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MSP430FR5962: ADC Characteristics when using AVCC as ADC reference source

Part Number: MSP430FR5962
Other Parts Discussed in Thread: MSP430FR2476

Dear All,

Is there any detailed information (characteristics) available when using AVCC as ADC reference source (ADC12VRSEL=0000b)?

Of interest are:

  • Integral linearity error (INL) for single-ended inputs
  • Offset error
  • Gain error
  • Total unadjusted error

AVCC test condition / Minimal AVCC for full ADC operation?

Thanks for your help,

Patrick

  • Hi Patrick,

    as like with any ADC measurement, the performance of the used reference is fully going into the ADC measurement result accuracy, one would be only able to make a statement like "with this AVCC (voltage level, noise, impedance......) you get these parameters..."

    As this does not make sense, we're not specifying this. One can assume a similar/same performance of the ADC core as with the reference specified in the datasheet, but all noise and variation effects of the AVCC will fully impact the ADC results.

    Best regards

    Peter

  • Hi Peter,

    Very well explained, that makes sense to me, Thanks.

     

    The other question I still have concerning the ADC of the MSP430FR5962.

    Table 5-25 in the datasheet (SLASE54C) list the ADC12_B linearity parameters. It notes: over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted).

    Does this mean that the ADC12_B linearity parameters apply from AVCC 1.8V min, because nothing else is otherwise noted?

    (snapshot recommended operating conditions from datasheet below)

     

    Reason for asking is because other MCUs from the MSP430FR family (e.g. MSP430FR2476) are specified from AVCC 2.4V min. concerning this linearity matter.

    Many thanks for your help,

    Patrick

     

     

  • Hi Peter,

    apparently something went wrong with the snapshot.

    I have the question re-inserted, see attachment.

    PatrickQuestion ADC MSPFR5962 specifications.pdf

  • Hi Patrick,

    when pasting in pictures or other material, you need to do this as attachments, and not do just copy paste.

    Coming to your questions, there are multiple things to keep in mind related to ADC operation and performance.

    With the MSP430FR2476, like with other derivatives, there is the generic specification for the operating voltage range for the ADC. This is specified for the MSP430FR2476 in Table 5-21 with 2.0V - 3.6V. So this is the recommended operating voltage range for the ADC as such.

    The other requirement is the value of the supply capacitors.

    In addition, looking at the linearity table 5-23, you can see two other conditions specified. On one hand it is for the supply voltage range limited from 2.4V - 3.6V and the other one is the reference. The supply range can be further limited by the reference selection, as supply voltage needs to be always somewhat higher than the selected reference voltage. The MSP430FR2476 has 3 different reference voltage levels 1.5V, 2.0V and 2.5V. This means when selecting 2.5V reference voltage level, even though the ADC can operate from 2.0V upwards, for this the minimum supply voltage level is specified with 2.7V.

    Best regards

    Peter

  • Hello Peter,

    On one hand it is for the supply voltage range limited from 2.4V - 3.6V >>>> I'm sorry I'm not able to find this specification in table 5-23.

    As mentioned before we are planning to use AVCC as ADC reference source (ADC12VRSEL=0000b) so we are not limited on supply voltage due to minimal reference supply voltage I assume.

    Let me rephrase my concern: for our application we want to use the MSP430FR5962, supply voltage available 2.1~2.3V, will the ADC run within spec. when using AVCC as ADC reference source? In other words will the ADC perform as mentioned in table 5-25 when the AVCC supply is free of noise, low impedance and stable?

    Best regards,

    Patrick

  • Hi Patrick,

    sorry for the table 5-23. I must have mixed it with some FRAM Value Line device datasheet.

    In terms of your question on table 5-25 the ADC Linearity Parameters, as you can see all the values are specified for certain conditions, let it supply or/and used reference voltage. Thus if you want to have an absolutely bullet proof statement on the linearity parameters under your specific conditions, I have unfortunately to disappoint you. We have not characterized the ADC for these conditions. Sorry for not being able to make a different statement on this.

    Best regards

    Peter

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