I'm looking to go surface mount. I see this very interesting array of 2 diodes in one package, found here: http://search.digikey.com/us/en/products/BAS40-04LT1G/BAS40-04LT1GOSCT-ND/917804 I would typically have 4 diodes, 2 on each MOTOR_OUT line, going to GND and MOTOR_VCC. But I'm thinking I could get by with 2 of these to replace my 4 PTH Schottky 5818 diodes. I'm I correct? Is there some rating on this that isn't what it should be to work well for this job? My H Bridge is the SI9986DY-T1-E3 http://search.digikey.com/us/en/products/SI9986DY-T1-E3/SI9986DY-T1-E3CT-ND/1850116 And my motor is just a small general purpose 12 Volt, less than 500mA motor. If some parameter of this is there something more suitable? thanks!
Not being a engineer, but having some knowledge of electronics, I would say that you do not want to exceed these specifications. Generally, you want things like capacitors, to have a 250% over supply voltage rating when it comes to voltage specification. I am not sure if that applies to diodes on not.
Current - Peak Output 1.5A Voltage - Supply 3.8 V ~ 13.2 V
I'm not sure what kind of current/voltage is suppressed when the motor shuts off. The schottky diodes I've seen used 8518, have a 1Amp 40Volt rating... So I guess these are okay... ?
I would feel safe if the diodes had the same or better amperage rating and voltage rating as the motor driver you are using. If you are exceeding the driver's limits you will have bigger problems anyway.
You could find a board schematic that is shared, like a lot of the boards at Sparkfun, and make your own clone.
SouthernAtHeart: I'm not sure what kind of current/voltage is suppressed when the motor shuts off. The schottky diodes I've seen used 8518, have a 1Amp 40Volt rating... So I guess these are okay... ?
The diodes take the current the winding was taking, so get ones rated for that current.
The issue with dual diodes like this is whether they are common anode or common cathode - for a full H-bridge you need one dual-anode and one dual-cathode.
If you can find dual diodes that are in line (ie anode-to-cathode on the common pin) then you need 2 of those.
You might as well find a schottky bridge rectifier which has all 4 diodes in the right circuit!
Thanks, i JUST discovered this! I’ll be back with what I come up with…
I think I found something that will work great. The MB110S-TPMSCT-ND http://search.digikey.com/us/en/products/MB110S-TP/MB110S-TPMSCT-ND/2075340 ...this will save a LOT of space over using 4 PTH diodes.
You don't need any external diodes because that H-bridge chip (like all mosfet H-bridge chips I know of) has them built in. If the current rating of the motor were a lot higher then there might be some advantage in using external Schottky diodes (to reduce power dissipation in the chip), but for 500mA I really don't think it's worthwhile. But if you do want to use external diodes, then that Schottky bridge rectifier looks OK.