Datasheet
MCP65R41/6
DS22269B-page 24 2010-2011 Microchip Technology Inc.
To determine the trip voltages (V
TLH
and V
THL
) for the
circuit shown in Figure 4-6, R
2
and R
3
can be simplified
to the Thevenin equivalent circuit with respect to V
REF
,
as shown in Figure 4-8:
FIGURE 4-8: Thevenin Equivalent Circuit.
By using this simplified circuit, the trip voltage can be
calculated using the following equation:
EQUATION 4-1:
Figures 2-25 and 2-28 can be used to determine the
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
4.5.1 OUT PIN
Reasonable capacitive loads (i.e., logic gates) have lit-
tle impact on the propagation delay (see Figure 2-34).
The supply current increases with the increasing toggle
frequency (Figure 2-22), especially with higher capaci-
tive loads. The output slew rate and propagation delay
performance will be reduced with higher capacitive
loads.
4.5.2 V
REF
PIN
The reference output is designed to interface to the
comparator input pins, either directly or with some
resistive network (e.g., a voltage divider network) with
minimal capacitive load. The recommended capacitive
load is 200 pF (typical). Capacitive loads greater than
2000 pF may cause the V
REF
output to oscillate at
power up.
V
23
V
OUT
V
DD
R
23
R
F
+
-
V
SS
V
PU
R
PU
*
* Pull-up resistor required for the MCP65R46 only.
Where:
R
23
R
2
R
3
R
2
R
3
+
------------------- -=
V
23
R
3
R
2
R
3
+
------------------- -V
REF
=
V
THL
V
OH
R
23
R
23
R
F
+
-----------------------
V
23
R
F
R
23
R
F
+
----------------------
+=
V
TLH
V
OL
R
23
R
23
R
F
+
-----------------------
V
23
R
F
R
23
R
F
+
----------------------
+=
Where:
V
TLH
= trip voltage from low to high
V
THL
= trip voltage from high to low