V-BAT Emulation Using PIC24F eXtreme Low-Power Microcontrollers

PublishTime：2021-11-16

●This document describes how to switch between the main power supply and battery backup (VBAT) in devices that do not support on-chip VBAT capability. The methods to achieve VBAT emulation using some of the Core-Independent Peripherals (CIPs) available on the PIC24F eXtreme Low-Power (XLP) microcontrollers and a few external passive components are described in this document. The proposed VBAT Emulation modes offer a comparable low-power performance, while adding minimal cost, and can be implemented with any of the PIC24F XLP microcontrollers.
●This document considers applications having two sources of power:
■Main power
■Backup power
●In most situations, an application makes use of the main power. The main power is the power supply that sources the current required to run the entire application. In the absence of main power, backup power acts as a secondary source. Backup power can be a battery, coin cell, super capacitor or another power source.
●Emulated VBAT offers several benefits:
■Flexibility to keep more than just RTCC and backup registers operational.
■Uses CIPs for the emulation that are functional in power-saving modes without any core intervention.
■Increases flexibility when selecting an ideal microcontroller from a large portfolio of PIC24F microcontrollers based on application needs.
●The user application should monitor the state of the main supply voltage. The main supply health can be monitored using various peripherals available on the device in a core-independent manner, such as High/ Low-Voltage Detect (HLVD), interrupt-on-change, ADC with Threshold Detect, Comparator, etc. The hardware should have a provision to switch to the backup source, on detection of main supply failure. In Emulated VBAT mode, it is advisable to put the CPU in Sleep mode for increased power savings. The user application can configure peripherals, such as RTCC and WDT, to function in V-BAT mode when needed, while the rest of the peripherals are shut off. This ensures maximum power conservation in VBAT mode to extend the battery life.
A high-level flow of the process is shown in Figure 1.

Brand of Product：	Microchip
Part#：	PIC24F 、 PIC24FJ More Part#
Product Category：	eXtreme Low-Power Microcontrollers 、 XLP microcontrollers More
Application：	More
Data Type：	Application note & Design Guide More
Safety & Environment Standards：	More
Operating Temperature：	Please see the document for details
Qualification Grade：	More
Qualification Approval：	More
Package：
Language：	English Chinese Chinese and English Japanese
Date of Creation：	05/14/19
Version Number：
Data Encoding：	AN3329,DS00003329A
Data Size：	217 KB

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