MCP6242 Ver la hoja de datos (PDF) - Microchip Technology
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MCP6242 Datasheet PDF : 38 Pages
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4.0 APPLICATION INFORMATION
The MCP6241/1R/1U/2/4 family of op amps is manu-
factured using Microchip’s state-of-the-art CMOS
process and is specifically designed for low-power and
general-purpose applications. The low supply voltage,
low quiescent current and wide bandwidth makes the
MCP6241/1R/1U/2/4 ideal for battery-powered
applications.
4.1 Rail-to-Rail Inputs
4.1.1 PHASE REVERSAL
The MCP6241/1R/1U/2/4 op amp is designed to
prevent phase reversal when the input pins exceed the
supply voltages. Figure 4-1 shows the input voltage
exceeding the supply voltage without any phase
reversal.
6
5
VOUT
VDD = 5.0V
G = +2 V/V
4
VIN
3
2
1
0
-1
Time (1 ms/div)
FIGURE 4-1:
The MCP6241/1R/1U/2/4
Show No Phase Reversal.
4.1.2
INPUT VOLTAGE AND CURRENT
LIMITS
The ESD protection on the inputs can be depicted as
shown in Figure 4-2. This structure was chosen to
protect the input transistors, and to minimize input bias
current (IB). The input ESD diodes clamp the inputs
when they try to go more than one diode drop below
VSS. They also clamp any voltages that go too far
above VDD; their breakdown voltage is high enough to
allow normal operation, and low enough to bypass
quick ESD events within the specified limits.
MCP6241/1R/1U/2/4
VDD
Bond
Pad
VIN+
Bond
Pad
Input
Stage
Bond
Pad
VIN–
VSS
Bond
Pad
FIGURE 4-2:
Structures.
Simplified Analog Input ESD
In order to prevent damage and/or improper operation
of these op amps, the circuit they are in must limit the
currents and voltages at the VIN+ and VIN– pins (see
Absolute Maximum Ratings †at the beginning of
Section 1.0 “Electrical Characteristicsâ€). Figure 4-3
shows the recommended approach to protecting these
inputs. The internal ESD diodes prevent the input pins
(VIN+ and VIN–) from going too far below ground, and
the resistors R1 and R2 limit the possible current drawn
out of the input pins. Diodes D1 and D2 prevent the
input pins (VIN+ and VIN–) from going too far above
VDD, and dump any currents onto VDD. When
implemented as shown, resistors R1 and R2 also limit
the current through D1 and D2.
VDD
D1 D2
V1
R1
MCP624X
V2
R2
R3
R1
>
VSS
–
(minimum expected
2 mA
V1)
R2
>
VSS
–
(minimum expected
2 mA
V2)
FIGURE 4-3:
Inputs.
Protecting the Analog
It is also possible to connect the diodes to the left of
resistors R1 and R2. In this case, current through the
diodes D1 and D2 needs to be limited by some other
mechanism. The resistors then serve as in-rush current
limiters; the DC current into the input pins (VIN+ and
VIN–) should be very small.
© 2008 Microchip Technology Inc.
DS21882D-page 11
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