ADP2504 Reference Design Reference Design PRD1198 FEATURES Single Buck-Boosted Output: 5 V Output Current: 600 mA Input voltage: 3.0-4.2 V Low Ripple Accurate constant current limit DESCRIPTION This ADP2504 Reference Design uses 3.0 V to 4.2 V for the input voltage. Design criteria are for small size and low cost. The ripple is less than 10mV. Transient response varies over the load range and is not considered high priority. The switching frequency is fixed at 2.5 MHz. The output is current limited to 600mA +/-10% and remains in constant current for Vout down to 2.5 V Table 1. User Target Specs, Vout1 Spec Target Value Actual Value Units Vout 5 5 Volts Iout 0.6 0.6 Amps Tamb 50 50 degC Vinmin 3.0 3.0 Volts Vinmax 4.2 4.2 Volts Table 2. Default Design Target Specs, Vout1 Spec Target Value Actual Value Units Vout ripple max N/A <0.010 Volts Ioutstep N/A 0.6 Apk Vout step error N/A N/A Volts MaxHeight N/A 1.25 mm Rev. 1 Reference designs are as supplied “as is” and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of reference designs. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Reference designs are not authorized to be used in life support devices or systems. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2009 Analog Devices, Inc. All rights reserved. Reference Design PRD1198 TABLE OF CONTENTS Features ......................................................................................................................................................................1 Description .................................................................................................................................................................1 Revision History.........................................................................................................................................................2 Schematic ...................................................................................................................................................................3 Bill of Materials..........................................................................................................................................................3 Simulation results .......................................................................................................................................................5 TABLE OF FIGURES Figure 1. Constant Current Limit Buck-Boost Schematic ....................................................................................3 Figure 2. Bode plot with 10 Ohm load..................................................................................................................5 Figure 3. Bode plot with 10 Ohm load and 470 uF aluminum output cap ............................................................6 Figure 4. Bode plot with 7 Ohm load (Vout = 4.2 V, constant current).................................................................7 Figure 5. Bode plot with 5 Ohm load (Vout = 3 V, constant current)....................................................................8 Figure 6. Transient with 10 Ohm load and 100 mA dynamic step ........................................................................9 Figure 7. Transient with 10 Ohm load and 100 mA dynamic step and 470 uF aluminum output cap ................10 REVISION HISTORY 12/24/2009—Revision 0: Initial Version 1/8/2010—Revision 1: Added bode plots for constant current operation Rev. 1 | Page 2 of 11 Reference Design PRD1198 SCHEMATIC Figure 1. Constant Current Limit Buck-Boost Schematic L1 Rout P Vin 5 Pvin Cin 1 Sw1 Pgnd Sw2 Vout Vout Co P Cout R1 P R2 P U1 R3 EN 6 EN Sync Vin Agnd Cbias FB 10 C1 D2a C2 A Rtop Rff Vs Vs Vin U2b Cff R4 D2b Vout A D1 Rbot U2a Cbyp A A P A A BILL OF MATERIALS Table 3. Bill of Materials Item # Des Mfg Part Number Component Specs 1 U1 ADI ADP2504ACPZ-R7 Current Mode Buck-Boost DC/DC Regulator 2 U2 ADI AD8542ARMZ-REEL 1MHz RtoR dual Opamp 3 L1 Coilcraft