MCP6544 MICROCHIP [Microchip Technology], MCP6544 Datasheet - Page 11

• Manufacturer Part Number: MCP6544
• Description: Push-Pull Output Sub-Microamp Comparators
• Manufacturer: MICROCHIP [Microchip Technology]

3.0
The MCP6541/2/3/4 family of push-pull output compar-
ators are fabricated on Microchip’s state-of-the-art
CMOS process. They are suitable for a wide range of
applications requiring very low power consumption.
3.1
The MCP6541/2/3/4 comparator family uses CMOS
transistors at the input. They are designed to prevent
phase inversion when the input pins exceed the supply
voltages.
exceeding both supplies with no resulting phase
inversion.
The input stage of this family of devices uses two
differential input stages in parallel: one operates at low
input voltages and the other at high input voltages. With
this topology, the input voltage is 0.3V above V
0.3V below V
measured at both V
proper operation.
The maximum operating input voltages that can be
applied are V
inputs that exceed this absolute maximum rating can
cause excessive current to flow and permanently
damage the device. In applications where the input pin
exceeds the specified range, external resistors can be
used to limit the current below ±2 mA, as shown in
Figure 3-1.
FIGURE 3-1:
should be used to limit excessive input current if
either of the inputs exceeds the Absolute
Maximum specification.
3.2
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 Figures 2-15, 2-17, 2-32 through 2-36
for more information).
2003 Microchip Technology Inc.
V
IN
R IN
APPLICATIONS INFORMATION
Comparator Inputs
R IN
Push-Pull Output
Figure 2-31
SS
SS
--------------------------------------------------------------------------------- -
R
V SS
----------------------------------------------------------------------------- -
Maximum expected V IN
- 0.3V and V
. Therefore, the input offset voltage is
IN
SS
–
Minimum expected V IN
- 0.3V and V
An input resistor (R
MCP654X
shows
2 mA
2 mA
DD
+ 0.3V. Voltages on the
an
DD
+ 0.3V to ensure
–
input
V DD
IN
V
)
OUT
voltage
DD
and
3.3
The MCP6543 is a single comparator with chip select
(CS). When CS is pulled high, the total current
consumption drops to 20 pA (typ); 1 pA (typ) flows
through the CS pin, 1 pA (typ) flows through the output
pin and 18 pA (typ) flows through the V
shown in Figure 1-1. When this happens, the
comparator output is put into a high-impedance state.
By pulling CS low, the comparator is enabled. If the CS
pin is left floating, the comparator will not operate
properly. Figure 1-1 shows the output voltage and
supply current response to a CS pulse.
The internal CS circuitry is designed to minimize
glitches when cycling the CS pin. This helps conserve
power, which is especially important in battery-
powered applications.
3.4
Greater flexibility in selecting hysteresis (or input trip
points) is achieved by using external resistors.
Input offset voltage (V
(input-referred) low-high and high-low trip points. Input
hysteresis voltage (V
the same trip points. Hysteresis reduces output
chattering when one input is slowly moving past the
other and thus reduces dynamic supply current. It also
helps in systems where it is best not to cycle between
states too frequently (e.g., air conditioner thermostatic
control). The MCP6541/2/3/4 family has internally-set
hysteresis that is small enough to maintain input offset
accuracy (<7 mV) and large enough to eliminate output
chattering caused by the comparator’s own input noise
voltage (200 µVp-p).
FIGURE 3-2:
comparators’ internal hysteresis eliminates
output chatter caused by input noise voltage.
-1
-2
-3
9
8
7
6
5
4
3
2
1
0
0
V
V
MCP6543 Chip Select (CS)
Externally-Set Hysteresis
DD
IN
+ = +2.75V
= 5.0V
100
V
OUT
MCP6541/2/3/4
200
V
IN
300
–
Time (100 ms/div)
OS
HYST
The MCP6541/2/3/4
400
) is the center (average) of the
) is the difference between
500
Hysteresis
600
700
DS21696C-page 11
800
DD
900
pin, as
1000
30
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30