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MSP430F5342: reference calibration information slau208o/p vs the data sheet

Part Number: MSP430F5342

I have read section 1.13.5 (not a problem) however there is some (on my part) of what the calibration value for the reference is based on.

1.13.5 shows this:

CAL_ADC_15VREF_FACTOR = (V_REF+/1.5V)* 2^15
However the data sheet states that the 1.5V reference is actually 1.49.
The same goes with the 2V reference the data sheet states 1.98.
So is the calibration factor based on what slau208n states or the value that is the nominal value for the reference in the data sheet.
I do appreciate the data at least being there. I don't know which value to go by for checking valid values and thus using them as well.
Thanks!
Stephen

CAL ADC VREF FACTOR REF
15 2
2.0
_ _ 20 _ = ´
+
V
V
CAL ADC VREF FACTOR REF
15 2
2.5
_ _ 25 _ = ´
+
V
V
CAL ADC VREF FACTOR REF
Device Descriptor Table www.ti.com
82 SLAU208P–June 2008–Revised October 2016
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Copyright © 2008–2016, Texas Instruments Incorporated
System Resets, Interrupts, and Operating Modes, System Control Module
(SYS)
1.13.5 Calibration Values
The TLV structure contains calibration values that can be used to improve the measurement capability of
various functions. The calibration values available on a given device are shown in the TLV structure of the
device-specific data sheet.
1.13.5.1 REF Calibration
The calibration data for the REF module consists of three words, one word for each reference voltage
available (1.5, 2.0, and 2.5 V). The reference voltages are measured at room temperature. The measured
values are normalized by 1.5 V, 2.0 V, or 2.5 V before being stored into the TLV structure:
(2)

  • The built-in reference voltage output is designed to be 1.5, 2, or 2.5 V but typically comes out to 1.49, 1.98, and 2.5 V, respectively, for the MSP430F534x. You can also see that there is some variance involved from part-to-part in the datasheet and these values will vary slightly across the F5xx/6xx family. The reference calibration equations from the User's Guide uses the expected values of the internal reference since it accounts for all F5xx/6xx devices but you can use the typical MSP430F543x values if you feel that these will give you more precise results.

    Regards,
    Ryan
  • Let me attempt to reword my question more specifically what I wanted to know was what the calibration information for the reference was based on. (I did say attempt).
    Is REF_CAL_FACTOR based on slau208p 1.5 / 2.0 / 2.5 volt for the reference or the data sheet which reads 1.49 / 1.98 / 2.5. So in other words is REF_VALUE 1.5 or 1.49 for the equation REF_CAL_FACTOR = (VALUE*2^15)/REF_VALUE. That is what I wanted to know.
    I am attempting to verify the calibration data for the reference is correct (or present for that matter).

    Thanks!

    Stephen
  • The CAL_ADC_REF_FACTOR words stored in the TLV vary per unit and account for the true internal reference value (VREF+) for that specific device as evaluated during production, they are normalized using the expected values before being stored as such.

    Regards,
    Ryan
  • Indeed CAL_ADC_REF_FACTOR TLV data (should) vary between units. I wish to know what the expected values are for the MSP430F5342 are. IE 1.5V or 1.49V (was 1.5V the expected value IE expected value originates from slau208p, or is the expected value what is listed for the reference in the data sheet 1.49). In this case I called the expected value REF_VALUE in the prior message. That is the area of interest.

    Thanks!

    Stephen
  • 1.5 V is the expected value.

    Regards,
    Ryan
  • I appreciate your patience.
    Thanks for the help too.

    Stephen

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