SBOA600 July   2024 ISOTMP35

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Calculating Thermal Response Time
    2. 1.2 Current Design with Non-Isolated Temperature Sensors
    3. 1.3 Proposed Design Using the ISOTMP35 Isolated Temperature Sensor
  5. 2Experiment Setup
    1. 2.1 Step 1: Prepare the Oil Bath
    2. 2.2 Step 2: Prepare the Liquid Gallium
    3. 2.3 Step 3: Submerge the Copper Pad
    4. 2.4 Step 4: Prepare Each PCB Configuration
    5. 2.5 Step 5: Testing Each PCB Configuration
    6. 2.6 Test Results
  6. 3Summary
  7. 4References

Abstract

Effective temperature monitoring in high-voltage environments, such as automotive on-board chargers (OBC), DC/DC converters, and EV DC fast chargers, is crucial for maintaining safety and performance. These applications require isolated ICs because direct electrical connections can be hazardous and lead to inaccurate readings due to electrical noise and interference. Traditionally, negative temperature coefficient (NTC) thermistors sense temperature across isolation boundaries. This typically involves either using a high-voltage NTC with an isolated ADC or amplifier, which adds cost and complexity, or placing a standard NTC across the clearance gap from the high-voltage heat source, which results in poor temperature response time and significant measurement errors due to the thermal lag across the gap.

ISOTMP35 or ISOTMP35-Q1 solves these issues by providing a new isolated temperature sensor technology that allows to directly connect to a high-voltage heat source. This direct connection enables a much faster temperature response time of 3.1 seconds, compared to 78.3 seconds for NTC without epoxy and 47.8 seconds with epoxy. Additionally, ISOTMP35 achieves a more accurate final temperature of 72.1°C, making sure of better performance and reliability.

This application note demonstrates how ISOTMP35 enhances temperature response over other temperature sensing designs. By leveraging advanced isolation techniques and thermal management strategies, ISOTMP35 helps improve the safety and efficiency of critical applications such as automotive OBCs, DC/DC converters, and EV DC fast chargers, addressing the increasing power density and thermal challenges in modern EVs.

Examples of Different Temperature Sensing Designs Figure 1-1 Examples of Different Temperature Sensing Designs