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Original question:

DRV3946-Q1: Using CMD1 does not let me change the state of the Channel 1 Solenoid

DRV3946-Q1: Relay turns off after locking config

Thom H
Prodigy 20 points
Part Number: DRV3946-Q1

Tool/software:

Hi!

I am working with the DRV3946-Q1EVM. I have hooked up a F280049C Launchpad to this, and use SPI to control the DRV.

I am implementing the 8.3 Initialization Setup from the datasheet. In 8.3.4 Turn On Relay, point 2 states to write CMD1 0x50 to enable output 1.
This works nicely, and our relay closes. However, when we follow it by writing CMD1 0x40 the relay opens again.

To test my theory, I put some delay between the 0x50 and 0x40 (e.g. 100ms), and exactly after the delay it opens.

Why is this happening?

SPI Log (with 1us delay between commands):


Thanks in advance.
Thom

  • 0
    TI__Mastermind 18725 points

    Hi Thom,

    Just to clarify I understood your question properly you are writing 0x50 to CMD1 (CH1_CTRL - 0b010) and then you write 0x40 (CH1_CTRL - 0b000), so it should shut off per the description below. Maybe I am missing something?

    Best,

    Keerthi

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 20 points

    Hi Keerthi,

    Indeed, from the register descriptions it could make sense. However, the actual manual with initialization steps does not show this:

    My initial thoughts were that since we are using SPI Command Read/Writes instead of regular SPI Read/Writes it would internally handle this.
    Could you clarify these steps for me?

    Secondly, we have gotten another issue. We do the following:

    1. We have a jumper connected to the associated IPROP output signal on the development board
    2. The other end of the jumper cable is not connected
    3. Close the relay

    The configuration looks as follows:

    Which matches with the jumpers on the EVM.

    We observe the following:
    1. When we try to measure the voltage on IPROP1, the current drops from 0.25A to 0.20A, and we hear a faint noise coming from the relay.
    2. The same happens when one probe touches the pin while the other probe touches nothing.

    Any idea where this could be coming from?

    Thanks in advance,
    Thom

  • 0 in reply to Thom H
    TI__Mastermind 18725 points

    Hi Thom,

    Could you get a capture of the IPROPI signal along with the load current, OUTx voltage, and supply?

    Can you set the center PWM frequency to 20 kHz and see if the audible noise goes away?

    Best,

    Keerthi

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 20 points

    Hi Keerthi,

    We will try and get that capture to you.

    In the meantime, would you mind answering my earlier question regarding the manual and SPI CMD?

    Thanks,

    Thom

  • 0 in reply to Thom H
    TI__Mastermind 18725 points

    Hi Thom, 

    I am checking internally if it is a typo. I will get back to you on this tomorrow.

    Best,

    Keerthi