Other Parts Discussed in Thread: INA821
IN a BLDC Motor application we use the DRV8350 to control a BLDC motor.
Via PWM-control the motor current is controlled. in the the middle of the PVM-cycle we measure the current through the active motor phase.
our problem is that the charge pump inside the DRV8350 which destroy our current measurement. WE find that the distortion contaminates the whole power generation in our design. THAT means the noise can be found on the +5V power. ON the 3,3V-Powerpath. see FIgure tbd.
VIA the 5V supply our current measurement circuit(INA 821) ist supplied. THE nOISE comes out on the current signal wit 800mV peaks which destroy the measurement on the AD-converter inside our motor controller CPU.
THE circuit design has followed the design instruction of the DRV8350 data sheet.
Has anyone a idea what can we do to eliminate thisa noisae from the charge pump?
THE circuit iss supplied wit 28vDC via MTR_DRV_PWR. THE CPU is able to switch on and off this power. see circuit above
THE second signal figure above shows on top four distortion pulses from the charge pump on a power path (+5V, 3,3V looks same.
THE single pulse below shows the gate voltage for the high side switch mosfet (signal 1).
THE second signal figure shows with (3) the current measurered with a current probe.
SIgnal (1) and (4) is the measured current from the INA821.
ON bottom side in the signal figure are measured the hall sensors.
the third signal figure shows the the Motorr current at 5% PWM.(3)
signal (1) shows the gate voltage pulse (pwm width).
signal below shows the charge bump distortion which happens during the current measurement.
