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No output for PWM inputs in DRV8412

sanoj kumar
Prodigy 60 points
Other Parts Discussed in Thread: DRV8412

Sir,

I am using DRV8412 in my PCB for dual TEC control and using Mode 1 for cycle-by cycle limit.

Currently I am trying to drive a 12V-2.5A TEC through Output C & D and  left open outputs A&B. Used 100K for R-OC adj resistor and same value of output inductor and capacitor as give in the reference TEC circuit of datasheet.

I am giving PWM input to input C and zero volts to D. But not getting any output even by increasing PWM upto 400kHz and

 changing duty cycle(giving minimum off time of 50ns for boot strap capacitors). No output even for giving complimentary PWMs (Measuring the current through a current probe of 100khz bandwidth). No outputs even when TEC is not connected. 

Fault pin is not asserting low. Is the capacitors after inductor is trying to draw heavy inrush currents and hitting the cycle by cycle limit?

What should be the PWM configurations for inputs, both inputs with complimentary PWMS or one with PWM and other with 0v?

what is the fault in the scheme?

thanks

Sanoj Kumar

 

  • 0
    TI__Guru** 114905 points
    Hi Sanoj,

    Please refer to the second to last paragraph on page 15. If a cycle by cycle limit is hit, the D input must be toggled to re-activate the output pair.

    Fault is not asserted when this occurs.

    Both inputs PWM'ing is preferred. To clear the cycle by cycle event a small high pulse (50 to 100ns) on the D input of your configuration is needed.