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Drv103 Oscillating at 1000Hz

Frank Zuhde
Prodigy 20 points
Other Parts Discussed in Thread: DRV103

Dear Support:  I am trying to get the DRV103 to oscillate at 1000 Hz.  We had it working at 20k Hz with a duty cycle of 50%.  The resisters used were Rosc: 220K and Rduty 150K.  Now I switched to Rosc of 5M and Rduty 1M.  All I get is a 380 usec pulse, one time when the chip is enabled.  I know these values are at the extremes of the tables.  We are trying to operate an inkjet valve which has a maximum frequency of 1kz.  I would really like to run it at 500hz.

Please let me know if there any special needs at that frequency or any application notes that are applicable.

  • 0
    TI__Genius 9975 points
    Hello Frank Zuhde,
    I think the problem in your circuit is the selection of RPWM. For a 1 kHz oscillator frequency, you will need about 2 Mohm in order to obtain a 10 % duty cycle. For a 50 % duty cycle you will need at least 3.4 Mohm for RPWM.
    At this level of high resistance the circuit will be VERY susceptible to noise pick-up. My suggestion is to be VERY careful with your PCB layout. Selecting the smallest size of footprint possible and diminishing the loop area of the circuit between DRV103 pins, resistor and ground will be key.
    Hope this helps.
    Best regards,
    Jose
  • 0 in reply to Jose Duenas
    Prodigy 20 points
    Thanks Jose: I took the resistors off, added wires to the 4 pads and experimented with different resistors. Using 5 Mohm for the Rosc, I got 1040 Hz. Using 3.3 Mohm for Rpwm, the DRV103 showed a near 50% duty cycle. (480 us vs 520 us). It is doing what I want now. Thanks.
    Frank