H Bridge DBH 01C - bjornburton/champbot GitHub Wiki

#Overview This 20 A, 24 V dual H-Bridge is from Wingxing (Ebay), Aliexpress store 325585 or Wangxin in Tianjin, China. This company isn't really into branding or documentation. It's nice for $25. It's SMT on what looks like FR4. Build looks OK. Some solder balls but not bad. Joints look good. Connectors are of a better construction than some. Heatsink mounting is poor as it result in board warpage which results in minimal contact with the MOSFETs. A backing plate would limit the warpage. There was no heat-sink compound.

They also have a 50A model (DBH 01B) that, as far as I can tell, just has different MOSFETs (IR7843 with RDS_on of 3.3 mΩ, and a VDSS of 30 V). I can't be sure at this moment as I don't have the 20 A devices MOSFET p/n handy. Odd thing about the 50 A is there is a layer of what looks like polyimide tape on the component-side of the heatsink. This probably doesn't do much for the performance, but it's better than air I guess.

#Function This uses a pair of LM393 dual comparators to control four ST L6384D and their MOSFETs. Those are nice drivers but it's important to consider that PWM must be less than 98% duty-cycle, since it uses a charge-pump that needs recovery. There's an on-board regulator, an MC34063, which can power the circuit from the main supply. This is set if R3 (SET) is closed with a 0 Ω resistor (not included). There is an analog current sensor output (CT).

The EN (Enable) input connects to the L6384D's pin 3 (DT/SD), a pin that both sets the dead-time and shuts it down. For this reason it should be considered open collector and not driven high. For this module, HiZ is Enabled. There is a warning in the chip's datasheet about noise susceptibility and lead length so the safe bet is not to use it and let the module have it for it's dead-time.

Signal pins are all on one vert. 2 X 6 male header, 0.1" pitch. A ribbon IDC would fit, as will Molex C-Line and the like. There is no box, latch or anything that ensures polarity. The contacts are tin so for long-term use in a vehicle it should have connector lube applied (Electrolube CG60 or Nyogel 760G).

##PWM goes into IN1, direction goes into IN2? I wish! This thing is an odd-ball and the datasheet is really awful. One part of the datasheet seemed to indicate that PWM is on IN1. Page two indicates that this is incorrect by giving an example titled "Simplest use" which seems to be right. Hold IN2 low and it's in forward. Hold IN1 low and it's in reverse. PWM goes to whichever pin is not low. This makes it a bit of a challenge to use with a microcontroller, at least Atmel's, since PWM outputs have dedicated pin assignments.

I needed to use a couple NOR gates to link it to the Pro Trinket.

#Enhancements I've added a backing-plate of 16 ga steel with a perf-board insulating layer. This was fitted with longer M3X12 screws. Heatsink-compound was use be added too to cover surface imperfections. For long term use, a non-silicone compound should be used, or maybe a sil-pad, but I only had the cheap stuff handy.