MCP6021/2/3/4
3.0
APPLICATIONS INFORMATION
3.3
MCP6023 Chip Select (CS)
The MCP6021/2/3/4 family of operational amplifiers
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.
The MCP6023 is a single amplifier with chip select
(CS). When CS is high, the supply current is less than
10 nA (typ) and travels from the CS pin to V
SS
, with the
amplifier output being put into a high-impedance state.
When CS is low, the amplifier is enabled. If CS is left
floating, the amplifier will not operate properly.
and supply current response to a CS pulse.
3.1
Rail-to-Rail Input
The MCP6021/2/3/4 amplifier family is designed to not
exhibit phase inversion when the input pins exceed the
supply voltages. Figure 2-27 shows an input voltage
exceeding both supplies with no resulting phase
inversion.
The input stage of the MCP6021/2/3/4 family of devices
uses two differential input stages in parallel; one
operates at low common-mode input voltage (V
CM
),
while the other operates at high V
CM
. With this topology,
the device operates with V
CM
up to 0.3V past either
supply rail (V
SS
- 0.3V to V
DD
+ 0.3V) at 25°C. The
amplifier input behaves linearly as long as V
CM
is kept
within the specified V
CMR
limits. The input offset voltage
is measured at both V
CM
= V
SS
- 0.3V and V
DD
+ 0.3V
to ensure proper operation.
Input voltages that exceed the input voltage range
(V
CMR
) can cause excessive current to flow in or out of
the input pins. Current beyond ±2 mA introduces
possible reliability problems. Thus, applications that
exceed this rating must externally limit the input current
with an input resistor (R
IN
), as shown in Figure 3-1.
3.4
MCP6021 and MCP6023 Reference
Voltage
The single op amps (MCP6021 and MCP6023) have
an internal mid-supply reference voltage connected to
the V
REF
pin (see Figure 3-2). The MCP6021 has CS
internally tied to V
SS
, which always keeps the op amp
on and always provides a mid-supply reference. With
the MCP6023, taking the CS pin high conserves power
by shutting down both the op amp and the V
REF
circuitry. Taking the CS pin low turns on the op amp and
V
REF
circuitry.
V
DD
50 kΩ
V
REF
50 kΩ
CS
R
IN
V
IN
MCP602X
V
OUT
V
SS
(CS tied internally to V
SS
for MCP6021)
R
IN
≥
R
IN
≥
(Maximum expected
V
IN
) -
V
DD
2 mA
V
SS
- (Minimum expected
V
IN
)
2 mA
FIGURE 3-2:
Simplified internal V
REF
circuit (MCP6021 and MCP6023 only).
See Figure 3-3 for a non-inverting gain circuit using the
internal mid-supply reference. The DC-blocking
capacitor (C
B
) also reduces noise by coupling the op
amp input to the source.
R
G
R
F
FIGURE 3-1:
into an input pin.
R
IN
limits the current flow
3.2
Rail-to-Rail Output
The Maximum Output Voltage Swing is the maximum
swing possible under a particular output load.
According to the specification table, the output can
reach within 20 mV of either supply rail when
R
L
= 10 kΩ. See Figure 2-31 and Figure 2-34 for more
information concerning typical performance.
C
B
V
IN
V
OUT
V
REF
FIGURE 3-3:
Non-inverting gain circuit
using V
REF
(MCP6021 and MCP6023 only).
DS21685B-page 12
2003 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
