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Application of SMD Type NTC Thermistor
2021/08/10 03:08:29

SMD type NTC thermistor produced by EXSENSE Electronics Technology Co., Ltd. has the characteristics of small size, high reliable ceramic structure, rapid reaction, great thermal cycle and so on, which is widely used in lithium battery, mixed-design multi-function module, IT equipment, etc. Due to SMD type NTC thermistor is suitable for no lead high density surface mounting, it plays a role in temperature monitoring and overheating protection in the following products:

First, temperature monitoring of smart phone, tablet personal computer

In smart phone or tablet personal computer, multiple SMD thermistors are used for temperature monitoring. The basic circuit is a bleeder circuit connected in series with the NTC thermistor and the fixed resistor. The resistance value of the NTC thermistor installed near the heating place, such as CPU and power module, will decrease with the increase of temperature, so the output voltage of the bleeder circuit will change, and the change will be transmitted to the micro controller to protect the circuit components from the influence caused by overheating.

Second, temperature monitoring of mobile device battery during charging

In addition to + terminals and - terminals, there are also temperature monitoring terminals in the battery packs of mobile devices such as smart phones (lithium-ion batteries), which are equipped with SMD thermistors. When the temperature of the battery increases, the temperature of the NTC thermistor will also increase and the resistance value will decrease. When the upper charging temperature is exceeded, the charging control IC will stop charging. A protective IC in the battery pack measures the battery voltage to prevent overcharging or over-discharging. In the case of rapid charging and other requirements for more precision charging control, it is necessary to connect the NTC thermistor with the charging control IC to measure the environmental temperature.

Third, temperature monitoring of thermal printer

The magnetic head temperature of thermal printer is correlated with the printing concentration. The higher the temperature, the higher the concentration, and the lower the temperature, the lower the concentration. According to the temperature of the thermal head monitored, the pulse current transported to the thermal magnetic head is changed and the voltage is controlled so as to maintain a certain printing concentration. Using SMD thermistor for temperature monitoring can effectively ensure the normal operation of thermal printer.

Fourth, overheating protection of semiconductor device

Semiconductor devices need SMD thermistor to protect them from overheating in order to avoid the influence of high temperature. NTC thermistor is configured on the internal base plate of the power module to facilitate temperature monitoring of the heat dissipation plate on which the module is installed. NTC thermistor is connected to the comparator of the controller, and when the resistance value of NTC thermistor falls below the set value, the controller will reduce the power of all semiconductor devices, thereby reducing the internal temperature.

Especially in power modules where wide-band gap semiconductors (GaN or SiC) are used, the operating temperature is higher than that of standard silicon, so there may be a need to change the mounting method of components. In the case of standard silicon, solders and adhesives maybe used. If higher temperatures are required, components may need to be mounted to DCB (directly bonded copper) during the sintering process, or bonded with gold, silver or aluminum wires for interconnecting mount work. When the temperature of the connection is reached, close the IGBT to avoid damage caused by excessive high temperature, which needs to install SMD type NTC thermistors for overheating protection.

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