LINEAR Triple Output DC-DC µModule® Regulator in 15mm x 15mm x 2.8mm SMT Package Replaces Up to 30 Discrete Components Design Note 469

Triple Output DC/DC µModule® Regulator in 15mm × 15mm × 2.8mm Surface Mount Package Replaces Up to 30 Discrete Components Design Note 469 Eddie Beville and Alan Chern Introduction to 5.5V and each delivers a resistor-set output voltage

When space and design-time are tight in multivoltage of 0.8V to 5V at 4A of continuous current (5A peak). The systems, the solution is a multioutput DC/DC regulator output voltages can track each other or another voltage IC. For more space and time constraint systems, a better source. Other features include, low output voltage ripple solution is an already-fabricated compact multioutput and low thermal dissipation.

DC/DC system that includes not only the regulator ICs

The VLDO regulator input voltage (1.14V to 3.5V) is ca-

but the supporting components such as the inductors,

pable of up to 1.5A of output current with an adjustable

compensation circuits, capacitors and resistors.

output range of 0.4V to 2.6V, also via a resistor. The VLDO Dual Switching 4A and 1.5A VLDO™ Regulators regulator has a low voltage dropout of 200m V at maxi- mum load. The regulator can be used independently, or

The LTM®4615 offers three separate power supply

in conjunction with either of the two switching regulators

regulators in a 15mm × 15mm × 2.8mm LGA surface

to create a high effi ciency, low noise, large-ratio step-

mount package: two switching DC/DC regulators and

down supply—simply tie one of the switching regulator’s

one very low dropout VLDO linear regulator (Figure 1).

outputs to the input of the VLDO regulator.

MOSFETs, inductors, and other support components are all built in. Each power supply can be powered individually Multiple Low Noise Outputs or together, to form a single input, three output design.

The LTM4615 is capable of operating with all three regu-

Moreover, for an otherwise complex triple output circuit

lators at full load while maintaining optimum effi ciency.

design, the task is eased to designing with only one device

A typical LTM4615 design (Figure 2) for a 3.3V input to

while the layout is as simple as copying and pasting the

three outputs has the VLDO input driven by VOUT2. The

LTM4615’s package layout. One LTM4615 replaces up to

effi ciency of this design is shown in Figure 3.

30 discrete components when compared to a triple-output

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

high effi ciency DC/DC circuit.

trademarks, and VLDO is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

The two switching regulators, operating at a 1.25MHz switching frequency, accept input voltages between 2.35V

VIN 3.3V

VOUT2

VIN1 VIN2

PGOOD1 PGOOD2

VOUT1 100μF

VOUT1 VOUT2

100μF FB1 LTM4615 FB2

COMP1 COMP2

TRACK1 TRACK2

VIN RUN/SS1 RUN/SS2 VIN

VOUT3

VOUT2 LDO_IN LDO_OUT

C3 EN3 FB3 C8

10μF BOOST3 PGOOD3 3.32k 4.7μF

GND1 GND2 GND3

DN469 F02

Figure 1. Three DC/DC Circuits in One Package Figure 2. Triple Output LTM4615: 3.3V Input,