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DRV8343-Q1: Robustness against overvoltage events in a 24V-system

Part Number: DRV8343-Q1
Other Parts Discussed in Thread: STRIKE

Hi,

I'm considering to use the DRV8343-Q1 in an application that takes place in a 24V system. Page 8 of the datasheet says:

"VM recommended operating condition for electrical characteristic table. Product life time depends on VM voltage. The device is intended for 12–V and 24–V battery automotive system with life-time nominal voltage of 5.5 V - 50 V. The device can be operated during additional overvoltage events as specified in ISO16750-2:2012"

So, can you tell me which overvoltage events the DRV8343-Q1 can withstand regarding the standards ISO 16750-2 and ISO 7637-2? I need to know that because I have to estimate the effort for the input protection for the application.

BR

Tom

  • Hi Tom,

    I am awaiting feedback on our automotive experts on the context of this ISO standard. Typically, an overvoltage condition can occur for a transient amount of time on our device beyond the 5.5V-50V nominal voltage range. 

    We can get a more detailed reply from our automotive experts by the end of the week to share with you. 

    Thanks,
    Aaron

  • Hi Tom, 

    Thanks for your patience - 

    From a device operating perspective, the general guidance is: 

    1. the rating of the DRV IC main supply rail (VM/VDRAIN) should be 1.5x to 2x as high as the nominal dc-bus voltage 
      1. in cases where you have a very well-regulated dc-bus voltage, rather than a battery, you may be able to get away with only having an abs max rating 30-50% higher than your operating voltage 
    2. in our DRV8343-Q1 device, the ratings for dc and transient voltage of VM are copied below
      1. we recommend that the user design their system in a way that these values are never exceeded for dc and transient respectively, to avoid immediate damage from electrical over-stress and also latent failures (over time)
    3. this FAQ highlights some of the key considerations for DRV devices to prevent overvoltage stress from occurring, and why it matters: 
      1. https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1041760/faq-how-to-not-damage-your-motor-drive-system-from-overvoltage

    Lastly, I am not too familiar with that ISO16750-2 line item in the datasheet footnote, but expect that it'll mimic the guidance above on avoiding overvoltage in the first place, based on the device specifications. 

    Please let us know if this resolves your question. Thanks! 

    Best Regards, 
    Andrew 

  • So your advice is to limit the voltage to a maximum of 60 V during overvoltage events. This is a challenge because I cannot use a TVS diode with a breakdown voltage lower than 50V. So the probability that the maximum clamp voltage is more than 60 V is quite high.

  • Hi Tom, 

    In your system, what's the nominal operating voltage of that VM pin for DC_BUS/battery voltage? 24V? 12V? 

    I am trying to get a better idea of what your ideal operating voltage would be, as well as what that voltage might spike up to as a result of motor operation. 

    The common approaches I see to protecting the VM voltage bus are:

    1. bulk and bypass capacitors to filter high freq noise and also stabilize nominal voltage
    2. power management IC (PMIC) to regulate the voltage bus 
    3. TVS diodes may be less common just due to the variations in breakdown voltage like mentioned

    Best Regards, 
    Andrew 

  • Hi,

    the nominal operating voltage of my application is going to be 28.5V. The voltage spikes i am considering are not generated by the driven motor. They are power supply line conducted and really harsh (pulses of -600V and 150V) as defined by ISO 7637-2. I guess to clamp the voltage by using a bulk capacitor is not working for this because of the high voltages and the low source impedance. The surge current would be too high for the bulk capacitor.

  • Hi Tom, 

    Thanks for the info. Nominal voltage (28.5V) seems within reasonable scale, albeit a bit higher than the target voltage of this device (12V, 24V). 

    Our products typically target ISO26262 standard for automotive applications and IEC61508 for industrial applications, so I am personally not too familiar with this ISO 7637-2 standard mentioned.

    • However, -600V and +150V are agreeably very harsh as described. 
      • is there any mention in that standard about the duration of those pulses? 
      • I am wondering if due to the large voltage expectation, this may be comparable to a very short duration ESD strike? 
    • Also, I may recommend posting a question to some of the other product forums (such as power management ICs) to see if there's a solution they recommend that can ensure that our DRV IC is kept within abs max voltage specifications? 

    I also found another resource that might be helpful for implement RPP: https://www.ti.com/lit/an/slva835a/slva835a.pdf

    Best Regards, 
    Andrew

  • Hi,

    yes, the pulses are of short duration (0.05ms to 1ms).

    BR

    Tom

  • Hi Tom,

    The device operation needs to stay within the abs max voltage ratings of the device that are listed in the datasheet, so you would need to implement external circuitry to ensure that the device voltages do not violate this if the system needs to withstand -600V to 150V for up to 1ms on the main power supply. Operating the device beyond the abs max ratings listed in the datasheet could result in damage to the device, and extended operation at the abs max ratings could effect device reliability.

    Regards,

    Anthony Lodi