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DRV110: Heat problem while driving relays

Jens Kathe
Prodigy 30 points
Part Number: DRV110

Hi,

we designed a relay driver using the DRV110. Connected are 1-4 relays of the type LEV200A6NAA with about 1m wire. Basically its the circuit of the DRV110EVM, but we added some components against EMI. The problem we get with this circuit is, that the resistor R3 reaches temperatures about 70 to 80 degree and also the temperature of the DRV110 and V8 rises to 50 degree. We already tried some other resistor combinations for hold current and frequency, but we didn't get it cold. The DRV110EVM in the same configuration does not get hot.

  • 0
    TI__Mastermind 44855 points
    V6 is 20V Zener now, I suggest to change it to 15V same as EVM. I think this is one of key item for this.
    DRV110 has internal zener diode at VIN pin which clamp Vin at approx. 15V(may vary). Zener 20V instead of 15V may cause difference.

    Secondly now R3 should have 1mA which means 200mW. If this 200mW causes 70-80C temp up, we can put 100Kohm x 2pcs to spread Ploss into two.

    For root cause analysis of DRV110 50C up, I suggest to remove R4 and supply VIN 12V externally. If it 50C goes away, I guess Zener 20V is root cause. I recommend to check V6 and VIN voltage if we still see the thermal issue.
  • 0 in reply to Shinya Morita
    Prodigy 30 points

    I tryied it again with a 15V Zener and two 100k resistors. Now the DRV110 doesn't get hot, but the two resistors reach 70-80 degree again. I tested it again in the same configuartion with the EVM, where the 200k resistor is used too, but it does does not get so hot. I added two pictures of our IR cam, one with our board and one with the EVM. You can see, that V8 gets hot again, too. We also measured the current between R3 and R4 at our board, which is about 1.5mA.

    1. EVM, 2. our relay driver:

  • 0 in reply to Jens Kathe
    TI__Mastermind 44855 points

    Good to know DRV110 does not get hot anymore.  For me it is very storange your 200K or 100Kohm R get hot. We should have 200-15 =185V on this R, then current should be 1mA only.

    Could you doblue check your R value? If your R is smaller(e.g 2Kohm), your heat makes sense.

    Or is it possible to swap TI EVM 200kohm and your EVM 200km ? Then let see how both EVM’s temp changes.

  • 0 in reply to Shinya Morita
    Prodigy 30 points
    The R value is for sure 200k. But we have a DC-Link voltage of 325V caused by the 10µF capacitor. We soldered the capacitor on the EVM too, but it still gets not as hot as our relay driver. Unfortunately the inner layers of the EVM are not printed in the datasheet, so we can not see your thermal management. Yesterday we measerud all value again, an we find out that the voltage drop across the 200k resistor is the same at our board as it is on the EVM. So we should have the same loses. The only reason for the difference could be our thermal management.