Basic operations of Thermoflagger™

Thermoflagger™ supplies a small constant current to PTC thermistors to detect changes in their resistance (temperature).

Example of PTC thermistor characteristics Resistance vs temperature

The left-hand figure shows the internal block diagram of Thermoflagger™. It consists of a constant-current source, a reference voltage source, a comparator, and a FLAG output function.

Explanation of operation

Next, we will briefly explain how it works.
When temperature is low, PTC thermistors have relatively small resistance. Therefore, the voltage at the PTCO pin is low. At this time, the PTCGOOD pin is driven High.
When the temperature of a PTC thermistor increases and reaches the critical temperature, its resistance increases dramatically, causing the voltage at the PTCO pin to increase. At this time, the PTCGOOD pin is driven Low.
As shown in this figure,  you can easily create an overtemperature detection circuit by combining Thermoflagger™ and PTC thermistors.

Basic of Thermoflagger™

The need for overheating (temperature) monitoring
What is Thermoflagger™ ?
Using Thermoflagger™
Feature 1: Simplifies circuit design for overtemperature detection
Feature 2: Low-cost solution for monitoring multiple locations for overtemperature conditions
Feature 3: Supports failsafe design (1)
Feature 3: Supports failsafe design (2)
Application example for Thermoflagger™
Application of Thermoflagger™ (reference design)

Related information

* Thermoflagger™ is a trademark of Toshiba Electronic Devices & Storage Corporation.
* Other company names, product names, and service names may be trademarks of their respective companies.