Analog to Digital Converter Type 2 FAQ for C2000

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Introduction

This topic is a list of frequently asked questions that users have when using the Analog to Digital Converter of type 2. ADC type 2 is the 3rd generation ADC module released for the C28x devices and is found on 2833x and 2823x devices.

Electrical Specifications

Electrical specifications can change between devices, peripheral types and device families. Always refer to the data manual and errata for a particular device for Electrical Specifications.


ADC Type Summary

The following table summarizes the different type of ADC modules found on C28x devices.

C2000 ADC Module Types
Type
Description
Devices
Documentation
0
Original C28x ADC module
281x
TMS320x281x Analog-to-Digital Converter (ADC) Reference Guide (spru060)
1
Added Offset Trim and Reference Select registers
2801, 2802, 2806, 2808, 2809, 28015, 28016, 28044
TMS320x280x 2801x, 2804x Analog-to-Digital Converter(ADC) Module Reference Guide (spru716)
2
Added Internal/External Trim registers
Trim by Device_cal() function call
2833x, 2834x
TMS320x2833x, 2823x Analog-to-Digital Converter (ADC) Module Reference Guide (spru812)
3
Different control register interface, converts from 0 to 3.3 V fixed scale range, supports ratiometric VREFHI/VREFLO references
2802x, 2803x

2806x
TMS320x2802x, 2803 Piccolo Analog-to-Digital Converter and Comparator Ref. Guide (spruge5)

TMS320x2806x Piccolo Technical Reference Guide (SPRUH18)


Frequently asked questions for ADC Type 2

Q: I measured ADCREFP and ADCREFM. In the datasheet only a typical value is specified not a min/max. How can I tell if my device is in spec?

These signals are internally generated voltages for use by the internal ADC only. These are fully tested at by TI at production time and will not be out of spec for the device. The only reason these signals are brought outside the device is for external bulk cap. The Data Manual values are only there to give a ballpark of where the voltages will be and this is why there is no max/min.

Q: Can you explain more about this ADC_Cal() routine that the boot ROM calls?

The ADC_cal() routine in the ROM of F2833x is just copying a couple of values to the ADCST and ADCOFFTRIM registers. This brings the ADC up to the specs in the datasheet.

Q: Does the ADC_cal() routine require a voltage on an ADC input pin?

It does not require the use of any ADCINx channels.

Q: Can we still perform manual calibration like on the 280x?

If you want to further improve the ADC offset and gain you can still do manual calibration AFTER running the ADC_cal() routine. The manual calibration would be the same as for the 280x.