MCP131X datasheet(23/44 Pages) MICROCHIP

23 / 44 page

DS21985A-page 23

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 is voltage supervisor devices

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

edges. If an edge transition is not detected within the

expected timeframe, 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 allows 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

VDD

MCLR

(Reset input)

(active-low)

VSS

PICmicro®

Microcontroller

RPU(1)

Note 1: Resistor RPU may be required with the

MCP1320, MCP1321 or MCP1322 due

to the open-drain output.

Resistor RPU 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

VDD

RST

VSS

RST (2)

WDI

I/O

To system

device that

requires active-

high resets

Push button

switch

VDD

Comparator

–

Output

Driver

RST

Reference

VSS

RST

Noise Filter

Watchdog

WDI

Note: Features available depend on the device.

Voltage

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