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MSP430I2041: SD24's input range

paddu2017
Expert 2885 points
Part Number: MSP430I2041
Other Parts Discussed in Thread: EVM430-I2040S,

Hi,

What is the recommended way to measure sensor with higher voltage than the
Differential input voltage range with internal reference?

As per the datasheet SD24's input range is ±928mV (@SD24GAINx = 1) but our
sensor output is 0 to 1.6V, so this cannot be directly fed into the SD24 input
and it may be necessary to add a circuit to float the minus side, so that may require an external reference IC.

Please let me know your suggestions and if there is any application notes
or guide on using MSP430's SD24.Should we choose external ADC in this case?

Best Regards
paddu

  • 0
    TI__Mastermind 49692 points
    Hello Paddu,

    You can use a voltage divider to bring the max input voltage to within the max full-scale range (FSR) of the MSP430i2041. For example, the EVM430-i2040S can measure an input voltage of 230VAC using a large voltage divider that reduces the input voltage to the SD24. For more details, you can refer to the schematic for the EVM430-i2040S.

    Regards,

    James

    MSP Customer Applications
  • 0 in reply to James Evans
    Expert 2885 points
    Hi James,

    Thank you,

    Actaully we are worried about the dynamic range when measuring the single ended signal,
    if the sensor range is 0 to 1.6V, grounding the negative input cuts the dynamic range in half.
    Is there any way to avoid this reduction and measure 0 to 1.6V with full dynamic range?

    Best Regards
    paddu
  • 0 in reply to paddu2017
    TI__Mastermind 49692 points

    The Sigma Delta ADC is targeted towards differential inputs. If you want to use it with a single-ended input configuration, you're going to limit the ADC performance as you mentioned. I would recommend a SAR ADC for single-ended inputs although I know the Sigma Delta ADC's have higher resolution but may have worse dynamic range performance.

    SD16 single-ended noise problem - MSP low-power microcontroller forum - MSP low-power microcontrollers...

    e2e.ti.com
    I'm measuring low-millivolt, low-frequency signals from two air-coil sensors using the SD16 ADC: gain of two, Fm = 1,048,576 Hz, 0SR = 128. When connected differentially

    Regards,

    James

    MSP Customer Applications

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