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| TLC2274M-MIL Datasheet, PDF (21/33 Pages) Texas Instruments – Advanced LinCMOS Rail-to-Rail Operational Amplifier | |||
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8.2 Typical Application
8.2.1 High-Side Current Monitor
VBAT
VOUT
47 kΩ
V1
0.1 µF
RS
R1
R2
V2
ILOUD
R
ILOAD
TLC2274M-MIL
SLOS985 â JUNE 2017
Rg
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.
VBAT
RSENSE
ILOAD
Table 3. Design Parameters
PARAMETER
Battery voltage
Sense resistor
Load current
Operational amplifier
VALUE
12 V
0.1 Ω
0 A to 10 A
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.
VOUT
=
Rg
R
æ
ç
ç
ç
ç
ççè
R - R1
Rg R2
1+ R1
R2
´
V1 + V2
2
1+
+
1
2
æ
ççè
R1
R2
+
1+ R1
R2
R
Rg
ö
ö
÷÷ø
(
V1
-
V2
)
÷
÷
÷
÷
÷÷ø
(1)
VOUT
=
Rg
R
æ
ç
R
- R1
ç
ç
Rg
R2
ç
ççè
1+ R1
R2
´ VBAT
1+
+
1
2
æ
ççè
R1
R2
+
R
Rg
1+ R1
R2
ö
÷÷ø ´ RS
ö
÷
÷
´
ILoad
÷
÷
÷÷ø
(2)
In an ideal case R1 = R and R2 = Rg, and VOUT can then be calculated using Equation 3:
VOUT
=
Rg
R
´ RS
´ ILoad
(3)
Copyright © 2017, Texas Instruments Incorporated
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