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Looking at the L297 datasheet, it references the use of "fast 2A type diodes".

What does that mean?

Would a 1N4001 qualify? Given the application, I'm assuming that it needs to be a higher power part. Not sure about the "fast" part though. The 4001 datasheet doesn't say anything about that.

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  • \$\begingroup\$ "fast 2A type" means faster than standard Si diodes, with at least 2A peak current capability. The term "fast" is common in diode descriptions. \$\endgroup\$
    – tyblu
    Aug 7, 2011 at 20:53

4 Answers 4

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The application example (on page 8) which you're looking at shows the diodes connected to an L298N driver, which is distinct from the L297. Here's is the datasheet you want to look at.

...Which shows that the L298N is just a generic motor driver. The purpose of the diodes is to prevent the inductance from the motor windings from generating voltages which will destroy the motor driver.

The 1N4001 is a standard recovery (not fast) diode rated at 1A of continuous current. Thus, it does not fit the datasheet recommendations, so very large currents may be shared by the transistors you're trying to protect, and the beginning of every cycle will admit some overvoltage to those same transistors. However, it may be adequate if you're just driving a low-power motor.

If you've got a high powered motor or are concerned about reliability, I'd recommend Schottky diodes like the common 1N5820 series, which will do a great job of protecting the silicon diodes integral to the L298N output transistors.

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  • \$\begingroup\$ I also buit a driver based on the L298N, and it heats a little (even with a radiator). I used 1N4007 diodes. The 2 motors that the board drives are rated 6V max. Do you recommend replacing all the diodes (6) with fast recovery diodes? Also, I noticed that when powering off the driver, the motors keep spinning a little. Would a fast recovery diode fix that also? \$\endgroup\$
    – binar
    Sep 9, 2013 at 21:50
  • \$\begingroup\$ @Latchup actually deserves the credit for this edit. I just fixed his typo. (electronics.stackexchange.com/users/122029/latchup) \$\endgroup\$
    – AaronD
    Nov 12, 2016 at 4:43
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When you invert the voltage on a diode it will continue to conduct in the reverse direction for a short time, the reverse recovery time trr. For fast diodes this time is shorter.

This conduction in the reverse direction wastes energy, which heats up the transistors in the H-bridge and the diodes.

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Try fast recovery diodes like these from Vishay.

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  • \$\begingroup\$ The link shows a list of more than 100 devices. Not really helpful. \$\endgroup\$ Jun 16, 2011 at 15:23
  • \$\begingroup\$ The OP didn't give any details of the voltage etc. Why the downvote? \$\endgroup\$ Jun 16, 2011 at 15:53
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You can use 1N5822 schottky diode they're rated at 3Amp and as they are Schottky diode they do not have a stage from where they have to return.

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