LINEAR Step-Down µModule Regulator Produces 15A Output from Inputs Down to 1.5V—No Bias Supply Required

Step-Down µModule Regulator Produces 15A Output from Inputs Down to 1.5V—No Bias Supply Required 1.5V to 5.5V Input, 0.8V to 5V Output from a 15mm × 15mm × 4.32mm LGA Package Design Note 488 Alan Chern and Jason Sekanina 15A High Efficiency Output from a Low Input Voltage

The LTM®4611 is a switch mode, step-down DC/DC µModule® 1.8V TO

regulator in a compact 15mm × 15mm × 4.32mm LGA surface 5.5V

mount package. The switching controller, MOSFETs, inductor CSS

0.1µF VIN PGOOD

18mΩ ESR

and supporting components are housed in the package. With VOUT

TRACK/SS VOUT 1.5V

a built-in differential remote sense amplifier, the LTM4611 can CFF

EF FI CI EN CY VFB 47p F

LTM4611

tightly regulate its output voltage from 0.8V to within 300m V of

VOUT_LCL

VIN and deliver 15A output efficiently from 1.5V to 5.5V input. RUN

DIFFVOUT

MODE_PLLIN ×4

Only a handful of components are needed to create a complete

VOSNS

point-of-load (POL) solution with the LTM4611 (see Figure 1).

VOSNS

SGND GND

The CSS capacitor provides smooth start-up on the output and limits the input surge current during power-up. CFF and

CP set the loop-compensation for fast transient response 69kΩ DN488 F01

and good stability. The output voltage, 1.5V, is set by a single

*OPTIONAL

resistor, RSET.

Efficiency is exceptional, even down to the lowest input volt- Figure 1. 1.8VIN to 5.5VIN to 1.5VOUT ages, as shown in Figure 2. with 15A Output Load Current

Input and Output Ripple Output capacitors should have low ESR to meet output volt- age ripple and transient requirements. A mixture of low ESR polymer and/or ceramic capacitors is sufficient for produc- ing low output ripple with minimal noise and spiking. Output capacitors are chosen to optimize transient load response and loop stability to meet the application load-step requirements by using the Excel-based LTpower CAD™ design tool. (Table 5 of the LTM4611 data sheet provides guidance for applications with 7.5A

1.8V TO 1.5V

L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered

2.5V TO 1.5V

trademarks and LTPower CAD is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners. 3.3V TO 1.5V 5V TO 1.5V

OUTPUT CURRENT (A)

DN488 F02

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informative videos. Figure 1 Circuit

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