TIDUEM8B March   2019  – February 2021

 

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2.2.4 TPS25921L

The TPS25921 device is a compact, feature-rich eFuse with a full suite of protection functions. The wide operating voltage allows control of many popular DC buses. The precise ±2% current limit, at room temperature, provides excellent accuracy making the TPS25921 device well-suited for many system protection applications. It provides robust protection for all systems and applications powered from 4.5 V to 18 V. For hot-plug-in boards, the device provides in-rush current control and programmable output ramp-rate.

The TPS25921 device integrates overcurrent and short-circuit protection. The precision overcurrent limit helps to minimize over design of the input power supply, while the fast response short circuit protection immediately isolates the load from input when a short circuit is detected. The device allows the user to program the overcurrent limit threshold between 0.4 A and 1.6 A via an external resistor.

The device provides precise monitoring of voltage bus for brown-out and overvoltage conditions and asserts fault for downstream system. Its threshold accuracy of 3% ensures tight supervision of bus, eliminating the need for a separate supply voltage supervisor chip. The TPS25921 device is designed to protect systems such as White Goods, STBs, DTVs, Smart Meters, and Gas Analyzers.

Additional features of the device include:

  • Overtemperature protection to safely shutdown in the event of an overcurrent event
  • Fault reporting for brown-out and overvoltage faults
  • A choice of latched or automatic restart mode

For electricity meters, many manufacturers are using wireless communication to transmit data. These wireless modules may require from hundreds of milliamps to a couple of Amps to operate during the signal emission. If there is a malfunction that causes the current drawn from the module to exceed the current allotted for the wireless module, the power supply could fail, which could affect the metrology side of the meter if it shares the same power supply source as the wireless module without some type of current limiting. To ensure that the metrology is working properly and accurately at any moment, it is important to have a way to control this current spike. The TPS25921 device resolves this issue by limiting the current provided to the wireless communication module.

In this design, the latched version (TPS25921L) of this part is used, which enable the system to choose when the eFuse is reset after a thermal shutdown event. When an overcurrent situation triggers the thermal shutdown event of the TPS25921L device, the current is limited by quickly opening it and triggering the FLT signal. This FLT signal is fed to the MSP432 MCU to let it know that an event happened. After a thermal shutdown event, the MSP432 MCU can pull the ENUV pin low to reset the device and start powering the wireless module again , assuming that the overcurrent condition is no longer present.