MCP602-I/SL View Datasheet(PDF) - Microchip Technology
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MCP602-I/SL Datasheet PDF : 34 Pages
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MCP601/1R/2/3/4
4.0 APPLICATIONS INFORMATION
The MCP601/1R/2/3/4 family of op amps are fabricated
on Microchip’s state-of-the-art CMOS process. They
are unity-gain stable and suitable for a wide range of
general purpose applications.
4.1 Inputs
4.1.1 PHASE REVERSAL
The MCP601/1R/2/3/4 op amp is designed to prevent
phase reversal when the input pins exceed the supply
voltages. Figure 2-34 shows the input voltage
exceeding the supply voltage without any phase
reversal.
4.1.2
INPUT VOLTAGE AND CURRENT
LIMITS
The ESD protection on the inputs can be depicted as
shown in Figure 4-1. 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.
VDD
Bond
Pad
VIN+
Bond
Pad
Input
Stage
Bond
Pad
VIN–
VSS
Bond
Pad
FIGURE 4-1:
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 Characteristics”). Figure 4-2
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
V2
R2
MCP60X
R3
R1
>
VSS
–
(minimum expected
2 mA
V1)
R2
>
VSS
–
(minimum expected
2 mA
V2)
FIGURE 4-2:
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.
A significant amount of current can flow out of the
inputs when the common mode voltage (VCM) is below
ground (VSS); see Figure 2-34. Applications that are
high impedance may need to limit the useable voltage
range.
4.1.3 NORMAL OPERATION
The Common Mode Input Voltage Range (VCMR)
includes ground in single-supply systems (VSS), but
does not include VDD. This means that the amplifier
input behaves linearly as long as the Common Mode
Input Voltage (VCM) is kept within the specified VCMR
limits (VSS–0.3V to VDD–1.2V at +25°C).
Figure 4-3 shows a unity gain buffer. Since VOUT is the
same voltage as the inverting input, VOUT must be kept
below VDD–1.2V for correct operation.
VIN
+
MCP60X
–
VOUT
FIGURE 4-3:
Unity Gain Buffer has a
Limited VOUT Range.
DS21314G-page 12
© 2007 Microchip Technology Inc.
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