Datasheet

 2010 Microchip Technology Inc. Preliminary DS39974A-page 395
PIC18F47J13 FAMILY
FIGURE 25-3: HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)
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 general battery applications, Figure 25-4 provides
a possible voltage curve.
Over time, the device voltage decreases. When the
device voltage reaches voltage, V
A, the HLVD logic
generates an interrupt at time, T
A. 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 T
B.
The HLVD, thus, would give the application a time
window, represented by the difference between TA and
T
B, to safely exit.
FIGURE 25-4: TYPICAL HIGH/
LOW-VOLTAGE DETECT
APPLICATION
VHLVD
VDD
HLVDIF
VHLVD
VDD
Enable HLVD
TIRVST
HLVDIF may not be Set
Enable HLVD
HLVDIF
HLVDIF Cleared in Software
HLVDIF Cleared in Software
HLVDIF Cleared in Software,
CASE 1:
CASE 2:
HLVDIF Remains Set since HLVD Condition still Exists
T
IRVST
IRVST
Internal Reference is Stable
Internal Reference is Stable
IRVST
Time
Voltage
VA
VB
TA
TB
VA = HLVD trip point
V
B = Minimum valid device
operating voltage
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