L298N and L297/1: low-pass filter usage

[UY1]

When using L298N and L297/1 Is it necessary to use a low-pass filter when connecting the L298N current detection terminal to the L297/1 sense?

[Peter BENSCH]

Welcome @UY1, to the community!

What happens if you connect a low-pass filter behind a current sense signal carrying high-frequency signals?

Exactly - you filter out the high-frequency components. As a result, however, you will also receive information about a possible coil current overshoot later - or not at all, because your motor has burnt out.

Summary: no, please do not insert a low-pass filter.

Hope that helps?

Good luck!
/Peter

[UY1]

Dear person in charge, is there anything that describes the relationship between the resistors connected to CURB and CURA in the circuit and the detection points? I can't understand it even after reading L297 and L298. Thank you in advance.

[Peter BENSCH]

Well, the full-bridge driver L298 has one pin per full-bridge for the current sense resistor (shunt). Each of these pins is connected directly to the current sense input of the stepper motor controller L297.

The current flowing through a stepper motor winding then causes a corresponding voltage to drop across the shunt. This voltage coming from the shunt is compared with the voltage at Vref (pin 15) via the comparator(s) the L297 contains. The data sheet of the L927, page 3 says for pin Vref:

Vref: Reference voltage for chopper circuit. A voltage applied to this pin determines the peak load current.

For more information please read AN235 Stepper Motor Driving.

Hope that helps?

Regards
/Peter