MCP6544 datasheet(20/46 Pages) MICROCHIP

20 / 46 page

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

DS21696G-page 20

 2011 Microchip Technology Inc.

4.4.2

INVERTING CIRCUIT

Figure 4-6 shows an inverting circuit for single-supply

using three resistors. The resulting hysteresis diagram

is shown in Figure 4-7.

FIGURE 4-6:

Inverting Circuit With

Hysteresis.

FIGURE 4-7:

Hysteresis Diagram for the

Inverting Circuit.

In order to determine the trip voltages (VTHL and VTLH)

for the circuit shown in Figure 4-6, R2 and R3 can be

simplified to the Thevenin equivalent circuit with

respect to VDD, as shown in Figure 4-8.

FIGURE 4-8:

Thevenin Equivalent Circuit.

Where:

Using this simplified circuit, the trip voltage can be

calculated using the following equation:

EQUATION 4-2:

Figure 2-20 and Figure 2-23 can be used to determine

typical values for VOH and VOL.

4.5

Bypass Capacitors

With this family of comparators, the power supply pin

(VDD for single supply) should have a local bypass

capacitor (i.e., 0.01 µF to 0.1 µF) within 2 mm for good

edge rate performance.

4.6

Capacitive Loads

Reasonable capacitive loads (e.g., logic gates) have

little impact on propagation delay (see Figure 2-31).

The supply current increases with increasing toggle

frequency

(Figure 2-19),

especially

with

higher

capacitive loads.

4.7

Battery Life

order

maximize

battery

life

portable

applications, use large resistors and small capacitive

loads. Avoid toggling the output more than necessary.

Do not use Chip Select (CS) frequently to conserve

start-up power. Capacitive loads will draw additional

power at start-up.

VIN

VOUT

MCP654X

VDD

VOUT

High-to-Low

Low-to-High

VDD

VOH

VOL

VSS

VDD

VTLH VTHL

VIN

V23

VOUT

MCP654X

VDD

R23

VSS

2R3

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



THL

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







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





TLH

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







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





VTLH = trip voltage from low-to-high

VTHL = trip voltage from high-to-low

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