DRV8701: The output of drv8701 is abnomal whe the loads switched in

Hello,

1) What kind of load are you driving with the external FETs.

2) Can you check if the FETs are compatible with the DRV8701 and the load current:

The continuous drain current I_D(max) must be greater than maximum current in your application.

The IDrive setting should be low enough to give a rise/fall time of at least 100-200ns. Please refer to the formula below.

T_rise/fall = Qgd / I_sink/source

3) Can you check what kind of fault it is by checking what is operating and disabled based on this table 

4) Are you using our EVM and if not, can you give me the Driver portion of your schematic.

Best,

Keerthi

（1）The driving load is a DC brush motor.

（2）The MOS model we use is TSM045NB06CR, with a VDS of 60V and ID of 16A (TA=25 ℃). We set the IDRIVE pin according to the schematic shown in Figure 1.

（3）We checked the AVDD pin is operating.

Fig1: the Driver portion of our schematic

Fig2: EN and Fault pins during motor drive(EN-orange,Fault-yellow)

Fig3: EN and Fault pin when unloaded(No motor connected)

(We have replaced other motors, so we can eliminate the fault on the motor)

                                         Fig1

                                       Fig2

                                         Fig3

Hi Han, 

It looks like either and OCP or PDF event.

Can you confirm the retry time is 2 ms. Can you also try increasing IDrive to either the 200 mA option and the capture the Vds and the Vsp voltage waveforms.

Best,

Keerthi 

Hi Keerthi，

I don't konw how to  check the retry time.

Our IDRIVE pin is suspended and there is no resistance connected.

We captured the waveform of VDS.

（VM-yellow，SH1-orange）

It seems that VM-SH1>1V.

Hi Han,

This is the retry time:

Can you also provide the gate waveform to make sure it is not a pre driver fault and truly an overcurrent event and not a false one either. Can I also get the charge pump waveform as well.

Best,

Keerthi

Hi Keerthi，

This is the gate waveform.

C1/C2/C3/C4 correspond to Q9/Q10/Q11/Q12 in the schematic.

↓

↓

The following is the VCP waveform.

The following is the corrected VM&SH1 waveform.

VM-yellow,SH1-orange

Could you determine the cause of DRV8701 fault based on these waveforms？

Hello Zeming.

Can you try increasing your VM to a higher value and looks like Vm dips below the UVLO threshold. The charge pump is not operational, which is the case when you have an UVLO fault:

Best,

Keerthi

The voltage of VM is pulled down during driving.What external reasons can cause VM voltage to decrease?

Hello Han, 

How are you providing VM. Is there some sort of current limit that you have set on the VM source, or can it handle the current demands of the system?

Best regards,

Keerthi 

Hi Keerthi,

We used battery to provide the VM and replaced battery with different ones to ensure that the batteries were functioning properly.

When starting to drive, the VM voltage is pulled down to 6V. Under normal conditions, it is 20V.

Hi Han, 

Can you check the current draw of the IC, it should be:

Is there anything else other than the FETs and the IC connected to those batteries and if so, can you remove those connections if possible and see what happens to VM. can you also check if the FETs are damaged.

Best regards,

Keerthi