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EVAL-VNH5019 motor driver problem

Hello,
I’m using EVAL-VNH5019 to control TEC element, and connect it as datasheet and databref in the link below, the power supply inserted to the driver is 20 VDC and PWM used (15625 HZ) but the problem is when I applied 50% duty cycle on PWM pin I have a voltage difference between OUTA and OUTB (output pins of the driver) is about 17 VDC ! instead of 10 VDC.
Thanks a lot for your help.

Link of EVAL-VNH5019: https://t.ly/y28k2

Hello.

What you are describing seems normal for the VNH5019. You can get a better idea of what kind of behavior to expect by reading this forum post that asks a similar question.

-Jon

Thanks for your response, I am expecting from H bridge driver to be linear with duty cycle and when I apply 50% duty cycle I should have 50% of input voltage at output pins (if the power supply 20 VDC the output pins should be 10 VDC and at 25% 5 VDC).
Is there any way to work with VNH5019 with a linear relation between duty cycle and output voltage?, note that I did not connect any load to the output pins when I tested this driver.

Unfortunately, it is not practical for the VNH5019 to operate that way, unless it is acceptable to use a very low PWM frequency (a few hundred Hertz or less), since the inputs required to do that are not capable of high-speed switching.

By the way, I recommend testing with the TEC connected since that could change the behavior of the driver’s outputs, and ideally you should probe the outputs with an oscilloscope instead of just measuring the voltage with a multimeter (the outputs are PWMed, not constant voltages, and you will get a better idea of what they are doing with a scope).

-Jon