PIC18F44J50-I Datasheet, PDF (399/562 Pages) Microchip Technology – 28/44-Pin, Low-Power, High-Performance USB Microcontrollers

PIC18F46J50 FAMILY
FIGURE 25-3:
CASE 1:
HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)
HLVDIF may not be set
VDD
HLVDIF
VHLVD
Enable HLVD
IRVST
TIRVST
Internal Reference is stable
HLVDIF cleared in software
CASE 2:
VDD
VHLVD
HLVDIF
Enable HLVD
IRVST
TIRVST
Internal Reference is stable
HLVDIF cleared in software
HLVDIF cleared in software,
HLVDIF remains set since HLVD condition still exists
25.5 Applications
In many applications, it is desirable to have the ability to
detect a drop below, or rise above, a particular threshold.
For example, the HLVD module could be enabled
periodically to detect Universal Serial Bus (USB) attach
or detach.
For general battery applications, Figure 25-4 provides
a possible voltage curve.
Over time, the device voltage decreases. When the
device voltage reaches voltage, VA, the HLVD logic
generates an interrupt at time, TA. The interrupt could
cause the execution of an ISR, which would allow the
application to perform “housekeeping tasks” and
perform a controlled shutdown before the device
voltage exits the valid operating range at TB.
Thus, the HLVD would give the application a time
window, represented by the difference between TA and
TB, to safely exit.
FIGURE 25-4:
TYPICAL HIGH/
LOW-VOLTAGE DETECT
APPLICATION
VA
VB
Time ^{TA TB}
Legend: VA = HLVD trip point
VB = Minimum valid device
operating voltage
 2011 Microchip Technology Inc.
DS39931D-page 399