MAXREFDES1120: 3.3V/4A Synchronous Step-Down DC-DC Converter Using the MAX15038

Introduction

The MAX15038 is a synchronous buck converter which delivers up to 4A load current at output voltages from 0.6V to 90% of VIN. The integrated circuit (IC) supports the input voltage from 2.9V to 5.5V. The total output error is less than ±1% overload, line, and temperature ranges. The MAX15038 features fixed-frequency pulse-width modulation (PWM) mode operation with a switching frequency range of 500kHz to 2MHz set by an external resistor. It also provides the option of operating in a skip mode to improve light-load efficiency. High-frequency operation allows for small-size external components and an all-ceramic capacitor design. The low-resistance integrated nMOS switches ensure high efficiency at heavy loads while minimizing critical inductances, making the layout a much simpler task with respect to discrete solutions.

The MAX15038 comes with a high-bandwidth (28MHz) voltage-error amplifier. The voltage-mode control architecture and the voltage-error amplifier permit a Type III compensation scheme to be utilized to achieve maximum loop bandwidth, up to 20% of the switching frequency. High loop bandwidth provides fast transient response, resulting in less required output capacitance and allowing for all-ceramic capacitor designs.

The MAX15038 provides two three-state logic inputs to select one of the nine preset output voltages. The preset output voltages allow users to achieve ±1% output-voltage accuracy without using expensive 0.1% resistors. In addition, the output voltage can be set to any custom value by either using two external resistors at the feedback with a 0.6V internal reference or applying an external reference voltage to the reference input (REFIN). The MAX15038 offers programmable soft-start time using one capacitor to reduce input inrush current.

特征

Internal 31mΩ RDS(ON) high-side and 24mΩ RDS(ON) low-side metal-oxide semiconductor field-effect transistors (MOSFETs)
Continuous 4A output current over temperature
±1% output accuracy overload, line, and temperature
Soft-start reduces inrush supply current
500kHz to 2MHz adjustable switching frequency
Monotonic startup for safe-start into prebiased outputs
Selectable forced PWM or skip mode for light-load efficiency
Overcurrent and overtemperature protection
Output current sink/source capable with cycle-by- cycle protection
Open-drain power-good output