MCP6546U MICROCHIP [Microchip Technology], MCP6546U Datasheet - Page 15

• Manufacturer Part Number: MCP6546U
• Description: Open-Drain Output Sub-Microamp Comparators
• Manufacturer: MICROCHIP [Microchip Technology]

EQUATION 4-1:
Using this simplified circuit, the trip voltage can be
calculated using the following equation:
EQUATION 4-2:
Figure 2-21
typical values for V
output current I
can be determined using the equation below:
EQUATION 4-3:
V
EQUATION 4-4:
As explained in Section 4.1 “Comparator Inputs”, it
is important to keep the non-inverting input below
V
4.5
With this family of comparators, the power supply pin
(V
capacitor (i.e., 0.01 µF to 0.1 µF) within 2 mm for good
edge rate performance.
© 2006 Microchip Technology Inc.
V
V
V
OH
DD
THL
DD
TLH
THL
+0.3V when V
can be calculated using the equation below:
for single supply) should have a local bypass
=
= trip voltage from low to high
= trip voltage from high to low
V
V
TLH
V
Supply Bypass
OH
PU
I
OL
and
=
⎛
⎜
⎝
=
--------------------------------------- -
R
=
OL
23
V
(
V
Figure 2-24
V
OL
⎛
⎝
+
23
as shown in
PU
PU
V
------------------------- -
OL
I
⎛
⎜
⎝
PU
R
R F
OL
R
---------------------- -
R
=
. This voltage is dependent on the
–
23
> V
R
23
23
–
V
PU
+
R
=
------------------
R
=
23
+
V
DD
23
2
R
I
R
OL
)
+
R F
PU
------------------
R
PU
.
3
×
R
2
R
⎞
⎠
can be used to determine
⎞
⎟
⎠
⎞
⎟
⎠
⎛
⎝
2
+
+
3
+
------------------------------------- -
R
R
Figure
+
+
×
I
R
23
3
⎛
⎝
RF
V
------------------------
3
V
V
V
R
R
+
23
DD
23
23
23
23
R
⎛
⎝
⎛
⎝
–
+
+
F
---------------------------------------
R
--------------------- -
R
4-4. This current
V
23
23
+
R
R
OL
R
R
F
F
R
+
+
F
F
⎞
⎠
PU
R
R
+
F
⎞
⎠
F
R
⎞
⎠
+
PU
R
PU
⎞
⎠
MCP6546/6R/6U/7/8/9
4.6
Reasonable capacitive loads (e.g., logic gates) have
little impact on propagation delay (see
The supply current increases with increasing toggle
frequency
capacitive loads.
4.7
In order to maximize battery life in portable
applications, use large resistors and small capacitive
loads. Avoid toggling the output more than necessary.
Do not use Chip Select (CS) too frequently in order to
conserve power. Capacitive loads will draw additional
power at start-up.
4.8
In applications where low input bias current is critical,
PCB (Printed Circuit Board) surface leakage effects
need to be considered. Surface leakage is caused by
humidity, dust or other contamination on the board.
Under low-humidity conditions, a typical resistance
between nearby traces is 10
would cause 5 pA of current to flow. This is greater
than the MCP6546/6R/6U/7/8/9 family’s bias current at
25°C (1 pA, typ.).
The easiest way to reduce surface leakage is to use a
guard ring around sensitive pins (or traces). The guard
ring is biased at the same voltage as the sensitive pin.
An example of this type of layout is shown in
Figure
FIGURE 4-7:
for Inverting Circuit.
1.
Inverting Configuration (Figures 4-4 and 4-7):
a.
b.
4-7.
Capacitive Loads
Battery Life
PCB Surface Leakage
Connect the guard ring to the non-inverting
input pin (V
to the same reference voltage as the
comparator (e.g., V
Connect the inverting pin (V
pad without touching the guard ring.
(Figure
V
2-30),
IN
IN
Guard Ring
+). This biases the guard ring
Example Guard Ring Layout
-
DD
especially
/2 or ground).
V
12
IN
Ω. A 5V difference
+
DS21714E-page 15
IN
–) to the input
Figure
with
V
SS
higher
2-27).