On 2/3/2011 12:25 PM, Michael Watterson wrote:
> On 03/02/2011 17:00, Wouter van Ooijen wrote:
>   =20
>> lousy 2.5V at 1A, so this is not a very good diode, but this is within
>> the "normal operating condition" for this chip. Of course, if you think
>> 2.5V is way too much, or you fear you will exceed the maximum power
>> dissipation of the chip, or you are afraid these diodes will be too slow
>> (I see no switching time info), external (better!) clamping diodes might
>> be a good idea (as shown on page 6), but basically this chip has
>> internal clamping diodes.
>>     =20
> All what he says and:
>
> For clamping, Fast and current rating may be more important than
> Schottky. Schottky is more important for series diodes in normal current
> path, especially in low voltage high current PSUs.
>
> Also you may want Snubber Network at Motor connections to reduce rise
> time and initial peak current.
>
> A reasonable overview
> http://en.wikipedia.org/wiki/Snubber
>
> On a Bridge driven motor you might put four diodes (ground to out1, out1
> to Vs, ground to out2, out2 to Vs) on the PCB, but have transorb (back
> to back zener rated more than supply volts) and/or R&  C snubber network
> to reduce RFI and current in cable to the on-board diodes. You might
> have transorb at 1.5 to x3 the supply volts. Power rating of C and R may
> be important! Many years ago a I saw C explode when large motor 1st
> turned off.
>
> A stepper or any multiple winding motor is a more complex issue as
> explained earlier.
>   =20
http://www.vishay.com/diodes/protection-tvs-esd/trans-zorb/related/

Vishay application notes for Transzorb.
--=20
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