Chip shortage, sweet finds, random magic knowledge

Hardware inside and outside of the ECU
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AndreyB
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Chip shortage, sweet finds, random magic knowledge

Post by AndreyB »

One day we would want at to develop a PDM and we would hit the ship shortage :(

Today you can buy VN7004CHTR on Newark but it's high side. Dave says
all of ST's drivers that offer current sensing REQUIRE external components on the current sensing output pin. Even if you put a pull-up to disable the CS functionality, you still must have at a minimum the R and C specified in the datasheet.
they consider it to be extremely bad form to run the driver into a dead short and let it thermal cycle
while it will not instantaneously explode, it will shorten the life of the driver a LOT.
with the VN700x series, they come in two variants. You'll have ones that have a "L" in the suffix and ones that do not.
The ones that have a L in the suffix have onboard circuitry to configure their behavior in a fault event.
You can choose between having them Latch in the off state on fault ("L" part) and reset as soon as the fault condition is removed.
The L parts were added for people like me that did not have the CS output hooked up for monitoring and were relying on the fault protection/reset of the driver

also, these drivers are not really intended for PWM. Look very carefully at the Eon and Eoff. You'll find that above about 1K, self heating from turn on and turn off energy because of just Eon/Eoff. Factoring in the losses in linear mode "in between" on and off due to the relatively slow switching speed and you end up with quite the toxic cocktail. you can do something like a boost control solenoid that is going to be cycling <= 100hz no problem but you wouldn't want to say try to run a fuel pump at 18-20K hz with this part.
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Re: Chip shortage, sweet finds, random magic knowledge

Post by blundar »

Also: there is a handy dandy table in the datasheets for these high side drivers. It tells you what each pin needs to be connected to. i.e:
-Can it float?
-Can it be connected to ground? Can it be connected to supply? Can it be connected to logic+ ?
-Maximum/suggested pull up/downs

PAY FUCKING ATTENTION TO THIS TABLE. The presentation is a little awkward in some of the datasheets but the ST FAE I spoke with made a real big deal of paying attention to this.
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Re: Chip shortage, sweet finds, random magic knowledge

Post by AndreyB »

This have certanly improved somewhat. TLE9201 is available, stm32f042 is pretty available, JLC has LQFP-176 and even LQFP-208 stm32 in stock for under $30.
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