MCP6561UT-ESLASHMS datasheet(17/42 Pages) MICROCHIP

17 / 42 page

DS22139B-page 17

MCP6561/1R/1U/2/4

4.3.2

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.

4.4

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.

4.5

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. The output slew rate and propagation

delay performance will be reduced with higher

capacitive loads.

VIN

VOUT

VDD

MCP656X

VOUT

High-to-Low

Low-to-High

VDD

VOH

VOL

VSS

VDD

VTLH VTHL

VIN

V23

VOUT

VDD

R23

VSS

MCP656X

2R3

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

THL

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

⎝⎠

⎜⎟

⎛⎞

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

⎝⎠

⎛⎞

TLH

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

⎝⎠

⎜⎟

⎛⎞

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

⎝⎠

⎛⎞

Where:

VTLH

trip voltage from low to high

VTHL

trip voltage from high to low

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