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TPS1HC30-Q1: part exploded on power on

Iain Milnes
Prodigy 130 points
Part Number: TPS1HC30-Q1
Other Parts Discussed in Thread: TPS272C45

Tool/software:

We control a linear motor. It takes about 2 A and can go in or out by reversing +24 V and GND. The relay switches the polarity. The software always switches the relay before turning on the HSS.

We have had two HSS blow up on power on. The 24 V comes from a 100 W ac to dc power supply that we have used for years on this product.

The chip seems to blow up as soon as the 24 V is present or it is ramping up. Because once we turn on the ac, the chip explodes within less than a second. The processor controlling the HSS is held at reset for 2½ s after the 24 V is present, so it has not yet controlled the HSS. The 5 V for the processor is derived from the 24 V.

We test the boards on the bench before putting it into the machine.

We can swap a board that has blown up with another identical board and it will work fine. But it's not every time that the boards will blow up.

What could be causing the chips to blow up?

  • 0
    TI__Intellectual 2530 points

    Hi Iain,

    The first thing I notice is that the voltage you are putting through the TPS1HC30-Q1 is 24V, the nominal voltage is only rated to go as high as 18V because the TPS1HC30-Q1 is designed to support 12v automotive systems.

    For your system I would recommend using the TPS272C45 which can easily handle the 24V supply.

    Another recommendation I have is that the DIA_EN pin and LATCH pin should both have 5k ohm resistors to limit the current going to the pins.

    I also don’t see any reverse current protection to protect the TPS1HC30-Q1 from reverse current events, if that could be a problem I would recommend adding a ground network.

    Does your load have any inductance? If so the reverse voltage when the load is turned off could also cause problems

    Regards,
    Nicholas

  • 0 in reply to Nicholas Petersilge
    Prodigy 130 points

    Nicholas,

    Thank you for the response. Here are some comments:

    1. I have attached a couple of extracts from the data sheet for the part. TI clearly indicates this is fully functional for 24 V systems. 

    Can you please comment on your thought that the device is inappropriate for 24 V supply?

    2. It is not possible for the 24 V to be connected back to front on our system. We have an active diode (LM74801) as the input to the board. (Besides, our technicians are always careful any rate to connect + and – correctly!)

    Does this address your concern about reverse current protection?

    3. The load is a linear motor. Yes, there is inductance there. Although the HSS part can handle inductive loads, we have added D44 to dump the fly back inductive load. This ensures that the energy in the motor is dumped so that the OUT pin of the device doesn't go below about –0.9 V.

    Does this address your concern about the problems that might arise when the load is turned off?

    4. I don't understand your point about the need for 5 kΩ resistors on the DIA_EN and LATCH pins. These signals come from a PIC processor that operates at 5 V. Since the 5 V is derived from the 24 V, the HSS gets powered up a short time before the PIC. But the PIC is held in reset for 2½ s after 5 V is stable.

    The input currents on these two pins are specified nominally at 14 µA. Can you please explain what the 5 kΩ resistor in series with these pins might accomplish?

    5. My concern is that we have had two of these chips blow up as soon as they are powered on. Are any of the things you have mentioned likely to cause this problem? If not, what could be the issue?

  • 0 in reply to Iain Milnes
    TI__Intellectual 2530 points

    Hi Iain,

    1.

    The device is not recommended for 24V systems because short-to-ground behavior might not be guaranteed as we don’t test it at 24V. Is there any way for the voltage to temporarily spike while it is running as that could cause damage?

    2.

    With the diode reverse current shouldn’t be a problem

    3.

    The load turning off shouldn’t cause any problems

    4.

    If the pic is protected then it shouldn’t be a problem

    5.

    Its hard for me to tell what the problem could be could you send a scope shot so that I can better identify the problem?

    The main method in which the TPS1HC30-Q1 get damaged is from overvoltage. The minimum voltage for clamping is 33V. Is there any way you are getting up to 33V while running the device?

    Are you running these tests on an eload?