AM2634-Q1: ADC CALIB pin and ADC VREF query

VISHNU AG

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

I have two doubts regarding the schematic design of AM2634 microcontroller.

1. How to configure or design the pin ADC_CALIB0 pin and AADC_CALIB1 pin of microcontroller? Should it be connected it to an external 3.3V regulator/

2. Should i connect ADC_VREFHI_G0, ADC_VREFHI_G1, ADC_VREFHI_G2 to three seperate 1.8V regulators. In the reference schematic design of TI i saw that ADC_VREFHI_G0 & ADC_VREFHI_G1 were connected to a single 1.8V regulator and ADC_VREFHI_G2 is connected to another 1.8V regulator.

over 2 years ago

0 Nilabh Anand over 2 years ago

TI__Mastermind 45154 points

Hi VISHNU AG,

The ticket has been assigned to our expert. Please expect a response by tommorow.

0 Sri Vidya Gunturi over 2 years ago in reply to Nilabh Anand

TI__Expert 7586 points

Hi Vishnu

To understand more on the VREF connections please refer to section 7.4.2.3.3.1 ADC Reference Buffer Control Registers in TRM:

https://www.ti.com/lit/ug/spruj17c/spruj17c.pdf?ts=1683190403107&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FAM2634

For the schematic Reference, please refer to the hardware design guide app note:

https://www.ti.com/lit/an/sprabj8/sprabj8.pdf?ts=1683786199192&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FAM2634

VISHNU AG said:
How to configure or design the pin ADC_CALIB0 pin and AADC_CALIB1 pin of microcontroller?

Please allow me sometime to get back on the CAL pin configuration.

Thanks & regards

Sri Vidya

0 Fleenor over 2 years ago in reply to Sri Vidya Gunturi

TI__Mastermind 23023 points

Hey Vishnu,

Regarding the ADC_CAL[0:1] pin usage, please find excerpt from our ADC expert below:

Abhijit Das said:
The CAL0 & CAL1 pins can be driven with any precision or ratio-metric voltage on the board and can be used to calibrate the error of the ADC reference or to validate the ADC from functional safety context. An example is given below

The built-in on-die reference has an accuracy of ~ +/- 2% and your ADC o/p can be written as Vcode=Vin/(Vref/2^12)=Vin*2^12/Vref --> Where Vin is the input voltage and Vref is the refernce which is 2% accurate making a 2% error in output computation.

If you have a known voltage on the board then you can pass it to CAL0/1 and based on ADC o/p you can calculate Vref_measured=Vin*2^12/Vcode and eliminate the 2% error.

Please note this equation is simplistic and ignore few details like input scaling, but as it is ratiometric, those approximations does not contribute any additional error.

You can use CAL0 and CAL1 for a two point reference measurement to qualify the ADC or even have a dynamic known voltage to qualify the ADC for the full input range in functional safety context.

https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1224068/mcu-plus-sdk-am263x-adc_cal0-1-pins

Best Regards,

Zackary Fleenor

Arm-based microcontrollers

Arm-based microcontrollers forum

AM2634-Q1: ADC CALIB pin and ADC VREF query