2004-2016 Microchip Technology Inc. DS20001889F-page 11
MCP111/112
4.0 APPLICATION INFORMATION
For many of today’s microcontroller applications, care
must be taken to prevent low-power conditions that can
cause many different system problems. The most
common causes is a brown-out condition, where the
system supply drops below the operating level momen-
tarily. The second most common cause is when a slowly
decaying power supply causes the microcontroller to
begin executing instructions without sufficient voltage to
sustain SRAM, thus producing indeterminate results.
Figure 4-1 shows a typical application circuit.
FIGURE 4-1: Typical Application Circuit.
4.1 V
TRIP
Operation
The voltage trip point (V
TRIP
) is determined on the falling
edge of V
DD
. The actual voltage trip point (V
TRIPAC
) will
be between the minimum trip point (V
TRIPMIN
) and the
maximum trip point (V
TRIPMAX
). There is a hysteresis on
this trip point to remove any “jitter” that would occur on
the V
OUT
pin when the device V
DD
is at the trip point.
Figure 4-2 shows the state of the V
OUT
pin as
determined by the V
DD
voltage. The V
TRIP
specification
is for falling V
DD
voltages. When the V
DD
voltage is
rising, the V
OUT
pin will not be driven high until V
DD
is at
V
TRIP
+ V
HYS
.
FIGURE 4-2: V
OUT
Operation as Determined by the V
TRIP
and V
HYS
.
4.2 Negative Going V
DD
Transients
The minimum pulse width (time) required to cause a
reset may be an important criteria in the implementa-
tion of a Power-on Reset (POR) circuit. This time is
referred to as transient duration, defined as the amount
of time needed for these supervisory devices to
respond to a drop in V
DD
. The transient duration time is
dependent on the magnitude of V
TRIP
– V
DD
. Generally
speaking, the transient duration decreases with
increases in V
TRIP
– V
DD
.
Figure 4-3 shows a typical transient duration vs. reset
comparator overdrive for which the MCP111/112 will
not generate a reset pulse. It shows that the farther
below the trip point the transient pulse goes, the
duration of the pulse required to cause a reset gets
shorter. Figure 2-18 shows the transient response
characteristics for the MCP111/112.
A 0.1 µF bypass capacitor, mounted as close as
possible to the V
DD
pin, provides additional transient
immunity (refer to Figure 4-1).
2
MCP11X
V
DD
V
DD
V
DD
V
OUT
MCLR
(Reset Input)
V
SS
GND
PIC
®
Microcontroller
3
1
R
PU
Note 1: R
PU
may be required with the MCP111
due to the open-drain output. Resistor
R
PU
is not required with the MCP112.
0.1
µF
(1)
V
DD
V
TRIPMAX
V
TRIPMIN
V
TRIPAC
V
TRIPAC
V
TRIPAC
+ V
HYSAC
V
OUT
1V
< 1 V is outside the
device specifications
