SPNA140 Datasheet, PDF (1/8 Pages) Texas Instruments – Interfacing the Embedded 12-Bit ADC in a TMS570LS31x/21x and RM4x Series Microcontrollers

Application Report
SPNA140 – February 2012
Interfacing the Embedded 12-Bit ADC in a
TMS570LS31x/21x and RM4x Series Microcontrollers
Weng, Haixiao .................................................................................................................................
ABSTRACT
The Texas Instruments Hercules™ ARM^® Safety Microcontrollers TMS570LS31x/S21x and RM4x series
of products have two 12-bit analog-to-digital converters (ADC). This document provides the device
configuration and layout recommendations to achieve the best performance of the embedded ADC. These
include layout requirements on power and ground, decoupling and bypass capacitor requirements on
voltage reference pins and power pins, typical circuit and requirements in front of ADC input channel,
recommendations on ADCLK configuration, phase-locked loop (PLL) settings and trigger signal to achieve
the best effective number of bits (ENOB), how to do calibrate and compensate, and how to use
over-sampling to improve resolution.
Contents
1 Description ................................................................................................................... 2
2 Circuit Design and Layout Requirement ................................................................................. 2
3 References ................................................................................................................... 7
List of Figures
1 Channel Assignments of Two ADC Cores............................................................................... 2
2 Ground Plane Example .................................................................................................... 3
3 Current Distribution on an Infinite and a Cut Ground Plane........................................................... 4
4 Signal Traces Crossing the Gap of Ground Plane ..................................................................... 4
5 Power and Reference Voltage Layout Strategy......................................................................... 5
6 ADC Input Strategy ......................................................................................................... 5
7 MibADC Input Equivalent Circuit.......................................................................................... 6
8 ADC Input Passive Circuit (No OP_AMP) ............................................................................... 6
Hercules is a trademark of Texas Instruments.
ARM is a registered trademark of ARM Limited.
All other trademarks are the property of their respective owners.
SPNA140 – February 2012
Submit Documentation Feedback
Interfacing the Embedded 12-Bit ADC in a TMS570LS31x/21x and RM4x Series
1
Microcontrollers
Copyright © 2012, Texas Instruments Incorporated