No. The motor is inductive, so you can't stop the current in the motor very quickly. When the IC turns off, the diodes give the motor current somewhere to go. Without them, you would get some very large voltage spikes each time the motor turned off.
No. The motor is inductive, so you can't stop the current in the motor very quickly. When the IC turns off, the diodes give the motor current somewhere to go. Without them, you would get some very large voltage spikes each time the motor turned off.
Back EMF voltage can reach 6 to 8 times the supply voltage level, e.g. supply voltage 12V, back EMF = 72/96V.
The diode must be able to reduce that back EMF to a level which won't "kill" the switching transistor.
Schottky-diodes work perfect for spike suppression when rated for the coil nominal power.
Fast recovery diodes work perfectly as well.
Here are some types to use: MR85X, where MR851 is 100V/3A, MR852 is 200V/3A, MR854 is 400V/3A and MR856 is 600V/3A. The strongest fast recovery diode is the RGP30M (1000V/3A)
The diodes must be able to terminate a relatively high voltage (hence high current) within a very short time repeatedly.
Fast diodes are not particularly required for the suppression of inductive kick. Fast diodes are rated for fast recovery turn-off. For suppressing an inductor, you just need a diode that turns on rapidly, and all diodes do that. So don't worry about the speed of the diode here. A Schottky diode does have a lower forward drop but that is likely not important for inductive suppression.
Fast diodes are not particularly required for the suppression of inductive kick. Fast diodes are rated for fast recovery turn-off. For suppressing an inductor, you just need a diode that turns on rapidly, and all diodes do that. So don't worry about the speed of the diode here. A Schottky diode does have a lower forward drop but that is likely not important for inductive suppression.
A Schottky diode has a lower forward drop than a silicium type diode. Lower voltage drop at high current means the diode has to dissipate less power than a silicium type diode.
The speed of the diode determines if the back EMF is reduced fast enough in order not to damage the driver transistor.
Most data sheets suggest Schottky diodes for recovery - certainly not without reason.
A Schottky diode has a lower forward drop than a silicium type diode. Lower voltage drop at high current means the diode has to dissipate less power than a silicium type diode.
Certainly you want to use Schottky diodes for the flyback in switching power supplies to improve efficiency. For spike suppression in inductive circuits, I don't see the need.
Carl is right, reverse recovery time isn't important if the forward conduction ends before a reverse bias is applied. Therefore diode speed isn't important in most 'catch diode' applications. Speed is only important if forward current is still flowing when the voltage reverses (as in many switching PS).
Reverse recovery of diodes is misunderstood by most engineers I know. Most of them don't need this information, so that's sort of OK. But that means that most engineers will give the wrong answer when asked.