L4979D

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L4979D Application Field and Working Principle

The L4979D is an integrated negative low dropout (LDO) linear voltage regulator that can supply up to 800 mA of output current. With a 3.3V input voltage and an output voltage of 1.2V, it is suitable for many applications like myriads of power supplies, level shifters and voltage followers. The low output voltage of 1.2V is especially suitable for voltage control circuits.

Features

• Input Voltage Range: 2.5V ~ 7V
• Output Voltage Range: 1.2V ~ 5V
• Output Current: Up to 800mA
• Low Dropout: 300mV at 800mA
• Internal Thermal Shutdown
• Max Quiescent Current: 40µA at No load
• Quiescent Current Rises to 200µA at Full Load
• Good Ripple Rejection and Low Noise
• Excellent Line and Load Regulation
• Low Offset Voltage
• Stable with Low Equivalent Series Resistance (ESR) Ceramic Capacitors
• Available in 8-Pin DIP and SOIC Packages

Application Field of L4979D

The L4979D is designed to provide an accurate low-voltage power source and current control for a wide variety of applications. With the low output voltage of 1.2V, it is particularly suitable for powering integrated circuits that require a steady and precise voltage input. Typical uses of the L4979D include battery-powered devices, portable electronic products, systems power supplies, small basestations and instrumentation.

The L4979D can also be used in wireless communication, networking, and military systems. It is especially suitable for voltage control circuits in portable and automotive electronics where a low voltage is required. The wide input voltage range of 2.5V to 7V, low quiescent current, and overall efficiency make the L4979D an excellent choice for these applications.

Operation Principle

The L4979D is an integrated negative low dropout (LDO) linear voltage regulator that is quite simple in its operation. It works by regulating the current through a resistor between the output and ground. Theregulated output is determined by the resistor network connected to the adjustment pin, which sets the output voltage. When the device is connected to the input supply, a voltage divides equally through each resistor, setting the output voltage. When the output voltage drops below the desired voltage, current flows through the resistor, causing the output voltage to return to its regulated value.

As the load current changes, the output voltage will shift in order to maintain a constant output voltage. As the load increases, more current will flow through the resistor network, which increases the output voltage to compensate for the drop in the load current. Conversely, as the load decreases, the output voltage will drop in order to maintain the regulated voltage.

The L4979D also features an internal thermal shutdown to protect the device from over temperature. When the device temperature reaches 175°C, the device will shut down preventing any further damage to the device. It will remain in this shut down state until the temperature has dropped back to 125°C, at which point it will resume normal operation.

As a linear voltage regulator, the L4979D supplies a regulated output voltage with a low noise and good ripple rejection. It is an efficient device with a wide input voltage range, good line and load regulation, and low offset voltage. The device has excellent load transient response and is stable with ceramic capacitors. The Industry Standard 8-pin Dual-In-Line (DIP) and Thin SmallOutline Package (TSOP) packages make the L4979D an easy to use and versatile voltage regulator suitable for a variety of applications.

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