topic Re: About VREF pin for MKM14Z128? in Kinetis Microcontrollers

About VREF pin for MKM14Z128?

mercysun — Thu, 12 Feb 2015 15:51:12 GMT

For SD ADC use in MKM14Z MCU,It’s not easy find the Pin VREF input properties.

How about the VREF pin input range if use an external voltage reference for SD ADC?

If use internal reference (1.2V bandgap),what's SD ADC accuracy?

What's the condition for SD ADC reach 24bit?

Re: About VREF pin for MKM14Z128?

apanecatl — Thu, 12 Feb 2015 19:37:04 GMT

You can find a detailed description of the VREF submodule and pin in the device's reference manual, check Chapter 3: Chip configuration and look for the VREF section, if you need to use an external reference you will have to use the VREFH pin to set the upper voltage reference.

Re: About VREF pin for MKM14Z128?

mercysun — Thu, 12 Feb 2015 21:58:57 GMT

Thanks for your quickly response!

For the 24 bit sigma delta ADC,

In RM Chapter 3, Case III, its only tell VREF use 1.2V reference, i'd like to know for use an upper(>1.2V) voltage reference is ok? if it's ok ,for a 3.3V external voltage reference, what's the SD ADC input range? still 1Vpp or >3Vpp?

In datasheet,6.4.1 ,VREFH input range is 1.13~VDDA, Is VREFH an output pin when use an external voltage reference?

Thanks

Re: About VREF pin for MKM14Z128?

apanecatl — Fri, 13 Feb 2015 12:53:42 GMT

VREF can only provide a 1.2V + trimm (.05mV per step) you CANNOT connect VREFout to an external power supply; if you need to use a higher voltage reference for any of the available ADCs you need to use the VREFH pin as the voltage reference, this pin can be connected to an external power supply which can range from 1.13 - VDDA, the ADC range remains the same with the exception that if you use an offset level you must take it into consideration. As I mentioned before, VREFH is an input pin which can be connected to an external power supply.