PIC18LF4331-ESLASHML datasheet(259/392 Pages) MICROCHIP

259 / 392 page

 2010 Microchip Technology Inc.

DS39616D-page 259

PIC18F2331/2431/4331/4431

22.1

Operation

When the LVD 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 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 LVDIF bit.

The trip point voltage is software programmable to any

one of 16 values, selected by programming the

LVDL<3:0> bits (LVDCON<3:0>).

The LVD module has an additional feature that allows

the user to supply the trip voltage to the module from an

external source. This mode is enabled when bits,

LVDL<3:0>, are set to ‘1111’. In this state, the compar-

ator input is multiplexed from the external input pin,

LVDIN. This gives users flexibility because it allows

them to configure the Low-Voltage Detect interrupt to

occur at any voltage in the valid operating range.

22.2

LVD Setup

The following steps are needed to set up the LVD

module:

Disable the module by clearing the LVDEN bit

(LVDCON<4>).

Write the value to the LVDL<3:0> bits that

selects the desired LVD trip point.

Enable the LVD module by setting the LVDEN

bit.

Clear the LVD interrupt flag (PIR2<2>), which

may have been set from a previous interrupt.

Enable the LVD interrupt, if interrupts are

desired, by setting the LVDIE and GIE bits

(PIE<2> and INTCON<7>).

An interrupt will not be generated until the IRVST bit is set.

22.3

Current Consumption

When the module is enabled, the LVD comparator and

voltage divider are enabled and will consume static cur-

rent. The total current consumption, when enabled, is

specified in electrical specification Parameter D022B.

Depending on the application, the LVD module does

not need to be operating constantly. To decrease the

current requirements, the LVD circuitry may only need

to be enabled for short periods where the voltage is

checked. After doing the check, the LVD module may

be disabled.

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