PIC18F2331/2431/4331/4431
start-up time, TIRVST, is an interval that is independent
of device clock speed. It is specified in electrical
specification Parameter 36.
22.4 LVD Start-up Time
The internal reference voltage of the LVD module,
specified in electrical specification Parameter D420,
may be used by other internal circuitry, such as the
Programmable Brown-out Reset. If the LVD, or other
circuits using the voltage reference, are disabled to
lower the device’s current consumption, the reference
voltage circuit will require time to become stable before
a low-voltage condition can be reliably detected. This
The LVD interrupt flag is not enabled until TIRVST has
expired and a stable reference voltage is reached. For
this reason, brief excursions beyond the set point may
not be detected during this interval (refer to Figure 22-2).
FIGURE 22-2:
LOW-VOLTAGE DETECT WAVEFORMS
CASE 1:
LVDIF may not be set
VDD
VLVD
LVDIF
Enable LVD
Internally Generated
Reference Stable
TIRVST
LVDIF cleared in software
CASE 2:
VDD
VLVD
LVDIF
Enable LVD
TIRVST
Internally Generated
Reference Stable
LVDIF cleared in software
LVDIF cleared in software,
LVDIF remains set since LVD condition still exists
DS39616D-page 260
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
