Datasheet

 2005-2012 Microchip Technology Inc. DS21985D-page 27
MCP131X/2X
4.0 OPERATIONAL DESCRIPTION
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 are brown-out conditions, 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 volatile memory (RAM),
thus producing indeterminate results. Figure 4-1 shows
a typical application circuit.
The MCP131X/2X family of voltage supervisor devices
are designed to keep a microcontroller in Reset, until
the system voltage has reached and stabilized at the
proper level for reliable system operation. These
devices also operate as protection from brown-out
conditions when the system supply voltage drops
below a safe operating level.
Some MCP131X/2X family members include a Watch-
dog Timer feature that after being enabled (by a falling
edge on the WDI pin), monitors the WDI pin for falling
or rising edges. If an edge transition is not detected
within the expected time frame, the MCP131X/2X
devices will force the Reset pin active. This is useful to
ensure that the embedded system’s Host Controller
program is operating as expected.
Some MCP131X/2X family members include a Manual
Reset feature that allow a push button switch to be
directly connected to the MCP131X/2X devices (on the
MR
pin). This allows the system to easily be reset from
the external control of the push button switch.
A superset block diagram is shown in Figure 4-2, with
device specific block diagrams shown in Figure 4-3
through Figure 4-12.
FIGURE 4-1: Typical Application Circuit.
FIGURE 4-2: Family Block Diagram.
V
DD
V
DD
MCLR
(Reset input)
(active-low)
V
SS
PIC
®
Microcontroller
R
PU
(1)
Note 1: Resistor R
PU
may be required with the
MCP1320, MCP1321 or MCP1322 due
to the open-drain output.
Resistor R
PU
may not be required with
the MCP1316M, MCP1318M or
MCP1319M due to the internal pull-up
resistor.
The MCP1316, MCP1317, MCP1318
and MCP1319 do not require the
external pull-up resistor.
2: Not all devices offer the active-high
Reset output pin.
0.1
µF
MCP13XX
V
DD
RST
V
SS
RST
(2)
WDI
I/O
To system
device that
requires active-
high resets
Push button
switch
MR
V
DD
Comparator
+
–
Output
Driver
RST
Reference
V
SS
RST
Noise Filter
Watchdog
MR
WDI
Note: Features available depend on the device.
Voltage