dsPIC30F Family Reference Manual
DS70056C-page 9-2 © 2004 Microchip Technology Inc.
9.1 Introduction
The LVD module is applicable to battery operated applications. As the battery drains its energy,
the battery voltage slowly drops. The battery source impedance also increases as it loses energy.
The LVD module is used to detect when the battery voltage (and therefore, the V
DD of the device)
drops below a threshold, which is considered near the end of battery life for the application. This
allows the application to gracefully shutdown its operation.
The LVD module uses an internal reference voltage for comparison. The threshold voltage, V
LVD,
is programmable during run-time.
Figure 9-1 shows a possible application battery voltage curve. Over time, the device voltage
decreases. When the device voltage equals voltage V
LVD, the LVD logic generates an interrupt.
This occurs at time T
A. The application software then has until the device voltage is no longer in
valid operating range to shutdown the system. Voltage point V
B is the minimum valid operating
voltage specification. This gives a time T
B. The total time for shutdown is TB – TA.
Figure 9-1: Typical Low Voltage Detect Application
Time
Voltage
VLVD
VMIN
TA
VLVD = LVD trip point
V
MIN = Minimum valid device operating voltage
Legend:
T
B
To Next Page
Loading...
