MCP6546 데이터 시트보기 (PDF) - Microchip Technology
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MCP6546 Datasheet PDF : 32 Pages
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MCP6546/6R/6U/7/8/9
8
25
7 VDD = 5.0V
20
6
5
4
VOUT
VIN–
15
10
5
3
0
2
-5
1
Hysteresis
-10
0
-15
-1
-20
-2
-25
-3
-30
Time (100 ms/div)
FIGURE 4-3:
The MCP6546/7/8/9
comparators’ internal hysteresis eliminates
output chatter caused by input noise voltage.
4.2 Open-Drain Output
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 MCP6548 Chip Select (CS)
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 VDD pin,
as 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.
4.4 Externally Set Hysteresis
Greater flexibility in selecting hysteresis, or input trip
points, is achieved by using external resistors.
Input offset voltage (VOS) is the center (average) of the
(input-referred) low-high and high-low trip points. Input
hysteresis voltage (VHYST) is the difference between
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
4.4.1 INVERTING CIRCUIT
Figure 4-4 shows an inverting circuit for a single-supply
application using three resistors, besides the pull-up
resistor. The resulting hysteresis diagram is shown in
Figure 4-5.
VIN
VDD
R2
R3
VDD
VPU
IPU
RPU
MCP654X
IOL
IRF
VOUT
RF
FIGURE 4-4:
hysteresis.
Inverting circuit with
VPU
VOH
VOUT
Low-to-High
High-to-Low
VOL
VSS
VSS
VTLH VTHL
VIN
VDD
VTLH = trip voltage from low to high
VTHL = trip voltage from high to low
FIGURE 4-5:
inverting circuit.
Hysteresis diagram for the
In order to determine the trip voltages (VTHL and VTLH)
for the circuit shown in Figure 4-4, R2 and R3 can be
simplified to the Thevenin equivalent circuit with
respect to VDD, as shown in Figure 4-6.
-
MCP654X
+
VPU
RPU
VOUT
V23
R23
FIGURE 4-6:
RF
Thevenin Equivalent Circuit.
© 2006 Microchip Technology Inc.
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