dc motor - H-Bridge flyback diode selection?

I am wanting to make a motor driver using a SN754410 Quadruple Half-H Driver IC.

The SN754410 requires external flyback diodes. Here is an example circuit:

My question is, how do I choose which diodes to use? Two popular choices seem to be the 1N5819 and the 1N4007, but I don't know why.

What factors are involved in choosing suitable flyback diodes?

I'll speculate:

1. Cost


2. Current rating (motor operating current, or higher?)


3. Voltage rating (motor operating voltage, or higher?)


4. Switching time (does this matter with flyback diodes?)

Answer

The H bridge chip you are using has 1 amp capability (2 A non-repetitive). If you are using it correctly i.e. within spec then the diode you need has only to be rated about 1 amp. A 1N4007 is rated at 1 amp continuous and 30A non-repetitive so on the face of it it fits the bill.

As for your choice of H bridge, there are far better choices (dependant on the voltage supply). See this.