MCP6021 View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'MCP6021' PDF : 42 Pages View PDF
4.6 MCP6021 and MCP6023 Reference
Voltage
The single op amps (MCP6021 and MCP6023), not in
the SOT-23-5 package, have an internal mid-supply
reference voltage connected to the VREF pin (see
Figure 4-7). The MCP6021 has CS internally tied to
VSS, 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 VREF circuitry. Taking
the CS pin low turns on the op amp and VREF circuitry.
VDD
VREF
50 kΩ
50 kΩ
CS
5 MΩ
VSS
(CS tied internally to VSS for MCP6021)
FIGURE 4-7:
Simplified internal VREF
circuit (MCP6021 and MCP6023 only).
See Figure 4-8 for a non-inverting gain circuit using the
internal mid-supply reference. The DC-blocking
capacitor (CB) also reduces noise by coupling the op
amp input to the source.
RG
RF
CB
VIN
VREF
VOUT
FIGURE 4-8:
Non-inverting gain circuit
using VREF (MCP6021 and MCP6023 only).
To use the internal mid-supply reference for an
inverting gain circuit, connect the VREF pin to the
non-inverting input, as shown in Figure 4-9. The
capacitor CB helps reduce power supply noise on the
output.
MCP6021/1R/2/3/4
RG
VIN
RF
VOUT
VREF
CB
FIGURE 4-9:
Inverting gain circuit using
VREF (MCP6021 and MCP6023 only).
If you don’t need the mid-supply reference, leave the
VREF pin open.
4.7 Supply Bypass
With this family of operational amplifiers, the power
supply pin (VDD for single supply) should have a local
bypass capacitor (i.e., 0.01 µF to 0.1 µF) within 2 mm
for good, high-frequency performance. It also needs a
bulk capacitor (i.e., 1 µF or larger) within 100 mm to
provide large, slow currents. This bulk capacitor can be
shared with nearby analog parts.
4.8 Unused Op Amps
An unused op amp in a quad package (MCP6024)
should be configured as shown in Figure 4-10. These
circuits prevent the output from toggling and causing
crosstalk. Circuits A sets the op amp at its minimum
noise gain. The resistor divider produces any desired
reference voltage within the output voltage range of the
op amp; the op amp buffers that reference voltage.
Circuit B uses the minimum number of components
and operates as a comparator, but it may draw more
current.
¼ MCP6024 (A)
VDD
R1
VDD
R2
VREF
¼ MCP6024 (B)
VDD
VREF
=
VDD
×
-------R----2-------
R1 + R2
FIGURE 4-10:
Unused Op Amps.
© 2009 Microchip Technology Inc.
DS21685D-page 19
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