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Integrating robust circuit protection is fundamental in circuit design, especially when designing or developing today’s demanding portable battery-operated devices. One of the most critical components that goes into a resilient circuit design is the fuse. Fortunately, engineers have a wide range of devices to choose from. Some of these options, like polymer positive temperature coefficient (PTC) fuses, are resettable; others, like chip and glass tube fuses, offer one-shot protection. Although these tried-and-true, single-function devices are viable options depending on the application, there are smarter, more effective, multifunctional circuit protection solutions to help alleviate circuit safety concerns and simplify designs.

This week’s New Tech Tuesday spotlights Toshiba's TCKE9 4A eFuse ICs. These cutting-edge resettable MOSFET switch ICs deliver enhanced circuit protection performance with integrated functionality into a compact device that is ideal for applications such as portable electronics requiring high-density soldering.

The Newest Products for Your Newest Designs^®

Toshiba’s TCKE9 series are single-input/single-output (SISO), multifunction, resettable electronic fuse (eFuse) devices. These eFuses combine exceptional fuse functionality with protection functions like adjustable overcurrent limit, short-circuit protection, high-speed overvoltage clamp, adjustable slew rate control, and adjustable undervoltage protection.

The TCKE9 eFuse power management modules are suitable for protecting the power supply circuit of the USB V_BUS line, storage power supply circuits, and battery charging applications in portable devices such as IoT sensors, smartphones, and wearable electronics.

The TCKE9 eFuse Advantage

In addition to a high 23V output voltage and 4A output current, the TCKE9 eFuse series offers current monitoring via an N-channel load MOSFET switch with ultra-low 34mΩ on-resistance and 0.03μA quiescent current. This function minimizes power losses, making the eFuses ideal for applications where power conservation is critical.

Additionally, the eFuses are available with auto-retry or latched fault responses (Table 1). For instance, when the overcurrent clamping operation is set to auto-retry, the TCKE9 will provide continuous resettable fuse functionality. If the current output is 1.6 times the overcurrent limit current (I_ILIM), then the device considers the output to be short-circuited (hard short) and will quickly fast-trip the MOSFET switch with a response time of 2.0μs. However, if the output I_ILIM is reached, the TCKE9 will sense an overcurrent condition with a response time of 80μs and throttle the MOSFET down to within the current limit.

If the overcurrent condition persists, the IC set to auto-retry will start to heat up until the temperature reaches the thermal shutdown temperature of 155°C, triggering the device to shut down. While in thermal shutdown, the TCKE9 will continue to monitor the temperature every 55ms and will automatically try to restart. If the overcurrent has not been resolved, it will once again limit the output current, and the recovery cycle will continue.

If the eFuse’s fault response is configured for latch, then the thermal shutdown recovery cycle will require a control signal trigger for the operation to continue. Like the overcurrent protection and short-circuit protection functions, the auto-retry type will attempt to recover from an overvoltage clamp, but the latched type will retain this state until it is restarted.

Table 1: The TCKE9's fault response according to the last two characters of the part number. (Source: Toshiba Electronic)

Tuesday’s Takeaway

The Toshiba TCKE9 eFuses offer an innovative, multifunctional circuit protection solution that is ideal for energy-conscious applications. These resettable eFuses help enhance system reliability with features like adjustable overcurrent limits, short-circuit protection, and ultra-low on-resistance for minimizing power losses. Their compact design and integrated protection capabilities make them the perfect choice for a wide range of applications.