MCP131X datasheet(32/44 Pages) MICROCHIP

32 / 44 page

MCP131X/2X

DS21985A-page 32

5.4

Modifying The Trip Point, VTRIP

Although the MCP131X/2X device has a fixed voltage

trip point (VTRIP), it is sometimes necessary to make

custom adjustments. This can be accomplished by

connecting an external resistor divider to the

MCP131X/2X VDD pin. This causes the VSOURCE volt-

age to be at a higher voltage than when the

MCP131X/2X

input

equals

it’s

VTRIP voltage

(Figure 5-5).

To maintain detector accuracy, the bleeder current

through the divider should be significantly higher than

the 10 μA maximum operating current required by the

MCP131X/2X. A reasonable value for this bleeder

current is 1 mA (100 times the 10 μA required by the

MCP131X/2X). For example, if VTRIP = 2V and the

desired trip point is 2.5V, the value of R1 + R2 is 2.5 kΩ

(2.5V/1 mA). The value of R1 + R2 can be rounded to

the nearest standard value and plugged into the equa-

tion of Figure 5-5 to calculate values for R1 and R2. 1%

tolerance resistors are recommended.

FIGURE 5-5:

Modify Trip-Point using

External Resistor Divider.

5.5

MOSFET Low-Drive Protection

Low operating power and small physical size make the

MCP131X/2X series ideal for many voltage detector

applications. Figure 5-6 shows a low-voltage gate drive

protection circuit that prevents overheating of the

logic-level MOSFET due to insufficient gate voltage.

When the input signal is below the threshold of the

MCP131X/2X, its output grounds the gate of the

MOSFET.

FIGURE 5-6:

MOSFET Low-Drive

Protection.

5.6

Low-Power Applications

In some low-power applications, the longer that the

microcontroller (such as a PICmicro MCU) can be in

the “Sleep mode”, the lower the average system cur-

rent consumption will be.

The WDT feature can be used to “wake-up” the PICmicro

MCU at a regular interval to service the required tasks

before returning to sleep. This “wake-up” occurs after the

PICmicro MCU detects a MCLR reset during Sleep mode

(for mid-range family; POR = ‘1’, BOR = ‘1’, TO = ‘1’ and

PD = ‘1’).

Note:

In this example, VSOURCE must be

greater than (VTRIP)

MCP131X/2X

VDD

RST

VSS

VSOURCE

or RST

VSOURCE

R1 R2

--------------------

VTRIP

Where:

VSOURCE = Voltage to be monitored

VTRIP = Threshold Voltage setting

VDD

RST

VSS

MCP131X/2X

270

MTP3055EL

VDD

VTRIP

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