PIC18F2331_10 Datasheet, PDF (260/392 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D

PIC18F2331/2431/4331/4431
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
start-up time, TIRVST, is an interval that is independent
of device clock speed. It is specified in electrical
specification Parameter 36.
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:
VDD
LVDIF may not be set
LVDIF
Enable LVD
Internally Generated
Reference Stable
TIRVST
VLVD
LVDIF cleared in software
CASE 2:
VDD
LVDIF
Enable LVD
Internally Generated
Reference Stable
VLVD
TIRVST
LVDIF cleared in software
LVDIF cleared in software,
LVDIF remains set since LVD condition still exists
DS39616D-page 260
 2010 Microchip Technology Inc.