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DRV595: Current issue

Shaifali Jain
Intellectual 400 points
Part Number: DRV595
Other Parts Discussed in Thread: , DRV8412, MSP430F5659

Hello,

I am using DRV595 to drive a 12v/7A peltier (1.9 ohm resistance). I am using DRV595EVM circuit design.

Operating supply voltage: 12V

Input voltage : 3.3V

When no load is connected across the load terminals there is 12v across the load terminals.

When the load  (peltier) is connected the voltage drops to 2V and current drawn is 0.5A.

When 2 peltier connected in series across the load the voltage is 5v and current remains the same.

Why voltage across load and current is not increasing ?

What is the issue?

Please help me.

  • 0
    TI__Mastermind 24835 points
    Hi Shaifali,
    How much Gain setting are you using on the board? Even though the min 20dB is used, the enlarged output should be 33V with 3.3V input signal. So the input signal amplitude is too large. Where is the power supply from? Make sure it has enough driving ability.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 400 points

    Hello,

    It was power supply issue, now i am using 12v, 25A SMPS to power the DRV595. But there is still two issues remain.

    issue 1 :Output voltage on the load terminal appears to be 11V and 3A .DRV595 is getting ON/OFF after every 2-3 sec, this issue is mainly because of fault condition(low on fault pin).

    Why the fault condition is arising and what kinf of fault it can be?

    Since it can not be over-current and under-voltage because supply voltage having capability of 25A.

    issue 2: When varying input voltage upto 3.3V there is no change in the output voltage/ output current. What is the role of input voltage ?

  • 0 in reply to Shaifali Jain
    TI__Mastermind 24835 points
    Hi Shaifali,
    For issue #1, if the VCC voltage is within the recommended range(4.5V~26V) and the output current is below the OC THR(7.5A), the fault should be OT FAULT. Make sure your thermal design on the PCB board is good.
    For issue #2, as I mentioned above, 3.3V input volatege is too high, which makes the output signal is clipped by the VCC voltage. Please limit your input signal amplitude.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 400 points

    Hello,

    Thanks for the reply,

    In issue 2 there is no change with respect to input voltage whether I apply the input voltage (increased / decreased) or not ?

    Why there is no effect of input voltage.

  • 0 in reply to Shaifali Jain
    TI__Mastermind 24835 points
    Hi Shaifali,
    The output voltage is limited by the PVCC power supply voltage. Could you please help to do following experiment: set input voltage from 0.1V to 3V with 0.1V step and measure the output on the load.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 400 points

    Hello,

    Thanx for the reply.

    I have already done the experiment as suggested by you but there is no effect on the output.

    DRV595 is getting off and on again after every 30-45sec when i connect heat sink to the thermal pad.

    Why now this is getting off after heat sink connection?

    I am also working on the DRV8412 to drive the peltier in parallel full bridge mode with 12v GVDD and 24V PVDD power supply.

    PWM_C and PWM_D pins are connected to ground and PWM_A and PWM_B pins are driven by PWM waveforms generated by msp430f5659.

    I have connected OUT_A , OUT_B together and OUT_C and OUT_D together to drive peltier (according to circuit suggested by TI).

    When I give PWM waveform to OUT_A and OUT_B there is no voltage difference across the load (12V on each pin).

    What type waveform (Inverted / Normal, duty cycle) is to be given to the A and B pin to get the desired output. I am not able to understand the working of this after reading the datasheet.

  • 0 in reply to Shaifali Jain
    TI__Mastermind 24835 points
    Hi Shaifali,
    DRV595 is a thermal pad-down device and the PCB GND plane is actually used for the heat dissipation, so how did you use a heatsink for it please? Is it still getting on and off even though there is no input signal applied(the voltage on the differential input is the same)? Could you please show your SCH to me?
    I'm sorry I'm not familar in DRV8412, please create a now post in the forum for it and the expert will give you most professional answer.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Intellectual 400 points

    Hello,

    I made the circuit on zero board PCB to check the working. I have connected heat sink above the DRV595 IC without any shorting also connected with the thermal pad down for better heat dissipation.

    I have used the circuit recommended by TI, there is no change in the circuit.

  • 0 in reply to Shaifali Jain
    TI__Mastermind 24835 points
    Hi Shaifali,
    It's really hard to debug without the SCH design. Make sure the voltage on the IN-/IN+ pins is around 3V, then meaure the voltage across the load. Adapt the voltage on IN+ pin and see how the voltage across the load changes. Make sure the output current don't exceed the OC THR and the thermal performance is good to avoid the OC and OT FAULT.
    Best regards,
    Shawn Zheng