MCP6546U MICROCHIP [Microchip Technology], MCP6546U Datasheet - Page 14

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

MCP6546/6R/6U/7/8/9
FIGURE 4-3:
comparators’ internal hysteresis eliminates
output chatter caused by input noise voltage.
4.2
The open-drain output is designed to make level-
shifting and wired-OR logic easy to implement. The
output can go as high as 10V for 9V battery-powered
applications. The output stage minimizes switching cur-
rent (shoot-through current from supply-to-supply)
when the output changes state. See Figures 2-15, 2-18
and 2-37 through 2-41, for more information.
4.3
The MCP6548 is a single comparator with a Chip
Select (CS) pin. 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
as shown in
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.
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.
4.4
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, thus reducing 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).
DS21714E-page 14
-1
-2
-3
8
7
6
5
4
3
2
1
0
V
Open-Drain Output
Externally Set Hysteresis
MCP6548 Chip Select (CS)
Figure 1-1
DD
= 5.0V
V
OUT
Figure
Time (100 ms/div)
HYST
shows the output voltage and
OS
1-1. When this happens, the
The MCP6546/7/8/9
) is the center (average) of the
) is the difference between
Hysteresis
V
IN
–
DD
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
pin,
4.4.1
Figure 4-4
application using three resistors, besides the pull-up
resistor. The resulting hysteresis diagram is shown in
Figure
FIGURE 4-4:
hysteresis.
FIGURE 4-5:
inverting circuit.
In order to determine the trip voltages (V
for the circuit shown in
simplified to the Thevenin equivalent circuit with
respect to V
FIGURE 4-6:
V
V
V
V
V
V
TLH
THL
V
OH
OL
SS
PU
V
V
IN
R
R
V
DD
23
= trip voltage from low to high
= trip voltage from high to low
2
3
SS
4-5.
Low-to-High
V
shows an inverting circuit for a single-supply
OUT
INVERTING CIRCUIT
DD
, as shown in
R
23
MCP654X
V
V
TLH
DD
Inverting circuit with
Hysteresis diagram for the
Thevenin Equivalent Circuit.
© 2006 Microchip Technology Inc.
+
Figure
-
MCP654X
V
THL
I
R
RF
Figure
F
I
4-4, R
PU
High-to-Low
I
R
OL
F
4-6.
V
2
PU
and R
R
THL
V
R
V
PU
DD
PU
PU
and V
V
V
3
OUT
OUT
can be
V
IN
TLH
)