DRV8873-Q1: is the PWM are set on this device?

Hi, Art,

Can you provide the register settings the customer is trying to use?

And, I don't understand what you mean by "Just like to inquire if the  PWM are set on this device?"  Can you clarify this statement?

Hi Art,

Were you able to get the PWM working?  Was the issue with the EVM GUI?

Regards,
Mike

Hi Mike,

I am still waiting for the customers response, but I will let you know guys as soon as I got their confirmation.

Thanks!

Art

Thank you Art!

Hello Mike,

Good day.

I just got the response from the customer. He bought drv8873h-q1evm and have specific questions he detailed below in verbatim.

(1)   When we apply PWM from 0 to 255 pulses, the board seems to apply the pulses in reverse. 0 generates the highest pulse counts, and 255 generates the lowest pulse counts. Is this the way the board is intended to work?

(2)   Which pin is related to DVDD? I am not referring the chip (u3). Rather I am referring to the 14 J1 pins. Which of these are related to DVDD? (I know the pin of u3 is DVDD, but I cannot seem to get access to it).

(3)   I am using the Independent Mode. The information below depicts the connections I am using.

1          GND                           

2          3.3v               

3          nFAULT                       10Kohm pullup resistor

4          SOD/MODE                200kohm

5          SDI/SR                        TO GND 53.2v/us

6          sCLOCK/nTRIP            TO DVDD (this is connected to external 5v)

7          nSCS/nOL                   TO DVDD (this is connected to external 5v)

8          EN/N1                         PWM/HIGH/LOW

9          PH/N2                         PWM/HIGH/LOW

10        DISABLE                      HIGH/LOW

11        IPRON1                       Resistors to convert mirrored current into a voltage

12        nSLEEP                        HIGH/LOW

13        IPRON2                       Resistors to convert mirrored current into a voltage

14        GND              

Do you agree this is an acceptable configuration?

(4)   One of the methods we are using to control the motor is with a joystick. After initiating movement with the joystick, the board works fine. However, if we release the joystick (return to neutral) too quickly, then we are experiencing a shut down of our power supply. I tried using a diode and am getting the same shut-down effect. Additionally, the board burns at the same time that the power supply shuts down. (We are using a 32v power supply, reduced to 28v). Can you please advise us as to reasons for power supply shut down and boards getting burned?

(5)   Inconsistent performance from board to board: I have configured my software to work with the boards. I achieved partial success with one board. However, after burning that board, I install a new one and the new board does not perform like the previous one I was using. For example, the polarity seems to change. With the previous board, I will actuate movement of my motor with a forward joystick push. However, when I connect the second board, a forward joystick push causes the motor to run in reverse. Another example… upon installing the new board and actuating motor movement, the motor reverses direction on its own without a change of direction from the joystick. Can you please advise us on (a) why the boards behave differently, and (b) why we would experience a change of direction in motor movement without a change of direction from our joystick? (Note: we are using an external controller – Atmega 2560)

(6)   Is your PWM range from 0 to 255, or 0 to 100?

Thanks in advance!

Art

Hi Art,

Here are some answers and follow-up questions:

1.  First to clarify, are we talking about entering the PWM ramp value in the GUI?  The 0-255 value is the number of PWM pulses over which the output is ramped to the specified duty cycle.  The 0-100 slider is the PWM duty cycle.  This should also answer question (6).

2.  DVDD is not routed to J1.

3.  Configuration seems OK - how is the load(s) connected to the output?

4.  Why is the power supply shutting down?  Over voltage?  Burning out the device could be due to back-EMF when the motor spins down.  This will need to be clamped if exceeding 40V (seems like this is the case).  This is another question where a simple diagram and description of the loads would be helpful.

5.  Again, having an understanding of how the load is connected would be helpful.  In independent half-bridge mode, it is assumed one side of load would be tied to GND or VM supply, so should not be seeing a change in direction since we can only move in a single direction.  Read page 16 of the datasheet.  Not sure if there is a single motor connected across OUT1 and OUT2 - this is not desired in independent half-bridge mode, and could explain why devices are getting burned up.

6.  Please see (1).

Regards,
Mike

Hello Mike,

Apologies for the delayed response for I was awaiting the info from the customer. He do have follow-up inquiries. See below.

1) You mentioned DVDD is not routed to J1. SO can he use an external 5v signal instead of DVDD?

2) On page19 of the datasheet for DRV8873-Q1, The IPOPI1 and IPROPI2 they are connected together, Will this configuration works for all the MODE's ?.  Also, Does he need to add an external Rsense-1 ?

Thanks to confirm!

Art