LINEAR LTM4616 User Guide

L DESIGN IDEAS

Dual 8A DC/DC µModule Regulator Is Easily Paralleled for 16A

by Eddie Beville and Alan Chern

Two Independent 8A

Regulator Systems in a Simple and Efficient

Single Package The LTM4616 can be used as com- one another, making the top value The LTM4616 is a dual input, dual pletely independent dual switching 5k. output DC/DC µModule regulator in a regulators with different inputs and It is preferred to connect CLKOUT1 15mm × 15mm × 2.8mm LGA surface outputs or paralleled to provide a to CLKIN2 when operating from a mount package. Only a few external single output. Figure 1 shows a typical single input voltage. This minimizes components are needed since the design for a 5V common input and two the input voltage ripple by running switching controller, MOSFETs, induc- independent outputs, 1.8V and 1.2V. the two regulators out of phase with tor and other support components are Figure 2 shows the efficiency of the each other. If more than 16A output integrated within the tiny package. circuit at both 5V and 3.3V inputs. current is required, then multiple Both regulators feature an input Few external components are needed LTM4616 regulators can be configured supply voltage range of 2.375V to since the integrated output capacitors for multiphase operation with up to 12 5.5V and an adjustable output voltage can accommodate load steps to the full phases via the PHMODE pin. Figure range of 0.6V to 5V with up to 8A of 8A. Each output voltage is set by a single 4 shows the expected efficiency of continuous output current (10A peak). set resistor from FB1 (or FB2) to GND. the parallel system at 5V and 3.3V For higher output current designs, the In parallel operation, the FB pins can inputs to 1.8V output. Note that the LTM4616 can operate in a 2-phase be tied together with a single resistor parallel mode allowing the part to for adjustable output voltage. deliver a total output current of 16A.

The default switching frequency is Parallel Operation for set to 1.5MHz, but can be adjusted Increased Output Current

EF FI CI EN CY

to either 1MHz or 2MHz via the You can double the maximum output PLLLPF pins. Moreover, CLKIN can be current to 16A by running the two externally synchronized from 750k Hz outputs in parallel as shown in Figure

A: 5VIN = 1.2VOUT

to 2.25MHz. The device supports 3. Note that the FB pins share a single

B: 3.3VIN = 1.2VOUT output voltage tracking for supply rail voltage-set feedback resistor that is C: 5VIN = 1.8VOUT D: 3.3VIN = 1.8VOUT

sequencing. Safety features include half the value of the feedback resistor protection against short circuit, in the usual two output configuration.

LOAD CURRENT (A)

overvoltage and thermal shutdown This is because the internal 10k top conditions. feedback resistors are in parallel with Figure 2. LTM4616 efficiency: dual output

VOUT2

SW1 CLKIN1 CLKOUT1 CLKIN2 CLKOUT2VIN1 VOUT1 1.8V

3.3V to 5V

C2 8AC3

SVIN1 FB1

C1 RSET2 C4

RUN1 ITH1

PLLLPF1 ITHM1

LTM4616 100µF

MODE1 PGOOD1

(15mm 15mm 2.8mm)

PHMODE1 BSEL1 TRACK1 MGN1

VOUT1

VIN2 VOUT2 1.2V

SVIN2 FB2

RSET1 C7

RUN2 ITH2

PLLLPF2 ITHM2

MODE2 PGOOD2 PHMODE2 BSEL2

TRACK2 SW2 SGND1 GND1 SGND2 GND2 MGN2

Figure 1. Dual output LTM4616 for a single 3.3V to 5V input, independent 1.8V and 1.2V outputs at 8A each

Linear Technology Magazine • September 2009