that will work.