PIC18F2682-I/PT MICROCHIP [Microchip Technology], PIC18F2682-I/PT Datasheet - Page 272

• Manufacturer Part Number: PIC18F2682-I/PT
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with ECAN Technology, 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2682/2685/4682/4685
FIGURE 22-3:
22.5
In many applications, the ability to detect a drop below,
or rise above a particular threshold is desirable. 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, Figure 22-4 shows a
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 perform a controlled shutdown
before the device voltage exits the valid operating
range at T
application a time window, represented by the
difference between T
DS39761B-page 270
A
, the HLVD logic generates an interrupt at time T
CASE 1:
CASE 2:
Enable HLVD
Applications
Enable HLVD
B
HLVDIF
. The HLVD, thus, would give the
HLVDIF
IRVST
IRVST
V
V
DD
DD
A
HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)
and T
HLVDIF may not be set
Internal Reference is stable
B
, to safely exit.
Internal Reference is stable
Preliminary
T
T
A
IRVST
IRVST
.
HLVDIF cleared in software,
HLVDIF remains set since HLVD condition still exists
FIGURE 22-4:
V
V
A
B
Legend:
HLVDIF cleared in software
V
V
A
B
= HLVD trip point
= Minimum valid device
HLVDIF cleared in software
TYPICAL LOW-VOLTAGE
DETECT APPLICATION
operating voltage
© 2007 Microchip Technology Inc.
Time
T
A
V
V
LVD
LVD
T
B