MCP6561_13 Datasheet, PDF (16/46 Pages) Microchip Technology – 1.8V Low-Power Push-Pull Output Comparator

MCP6561/1R/1U/2/4
A significant amount of current can flow out of the
inputs when the Common-mode voltage (V_CM) is below
ground (V_SS); see Figure 2-32. Applications that are
high impedance may need to limit the usable voltage
range.
4.1.3 PHASE REVERSAL
The MCP6561/1R/1U/2/4 comparator family uses
CMOS transistors 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 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 Figure 2-15 and Figure 2-18 for
more information).
4.3 Externally Set Hysteresis
Greater flexibility in selecting hysteresis (or 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.
V_REF
V_DD
-
MCP656X
+
V_OUT
V_IN
R₁
R_F
FIGURE 4-4:
Non-inverting Circuit with
Hysteresis for Single-Supply.
V_DD
V_OH
V_OUT
High-to-Low
Low-to-High
V_OL
V_SS
V_SS
V_THL V_TLH
V_IN
V_DD
FIGURE 4-5:
Hysteresis Diagram for the
Non-inverting Circuit.
The trip points for Figure 4-4 and Figure 4-5 are:
EQUATION 4-1:
VTLH
=

VREF_1
+
R-R---F-1-



–
VOL_{R-R---F-1-}



VTHL
=
VRE

F_
1
+
-R----1-
RF



–
VOH_{R-R---F-1-}



Where:
V_TLH = trip voltage from low-to-high
V_THL = trip voltage from high-to-low
DS22139C-page 16
 2009-2013 Microchip Technology Inc.