MCP6566_13 Datasheet, PDF (19/48 Pages) Microchip Technology – 1.8V Low-Power Open-Drain Output Comparator

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.
V_DD
V_PU
V_IN
V_DD
MCP656X
R_PU
V_OUT
R₂
R₃
R_F
FIGURE 4-6:
Hysteresis.
Inverting Circuit with
V_DD
V_OH
V_OUT
Low-to-High
High-to-Low
V_OL
V_SS
V_SS
V_TLH V_THL
V_IN
V_DD
FIGURE 4-7:
Hysteresis Diagram for the
Inverting Circuit.
In order to determine the trip voltages (V_THL and V_TLH)
for the circuit shown in Figure 4-6, R₂ and R₃ can be
simplified to the Thevenin equivalent circuit with
respect to V_DD, as shown in Figure 4-8.
V₂₃
R₂₃
FIGURE 4-8:
V_DD
V_PU
-
MCP656X
+
V_SS
R_PU
V_OUT
R_F
Thevenin Equivalent Circuit.
MCP6566/6R/6U/7/9
Where:
R₂₃
=
----R----²---R---³----
R₂ + R₃
V₂₃
=
-------R----³-------
R₂ + R₃

V_DD
Using this simplified circuit, the trip voltage can be
calculated using the following equation:
EQUATION 4-2:
V_THL
=
V_O

H_
R----₂^---₃^{-R---+-2--3--R----F--}_{}
+ V_{23}-R---₂---₃-R---+-^F----R----_F-_
V_TLH
=
V_O

L_
R----₂^---₃^{-R---+-2--3--R----F--}_{}
+ V_{23R----2}---₃-R---+-^F----R----_F-_
Where:
V_TLH = trip voltage from low-to-high
V_THL = trip voltage from high-to-low
Figure 2-21 and Figure 2-24 can be used to determine
typical values for V_OH and V_OL.
4.4 Bypass Capacitors
With this family of comparators, the power supply pin
(V_DD 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 2-32).
The supply current increases with increasing toggle
frequency (Figure 2-20), especially with higher
capacitive loads. The output slew rate and propagation
delay performance will be reduced with higher
capacitive loads.
 2009-2013 Microchip Technology Inc.
DS22143D-page 19