Track Current Detection IC – FP137/FP137A, suitable for battery chargers and SPS (adapters)

In recent years, with the proliferation and advancement of electronic devices, demand for power supply products such as battery chargers, SPS (adapters), and high-side busbar current detectors has steadily increased.

Transportation systems including freight trains, high-speed rail, underground railways, and other rail transit rely heavily on rail current detection capabilities. This technology not only enables real-time monitoring and control of current flow but also provides power quality protection functions, ensuring the proper operation of chargers. Next, we shall explore the rail current detection IC—FP137/FP137A.

I. FP137 Overview

The FP137 is a high-side rail current measurement IC featuring a wide common-mode range. It is suitable for power supply systems such as battery chargers or switching power supply applications. The device incorporates a differential input amplifier and a MOSFET with a source output. With three external resistors, the rail current signal can be readily converted into an amplified voltage signal at the IC's output pin. Furthermore, the gain can be adjusted by altering the values of these three external resistors.

II. FP137 Features

• Independent supply voltage: 3.3V to 45V
• Wide common-mode input voltage: 3.3V to 45V
• Maximum usable output voltage (output pin): 6V
• Three resistor gain settings
• Wide temperature range: -40°C to +125°C
• Quiescent current: 220μA
• Package: SOT23-6L
• RG1=RG2=1K Ω (FP137), RG1=RG2=200 Ω (FP137A)

III. FP137 Applications

• High-side rail current detector
• SPS (adapter), battery charger
• Sensing network system

In summary, the track current detection IC—FP137/FP137A—is a highly functional, easy-to-install electronic component with broad applicability. Its introduction not only provides reliable protection for power products such as chargers and adapters but also greatly facilitates the application of high-side track current detectors in industrial control equipment. Whether in the railway transport sector or industrial fields, it will play an irreplaceable role.

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