Self-Contained 3A μModule Buck Regulator Produces 0.8V–24V Output from 3.6V–36V Input

by David Ng

2009-09-01

186.9 K

Introduction

Ask any group of engineers, “What would you do with a 3A DC/DC converter?” and you will probably get a wide range of answers—from powering a DSP rail at 1.8V to running a bank of 24V switching I/O. Typically, these two particular applications would require completely different DC/DC controller ICs and topologies. However, the LTM8025 μModule DC/DC converter can satisfy the requirements of these and just about any other 3A applications.

The LTM8025 3A μModule DC/DC buck converter operates from 3.6V to 36V inputs to produce output voltages as low as 0.8V and as high as 24V. Furthermore, the LTM8025 features single cycle Burst Mode^® operation, so it is able to handle a wide range of load currents, from no load to 3A, with minimum ripple.

The LTM8025 integrates the controller, control circuitry, inductor, power switch and rectifier all into a single IC form factor 15mm × 9mm × 4.32mm package. This LGA package is RoHS (e3) compliant, and features gold pads for easy assembly in both leaded and unleaded solder processes.

Easy Layout

The LTM8025’s high level of integration simplifies the design of just about any 3A power supply. Just add two resistors, input and output capacitance to make a complete power supply. Layout is easy, as shown in Figure 1. Figures 2 and 3 show the schematic and efficiency of the LTM8025 producing 12V bus power from a 24V source, while Figure 4 shows the LTM8025 producing 1.8V from an input range of 3.6V to 36V.

Figure 1. Layout is easy with the LTM8025.

Figure 2. A complete 12V at 3A power supply requires only the LTM8025, two capacitors and two resistors.

Figure 3. The LTM8025 boasts high efficiency.

Figure 4. The LTM8025 can produce low voltages from a wide input range.

Versatile Feature Set

The LTM8025 may be operated over a wide frequency, from 200kHz to 2.4MHz, and may be synchronized to an external clock source through the SYNC pin. The LTM8025 start-up is controlled through its RUN/SS pin, which also serves to put the part into a low power off state in which the part draws less than 1μA. Furthermore, the part comes with a PGOOD pin to indicate that the output is within 90% of its target voltage.

Parallel Multiple LTM8025s for High Current Capability

The LTM8025 is equipped with a SHARE pin to allow parallel operation for applications requiring more than 3A load current. Figure 5 shows two synchronized LTM8025’s providing 2.5V_OUT at 5.6A.

Figure 5. Two LTM8025s can be operated in parallel for more than 3A load current.

Conclusion

The highly versatile LTM8025 3A μModule DC/DC buck converter is easy to use and fits just about any step-down regulator need. Its wide input and output ranges and high level of integration reduce design effort and associated costs.