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DRV8323: DRV8323

Prodigy 70 points

Replies: 9

Views: 227

Part Number: DRV8323

Hi there,

We are evaluating the DRV8323H for a new design. Each DRV will be driving 3 half-bridges which forms a part of 3 h-bridges. The other low side MOSFET has a separate low side driver, which needs a sense resistor between its source and ground for this application.

Thus, connecting the SPx and SNx pins as shown in the schematic (a) the low side VDS monitor will be compromised as it will include the voltage across Rsense.
We do not want to disable the VDS monitoring as we need the half-bridge VDS monitor for the high side.

We know that this problem can be avoided by using SPI in DRV8323S, but we do not want to deal with SPI.

The question is:
Is it possible to swap the SPx and SNx pins of the Current Sense Amplifiers across the sense resistor in such a manner that the Px will be connected to the ground (as shown in the schematic (b))?

Thank you in advance.

Andriy.

  • Andriy,

    Thanks for posting on the MD forum!

    On the hardware device Vds is measured from SHx to SPx. The current shunt amplifier is separate and measures Rsense from SPx to SNx. 

    Are you trying to use the CSA on the DRV or are you only wanting the VDS protection to function correctly?

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    Thank you for your quick reply!

    I want both: to use CSA on the DRV8323 and I want the VDS protection to function correctly.
    For that reason, I want to swap SPx and SNx pins to get SPx/low-side_VDS to be referenced to ground, as shown in the schematic (b).

    Will the CSA and VDS on the DRV8323H work correctly if connected as shown in the schematic (b)?

    Thank you.

  • In reply to Andriy Tkachuk:

    Andriy,

    Can you explain the need for the second LS FET?

    I don't follow why SPx needs to be referenced to GND, could you explain?

    The other issue I see here is the load and second FET are in parallel with the regular FET controlled by GLx which will likely cause issues with either A or B configuration.

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    The purpose of the second LS FET is to drive an inductive load (the circuit is an H-bridge).
    When HS FET is off, the slow-decay current is recirculating through the LS FTEs, which will be measured by SCA on the DRV.
    And we would like to keep the possibility to monitor the VDS of the HS FET.

    So, will the CSA on the DRV work properly at configuration as shown on schematic (b), (with swapped SPx and SNx pins across Rsense when SPx is referred to the ground ).

    Thanks.

  • In reply to Andriy Tkachuk:

    Andriy,

    I don't follow why SPx needs to be referenced to GND, could you explain?

    The other issue I see here is the load and second FET are in parallel with the regular FET controlled by GLx which will likely cause issues with either A or B configuration.

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    We are happy with our H-bridge configuration having the load and the second FET are in parallel with the regular FET controlled by GLx.
    Unfortunately, I am not allowed to disclose more information on this forum. The reason why SPx needs to be referenced to GND is just for evaluation purposes only in our application.

    I would really appreciate it if you could answer the following question:

    Will the CSA on the DRV works properly configured as shown on schematic (c), (with swapped SPx and SNx pins across Rsense when SPx is referred to the ground )?

    Thank you for your collaboration.

    Sincerely,
    Andriy.

  • In reply to Andriy Tkachuk:

    Andriy,

    Commenting on schematic C only:

    Assuming you are okay with the sense resistor being added to the VDS measurement and sensing then this configuration is fine since the CSA is designed to be operated in biderectional mode and can handle current in either direction.

    Regards,

    -Adam

  • In reply to Adam Sidelsky:

    Hi Adam,

    Thank you very much for your assistance.

    Best regards,
    Andriy.

  • In reply to Andriy Tkachuk:

    Andriy,

    If your issue has been resolved, please help us out by clicking the green “This Resolved My Issue” button.

    If you have a related question, please use the orange "Ask a related question" in the top right corner of the page.

    Regards,

    -Adam

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