g

OUT

S

Load

R

V

R

I

R

=

´

´

1

1

2

g

g

g

2

OUT

BAT

S

Load

1

1

2

2

R

1

R

R

R

1

2 R

R

R

R

R

V

V

R

I

R

R

R

1

1

R

R

æ

ö

æ

ö

ç

÷

+

+

ç

÷

-

ç

÷

ç

÷

è

ø

=

´

+

´

´

ç

÷

ç

÷

+

+

ç

÷

ç

÷

è

ø

1

1

2

g

g

g

2

1

2

OUT

1

2

1

1

2

2

R

1

R

R

R

1

2 R

R

R

R

R

V

V

V

(V

V )

R

R

R

2

1

1

R

R

æ

ö

æ

ö

ç

÷

+

+

ç

÷

-

ç

÷

ç

÷

+

è

ø

=

´

+

-

ç

÷

ç

÷

+

+

ç

÷

ç

÷

è

ø

_

+

RS

V1

V2

VBAT

R1

VOUT

ILOAD

ILOUD

R2

0.1 µF

R

Rg

47 k

21

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8.2 Typical Application

8.2.1 High-Side Current Monitor

Figure 54. Equivalent Schematic (Each Amplifier)

8.2.1.1 Design Requirements

For this design example, use the parameters listed in Table 3 as the input parameters.

Table 3. Design Parameters

PARAMETER

VALUE

VBAT

Battery voltage

12 V

RSENSE

Sense resistor

0.1 Ω

ILOAD

Load current

0 A to 10 A

Operational amplifier

Set in differential configuration with gain = 10

8.2.1.2 Detailed Design Procedure

This circuit is designed for measuring the high-side current in automotive body control modules with a 12-V

battery or similar applications. The operational amplifier is set as differential with an external resistor network.

8.2.1.2.1

Differential Amplifier Equations

Equation 1 and Equation 2 are used to calculate VOUT.

(1)

(2)

In an ideal case R1 = R and R2 = Rg, and VOUT can then be calculated using Equation 3:

(3)