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ADS131B04-Q1: Absolute input voltage range question

Part Number: ADS131B04-Q1
Other Parts Discussed in Thread: ADS131M04, ADS131M04-Q1

Dear team,

I noticed ADS131M04 and ADS131B04-Q1 are P2P compatible. But the absolute input range is different. ADS131M04's range is wide. Currently my customer needs AECQ100 device, and they need to monitor -1.2V power rail. Based on the datasheet, our ADS131B04-Q1 can't meet the requirement, right? Do we have Q1 version of ADS131M04?

Thanks & Best Regards,

Sherry

  • Hi Sherry,

    your observation is absolutely correct. The ADS131B04-Q1 is pin2pin compatible with the ADS131M04 but because it integrates additional input buffers to increase the input impedance and to improve the offset performance, the input voltage range is more limited.

    I'll contact you via email regarding the ADS131M04-Q1.

    Regards,
    Joachim

  • Hello,

    To add to Joachim's correct response, here is a circuit document that helps show methods to protect the ADS131M0x devices from overstress.  Even though the ADS131B04-Q1 has a reduced linear input range versus the ADS131M04, they share the same absolute maximum input ratings which makes the ADS131B04-Q1 a little easier to protect against negative damaging transients than some devices.

    Circuit for protecting ADS131M0x ADC from electrical overstress

  • Hi Collin,

    If adding the protection circuit, it is still not suggesting to use ADS131B04-Q1  to monitor -1.2V, right? After all our recommended is -0.3V.

    Thanks & Best Regards,

    Sherry

  • Hi Sherry,

    The recommended/linear/usable input range is defined to -0.3V (for G>=4) as Joachim confirmed in the first reply.  The device has an abs max rating that extends down to -1.6V which makes the device relatively easy to protect against negative transients without worrying about the protection circuitry conducting within the recommended input range.  

  • Hi Collin,

    If the customer monitors -1.2 power rail, then the input will always be the negative signal instead of negative transients, is it ok? Will this impact the sampling accuracy? My customer's requirement is that they need a ADC to monitor -1.2V power rail. Is this device applicable?

    Thanks & Best Regards,

    Sherry

  • Hi Sherry,

    No, it wont' work with the ADS131B04-Q1.  We've confirmed several times that the linear (recommended, usable, allowable) input range for the ADS131B04-Q1 extends down only a few hundred mV below GND (see images you pasted in the first post). 

    The ADS131M04 has an linear input range that extends down to -1.3V.  This is still very close to the -1.2V levels you mention and the customer would need to understand that if they apply voltages lower than -1.3V that the ADS131M04 won't product accurate conversion results.  If they apply voltages lower than -1.6V to the ADS131M04 it will exceed the abs max ratings for the product.