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SLA7026 missing diodes ?!?

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florinasdragalas

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Hi,
In datasheets from Allegro and Sanken the typical application are without diodes across stepper coils.
Same implementation on real printer drivers.
So , a few questions:

1) is correct to think they use avalanche breakdown of rugged MOSFETs for BEMF decay ?
2) What will happen with torque if I'm putting diodes across coils ?(guess I'll get slow instead fast decay)
3) Can I use avalanche rated MOSFETs in a discrete unipolar driver without diodes across coils?
4) I never seen a fried SLA 7026(7024,7029), is a discrete driver a reliable circuit (without diodes ) ?

Regards
F
 

bakupcpu

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Can't really remember what's the main difference between the avalanche and non avalanche mosfet but thechnically when speaking of stepper motor if you short coil it will be harder to turn so putting diode will do the same thing at high speed. most stepper motor driver are protected for that I'm not quite sure if they use mosfet of plain power transistor. Hope this help you a little Cheer!
 

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