• State
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 29 views
  • Users 0 members are here
Support feedback
Options
Options
Related

DRV8703-Q1: For inquiries about the output waveform of DRV8703QRHBRQ1 GH1

ian wu
Intellectual 795 points
Part Number: DRV8703-Q1

Tool/software:

During the current product debugging process, the waveform of GH1 to GND is abnormal. The waveform is shown in the following figure. The GH1 waveform obviously shows a downward slope when the PWM is turned off, which is quite different from that of GH2.

Driver configuration information: MODE is high-impedance state, controlled by PWM mode; Among the five sets of simultaneous surface mount devices, the two currently under debugging both have the same issue with the GH1 waveform.

Waveforms of GH1 and GL2 to GND:

Waveforms of GH2 and GL1 to GND:

Waveform of GH1 when the external connection is disconnected

What's the reason for this? 

  • 0
    TI__Mastermind 45125 points

    Hi Ian,

    Thanks for your question.

    ian wu said:
    During the current product debugging process, the waveform of GH1 to GND is abnormal. The waveform is shown in the following figure. The GH1 waveform obviously shows a downward slope when the PWM is turned off, which is quite different from that of GH2.

    Technically GH1 must be referenced with SH1 not with GND. GL1 is GND referred - to se the base line. When the dropping GH1 waveform was observed was the LS-FET1 conducting? If not this would change how GH1 looks like when referenced to GND.

    Because GH2 looked normal, was LS-FET2 conducting at the time of this measurement? While LS-FET2 is conducting SH2 and GND would be at the same potential, so GH2 referred to SH2 is same as GH2 referred to GND. 

    Note, as scope probes are not isolated care must be taken to have no other scope GND is connected to system GND while connecting one probe for measuring between GH1 and SH1. Alternate options would be to use a differential voltage probe between GH1 and SH1 or have two probes one for GH1 and one for SH1 and do a MATH GH1-SH1. 

    How is this affecting the functionality of the application? How does the output waveform voltage at SH1 and SH2 look like? Can the motor current be captured with a current probe as well? Please also share the schematic and Register configuration if further debug is necessary. Thank you.

    Regards, Murugavel  

  • 0 in reply to Murugavel4637
    Intellectual 795 points

    hi 

    This is the schematic diagram

    Channel 2 is the GH1 waveform, while Channel 3 is the waveform given by the mcu to the pre-drive. The descent is slowly turned off, but gh2 is directly turned off

    what's the reson for this ？

  • 0 in reply to ian wu
    TI__Mastermind 45125 points

    Hi Ian,

    Thanks for the schematic. It does not show the output FETs. I assume they're connected directly as suggested in the datasheet.

    ian wu said:

    Channel 2 is the GH1 waveform, while Channel 3 is the waveform given by the mcu to the pre-drive. The descent is slowly turned off, but gh2 is directly turned off

    Can we also get the GL1 and SH1 capture along with this GH1 and INx? Then a second capture showing the GH2, INx, GL2 and SH2 for comparison? 

    The MODE pin is 0 in the schematic, so PH/EN mode of bridge control is used. When the above waveform of GH1 was captured which row of the below table used for the control logic? 

    Can we get all the Registers readout at the time of this waveform capture? Do all units exhibit this behavior or only some samples have this issue? Thank you.

    Regards, Murugavel