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AM2634-Q1: ADC example using internal reference buffer

Sung-IL
Mastermind 31440 points

Part Number: AM2634-Q1
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Dear Champs,

My customer is looking for some ADC example implementing internal reference without HW ADC_VREF pin connected as in below.

Is there any example to use internal reference?

https://dev.ti.com/tirex/explore/content/am26x_academy_2_01_00_00/_build_am26x_academy_2_01_00_00/source/real_time_control/adc.html#adc-reference

Internal reference are disabled by default. If external reference is not used, internal reference buffers can be enabled by the application for driving the ADC reference. The ADC_REFBUF0_CTRL register is used to enable ADC Reference Buffer 0. Similarly, the ADC_REFBUF1_CTRL register is used to enable ADC Reference Buffer 1. The MASK_ANA_ISO register must be set to 0x7 before ADC reference buffers are enabled. This prevents any undesirable behavior from voltage monitors triggering SOC reset.

Thanks and Best Regards,

SI.

  • 0
    TI__Mastermind 29283 points

    Hello SI,

    All of our EVM's and related software examples are using the Internal ADC VREF reference voltage.

    I think this statement is still true, the Internal references are disabled by default, but all of the example application code configures the device to use the internal reference.

    Best Regards,

    Zackary Fleenor

  • 0 in reply to Fleenor
    TI__Mastermind 31440 points

    Hi Zackary Fleenor,

    Thanks for your response.

    Then, where I can find the code to enable internal reference ADC VREF?

    When my customer tried to enable internal reference ADC VREF using SOC, they just added SOC_enableAdcReference(0) in below.

    Is it ok only to use this API to enable internal ADC VREF?

    When they tried to get ADC value, the ADC value is very unstable.

    Fleenor said:
    all of the example application code configures the device to use the internal reference.

    When I checked ADC examples of MCU+ SDK v9.1, I could not find any examples using this API - SOC_enableAdcReference(0) except below.

    \\mcu_plus_sdk_am263x_09_01_00_41\examples\drivers\adc\adc_high_priority_soc

    Thanks and Best Regards,

    SI.

  • 0 in reply to Sung-IL
    TI__Mastermind 31440 points

    Hi Zackary Fleenor,

    Is it possible to use internal reference ADC VREF without connecting decoupling cap between VREF_Hi pins and VREF_Lo pins?

    It is hard for My customer to modify their HW to attach decoupling cap. Is it ok only to connect VREFLO pins to GND to use internal reference ADC VREF?

    Thanks and Best Regards,

    SI.

  • +1 in reply to Sung-IL
    TI__Mastermind 29283 points

    Hey SI,

    The decoupling caps for VREFHI/LO are hard requirements if you plan on using the internal voltage reference. This is probably the reason for such unstable ADC readings up to this point. 

    They should use the SOC_enableAdcReference() function. I will have to dig a little deeper to understand why only one of the ADC examples utilize this function.

    Best Regards,

    Zackary Fleenor

  • +1 in reply to Fleenor
    TI__Expert 4230 points

    Hey SI,

    This function is called directly through sysconfig and is present in generated/ti_drivers_config.c (Post Build) for all ADC examples in the SDK.

    Regards,
    Akshit