MCP6043T-I Datasheet, PDF (15/34 Pages) Microchip Technology – 600 nA, Rail-to-Rail Input/Output Op Amps

4.9 Application Circuits
4.9.1 BATTERY CURRENT SENSING
The MCP6041/2/3/4 op amps’ Common Mode Input
Range, which goes 0.3V 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, typical) help prolong battery life, and
the rail-to-rail output supports detection low currents.
Figure 4-7 shows a high side battery current sensor
circuit. The 10Ω resistor is sized to minimize power
losses. The battery current (I_DD) through the 10Ω
resistor causes its top terminal to be more negative
than the bottom terminal. This keeps the common
mode input voltage of the op amp below V_DD, which is
within its allowed range. The output of the op amp will
also be below V_DD, which is within its Maximum Output
Voltage Swing specification.
.
1.4V
to
6.0V
I_DD
10Ω
100 kΩ
MCP604X
V_DD
V_OUT
1 MΩ
I_DD = ₍---₁---_0V----^D-_V---^D_/--_V---–-₎---^V-_â‹---₍^O--₁--^U-₀--^T--_Ω-----₎
FIGURE 4-7:
Sensor.
High Side Battery Current
MCP6041/2/3/4
4.9.2 INSTRUMENTATION AMPLIFIER
The MCP6041/2/3/4 op amp is well suited for
conditioning sensor signals in battery-powered
applications. Figure 4-8 shows a two op amp instru-
mentation amplifier, using the MCP6042, that works
well for applications requiring rejection of common
mode noise at higher gains. The reference voltage
(V_REF) is supplied by a low impedance source. In single
supply applications, V_REF is typically V_DD/2.
.
R_G
V_REF ^R1
R₂
R₂
R₁
V_OUT
V₂
½
½
V₁
MCP6042
MCP6042
V_OUT
=
(V₁
–
V₂)
⎛
⎝
1
+
R_----1-
R₂
+
2--_R--R_{--G--1⎠⎞}
+ V_REF
FIGURE 4-8:
Two Op Amp
Instrumentation Amplifier.
© 2008 Microchip Technology Inc.
DS21669C-page 15