Datasheet

PIC18F47J13 FAMILY
DS39974A-page 392 Preliminary  2010 Microchip Technology Inc.
The module is enabled by setting the HLVDEN bit.
Each time the module is enabled, the circuitry requires
some time to stabilize. The IRVST bit is a read-only bit
that indicates when the circuit is stable. The module
can generate an interrupt only after the circuit is stable
and IRVST is set.
The VDIRMAG bit determines the overall operation of
the module. When VDIRMAG is cleared, the module
monitors for drops in V
DD below a predetermined set
point. When the bit is set, the module monitors for rises
in VDD above the set point.
25.1 Operation
When the HLVD module is enabled, a comparator uses
an internally generated reference voltage as the set
point. The set point is compared with the trip point,
where each node in the resistor divider represents a
trip point voltage. The “trip point” voltage is the voltage
level at which the device detects a high or low-voltage
event, depending on the configuration of the module.
When the supply voltage is equal to the trip point, the
voltage tapped off of the resistor array is equal to the
internal reference voltage generated by the voltage
reference module. The comparator then generates an
interrupt signal by setting the HLVDIF bit.
The trip point voltage is software programmable to any
one of 16 values. The trip point is selected by
programming the HLVDL<3:0> bits (HLVDCON<3:0>).
Additionally, the HLVD module allows the user to
supply the trip voltage to the module from an external
source. This mode is enabled when bits, HLVDL<3:0>,
are set to ‘1111’. In this state, the comparator input is
multiplexed from the external input pin, HLVDIN. This
gives users flexibility because it allows them to
configure the HLVD interrupt to occur at any voltage in
the valid operating range.
FIGURE 25-1: HLVD MODULE BLOCK DIAGRAM (WITH EXTERNAL INPUT)
Set
VDD
16-to-1 MUX
HLVDCON
HLVDL<3:0>
Register
HLVDIN
V
DD
Externally Generated
Trip Point
HLVDIF
HLVDEN
Internal Voltage
Reference
VDIRMAG
1.2V Typical