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VNL5090 specifications are not guaranteed with 3.3V supply #27
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A bit related to mck1117/proteus#125 |
Spent some time running tests on the VNL5090 all seem to trigger by 2.7v and we reliably see 3.2v on the brain boards at the VNL pin. No one has yet had an issue with the lowsides and there must be 100 cars and over 50,000 miles driven. Probably on a V2 of the brain board we will do something to bump the voltage up but it currently seems to be a spec vs reality thing. |
@OrchardPerformance please clarify temperature conditions of your test. |
What temperature conditions would you like? |
I wonder how the supply affects switching characteristics: that's probably where an issue would arise if any, given your tests @ 3.3V. |
Yes, that would certainly be my primary concern. In terms of what it would directly affect the most obvious would be injector dead times. Something that can certainly be verified using a spare rover 4cu ecu as they have VNL5090s on the base board and 5v pull ups. |
Repeated the same testing on the same VNL5090s today at 70c PCB temperature, increased temperature actually lowers the activation voltage. At 70c the activation is 0.1v lower than at 15c. |
Also, please note that transition process is bit extended with lower drive voltage. This may affect injector dead time calculation mentioned above. And cause additional heating of MOSFET |
That is exactly what my main concern would be and the reason for making V2 work off 5v. I'll pop this one back open for now and take some measurements of the resistance and on time of the VNL5090 actually on brain board. |
SO-8 version has dedicated supply voltage pin, BTW.
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