PT4485A

DC-DC Converters

DC-DC converters are electronic devices used for converting direct current (DC) from one voltage level to another. They are a common power source for a variety of applications, and can be used to boost, buck, or invert the input voltage. A popular DC-DC converter is the PT4485A from Powertech, which is capable of converting a DC input of 4.5 to 40 VDC to a regulated output voltage of 0.8 to 38 VDC.

PT4485A Application Field and Working Principle

The PT4485A is a highly efficient buck DC-DC converter, featuring integrated MOSFETs and low output voltage ripple. It features a wide range of input and output voltage options (4.5 to 40 VDC, 0.8 to 38 VDC), making it suitable for a range of applications, such as powering embedded systems, medical equipment, and UPS systems. It is also commonly used in point-of-load rails in power distribution systems. It has an internal switch frequency of 800 kHz, and delivers a high power density in a compact 12-pin package.

The PT4485A operates on the principle of the buck converter. It works by regulating the output voltage by varying the on time of an internal MOSFET switch. When the internal switch is on, it draws current from the input voltage and charges an inductor (L1). When the switch is off, the inductor delivers current to the output. The ratio between the on time and off time of the switch (known as duty cycle) determines the voltage at the output. By maintaining a constant duty cycle, the output voltage of the converter can be regulated.

The other components of the converter also play important roles: the diode (D1) helps convert high frequency current generated from the switch into a DC voltage, and the capacitor (COUT) is used for filtering the output voltage to minimize ripple. The controller (U1) is an integral part of the converter, and regulates the switches’ on time to maintain the expected output voltage. The feedback resistor divider (R1, R2) is used to measure the output voltage and send the information back to the controller. The internal control loop is then used to adjust the duty cycle of the switch accordingly.

Benefit of the PT4485A

The PT4485A offers several advantages over traditional buck converters. It features high efficiency, with up to 95% efficiency at full load, as well as low output voltage ripple (typically less than 10 mV). It also features an adjustable soft-start feature, which helps reduce the inrush current typically observed during power-up. Additionally, it has built-in thermal shutdown, current limit, overvoltage protection, and short-circuit protection, providing robust protection to the system.

Conclusion

The PT4485A is a highly efficient buck DC-DC converter, capable of converting a DC input of 4.5 to 40 VDC to a regulated output voltage of 0.8 to 38 VDC. It features built-in protections and soft-start features, as well as low output voltage ripple and high efficiency. The device is suitable for a range of applications, such as powering embedded systems, medical equipment, and UPS systems. It is also commonly used in point-of-load rails in power distribution systems.