MCP6N16 Datasheet, PDF (45/58 Pages) Microchip Technology – Rail-to-Rail Input and Output

When the signal is sampled by an ADC, these AC
signals can also be aliased to DC, causing an apparent
shift in offset.
To reduce interference:
- Keep traces and wires as short as possible
- Use shielding
- Use ground plane (at least a star ground)
- Place the input signal source near to the DUT
- Use good PCB layout techniques
- Use a separate power supply filter (bypass
capacitors) for these zero-drift INAs
4.4.13.3 Miscellaneous Effects
Keep the resistances seen by the input pins as small
and as near to equal as possible, to minimize bias
current-related offsets.
Make the (trace) capacitances seen by the input pins
small and equal. This is helpful in minimizing switching
glitch-induced offset voltages.
Bending a coax cable with a radius that is too small
causes a small voltage drop to appear on the center
conductor (the triboelectric effect). Make sure the
bending radius is large enough to keep the conductors
and insulation in full contact.
Mechanical stresses can make some capacitor types
(such as some ceramics) output small voltages. Use
more appropriate capacitor types in the signal path and
minimize mechanical stresses and vibration.
Humidity can cause electrochemical potential voltages
to appear in a circuit. Proper PCB cleaning helps, as
does the use of encapsulants.
4.5 Typical Applications
4.5.1
HIGH INPUT IMPEDANCE
DIFFERENCE AMPLIFIER
Figure 4-14 shows the MCP6N16 used as a difference
amplifier. The inputs are high-impedance and give
good CMRR performance.
V_{DD U1}
V_IP
MCP6N16
V_OUT
V_IM
V_FG
R_F
FIGURE 4-14:
R_G
V_REF
Difference Amplifier.
MCP6N16
4.5.2
DIFFERENCE AMPLIFIER FOR
VERY LARGE COMMON MODE
SIGNALS
Figure 4-15 uses the MCP6N16 INA as a difference
amplifier for signals with a very large common mode
component. The input resistor dividers (R₁ and R₂)
ensure that the INA’s inputs are within their normal
range of operation. The capacitors (C₁ and C₂) set the
same voltage division ratio for high-frequency signals
(e.g., a voltage step). C₂ includes the INA’s C_CM. R₁
and R₂’s tolerances affect CMRR.
V₁
R₁
R₂
C₁
C₂
V_{DD U1}
MCP6N16
C₁
C₂
V_FG
V_OUT
R_F
R₁
R₂
V₂
R_G
V_REF
FIGURE 4-15:
Difference Amplifier with
Very Large Common Mode Component.
4.5.3 RTD TEMPERATURE SENSOR
Figure 4-16 shows an RTD temperature sensor circuit,
which measures over the -55°C to +155°C range. The
sensor chosen changes from 78Ω to 159Ω over this
range. The 2.49 kΩ and 4.99 kΩ resistors set the
current through the RTD and 68.1Ω resistor. The INA
provides a high-differential gain. The 10 µF capacitor
filters common mode interference on the bridge.
V_DD
2.49 kΩ 10 µF
4.99 kΩ 4.99 kΩ
EN
MCP6N16-100
68.1Ω
4.99 kΩ
RTD
100Ω
100Ω
20 kΩ
100Ω
V_OUT
FIGURE 4-16:
RTD Temperature Sensor.
 2014 Microchip Technology Inc.
DS20005318A-page 45