LX1553ID

LX1553ID Application Field & Working Principle

The LX1553ID is a switching controller that belongs to the PMIC – Voltage Regulators – DC DC Switching Controllers. It has various application fields, such as automotive, industrial, medical, communications, and networking applications.

This device is a high efficiency, integrated, and low cost switching controller specifically designed for high current, high voltage DC-DC converters. The LX1553ID operates in a wide supply voltage range from 4.5V to 90V with fast transient response and high switching frequency, up to 1 MHz, thus allowing for higher integration of devices and components.

The operating principles and specifications of the LX1553ID can be best explained with the help of the block diagram shown below (Figure 1). In this block diagram, the main components are the voltage sense mechanism, the current sense mechanism, the power MOSFET gate driver, the error amplifier, the PWM comparator, and the connections with the external components that include a frequency set resistor, compensation networks, and so forth.

The sense of the voltage and current is done using a closed loop system. The voltage at the output is sensed by an error amplifier which is connected to the voltage comparator inside the device. The error amplifier then compares this sensed voltage to an external reference voltage and adjusts the necessary input to keep the output voltage constant. The same mechanism is used to sense the current and adjust the PWM comparator\'s input, thus ensuring that the maximum current of the output stays within the limits specified by the device.

The power MOSFET gate driver inside the device is responsible for driving the external MOSFETs connected to the device, thus regulating the power delivered to the load. The gate driver also ensures the MOSFETs are properly turned on and off to prevent overloading and ensure a smooth operation. The PWM comparator inside the device is also used to ensure a proper switching of the MOSFETs. This comparator compares the error amplifier\'s output to an externally set frequency, and accordingly, either turns the MOSFETs on or off.

The LX1553ID also includes an internally integrated oscillator circuit and requires only an external resistor (R3) to set the frequency of the PWM. It also provides two enable pins (EN1 and EN2) to enable/disable the operation and helps preventing the device to be damaged in the case of an overtemperature condition. Finally, the device also provides an output voltage accuracy range of 0.5%.

Overall, this feature set makes the LX1553ID an ideal switching controller for high-current, high-voltage applications. Its low cost, wide supply voltage range, fast transient response, and high switching frequency allow for smaller and more integrated designs, making it a versatile device for various DC-DC converter applications.