DEMO CIRCUIT 1324A PDC QUICK START GUIDE LTC3672BEDC-2: Monolithic Fixed-Output 400mA Buck Regulator with Dual 150mA LDOs in 2mm X 2mm DFN DESCRIPTION Demonstration Circuit 1324A is a monolithic 400mA Design files for this circuit board are available. Call Buck regulator, with fixed output, and two 150mA, the LTC factory. Low Drop Out linear regulators. These are housed in L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy an 8 lead, 2mm X 2mm DFN package. Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VIN Input voltage 2.9 5.5 V VOUT1 Output of regulator (buck) 1 I 400mA 1.17 1.23 V OUT1 VOUT2 Output of LDO1 I 150mA. Subject to dropout limitations. 2.73 2.87 V OUT2 VOUT3 Output of LDO2 IOUT3 150mA 1.755 1.845 V OPERATING PRINCIPLES The LTC3672BEDC-2 is a monolithic fixed output, LTC3672BEDC-1 400mA, synchronous buck regulator and two 150mA VOUT = 1.2V LDOS. VOUT1 is driven by a high efficiency synchronous buck 100 90 regulator with a fixed output of 1.2V. The buck regulator 80 on the LTC3672BEDC-2 operates at approximately 70 2.25MHz, allowing the use of small inductors and 60 50 capacitors. 40 30 The two fixed output LDOs, have a maximum dropout 20 voltage of 250mV, over process and temperature. This 0 100 200 300 400 allows all three outputs to remain in regulation with VIN LOAD CURRENT mA as low as 2.98V. Efficiency of the Buck regulator at VIN = 3.6V All of the regulators on the LTC3672BEDC-2 are enabled via the ENALL pin, controlled by JP1. 1 Efficiency % QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1324A FIXED-OUTPUT 400MA BUCK REGULATOR WITH DUAL 150MA LDOS LTC3672BEDC-2 AM1 - + + + LD1 VM2 0V-5V - - 1A - LD2 - 0V-5V VM3 + 1A AM2 + - + - PS1 - 0V-6V 2A Supply VM1 - LD3 - + + VM4 0V-5V + 1A + AM3 - + Figure 1: Test Equipment Hookup Diagram 1) Connect test equipment as shown in Figure 1. Set PS1 = 0V, set PS1 Ilimit = 1A, set LD1 = 0A, LD2 = 0A, LD3 = 0A, and JP1 = ON. 2) Slowly increase PS1 and verify that all regulators are operational at VIN 2.9V. 3) Set PS1 = 3.6V, and JP1 = ON. Verify VM2 = 1.17V~1.23V, VM3 = 1.755V ~ 1.845V, and VM4 = 2.73V~2.87V. 4) Set PS1 = 2.9V, LD1 = 400mA. Verify VM2 = 1.17V~1.23V. 5) Set LD2 = 150mA, LD3=150mA. Verify that VM3 = 1.755V~1.845V, and VM4 = 2.65~2.87V. 6) Set PS1 = 5.5V, and repeat step 5. 7) Set JP1 = OFF, set PS1 = 2.9V, verify that all output voltages (VM2-4) are 0V. 8) Set PS1 = 5.5V, verify that all output voltages (VM2-4) are 0V. 9) Set PS1 = 0V, set JP1 = ON. 2