TIDUDJ6B August   2022  – February 2023 OPA388-Q1

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagrams
    2. 2.2 Highlighted Products
      1. 2.2.1 TPSI2140-Q1
      2. 2.2.2 AMC1301-Q1
      3. 2.2.3 SN6501-Q1
    3. 2.3 System Design Theory
      1. 2.3.1 Isolation Leakage Current Theory
      2. 2.3.2 High-Voltage Measurement
  8. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Required Hardware
    2.     Hardware with Solid-State Relay
    3. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Isolation Tests
        1. 3.2.2.1 Normal Conditions
        2. 3.2.2.2 Isolation Error at HV Positive
        3. 3.2.2.3 Isolation Error at HV Negative
        4. 3.2.2.4 Isolation Error at ¼ HV Battery Voltage
        5. 3.2.2.5 Isolation Error at ¾ HV Battery Voltage
        6. 3.2.2.6 Isolation Error at the Middle of an HV Battery Voltage
      3. 3.2.3 Solid-State Relay Isolation Tests
        1. 3.2.3.1 Normal Conditions
        2. 3.2.3.2 Isolation Error at HV Positive
        3. 3.2.3.3 Isolation Error at HV Negative
        4. 3.2.3.4 Isolation Error at ¼ HV Battery Voltage
        5. 3.2.3.5 Isolation Error at ¾ HV Battery Voltage
        6. 3.2.3.6 Isolation Error at the Middle of an HV Battery Voltage
      4. 3.2.4 High Voltage Measurements
      5. 3.2.5 Isolation Measurement Analysis
      6. 3.2.6 Error Analysis
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
  12. 7Trademarks
  13. 8Revision History

2.3.2 High-Voltage Measurement

High-voltage measurement is required to calculate the isolation leakage current. In TIDA-01537 , the AMC1301-Q1 device is used to perform these measurements. The AMC1311B has a high input resistance, a 2-V input range, and can also be used for high-voltage measurements.

As #T5081059-27 shows, the Rsh monitoring resistor is placed in series to a high-ohmic potential divider network. Voltage measurements are performed with a floating ground of the AMC1301-Q1. The OPA320-Q1 device is used to amplify the signal range and give a single-ended output to an MCU or logic interface. The AMC1301-Q1 can measure a bidirectional signal of ±250 mV. In HEV or EV motors, battery voltages are only in the positive range, so the usable range of the AMC1301-Q1 is 250 mV. A potential divider network must be chosen in such a way that the voltage drop in shunt resistance must be ≤ 250 mV at the maximum battery voltages.

GUID-67365636-6DC3-4661-8654-4019F023CB29-low.gifFigure 2-11 High-Voltage Measurements

Use #T5081059-57 to calculate the high battery voltage.

Equation 5. HV_BATT=VOUT_OPA320×Rs2Rs×G_AMC1301×G_OPA320

where

  • VOUT_OPA320 is the output voltage measured by the ADC or relevant device from the output of the OPA320-Q1
  • Rsx is the sum of the series resistors from HV_BATT positive to negative including the shunt resistor
  • Rsh is the shunt resistor for the AMC1301-Q1
  • G_AMC1301 is the gain of the AMC1301-Q1 internal circuit
  • G_OPA320 is the gain set by the external resistors for the OPA320-Q1 circuit

#T5081059-57 is a simple equation that does not consider the influences of bias currents or offset voltages, which can lead to deviations in measurements.