PIC18F010T-I/SO View Datasheet(PDF) - Microchip Technology
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MFG CO.
'PIC18F010T-I/SO' PDF : 176 Pages View PDF
PIC18F010/020
11.0 LOW VOLTAGE DETECT
In many applications, the ability to determine if the
device voltage (VDD) is below a specified voltage level
is a desirable feature. A window of operation for the
application can be created, where the application soft-
ware can do "housekeeping tasks" before the device
voltage exits the valid operating range. This can be
done using the Low Voltage Detect module.
This module is a software programmable circuitry,
where a device voltage trip point can be specified.
When the voltage of the device becomes lower then the
specified point, an interrupt flag is set. If the interrupt is
enabled, the program execution will branch to the inter-
rupt vector address and the software can then respond
to that interrupt source.
The Low Voltage Detect circuitry is completely under
software control. This allows the circuitry to be "turned
off" by the software, which minimizes the current con-
sumption for the device.
Figure 11-1 shows a possible application voltage curve
(typically for batteries). Over time, the device voltage
decreases. When the device voltage equals voltage VA,
the LVD logic generates an interrupt. This occurs at
time TA. The application software then has the time,
until the device voltage is no longer in valid operating
range, to shut down the system. Voltage point VB is the
minimum valid operating voltage specification. This
occurs at time TB. TB - TA is the total time for shut
down.
FIGURE 11-1:
TYPICAL LOW VOLTAGE DETECT APPLICATION
VA
VB
Legend:
VA = LVD trip point
VB = Minimum valid device
operating voltage
Time TA TB
2001 Microchip Technology Inc.
Preliminary
DS41142A-page 77
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