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DRV8305: VREF and SO signals of SPI

Part Number: DRV8305

Hi,

I need to interface the DRV8305N current amplifier output (SO1, SO2, SO3) with an ADC which accepts max. 2.5V in input. Thus, I thinked to connect VREF(pin 48) at 2.5V in order to have a VBias of the current amplifiers exaclty half of the VREF. Then, I want to connect the DRV through SPI with an MCU at 3.3V but what about SDO? Because in the datasheet is reported that:

"For the DRV8305NQ and DRV8305NE, the VREG voltage regulator is disabled(VREG pin usedf or reference voltage) and the reference voltage for SDO and the amplifier output bias must be supplied from an external supplyto the VREGpin."

What is the meaning of VREF is used as reference voltage for SDO? Normally, in the SDO pin of SPI, I always have used a pull-up to VCC (3.3V in this case).

Can I use 2.5V as VREF and 3.3V as SPI with a pull-up at 3.3V in the SDO pin?

Thank you.

  • Hi Alessio,

    The team will get back to you soon on this!

    Thanks,

    Matt

  • Hi Alessio,

    The SDO pin is pulled up to VREF internally in the device, so this results in the SDO pin being referenced to the VREF voltage. The benefit is that this eliminates the need for an external pullup resistor, but the downside is that in your case the SDO pin will be referenced to 2.5V instead of 3.3V. You will need to confirm to see if 2.5V is high enough for your MCU to consider as a logic high voltage for the SDO signal.

    Regards,

    Anthony