Microchip Technology MA160014 Data Sheet

DS41412F-page 352

 2010-2012 Microchip Technology Inc.

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, 

 shows a

possible voltage curve. Over time, the device voltage
decreases. When the device voltage reaches voltage
V

A

, the HLVD logic generates an interrupt at time, T

A

.

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

B

.

This would give the application a time window,
represented by the difference between T

A

 and T

B

, to

safely exit.

V

HLVD

V

DD

HLVDIF

V

HLVD

V

DD

Enable HLVD

T

IRVST

HLVDIF may not be set

Enable HLVD

HLVDIF

HLVDIF cleared in software

HLVDIF cleared in software

HLVDIF cleared in software, 

HLVDIF remains set since HLVD condition still exists

T

IRVST

IRVST

Internal Reference is stable

Internal Reference is stable

IRVST

V

A

 = HLVD trip point

V

B

 = Minimum valid device

         operating voltage