L9911K

Special Purpose Voltage Regulators are specifically used to control the voltage that is applied to an electronic device or an electrical circuit, making it an essential component in electrical engineering. The L9911K is a voltage regulator IC which is mainly used in Li-ion battery charging, DC-DC voltage conversion, and adjustable current control applications. This article seeks to explain the application fields and working principles of the L9911K voltage regulator.

Features of L9911K Voltage Regulator

The L9911K is a highly versatile voltage regulator that offers several key features, including:

• Input Current limit up to 1000mA
• Operating voltage between 6V and 40V
• Minimum programmable output current of 150mA and maximum current of 950mA
• Programmable output voltage ranging between 0.8V and 5V
• Disable active low function and an open-drain enable pin
• Programmable Device Shutdown Temperature of 120’C
• Low Power Consumption of 4mW
• 1.2MHz switching frequency
• Integrated Undervoltage Lockout (UVLO)
• Cycle-by-cycle current limit

Application Fields of L9911K Voltage Regulator

The L9911K is mainly used in three areas:

Li-ion Battery Charging

The L9911K can be used to control the charging of Li-ion batteries. It offers precise adjustable voltage and current regulation for optimal and safe charging of Li-ion batteries. It also has an integrated safety timer that helps in limiting the duration of the charge cycle, thereby preventing over-charging and damage to the battery cells.

DC-DC Voltage Conversion

The L9911K can be used to control the conversion of voltage between a DC input and a DC output. It can be used to convert and regulate a wide range of input and output voltages, making it suitable for a variety of applications. It has an integrated circuit protection mechanism which helps in protecting the entire system from overvoltages, short circuits, overcurrents, and thermal overloads.

Adjustable Current Control

The L9911K also offers a precise adjustable current control feature, which makes it suitable for driving a wide range of loads. It can accurately regulate a constant current to a load, regardless of the input voltage or load conditions. This feature helps in maintaining a steady current across the entire system, allowing for advanced control and stable operation.

Working Principle of L9911K Voltage Regulator

The L9911K voltage regulator is based on a Pulse Width Modulation (PWM) step-up topology. It has an internal oscillator that produces a switching waveform at a frequency of up to 1.2MHz. This waveform is used to turn on and off two power transistors that drive the output voltage. The width of the switching waveform is then used to control the current flowing through the output section.

The output voltage of the L9911K voltage regulator is regulated by an on-chip error amplifier that compares it to a reference voltage. When the output voltage is lower than the reference voltage, the error amplifier switches on the transistor, causing more current to flow through the output section of the regulator, thus increasing the output voltage. On the other hand, when the output voltage is higher than the reference voltage, the error amplifier switches off the transistor, causing less current to flow through the output section, thus lowering the output voltage.

Conclusion

The L9911K voltage regulator is a highly versatile device that can be used in various applications requiring precise current and voltage regulation. Its features, such as its wide input/output range and its precise adjustable current and voltage regulation, make it an ideal choice for Li-ion battery charging, DC-DC voltage conversion, and adjustable current control applications. Its working principle of utilizing a PWM step-up topology and an on-chip error amplifier for output voltage regulation further adds to its versatility and reliability.