SLPS764 September   2024 RES60A-Q1

ADVANCE INFORMATION  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
  7. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Ratiometric Matching
      2. 6.3.2 Ultra-Low Noise
    4. 6.4 Device Functional Modes
  8. Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Battery Stack Measurement
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 PSpice® for TI
        2. 8.1.1.2 TINA-TI™ Simulation Software (Free Download)
        3. 8.1.1.3 TI Reference Designs
        4. 8.1.1.4 Analog Filter Designer
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Battery Stack Measurement

The RES60A-Q1 can be used in conjunction with an automotive precision amplifier, such as the OPA192-Q1, for single-ended measurement of the high side (BAT+) of an EV battery relative to a fixed potential. For those systems where BAT– and GND are equivalent, as in Figure 7-1 (a), the configuration shown in Figure 7-2 applies. An alternative approach is to measure directly across the battery from BAT+ to BAT–, as shown in Figure 7-3. This approach is useful for systems referenced to the low side of the battery, BAT–, as in Figure 7-1 (b).

RES60A-Q1 Common Battery and System
                    Configurations Figure 7-1 Common Battery and System Configurations
RES60A-Q1 Single-Ended Measurement, BAT+ to GND Figure 7-2 Single-Ended Measurement, BAT+ to GND
RES60A-Q1 Single-Ended Measurement, BAT+ to
                    BAT– Figure 7-3 Single-Ended Measurement, BAT+ to BAT–

For some system architectures, BAT– floats relative to the chassis GND; see also Figure 7-1 (c). If for example a microcontroller referenced to chassis ground needs to measure the voltage across the entire battery stack, a difference amplifier can be constructed using two RES60A-Q1 devices and an OPA192-Q1. Figure 7-4 shows this approach. If two ADC channels are available, two single-ended measurements can be done using two RES60A-Q1 devices and an OPA2192-Q1.

RES60A-Q1 Differential Measurement, BAT+ to BAT– Figure 7-4 Differential Measurement, BAT+ to BAT–

Leakage in the system and quiescent current from the amplifier input reduce the precision of the measurement. In some cases, a guard buffer can be used to reduce leakage currents. Follow best practices to reduce board contamination and leakage.

For an 800V single-ended battery measurement (see also Figure 7-2), the static current through the divider is:

Equation 8. I S T A T I C = V B A T T R H V + R L V = 800 V 12.5 M   + 20.49 k   = 63.9 μ A

Therefore, the buffer amplifier used must have a low bias current, such that IB << ISTATIC. The low bias current of the OPA192-Q1 (5pA typical at 25°C, 5nA maximum from –40°C to +125°C) makes the device an excellent choice for this role.