Hi all. Reaching out to you for some help selecting resistor for ST VN7003AH High-side driver with CurrentSense analog feedback for automotive applications.
It's basically a "smart" power switch from ST with the possibility to measure the current that flows thru it. Neat! But when I read the datasheet I cant understand how to select resistor value. Please see bellow.
Its saying the current out of the sense pin is 1/K times the current being sensed. K is given in the datasheet,
its very roughly 17000, with lots of variation between devices and over time.
With the 1k resistor shown then the voltage will be about 1000/17000 x current, so that if the current is 20A,
the output voltage is roughly 1.2V
Or in more detail 20A / 17000 = 1.2mA, and 1.2mA through 1k drops 1.2V
Thank you for quick reply Mark!
I wont be pulling that many amps thru it. More like 0-5 Amps at 12V. So If I use your calculation:
At 5 Amp the current at the CurrentSense pin is 5000mA / 17000 = 0.29 mA.
If I use a 10K ohm resistor to ground, the output voltage will be 3.00V.
At 2.5 Amp the current at the CurrentSense pin is 2500mA / 17000 = 0.15 mA.
With the same 10K ohm resistor to ground, the output voltage will be 1.50V.
Am I on the right track?
How does the Rprot resistor of 1K in series with the ADC pin interfere with this?
Thanks in advance!
Yes, but at the very low end of the current scale it may not be very accurate, so don't expect too much.
Analog pins don't take current, so the 1k in series doesn't have any voltage across it, except in a fault.
Thank you! I don't need any mA resolution in this case. Just want to be able to monitor that the load takes an "reasonable amount" of current.
While you are being so helpful, can I ask you if you know what "High-Z" in the truth table above?