ADC Voltage Reference Selection for K32

aberger — Fri, 01 Nov 2024 23:08:12 GMT

I am using the FRDM-K32L2B3 and trying to understand the voltage reference selection for the ADC.

In the ADC Chapter, the SC2[REFSEL] bits provide the following options:

00 Default voltage reference pin pair, that is, external pins VREFH and VREFL
01 Alternate reference pair, that is, VALTH and VALTL . This pair may be additional external pins or internal sources depending on the MCU configuration. See the chip configuration information for details specific to this MCU
10 Reserved
11
Reserved

This seems to conflict with the information from 2.3.3 Analog reference options:

How can I select between the 3 options VREFH, 1.2V VREF_OUT, and VDDA?

Re: ADC Voltage Reference Selection for K32

Ben_Xu1 — Mon, 04 Nov 2024 09:19:47 GMT

Hi @aberger,

VREFH pin can be used as filter capacitor pin for high precision 1.2V VREF_OUT. When 1.2V VREF is enabled, VREFH is 1.2V VREF_OUT. Also, when 1.2V VREF module is enabled, adding supply to VREFH pad, which is a dedicated 1.2 VREF_OUT pad, from external is prohibited.

1. ADC0_SC2[REFSEL] = 00b, VREFV1 module disabled, ADC reference voltage is VREFH.

2. ADC0_SC2[REFSEL] = 00b, VREFV1 module enabled, ADC reference voltage is 1.2V VREF_OUT.

3. ADC0_SC2[REFSEL] = 01b, ADC reference voltage is VDDA.

Thanks & Regards,

Ben

00	Default voltage reference pin pair, that is, external pins VREFH and VREFL
01	Alternate reference pair, that is, VALTH and VALTL . This pair may be additional external pins or internal sources depending on the MCU configuration. See the chip configuration information for details specific to this MCU
10	Reserved
11	Reserved

topic ADC Voltage Reference Selection for K32 in Kinetis Microcontrollers

ADC Voltage Reference Selection for K32

Re: ADC Voltage Reference Selection for K32