MCP6141 N/A, MCP6141 Datasheet - Page 13

• Manufacturer Part Number: MCP6141
• Description: MCP6141-2-3-4
• Manufacturer: N/A

3.8.3
The input pins of the MCP6141/2/3/4 family of op amps
are high impedance, which allows noise injection. This
noise can be capacitively or magnetically coupled. In
either case, using a ground plane helps reduce noise
injection.
When noise is coupled capacitively, the ground plane
provides shunt capacitance to ground for high fre-
quency signals (Figure 3-8 shows the equivalent cir-
cuit). The coupled current, I
(V
plane capacitance (C
resistor (R
traces and using wider traces also helps.
FIGURE 3-8:
capacitive coupling between traces on a PC
board (with ground plane).
When noise is coupled magnetically, the ground plane
reduces the mutual inductance between traces. This
occurs because the ground return current at high fre-
quencies will follow a path directly beneath the signal
trace. Increasing the separation between traces makes
a significant difference. Changing the direction of one
of the traces can also reduce magnetic coupling.
If these techniques are not enough, it may help to place
guard traces next to the victim trace. They should be on
both sides of the victim trace and be as close as possi-
ble. Connect the guard traces to ground plane at both
ends and in the middle for long traces.
V
2002 Microchip Technology Inc.
TRACE 2
TRACE 1
) on the victim trace when the trace to ground
T2
C
SIGNAL COUPLING
SH1
) is small. Increasing the distance between
SH2
Equivalent circuit for
C
C
) is large and the terminating
M
SH2
M
, produces a lower voltage
I
M
V
TRACE 2
R
T2
3.9
3.9.1
The MCP6141/2/3/4 op amps’ Common Mode Input
Range, which goes 300 mV beyond both supply rails,
supports their use in high side and low side battery
current sensing applications. The very low quiescent
current (0.6 µA, typ.) help prolong battery life, while the
rail-to-rail output allows you to detect low currents.
Figure 3-9 shows a high side battery current sensor cir-
cuit. The feedback and input resistors are sized to min-
imize power losses. The battery current (I
the 1 k
negative than the bottom terminal. This keeps the com-
mon mode input voltage of the op amp
within its allowed range. The output of the op amp can
reach V
smaller error than the offset voltage.
FIGURE 3-9:
Sensor.
3.9.2
The rail-to-rail input and output, the 600 nA (typ.) qui-
escent current and the wide bandwidth make the
MCP6141/2/3/4 family of operational amplifiers fit well
in a summing amplifier circuit, as shown in Figure 3-10.
FIGURE 3-10:
V
REF
+1.4 V
5.5 V
V
V
V
1k
2
3
to
1
DD
Typical Applications
resistor causes its top terminal to be more
BATTERY CURRENT SENSING
SUMMING AMPLIFIER
V
- 0.1 mV (see Figure 2-26), which is a
DD
R
R
R
MCP6141/2/3/4
1
2
3
I
I
I
DD
I
100 k
2
3
1
High Side Battery Current
Summing amplifier circuit.
MCP614X
+
-
R
MCP614X
F
1 M
I
V
F
DD
V
SS
21668A-page 13
V
DD
DD
V
, which is
) through
OUT