LPS4012-152 1.5H, 70 mOhm 4.0x4.0 inductor 4 D1 Diodes Inc. 1N4448HWT-7 5 D2 Fairchild 6 Cin TaiyoYuden Package Qty Area (mm^2) Height (mm) *Cost LFCSP-10 1 9 .8 1.40 MSOP-8 1 16.5 1.1 0.38 4x4 1 16.0 1.2 0.43 Single 125mA, 100V Signal Diode SOD-523 1 1.5 0.8 0.056 BAT54CWT1G Dual Common Cathode, 200mA, 30V Schottkey Diode SOT-323 1 5.3 1.1 0.041 JMK212 BJ106MG-T 10uF, 6.3V, X5R 0805 1 2.5 1.25 0.025 Rev. 1 | Page 3 of 11 Reference Design Item # PRD1198 Des Mfg Part Number Component Specs Package Height (mm) *Cost 7 Co TaiyoYuden JMK212 BJ106MG-T 10uF, 6.3V, X5R 0805 1 2.5 1.25 0.025 8 Cout TaiyoYuden JMK212BJ226MG-T 22uF, 6.3V, X5R 0805 2 5.0 1.25 0.154 9 Cbias Vishay 10% tolerance 100nF, X7R 0402 1 0.5 0.5 0.010 10 Cbyp Vishay 10% tolerance 100nF, X7R 0402 1 0.5 0.5 0.010 11 C1 Vishay 10% tolerance 1.0nF, 50V, X7R 0402 1 0.5 0.5 0.010 12 C2 Vishay 10% tolerance 1.0nF, 50V, X7R 0402 1 0.5 0.5 0.010 13 Cff Vishay 10% tolerance 330pF,50V,C0G 0402 1 0.5 0.5 0.010 14 Rout Susumu RL1220S-0R1-G 0.1 Ohm, 2% tol, 0.25W 0805 1 3.2 0.4 0.100 15 Rtop Vishay 1% tolerance 102 kohm 0402 1 0.5 0.4 0.005 16 Rbot Vishay 1% tolerance 11.3 kohm 0402 1 0.5 0.4 0.005 17 Rff Vishay 1% tolerance 30.1 kohm 0402 1 0.5 0.4 0.005 18 R1 Vishay 1% tolerance 10.0 kohm 0402 1 0.5 0.4 0.005 19 R2 Vishay 1% tolerance 10.0 kohm 0402 1 0.5 0.4 0.005 20 R3 Vishay 1% tolerance 82.5 kohm 0402 1 0.5 0.4 0.005 21 R4 Vishay 1% tolerance 82.5 kohm 0402 1 0.5 0.4 0.005 22 67.5 1.25 Total: Qty Area (mm^2) *BOM prices shown are 1000 piece estimates in US Dollars that should be used for comparison purposes only. Rev. 1 | Page 4 of 11 2.70 Reference Design PRD1198 SIMULATION RESULTS Figure 2. Bode plot with 10 Ohm load 35.53324k 35.69699k 163.75290 160 140 Phase / 120 100 80 60 59.939404 40 20 0 59.939404 40 Gain / dB 20 0.0000000 0 -20 -40 10 20 40 100 200 400 1k 2k 4k 10k freq / Hertz Rev. 1 | Page 5 of 11 20k 40k REF A 100k 200k 400k 1M Reference Design Figure 3. PRD1198 Bode plot with 10 Ohm load and 470 uF aluminum output cap 3.569699k 3.631396k -61.69707 160 140 Phase / 120 100 80 67.786480 60 40 20 0 67.786480 40 Gain / dB 20 0.0000000 0 -20 -40 10 20 40 100 200 400 1k 2k 4k REF A 10k freq / Hertz Rev. 1 | Page 6 of 11 20k 40k 100k 200k 400k 1M Reference Design Figure 4. PRD1198 Bode plot with 7 Ohm load (Vout = 4.2 V, constant current) 27.38420k 27.49429k -110.0944 180 160 140 Phase / 120 100 80 60 48.557945 40 20 0 48.557945 40 Gain / dB 20 0 0.0000000 -20 -40 10 20 40 100 200 400 1k 2k 4k 10k 20k 40k REF A freq / Hertz Rev. 1 | Page 7 of 11 100k 200k 400k 1M Reference Design Figure 5. PRD1198 Bode plot with 5 Ohm load (Vout = 3 V, constant current) 37.48979k 37.50652k 16.722743 160 140 Phase / 120 100 80 60 55.829144 40 20 0 -56.06080 40 Gain / dB 20 -231.660m 0 -20 -40 10 20 40 100 200 400 1k 2k 4k 10k freq / Hertz Rev. 1 | Page 8 of 11 20k 40k REF A 100k 200k 400k 1M Reference Design Figure 6. PRD1198 Transient with 10 Ohm load and 100 mA dynamic step 5.04 5.02 5 Vout / V 4.98 4.96 4.94 4.92 4.9 4.88 0 0.5 1 1.5 2 2.5 time/mSecs 3 3.5 4 4.5 500uSecs/div Rev. 1 | Page 9 of 11 Reference Design Figure 7. PRD1198 Transient with 10 Ohm load and 100 mA dynamic step and 470 uF aluminum output cap 5.02 5 4.98 Vout / V 4.96 4.94 4.92 4.9 4.88 0 2 4 6 8 time/mSecs 10 12 14 2mSecs/div Rev. 1 | Page 10 of 11 Reference Design PRD1198 NOTES Simulations show the voltage loop is stable with the output caps listed in the BOM and with the addition of 470 uF of additional aluminum output cap. Transient response shows the constant current mode is stable with the output caps listed in the BOM and with the addition of 470 uF of additional aluminum output cap. The transient response also shows minimal overshoot when transitioning from one mode to the other. Simulations also shows that the constant current loop is stable when loaded with 7 Ohms and with 5 Ohms. ©2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. Error! Unknow Rev. 1 | Page 11 of 11