LD1117V

LD1117V Application Field and Working Principle

LD1117V is a versatile and high-performance adjustable series of linear voltage regulators from STMicroelectronics. It is designed for use in a wide range of applications, from general purpose power supply circuits to professional gaming and consumer electronics. The device offers a wide input voltage range, low noise operation and low output voltage ripple. It is suitable for use in applications where the output voltage needs to be precisely and accurately controlled.

Features

• Wide input voltage range (from 4.5V to 12V)
• Low dropout voltage (1.3V)
• Stable output voltage from 1.2V to 5.2V
• High power efficiency (over 90%)
• Up to 1.5A output current
• Low output voltage ripple (< 50mV)
• Thermal regulation (with external PNP pass transistor)
• Thermal shutdown protection

Applications

• Power supply for embedded system
• Portable power devices, such as laptops and cell phones
• Digital cameras and camcorders
• High performance TVs and set-top boxes
• Audio amplifiers and players
• Portable instrumentations
• Battery charger systems
• Game consoles and portable gaming devices

Working Principle

LD1117V is an adjustable linear voltage regulator that utilizes a standard three terminal design to provide a regulated output voltage from 1.2V to 5.2V. The device features a low dropout voltage of 1.3V and can provide up to 1.5A of output current. It achieves a high degree of accuracy and stability by using an internal bandgap reference voltage. The output voltage can be adjusted via a single external resistor.

At the heart of the device is a PNP pass transistor connected in series with an NMOS current source and an NPN current-balancing transistor. The PNP transistor is used to regulate the output voltage while the NMOS current source ensures that the PNP transistor remains in the active region. The NPN transistor is connected in parallel with the PNP transistor and helps to maintain stability by absorbing excess current.

When the device is powered up, the output voltage is regulated to the desired level. The internal bandgap reference sets the potential across the external resistor and the voltage is continuously monitored and adjusted in order to maintain the desired output voltage. If the output voltage rises too high, the current-balancing NPN transistor will switch off, limiting the output voltage and preventing it from rising any further. In the event that the output current is too high, the thermal protection circuit will shut down the output, preventing the device from overheating.

Conclusion

The LD1117V is an adjustable linear voltage regulator from STMicroelectronics. It offers a wide input voltage range, low dropout voltage, high power efficiency and excellent output voltage ripple performance. It is suitable for a wide range of applications, from embedded systems to consumer electronics. The device is easy to use and provides a simple, efficient and cost-effective way of regulating voltage levels.