PIC18F25K80 MICROCHIP [Microchip Technology], PIC18F25K80 Datasheet - Page 393

• Manufacturer Part Number: PIC18F25K80
• Manufacturer: MICROCHIP [Microchip Technology]

FIGURE 26-3:
26.5
In many applications, it is desirable to detect a drop
below, or rise above, a particular voltage threshold. For
example, the HLVD module could be periodically
enabled to detect Universal Serial Bus (USB) attach or
detach. This assumes the device is powered by a lower
voltage source than the USB when detached. An attach
would indicate a high-voltage detect from, for example,
3.3V to 5V (the voltage on USB) and vice versa for a
detach. This feature could save a design a few extra
components and an attach signal (input pin).
For general battery applications,
possible voltage curve. Over time, the device voltage
decreases. When the device voltage reaches voltage,
V
The interrupt could cause the execution of an ISR,
which would allow the application to perform “house-
keeping tasks” and a controlled shutdown before the
device voltage exits the valid operating range at T
This would give the application a time window, repre-
sented by the difference between T
exit.
 2011 Microchip Technology Inc.
A
, the HLVD logic generates an interrupt at time, T
CASE 1:
CASE 2:
Enable HLVD
Enable HLVD
Applications
HLVDIF
HLVDIF
IRVST
IRVST
V
V
DD
DD
HIGH-VOLTAGE DETECT OPERATION (VDIRMAG =
HLVDIF may not be set
Internal reference is stable
Figure 26-4
A
and T
B
, to safely
shows a
Internal reference is stable
Preliminary
T
T
IRVST
IRVST
A
B
.
.
PIC18F66K80 FAMILY
HLVDIF cleared in software,
HLVDIF remains set since HLVD condition still exists
FIGURE 26-4:
V
V
A
B
Legend:
HLVDIF cleared in software
V
V
1
A
B
)
= HLVD trip point
= Minimum valid device
TYPICAL LOW-VOLTAGE
DETECT APPLICATION
operating voltage
Time
HLVDIF cleared in software
T
A
V
V
DS39977C-page 393
HLVD
HLVD
T
B