MCP65R41 datasheet(22/34 Pages) MICROCHIP

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MCP65R41/6

DS22269A-page 22

 2010 Microchip Technology Inc.

It is also possible to connect the diodes to the left of the

resistors R1 and R2. In this case, the currents through

the diodes D1 and D2 need to be limited by some other

mechanism. The resistor then serves as an in-rush cur-

rent limiter; the DC current into the input pins (VIN+ and

VIN–) should be very small.

A significant amount of current can flow out of the

inputs when the Common mode voltage (VCM) is below

ground (VSS); see Figure 4-3. The applications that are

high impedance may need to limit the usable voltage

range.

4.1.3

PHASE REVERSAL

The MCP65R41/6 comparator family uses CMOS tran-

sistors at the input. They are designed to prevent

phase inversion when the input pins exceed the supply

voltages. Figure 2-3 shows an input voltage exceeding

both supplies with no resulting phase inversion.

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 a 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 2-18 and 2-19 for

more information).

4.3

Externally Set Hysteresis

A greater flexibility in selecting the hysteresis (or the

input trip points) is achieved by using external resistors.

Hysteresis reduces output chattering when one input is

slowly moving past the other. It also helps in systems

where it is best not to cycle between high and low

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

control). Output chatter also increases the dynamic

supply current.

4.3.1

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:

EXAMPLE 4-1:

VREF

VIN

VOUT

VDD

VPU

RPU*

VREF

* Pull-up resistor required for the MCP65R46 only.

VOUT

High-to-Low

Low-to-High

VDD

VOH

VOL

VSS

VDD

VTHL VTLH

VIN

TLH

REF

-------







-------







–

THL

REF

-------







-------







–

Where:

VTLH = trip voltage from low to high

VTHL = trip voltage from high to low

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