AON7421 Discrete Semiconductor Products

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AON7421 is a single chip, monolithically integrated logic level enhancement mode N-channel MOSFET. It is designed and developed by a company called ams, specifically targeting to provide a low cost digital Logic-IN feature, which is useful in recognizing small positive digital signals when these signals source relatively large capacitive loads. This digital Logic-IN feature is often needed in automotive, consumer, industrial and many other digital applications. This article explains AON7421 application field and working principle in detail and categorizes it under the umbrella of Transistors, FETs and MOSFETs - Single.

Application field and features

AON7421 is mainly used in three distinct application fields, namely automotive, consumer and industrial. In consumer application field, AON7421 is often used to provide a high current signal path for many operations, such as backlight initialization. In the automotive field, AON7421 is mainly used for controlling the output of powertrain systems for engine management applications. Finally, in industrial application field, AON7421 is utilized for controlling motion and power management.

AON7421 not only provides a low cost digital logic-in feature but also presents several other features. These features mainly include a wide operating supply voltage range, improved channel-to-channel tolerance and digital logic level threshold. The device is offered in a small, surface mount 1.6mm x 0.8mm package. Furthermore, it enjoys high level of ruggedness due to its small die size, hence making it more suitable for applications that require long life time.

Working Principle

AON7421 encompasses both the design logic and a special circuit as a combination. The design logic involves designing a logic circuit with logic level shift in order to accommodate the lower logic levels needed for high current operation. The circuit generalization that is used for this purpose is the controlled current source, which is basically a current source connected between VGS and GND. The logical implication for this circuit is that when the input signal rises above a specified level, the voltage is blocked from going to the drain in order to limit the current through the MOSFET.

The circuit also includes a special feature called the input leakage path. Basically, this leakage path helps to prevent any unused current from leaking away from the transistor gate. The input leakage path consists of an additional resistor or capacitor that is placed immediately adjacent to the gate in order to provide a low resistance path for any unused current. The primary benefit of this addition is that it makes sure that the transistor gate is not sitting idle and leaking away any current.

In order to protect the device from parasitic device damages generated during switching, AON7421 also comprises an avalanche diode along with built-in avalanche protection. The avalanche diode shunt any output or input switching transients which occurs when the power supply is switched off. This realizes an improved robustness in the applications where the AON7421 is utilized.

In summary, AON7421 is a single chip, monolithically integrated logic level enhancement mode N-channel MOSFET specifically designed and developed to provide a low cost digital Logic-IN feature that can be used in multiple applications. It mainly enjoys a wide operating supply voltage range, improved channel-to-channel tolerance, digital logic level threshold, earthquake protection and input leakage path. These features make it suitable for robust and reliable applications, specifically in automotive, consumer and industrial fields.

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