SBOS472B March   2009  – June 2016 INA148-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics Dual Supply
    6. 6.6 Electrical Characteristics Single Supply
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Operating Voltage
      2. 7.3.2 Gain Equation
      3. 7.3.3 Common-Mode Range
      4. 7.3.4 Offset Trim
      5. 7.3.5 Input Impedance
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Battery Monitor Circuit
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Quasi-AC-Coupled Differential Amplifier
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
      3. 8.2.3 Single-Supply Differential Amplifier
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
      4. 8.2.4 AC-Coupled Difference Amplifier
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Detailed Design Procedure
      5. 8.2.5 50-mV Current-Shunt Amplifier With ±200-V Common-Mode Voltage Range
        1. 8.2.5.1 Design Requirements
        2. 8.2.5.2 Detailed Design Procedure
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

INA148-Q1 is a unity-gain difference amplifier with a high common-mode input voltage range. It is suitable to be used in many different applications that need bidirectional measurments in a high input common-mode environment.

8.2 Typical Applications

8.2.1 Battery Monitor Circuit

INA148-Q1 ai_batt_mon_cx_bos472.gif Figure 24. Battery Monitor Circuit Diagram

8.2.1.1 Design Requirements

For this design example, use the parameters listed in Table 1 as the input parameters.

Table 1. Design Parameters

PARAMETER EXAMPLE VALUE
Battery voltage 28 V
Sense resistor 0.01 Ω
Load current bidirectional –50 A to 50 A
Reference voltage (LM4041-N-Q1) 1.235 V ± 0.1%

8.2.1.2 Detailed Design Procedure

This circuit is designed for measuring the high-side current bidirectional in automotive battery monitor such as charging or body control modules with a 28-V battery or similar applications. The voltage difference amplifier REF pin is set at 1.235 V for bidirectional current measurement.

The LM4041-V-Q1 supply current is around 100 µA. It is provided from the 28-V battery through 271-kΩ resistor. The INA148-Q1 has a gain of 1 and output voltage as shown in Equation 3:

Equation 3. VO = RS × IC + 1.235 V

The sense resistor value can be changed according to measured current range. TI recommends choosing the right value for minimizing the error and the dissipating power. The measured differential voltage is given as Equation 4 and the dissipated power is given as Equation 5.

Equation 4. RS × IC
Equation 5. RS × IC2

8.2.1.3 Application Curves

INA148-Q1 D002_sbos472.gif Figure 25. Output Voltage vs Load Current –10 A to 10 A
INA148-Q1 D003_sbos472.gif Figure 26. Output Voltage vs Load Current –50 A to 50 A

8.2.2 Quasi-AC-Coupled Differential Amplifier

INA148-Q1 ai_quasi_ac_coupl_bos472.gif Figure 27. Quasi-AC-Coupled Differential Amplifier Diagram

8.2.2.1 Design Requirements

For this design example, use the parameters listed in Table 2 as the input parameters.

Table 2. Design Parameters

PARAMETER EXAMPLE VALUE
Common-mode supply voltage (–200 V to 200 V) 15 V
Common-mode supply voltage (–100 V to 750 V) 5 V
U2 OPA171-Q1
External resistor 1 MΩ
External capacitor 0.22 µF

8.2.2.2 Detailed Design Procedure

A quasi-AC coupled differential amplifier can be simply made by adding a general-purpose op amp configured as an integrator externally to the device. Equation 6 shows the output of OPA171-Q1.

Equation 6. INA148-Q1 eq_vo1.gif

where

  • ZC is the impedance of the external capacitor
  • R is the value of the external resistor

Equation 7 shows the output of INA148-Q1.

Equation 7. VO = VO1 + V+IN – V–IN

Equation 8 is the result of combining the previous two equations.

Equation 8. INA148-Q1 eq_vo.gif

where

  • S = j × 2π × ƒ

The transfer function INA148-Q1 eq_transfer.gif has a zero and a pole at INA148-Q1 eq_transfer_zeropole.gif. Making a gain slope of 20 dB/decade below the cutoff frequncy and flat 0 dB above.

VREF can be set to 0 V in case of dual supply.

8.2.3 Single-Supply Differential Amplifier

INA148-Q1 ai_singl_suppl_diff_amp_bos472.gif Figure 28. Single-Supply Differential Amplifier Diagram

8.2.3.1 Design Requirements

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

Table 3. Design Parameters

PARAMETER EXAMPLE VALUE
Common-mode voltage –23 V to 56 V
Load current Bidirectional
Reference voltage (LM4041-N-Q1) 1.235 V ± 0.1%
Supply voltage (INA148-Q1) 5 V

8.2.3.2 Detailed Design Procedure

For applications that have –23-V to 56-V common-mode voltage and a single 5-V supply, the common-mode rejection ratio is in the order of 80 dB. The INA148-Q1 is not a rail-to-rail output. An external reference voltage is necessary for bidirectional measurment or low differential output. The external resistor is necessary to provide a 100-µA supply to LM4041-N-Q1.

8.2.4 AC-Coupled Difference Amplifier

INA148-Q1 ai_ac_coupl_diff_amp_bos472.gif
1. Metallized polypropylene, ±5% tolerance
Figure 29. AC-Coupled Difference Amplifier Circuit Diagram

8.2.4.1 Design Requirements

For this design example, use the parameters listed in Table 4 as the input parameters.

Table 4. Design Parameters

PARAMETER EXAMPLE VALUE
Decoupling capacitors 4.7 µF, 250 V ± 5%
Differential input voltage range –14 V to 14 V

8.2.4.2 Detailed Design Procedure

An AC-coupled voltage difference amplifier requires 2 series capacitors. These capacitors must be high quality with tolerance of less than 5% and a rated voltage of 250 V at 200-V common-mode.

8.2.5 50-mV Current-Shunt Amplifier With ±200-V Common-Mode Voltage Range

INA148-Q1 ai_50mv_curr_shunt_bos472.gif Figure 30. 50-mV Current-Shunt Amplifier With ±200-V Common-Mode Voltage Range Diagram

8.2.5.1 Design Requirements

For this design example, use the parameters listed in Table 5 as the input parameters.

Table 5. Design Parameters

PARAMETER EXAMPLE VALUE
Common-mode voltage ±200 V
Differential input voltage –50 mV to 50 mV
Gain (OPA171-Q1) 200
Isolated power supply ±15 V

8.2.5.2 Detailed Design Procedure

The OPA171-Q1 gain is 200, set by 1 kΩ and 200 kΩ resistors. The OPA171-Q1 positive input and the INA148‑Q1 are both tied to the isolated power supply common ground. The OPA171-Q1 output is calculated by Equation 9.

Equation 9. VO = –200 × VSENSE

where

  • VSENSE is the voltage across the shunt resistor

The INA148-Q1 output is calculated by Equation 10.

Equation 10. VO = –(–200 × VSENSE) = 200 × VSENSE