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Circuit Breaker IC Does Just That and Much More

Like the IC eFuse, which adds functions and features to a classic passive overcurrent and safety device, the LTC4249 does the same for the venerable electromagnetic or thermal circuit breaker. The traditional circuit breaker, also known as a resettable overcurrent cutoff device, has been around since the 1920s and is well-known for its consistent and reliable function as well as a simple schematic representation (Fig. 1). Whether the breaker is designed to activate in response to a current overload identified by thermal or electromagnetic circumstances (both are employed), the design goal and subsequent implementation are laser-focused on performing one thing well. (Of fact, circuit breakers and fuses aren’t the only circuits and overcurrent protection devices, but that’s another subject.)
1- The original standard circuit breaker (with its deceptively simple schematic symbol) is actuated by thermal or electromagnetic energy and has only one function: to provide overcurrent protection, which it performs consistently and reliably. (Photo courtesy of Wikipedia)
While having a singular concentration is admirable, it can be constraining in terms of system design flexibility and variety. An electronic circuit breaker (ECB), such as Analog Devices’ LTC4249, comes in handy in this situation (Fig. 2). This dual ECB has capabilities, functionalities, and flexibility that a traditional circuit breaker does not have.
2- The LTC4249 dual electronic circuit breaker (ECB) is rated at 65 V/1.2 A and has capabilities and functions that a normal breaker does not have. It’s used to provide bias for the 1-A servo function of a sequenced GaN power amplifier with 1.2-A protection.

Due to its relatively high voltage rating along with a 1.2-A current rating, it’s able to deliver current oversight and protection across a wide range of applications, including protection for power-amplifier arrays, industrial safety, equipment-condition monitoring, relay replacement, and load switching.

It may provide current supervision and protection across a wide range of applications, including protection for power-amplifier arrays, industrial safety, equipment-condition monitoring, relay replacement, and load switching, thanks to its comparatively high voltage rating and 1.2-A current rating. Overcurrent protection for two loads is provided by the LTC4249 dual ECB. With a single resistor to define the ECB threshold, each channel includes a precision enable input, current-monitor output, and ready status output. The associated breaker disconnects the input from the load if an overcurrent condition is detected on either channel.
It’s worth noting that the relationship between a traditional circuit breaker and an electronic circuit breaker is similar in some respects to the relationship between a traditional fusible-link device (fuse) and an electronic fuse (eFuse). The former has a single-minded functionality but lacks flexibility—which may be good or bad, depending on your point of view—while the latter is more sophisticated but adds more features, functions, and alternatives to the designer and circuit approach. The open-drain RDY status output pulls low after any circuit-breaker “event,” and the ECB latches into the off state. After a one-second cool-off time, the user can switch the ECB back on by toggling the enable input. The circuit breakers’ cool-off timer, overtemperature sensor, short-circuit detector, and inrush controller all prohibit operation outside the circuit breakers’ safe working region.
Voltage sequencing and closed-loop-bias current-control applications are made easier by the LTC4249’s precision enable inputs, ready outputs, and analog current-monitor outputs. 5 percent accurate analog current-monitor outputs, filtered (50 s) main overcurrent threshold, quick (2 s) secondary overcurrent threshold, and integrated 75-m switches are among the other significant requirements. The LTC4249, with a temperature range of 40 to +125°C, costs $2.39. (1,000 pieces). The chip is packaged in a 16-lead, 3-mm LQFN package. A 12-lead “skipped leading” 3- 4″ mm LQFN package is also available for applications that must fulfill creepage and clearance specifications up to 65 V.

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