LINEAR Dual Module DC/DC Regulator Produces High Ef ciency 4A Outputs from a 4.5V to 26.5V Input Design Note 474 Alan Chern
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1. DESIGN ECHNOLOGY NO T P S Dual uModule DC DC Regulator Produces High Efficiency 4A Outputs from a 4 5V to 26 5V Input Design Note 474 Alan Chern Dual System in a Package Regulator systems and PC boards that use FPGAs and ASICs are often very densely populated with components and ICs This dense real estate especially the supporting circuitry for FPGAs such as DC DC regulators puts a burden on system designers who aim to simplify layout improve performance and reduce component count A new fam ily of DC DC uModule regulator systems with multiple outputs is designed to dramatically reduce the number of components and their associated costs These regula tors are designed to eliminate layout errors and to offer a ready made complete solution Only a few external components are needed since the switching controllers 15mm eam P LINEAR A MUG19V kd dn474 F01 Figure 1 The LTM4619 LGA Package Is Only 15mm x 15mm x 2 82mm and Houses Dual DC DC Switching Circuitry Inductors MOSFETs and Support Components power MOSFETs inductors compensation and other sup port components are all integrated within the compact Surface mount 15mm x 15mm x 2 82mm LGA package such easy layout saves board space and design time by implementing high density point of load regulators The LTM 4619 switching DC DC Module converter regulates two 4A outputs from a single wide 42. 5V to 26 5V input voltage range Each output can be set be tween 0 8V and 5V with a single resistor In fact only a few components are needed to build a complete circuit See Figure 2 Figure 2 shows the LIM4619 Module regulator in an application with 3 3V and 1 2V outputs The output volt ages can be adjusted with a value change in Rsgeq4 and Ref7o Thus the final design requires nothing more than a few resistors and capacitors Flexibility is achieved by pairing outputs allowing the regulator to form different combinations such as single input dual independent outputs or single input parallel single output for higher maximum current output 47 LI LTC LTM Linear Technology the Linear logo Burst Mode and Module are registered trademarks of Linear Technology Corporation All other trademarks are the property of their respective owners V MODE INTV FREQ 265V 10uF FSET LLIN PLLFLTR RSET2 D 431k 19 1k _L VFB1 VFB2 22pF COMP1 ane COMP2 22pF VouT1 VouT2 1 2V 4A Vout VouT2 3 3V 4A T TK SS1 TK SS2 J e PGOOD SGND PGND EXTVcc dn474 F02 Figure 2 4 5V to 26 5V Input to Dual 3 3V and 1 2V Outputs with 4A Maximum Output Current Each 01 10 474 The efficiency of the system design for Figure 2 is shown in Figure 3 and power loss is shown in Figure 4 both at various input voltages Efficiency at light load operation can be improved with selective pulse skipping mode or Burst Mode operati
3. dual output voltage regulation from a single package making the LTM4619 an easy choice for system designs needing multiple voltage rails 3 0 a on POWER LOSS W T Oo 2 CURRENT A azaroa Figure 4 Power Loss of the Circuit in Figure 2 at Different Input Voltages for 3 3V and 1 2V Outputs 546 tE 2500 630CUIFNLT1 Figure 5 LTM4619 Exceptional Thermal Performance of a Paralleled Output Module Regulator 12Vjy to Paralleled 1 5Voyr at 8A Load Data Sheet Download www linear com T Ae abge 28 Corporation 1630 McCarthy Blvd Milpitas CA 95035 7417 408 432 1900 FAX 408 434 0507 www linear com For applications help call 408 432 1900 Ext 2593 dn474 LT TP 1110 116K PRINTED IN THE USA LT MYR LINEAR TECHNOLOGY CORPORATION 2009
4. on by tying the mode pin high or leaving it floating Multiphase Operation for Four or More Outputs For a 4 phase 4 rail output voltage system use two LTM4619s and drive their MODE_PLLIN pins with a LTC 6908 2 oscillator such that the two Module devices are synchronized 90 out of phase Reference Figure 21 in the LTM4619 data sheet Synchroniza tion also lowers voltage ripple reducing the need for high voltage capacitors whose bulk size consumes board space The design delivers four different out put voltage rails 5V 3 3V 2 5V and 1 8V all with 4A maximum load EFFICIENCY CURRENT A Figure 3 Efficiency of the Circuit in Figure 2 at Different Input Voltage Ranges for 3 3V and 1 2V Outputs Thermal Performance Exceptional thermal performance is shown in Figure 5 where the unit is operating in parallel output mode Single 12Viy to a single 1 5Voy7 at 8A Both outputs tied together create a combined output current of 8A with both channels running at full load 4A each Heat dissipation is even and minimal yielding good thermal results If additional cooling is needed add a heat sink on top of the part or use a metal chassis to draw heat away Conclusion The LTM4619 dual output Module regulator makes it easy to convert a wide input voltage range 4 5V to 26 5V to two or more 4A output voltage rails 0 8V to 5V with high efficiency and good thermal dissipation simplicity and performance are achieved through
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