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I cannot figure out why my setup with DRV8843 is not working

Anton Shmagin
Prodigy 20 points
Other Parts Discussed in Thread: DRV8843

Hello,

I am trying to use the DRV8843 in my robot setup and unfortunately all my attempts are not successful at the moment.
Here is my setup:

1  CP1 -- capacitor in between 50V 0.01uF
2  CP2 /
3  VCP - connected through 0.1uF to VM (actually I am using 50V rated capacitor as I don't have 16V handy)
4  VMA -  10V (power supply)
5  AOUT1 -  motor lead
6  ISENA -  GND
7  AOUT2 - another motor lead
8  BOUT2 - N/C
9  ISENB -  GND
10 BOUT1 - N/C
11 VMB - 10V (power supply)
12 AVREF - 3.3V (also tried N/C)
13 BVREF - 3.3V (also tried N/C)
14 GND - GND

15 V3P3OUT - N/C
16 nRESET - 3.3V
17 nSLEEP - 3.3V
18 nFAULT - N/C
19 DECAY - N/C (tried 3.3V)
20 AIN 2 - GND
21 AIN1 - 3.3V
22 BIN1 - N/C
23 BIN2 - N/C
24 AI0 - GND
25 AI1 - GND
26 BI0 - N/C
27 BI1 - N/C
28 GND - GND

If the motor is not connected I can see almost proper voltage between AOUT1 and AOUT2 (~8.8V). But as soon as I am connecting motor - voltage drops till 0V.
The motor when running just with power supply draws ~ 100mA.

The GND PPAD is not connected to the copper (I solder the IC to protoboard). Can it be the reason ?

I am seriously running out of ideas what can be wrong.

Regards,
             Anton 

  • 0
    TI__Prodigy 560 points

    Hi;anton,

           you have better connect the PPAD to the copper ,and the copper connect to ground. But i don't think it is the reason.

           you can pull up the PIN nfault to see if any fault output, because you  disable the current regulation (connect the iSENSA to ground), and  if  the motor's resistance is very small ,it  may overcurrent.

          the V3P3OUT PIN should connect a 0.47-μF 6.3-V ceramic capacitor  to ground.

          and you mention above "1  CP1 -- capacitor in between 50V 0.01uF     2  CP2 /    '',  what does it mean ?  the 0.01UF capacitor  should be connected between CP1 and CP2,i just want to make sure that.

  • 0 in reply to Brady Lin
    Prodigy 20 points

    Brady,

    Thank you for swift reply. Indeed I am getting fault condition almost immediately after I reset the chip (pull nRESET high).
    Motor spin for might be not even one turn and nFAULT pin goes low.

    Waiting for capacitors from Mouser to arrive (the one with exact specs) and will try once more.

    What is the consequences if V3P3OUT is not connected to the ground through cap ?

    Thank you for the guidance once more. It is fantastic driver IC - cannot wait to make it work.

    Regards,
                Anton 

    P.S. You are right, CP1 and CP2 connected through 50V 0.01uF capacitors