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DRV2510-Q1: Noise on output signal and relation to reserved bits in register 0x03

tianshao ni
Prodigy 120 points
Part Number: DRV2510-Q1

We're currently developing firmware for the TI DRV2510-Q1 driver in one of our medical imaging applications. We’re driving a couple square waves into the IN+/IN- pins of the driver. We’re seeing a lot of noise on the OUT+(yellow trace)/OUT-(blue trace) pins which could cause issues in our image quality:

 

Zooming in, we found the noise to be 400kHz, the driver PWM frequency:

If I write 1 to register 0x03 bit0 I could change the frequency of the noise to 500kHz, confirming the noise source.

 

Here’s where things get interesting, I accidentally discovered that if I write 1 to bit 2(a reserved bit) of register 0x03, the noise goes away:

 

Although the datasheet didn’t specify a default value, I could read the default value on power up to be 0x78 for register 0x03.  Bit 2 is zero by default.

 

In fact, I found that both reserved bits bit 1 and bit 2 has some effect on noise, writing a 1 to bit 2 appears to remove it. While doing this yields the desired behavior, I’m not comfortable driving a reserved bit. Please let me know if this is safe.

 

FYI, in these tests the driver is not connected to any load, standby pin is set to 0, en pin set to 1, register dump:

register 0x00 : 0x04

register 0x01 : 0x04,

register 0x02 : 0x84

register 0x03:  0xBE ( no noise with this value)

Thanks,

Tian

  • 0
    TI__Guru* 84915 points

    Hi, Tian,

    Welcome to E2E and thank you for your interest in our products.

    There's no problem writing '1' on the reserved bits that you mentioned. Actually, I think that the datasheet should include details on this since the reserved bits must be written '1' to have the output properly enabled.

    I don't have the exact function for these bits (probably related to a circuit protection or filtering), but the previous register table version looked like this:

    As you see, this register table had the reserved pins as '1'. I suspect that these values are not marked as default in the datasheet new version since they are '0' in default state as you mentioned.

    Please feel safe to keep using these reserved bits as '1'. For additional questions or comments, please post your reply in this E2E thread. We will be glad to help you.

    Best regards,
    Luis Fernando Rodríguez S.