I'm designing a circuit using an ST VN7020AJ high side driver. The application diagram recommends placing a diode from VCC to ground. The document doesn't provide any recommendations on the type of diode. The diagram, below, seems to suggest a Schottky diode, so I selected a BAT60J.

The board will be used in an automotive application and the load will vary with use and will at times be an inductive load. Sometimes it could be LED lighting, other times it might be a motor or mechanical solenoid.

Am I misreading this diagram, and should I be using a different diode? Also, is the diode necessary?

The document also doesn't say anything about Cext

enter image description here

  • 1
    \$\begingroup\$ That is a symbol for a Zener diode, not a Schottky diode. Its purpose is to clamp any over voltage at Vcc. We can do no more without documentation. \$\endgroup\$
    – user105652
    Apr 6, 2018 at 2:22
  • \$\begingroup\$ There are hundreds of pages of documentation in at least 3 separate documents for this chip- plus whichever standards you are required to meet. You should read them all. Dld is to meet load dump requirements. \$\endgroup\$ Apr 6, 2018 at 3:50
  • \$\begingroup\$ I read the devices data sheet cover to cover and didn't find any documentation on Dld, however after reading your comment, I went in search of other documents and found another "Application Notes" document that describes the purpose of Dld. I'll post my findings as an answer. Thank you! \$\endgroup\$
    – Prdufresne
    Apr 6, 2018 at 8:48

1 Answer 1


Thanks to a comment on the question, I found the answer in a separate document associated with the device. Lesson learned, don't assume all the documentation is in the data sheet.

The VN2070AJ is

designed to successfully pass the 1, 2, 3a, 3b and 4 ISO-7637 standard pulses test - simulating the low energy voltage spikes. These values must be added to the voltage battery (for cars about 13.5V) to obtain the actual voltage. The N.5 ISO7637 pulse simulates the alternator load dump in the case of a Generator with an internal impedance of 2Ω and different values of magnetic field of the excitation circuit (see figure 8 for the level IV pulse); this occurs when the battery is disconnected whilst being charged by the alternator. The voltage spike can reach duration of approximately ½ second and it is of high-energy nature because of the alternator's low source impedance. Where a centralized clamp circuit is not provided or ISO7637 rated devices are not used, an external zener Dld diode is necessary to clamp the transient voltage battery.

Therefore, Dld is a Zener diode.


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