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ALM2403-Q1: ALM2403 as motor driver, soft start

Evan Peng
Intellectual 1115 points
Part Number: ALM2403-Q1

Dear expert,

This is Shenzhen FAE Anker, my customer is using our ALM2403 as a micro motor driver in projector product, the schematic are as below, the input of DAC is from our DLP. In their application, the startup serial is:

1. DAC input signal OK,

2. ALM2403 V+ V- power up

3.ALM2403 EN pin pull up

However, the problem is that, when EN pin pull up, ALM2403 will experience a hard startup process, the motor will make noise, and the output voltage of ALM2403 will also ramp high in this process. Can you please give some advice to soften the startup process?

  • 0
    TI__Guru 63041 points

    Hi Evan,

    Evan Peng said:
    when EN pin pull up, ALM2403 will experience a hard startup process, the motor will make noise, and the output voltage of ALM2403 will also ramp high in this process.

    It is likely that customer is driving the motor in square wave. The issues are the motor is LC & R load, the motor coil inductance will generate Ldi/dt voltage spikes at the moment the ALM2403-Q1 is sourcing current. The customer has to change the power on sequences and/or waveform pattern at the input. 

    I am not certain I understand the circuit. Please provide me the driving requirements at the motor, so we can simulate it properly. 

    ALM2403-Q1 Bidir Motor Driver not working 05172024.TSC

    Evan Peng said:
    Can you please give some advice to soften the startup process?

    The customer needs to alter the power on sequences, where step 1 in DAC should be engaged at last. In addition, Vdac may need to be ramped up instead of square wave  to reduce the start up voltage and/or current spikes. I need to know more about the motor driving parameters in order to simulate.  

    In addition, I am not sure that OTF/SH_DN pin is configured properly. If V- = -12Vdc, then OTF/SH_DN pin should be > -12V + 1.2V = -10.8Vdc in enable logic, see the slide below. In ALM2403-Q1, OTF/SH_DN is referenced to V- supply rail. The simulation is shown that OTF/SH_DN pin is configured at the minimum requirements approximately, which it has no design margins over wide operating temperature. Please check on it. 

      

     

    If you have other questions, please let me know. 

    Best,

    Raymond