MCP6141 datasheet(15/34 Pages) MICROCHIP

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DS21668B-page 15

MCP6141/2/3/4

4.9

Application Circuits

4.9.1

BATTERY CURRENT SENSING

The MCP6141/2/3/4 op amps’ Common Mode Input

Range, which goes 0.3V beyond both supply rails, sup-

ports 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, and the

rail-to-rail output supports detection low currents.

Figure 4-9 shows a high side battery current sensor

circuit. The 1 k

Ω resistor is sized to minimize power

losses. The battery current (IDD) through the 1 kΩ

resistor causes its top terminal to be more negative

than the bottom terminal. This keeps the Common

mode input voltage of the op amp at VDD, which is

within its allowed range. When no current is flowing, the

output will be at its Maximum Output Voltage Swing

(VOH), which is virtually at VDD.

FIGURE 4-9:

High Side Battery Current

Sensor.

4.9.2

INVERTING SUMMING AMPLIFIER

The MCP6141/2/3/4 op amp is well suited for the

inverting summing amplifier shown in Figure 4-10

when the resistors at the input (R1, R2, and R3) make

the noise gain at least 10 V/V. The output voltage

(VOUT) is a weighted sum of the inputs (V1, V2, and V3),

and is shifted by the VREF input. The necessary

calculations follow in Equation 4-3.

FIGURE 4-10:

Summing Amplifier.

EQUATION 4-3:

VDD

IDD

VDD

VSS

MCP6141

100 k

VSS

1.4V to

5.5V

VOUT

MCP614X

VOUT

VREF

------

⎝⎠

⎛⎞

10 V/V

≥

Noise Gain:

Output Signal:

OUT

1G1

2G2

3G3

REFGN

+++

F R1

⁄

–

Signal Gains:

F R2

⁄

–

F R3

⁄

–

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