LMP8481-Q1: Three-phase brushless DC motor(BLDC) phase current detection distortion

Part Number: LMP8481-Q1
Other Parts Discussed in Thread: LMP8481

我在做一款三相直流无刷电机(BLDC)的电机驱动电路,电机功率是28V/100W,我需要三颗同型号的相电流(双向)检测芯片,目前使用了贵司的LMP8481ATQDGKRQ1:

主要参数如下:

I am making a motor drive circuit for a three-phase brushless DC motor (BLDC), the motor power is 28V/100W, I need three phase current (bidirectional) detection chips of the same model, currently I use your company's LMP8481ATQDGKRQ1:

The main parameters are as follows:

GAIN=20

VCC=5V,VCC via C=0.1uF and 4.7uF to GND

REFA short REFB=2.5V:via 0.1uF to GND

Rsense=5mΩ

Rsense_left   via R=0Ω to RSP

Rsense_right via R=0Ω to RSN

RSP via C=0.1uF to RSN

Vout via RC(R=100Ω,C=4.7nF) to MCU GPIO

But I ran into a problem, as shown below: Vout of LM8481-Q1 is wrong !

CH4(green:current from UA to Motor

CH2(yellow):Vout of LMP8481-Q1

CH3(red):UA, phase Voltage

Please help analyze it, thank you!

  • “”Vout via RC(R=100Ω,C=4.7nF) to MCU GPIO“”,给电路引入了附加相移,降低了相位裕度。导致电压过冲甚至自激震荡,CH2(yellow)清晰体现此现象。

    应使电容C<500pF甚至更低,可以解决该问题。必要情况考虑使用有源滤波器。

  • I use electronic load to replace Motor,phase Voltage UA via a electronic load to UB,but LMP8481 Vout unable to display negative current。

    Iout=2A,RSP to RSN is 10mV,Vout=2.5V+2A*5mΩ*20=2.5V+0.2V=2.7V,it’s true!

    Iout=-2A,RSP to RSN is -10mV,Vout=2.5V.  it‘s wrong,why Vout≮ 2.5V?