Part Number: DRV8320
I am designing a system level reverse battery (RB) protection scheme for several DRV ICs, as part of a surge stopper design. The potential issue I have is that the disconnect time of the RB circuit during a fault condition is most likely not fast enough to prevent large reverse currents passing through the DRVs and causing EOS. My intention, therefore, is to add a diode from VDRAIN to VM, and a 100 Ohm resistor into VDRAIN to limit the reverse clamp current to <20mA (assuming the VDS monitor accuracy isn't compromised). There is a FET body diode from ground to VM as part of the surge stopper regulator so the DRV supply will be transiently clamped to <-2V until the RB pass FET is switched off. I'm aware that the VM and VDRAIN voltages need to be close to maintain the high-side VGS drive. The VCP cap will be referenced to the VM pin.
I'd be obliged if you could let me know if the above is acceptable and if there are any other DRV paths I need to protect.
Can you also provide me with the input impedance spec for the VDRAIN pin?
Could you share a snippet of your schematic with us?
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Adam Sidelsky:
In reply to Stu:
D24 connects to the 24V power plane. R44 (100R) is kelvin connected to top of bridge, which is also connected to the 24V plane.
The surge stopper body diode that I previously mentioned across ground to VM, is actually from ground to 24V plane with D24 being added into the circuit. This body diode is effectively in parallel with the half bridges.
Hi Stu,Your circuit is fine in using a series diode and surge stopper, but using the series diode D24 makes the system less efficient and lowers the usable voltage range from your supply. Furthermore, the surge stopper is a much more expensive solution than other possible reverse polarity solutions.
Please take a look at our application note on Protecting Automotive Motor Drive Systems from Reverse Polarity Conditions: https://www.ti.com/lit/an/slva835a/slva835a.pdf?ts=1593466039266&ref_url=https%253A%252F%252Fwww.google.com%252FYou can find many options of reverse polarity protection circuits that trade off in cost versus efficiency.
In reply to Aaron Barrera:
Thanks for your reply and the additional information. Do you know if someone from TI will be replying to my question about fitting a resistor into the VRAIN signal?
The reverse battery protection circuit that I am using is part of the surge stopper design and the RB section is very similar to one of the circuits described in the apps note you attached, using the boost node of the surge stopper to drive the RB FET. The surge stopper is needed to cope with fast transient pulses and 200V load dumps in association with power clamps. It also has feed through capability to keep many DRVs running during load dump and other conditions, regulating its output to 40V.
As this is a new design and I'm ready to get the first dev boards manufactured, I'd very much appreciate getting some feedback on the how to protect the VDRAIN from reverse voltages, if possible. As mentioned, VDRAIN and VM would see -1V transiently, unless the diode and resistor are fitted (VDRAIN spec is -0.3V). I chose 100 Ohms on the assumption that the VDRAIN ESD structures should handle 10mA (1V / 100 Ohms), but without knowing the VDRAIN input impedance, and other limitations, this resistor might be an issue.
Correction to previous post - the clamp is -2V therefore the expected reverse VDRAIN current will 20mA with 100 Ohms
Hi Stu,It is absolutely fine to use a 100-ohm resistor between VM and VDRAIN to limit the current into the VDRAIN pin from voltage transients.
I will check with the team and get you a response by the end of the week to see if VDRAIN input impedance should be accounted for or if it is negligible when used with a 100-ohm resistor.
Thank you for the quick reply and for the confirmation - it's very much appreciated. All going well, the resistor will not need to do much work as any potential transients will be very short <<100us.
The impedance on the VDRAIN pin is negligible to the 100-ohm resistor due to an internal ESD diode from GND to VDRAIN.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.