MCP6544 datasheet(18/46 Pages) MICROCHIP

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MCP6541/1R/1U/2/3/4

DS21696G-page 18

 2011 Microchip Technology Inc.

FIGURE 4-3:

The MCP6541/1R/1U/2/3/4

comparators’ internal hysteresis eliminates

output chatter caused by input noise voltage.

4.2

Push-Pull Output

The push-pull output is designed to be compatible with

CMOS and TTL logic, while the output transistors are

configured to give rail-to-rail output performance. They

are driven with circuitry that minimizes any switching

current (shoot-through current from supply-to-supply)

when the output is transitioned from high-to-low, or from

low-to-high (see Figures 2-15, 2-18, 2-32 through 2-36

for more information).

4.3

MCP6543 Chip Select (CS)

The MCP6543 is a single comparator with Chip Select

(CS). When CS is pulled high, the total current

consumption drops to 20 pA (typ.); 1 pA (typ.) flows

through the CS pin, 1 pA (typ.) flows through the out-

put pin and 18 pA (typ.) flows through the VDD pin, as

shown

Figure 1-1.

When

this

happens,

the

comparator output is put into a high-impedance state.

By pulling CS low, the comparator is enabled. If the CS

pin is left floating, the comparator will not operate

properly. Figure 1-1 shows the output voltage and

supply current response to a CS pulse.

The internal CS circuitry is designed to minimize

glitches when cycling the CS pin. This helps conserve

power, which is especially important in battery-powered

applications.

4.4

Externally Set Hysteresis

Greater flexibility in selecting hysteresis (or input trip

points) is achieved by using external resistors.

Input offset voltage (VOS) is the center (average) of the

(input-referred) low-high and high-low trip points. Input

hysteresis voltage (VHYST) is the difference between

the same trip points. Hysteresis reduces output

chattering when one input is slowly moving past the

other and thus reduces dynamic supply current. It also

helps in systems where it is best not to cycle between

states too frequently (e.g., air conditioner thermostatic

control).

4.4.1

NON-INVERTING CIRCUIT

Figure 4-4 shows a non-inverting circuit for single-

supply applications using just two resistors. The

resulting hysteresis diagram is shown in Figure 4-5.

FIGURE 4-4:

Non-inverting circuit with

hysteresis for single-supply.

FIGURE 4-5:

Hysteresis Diagram for the

Non-Inverting Circuit.

The trip points for Figures 4-4 and 4-5 are:

-3

-2

-1

Time (100 ms/div)

-30

-25

-20

-15

-10

-5

VOUT

VIN–

VDD = 5.0V

Hysteresis

VREF

VIN

VOUT

MCP654X

VDD

VOUT

High-to-Low

Low-to-High

VDD

VOH

VOL

VSS

VDD

VTHL VTLH

VIN

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