Datasheet

MCP65R41/6
DS22269B-page 22  2010-2011 Microchip Technology Inc.
FIGURE 4-3: Protecting the Analog
Inputs.
It is also possible to connect the diodes to the left of the
resistors R
1
and R
2
. In this case, the currents through
the diodes D
1
and D
2
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 (V
IN
+ and
V
IN
-) should be very small.
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 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 preferable not to cycle between high and low
states too frequently (e.g., air conditioner thermostatic
controls). Output chatter also increases the dynamic
supply current.
V
1
R
1
V
DD
D
1
R
2

V
SS
– (minimum expected V
2
)
2mA
V
OUT
V
2
R
2
R
3
D
2
+
–
R
1

V
SS
– (minimum expected V
1
)
2mA
V
PU
R
PU
*
* Pull-up resistor required for the MCP65R46 only.