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DRV103: Can't get circuit working

TI-CSC
Genius 12965 points
Part Number: DRV103

Hello E2E Experts,

Good day.

I am trying to design an economizer circuit for the main electrical contractors on my EV conversion, but I can't get the circuit to work. I followed the basic circuit diagram from the datasheet and selected the resistors and capacitors from the tables provided there.

I wanted to use a 25kHz pwm frequency, 20% duty cycle, and 110ms delay time. The system voltage is between 12v-13.5v DC. When I power up the circuit, nothing happens (the LEDs don't turn on and nothing happens when I signal the input pin on the DRV103).

I am attaching a screenshot of my KiCAD circuit. The wires going off the bottom of the screen are connecting to a second DRV103 for the second coil I am driving. Since my EV controller outputs ground to engage the contractors, I had to use a transistor and a 5v regulator to supply the 5v input signal to the DRV103.

8103.schematic2.zip

Thank you in advance for your help.

Regards,

CSC

  • 0
    TI__Genius 13300 points

    Hello CSC,

    I have a few questions to clarify my understanding of your setup:

    1. STATUSOKFLAG is connected to the 12V supply with a status LED and inline resistor- is this correct?

    2. U3 connects Vout (assuming it drops to ~ 1.8V-5.5V) of U1 to INPUT of U2 when coil 1 signal asserts?

    In terms of your component choices and the general setup (aside from STATUS) I do not see any issues. Are you able to gather scope shots of INPUT, STATUS, VS and OUT?

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    TI__Genius 12965 points

    Hello Kalin,

    1. Yes, STATUSOKFLAG is connected to the 12V supply with a status LED and inline resistor. Is this a problem? I was trying to follow the example on the datasheet.

    2. Yes, U3 connects Vout of U1 to INPUT of U2 when coil 1 signal asserts.

    I have probed the board and discovered something interesting. It seems that the full 5V from U1 is not reaching the INPUT pin on the DRV103. I was only reading about 2.5-3v at that pin. However, while the multimeter was connected, the relay began to trigger. When removing the probes, the relay turned off. I believe there must be a problem with the transistor part of the circuit. My control device simply grounds a pin when the coil must engage, so I used the voltage regulator (U1) and transistor (U2) to change this to a 5v signal to the DRV103 INPUT pin. Do you think there is a better way to do this?

    Thank you and I look forward to your advise.

    Regards,

    CSC

  • +1 in reply to TI-CSC
    TI__Genius 13300 points

    Hello CSC,

    I mistakenly mixed up the INPUT and OK_FLAG ABS ratings. its typ is 5V; however, it indicates in ABS max it can go up to Vs.

    From your setup the device should turn on. The enabling of the relay when applying the probes is very odd, unless your probes have a low enough resistance to change the leakage (doubtful). Are you able to measure the current into the INPUT pin? passing through the BJT or even base input current? The input leakage for the DRV103 is ~150uA so I would be shocked if your setup is unable to provide this unless you're not fully supplying your BJT base current.

    Regards,

    Kalin Burnside

  • 0 in reply to Kalin Burnside
    TI__Genius 13300 points

    Hello CSC,

    As you have not replied in two weeks I will be closing this thread. If you need additional help please reopen or make a new thread.

    Regards,

    Kalin Burnside