S32K3xx: Need more information on how to use ADC bandgap to measure ADC signals

[tecprasant]

Hi,

I need help regarding the internal bandgap signal in the ADC.

I am suing S32K312 to measure external signals using ADC (MCU VCC is 5V, VDD IO is 3.3V & Vref is 5V).

My hardware will be used in a noisy environment & I forsee that the Vref will have occasional glitches.

I have come questions regarding bandgap:

1) Can I use bandgap to measure the VrefH & VrefL & correct the Vref if there are glitches?
2) Which voltage source is used for generating the Bandgap voltage?
3) If in future, I were to increase Vref to 12V, can I continue to use bandgap to correct the Vref glitches (in software)?
4) If in future, I were to decrease Vref to 1.8V, can I continue to use bandgap to correct the Vref glitches (in software)?
5) Is there any example that uses badgap to measure external ADC signals?

Any inputs will be of help. Thanks in advance.

Regards, 

[Robin_Shen]

Hi

A1: The bandgap is ADC input channel, it can not be selected as VREF for ADC.

Please refer to Using bandgap to monitor reference voltage section of AN12217: S32K1xx ADC guidelines, specs, and configuration – Application Note

Q3\4: I am suing S32K312 to measure external signals using ADC (MCU VCC is 5V, VDD IO is 3.3V & Vref is 5V).
A3\4: Please download the S32K3xx MCU Family Data Sheet:
Refer to Figure 20. 172-pin HDQFP decoupling capacitor pinout diagram (S32K312) , VDD_HV_A supplies the analog circuitry, GPIOs, I don't understand what you mean: VCC is 5V, VDD IO is 3.3V.
VREFH should always be equal to or less than VDD_HV_A +0.1. Any positive differential voltage between VREFH and VDD_HV_A i.e., VDD_HV_A < VREFH <= VDD_HV_A + 0.1V) is for RF-AC only.

A5: Adc_Sar_Bctu_Ip_example_S32K344 will show you the ADC_BANDGAP that measured by ADC.

Best Regards,
Robin
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