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DRV8844: Stepper motor driver chip

Part Number: DRV8844
Other Parts Discussed in Thread: DRV8880

Hi Team,

The customer is experiencing below issue and needs your help.

The customer wants to use the DRV series stepper motor driver chip to drive a small stepper motor. The internal resistance of the motor is very large, it is 190 ohms. The drive current requirement is very small. It hopes to be a STEP/DIR control method. 

When choosing a resistor, whether there is a maximum value of the resistance?

The maximum and minimum values of ISENCEX PIN VOLTAGE in the manual are 0.8V. If he chooses a very large resistor, such as a few ohms, will the chip lose its protection in the case of a motor short circuit? If he chooses a large sampling resistor to achieve small current drive, what adverse effect will it have on the chip? 

Is there any other STEP/DIR type IC recommendation? The driving current is about 100mA. The voltage is 24V, and a lower voltage can also be considered.

Thanks.

Annie

  • Annie,

    If the input is 24V and output current is 100mA, the maximum loop resistance could 240ohm (= 24V/100mA).

    DRV8844 doesn't have current regulation loop. So, it is hard to do micro-stepping control, decay mode setting and need external current regulation control which can avoid the switching noise on the current sensing resistor. So, I would pick DRV8880 to save the external current regulation circuit and have a quick decay mode setting.

    If the motor winding shorted, DRV8880 has an analog current limit circuit on each FET which limits the current through the FET by removing the gate drive. It is independent from the current sensing circuit. For OCP protection please check "7.3.17 Overcurrent Protection (OCP)" section.

    Regards,

    Wang