|Input Type||VIN (MIN)
|DC||24||24||0.05 to 2||Multiple||-20 to 20||1 to 40||Non-Isolated||Synchronous Buck|
This document describes a circuit that uses three MAX17541G buck converters and one MAX17504 step-down DC-DC converter. The circuit is arranged so that each buck converter uses the same input with four separate outputs. Each output has a different power specification. The MAX17541G regulator and features are given first, followed by the MAX17504 features.
The MAX17541G high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs operates over a 4.5V to 42V input. The converter can deliver up to 500mA and generates output voltages from 0.9V up to 0.92 x VIN. The feedback (FB) voltage is accurate to within ±1.7% over the -40°C to +125°C operating temperature range. The MAX17541G uses peak-current-mode control with pulse-width modulation (PWM) and operates with fixed 600kHz switching frequency at any load.
The MAX17504 is also a high-efficiency, high-voltage, synchronous step-down DC-DC converter with integrated MOSFETs and operates over a 4.5V to 60V input. The converter can deliver up to 3.5A current. Output voltage is programmable from 0.9V to 0.9 x VIN. The feedback voltage regulation accuracy over -40°C to +125°C is ±1.1.%. The MAX17504 also features a peak-currentmode control architecture. The device can be operated in the pulse-width modulation (PWM), pulse-frequency modulation (PFM), or discontinuous-conduction mode (DCM) control schemes. A programmable soft-start feature allows users to reduce input inrush current. The device also incorporates an output enable/undervoltage lockout pin (EN/UVLO) that allows the user to turn on the part at the desired input voltage level. An open-drain active-low RESET pin provides a delayed power-good signal to the system upon achieving successful regulation of the output voltage.
A multiple buck converter circuit using three MAX17541G devices (VOUT1,2,3) and one MAX17504 device (VOUT4) is demonstrated for a single 24V input application. The power supply delivers up to four separate outputs.
This document describes the hardware shown in Figure 1. It provides a detailed systematic technical guide to designing a buck converter circuit using Maxim’s MAX17541G and MAX17504 current-mode controllers. The power supply has been built and tested, details of which follow later in this document.