ADP1877 Reference Design Reference Design PRD 01135 FEATURES Four Output Voltages: 1.2V, 1.8V, 3.3V, 5V Output Current: 1A to 2.2A Input Voltage: 10.8-13.2V DESCRIPTION This ADP1877 Reference Design uses 10.8 V to 13.2 V for the input voltage. The output voltages and currents are as follows: VOUT1 = 1.2 V with a maximum output current of 2 A, VOUT2 = 1.8 V with a maximum output current of 1.8 A, VOUT3 = 3.3 V with a maximum output current of 1 A, VOUT4 = 5.0 V with a maximum output current of 2.2 A, Design criteria are for simultaneous enable with coincidental tracking of VOUT1, VOUT2 and VOUT4 with VOUT3 for turn on and enable turn off. The ripple and transient assumptions are 50 mV peak to peak voltage ripple and 5% deviation due to 50% instantaneous load step. The switching frequency is fixed at 650 kHz for VOUT1 and VOUT2, 1000kHz for VOUT3 and VOUT4. The design is optimized for additional output capacitance on each rail to simulate system usage and can be recompensated easily for changes in the output capacitance. ADP1877 The ADP1877 is a current mode dual-phase step-down switching controller with integrated drivers that drive Nchannel synchronous power MOSFETs. The two PWM outputs are phase shifted 180º, which reduces the input RMS current thus minimizing required input capacitance. The boost diodes are built into the ADP1877, thus lowering the overall system cost and component count. The ADP1877 can be set to operate in pulse skip high efficiency mode under light load or in forced PWM (continuous conduction mode). The ADP1877 includes programmable soft start, output overvoltage protection, programmable current limit, power good, tracking function, and programmable oscillator frequency that ranges from 200 kHz to 1.5 MHz. The ADP1877 provides an output voltage accuracy of ±1% over temperature, superior transient response and reduced output capacitance. This part can be powered from a 2.75V to 15V supply and is available in 32 pin LFCSP package. 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 PRD 01135 TABLE OF CONTENTS Features ......................................................................................................................................................................1 Description .................................................................................................................................................................1 ADP1877 ....................................................................................................................................................................1 Revision History .........................................................................................................................................................2 Schematic ...................................................................................................................................................................3 Notes...........................................................................................................................................................................8 Graphs ........................................................................................................................................................................9 Performance Data .....................................................................................................................................................14 TABLE OF FIGURES Figure 1. Figure 2. Schematic: Vout1 and Vout2 (built on eval board 1) ..................................................................................3 Schematic: Vout3 and Vout4 (built on eval board 2) ..................................................................................4 Figure 3. Schematic: Motherboard ........................................................................................................................5 Figure 4. Vout1 (1.2V) Efficiency .........................................................................................................................9 Figure 5. Vout2 (1.8V) Efficiency .........................................................................................................................9 Figure 6. Vout3 (3.3V) Efficiency .......................................................................................................................10 Figure 7. Figure 8. Vout4 (5.0V) Efficiency .......................................................................................................................10 Enable Waveforms ............................................................................................................................... 11 Figure 9. Disable Waveforms (full load) ............................................................................................................. 11 Figure 10. Ripple Waveforms (full load) ..............................................................................................................12 Figure 11. Vout1 and Vout2 Transient Response (50% step) ................................................................................12 Figure 12. Vout3 and Vout4 Transient Response (50% step), Vin=12.0V ............................................................13 REVISION HISTORY 5/11/2007—Revision 1: Initial Version 8/14/2008—Revision 2: Provided Descriptions 4/22/2009—Revision 3: Changed to standard Windows fonts and sizes Rev. 1 | Page 2 of 15 Reference Design PRD 01135 SCHEMATIC Figure 1. Schematic: Vout1 and Vout2 (built on eval board 1) Rf11 Rf12 PGOOD1 Rc1 Vin = 12V Vout3 = 3.3V CIlim1 Rt11 Cc12 Cc11 Rr1 Css1 RIlim1 Rt12 32 31 30 29 28 27 26 25 Cbst1 CiV1 TRK1 FB1 COMP1 RAMP1 SS1 PGOOD1 ILIM1 BST1 EN 1 Vin = 12V 2 3 Cvin RVcco 4 Cvcc 5 6 Cdr Rfreq 7 EN 8 Vout3 = 3.3V EN1 SW1 U1 SYNC DH1 VIN PGND1 ADP1877 VCCO DL1 VDL DL2 AGND PGND2 FREQ DH2 EN2 SW2 QH1 24 Rgcs1 CoV1 22 QL1 21 20 19 Rgcs2 QL2 18 10 11 12 13 14 15 Vout2 = 1.8V L2 17 TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2 9 Vout1 = 1.2V L1 23 CoV2 16 Cbst2 QH2 Rt21 Rr2 Css2 Vin = 12V Cc22 Cc21 CiV2 Rt22 CIlim2 RIlim2 Rc2 PGOOD2 Rf22 Rf21 Note: Tracking resistors are on motherboard, not the eval board Rev. 1 | Page 3 of 15 Reference Design PRD 01135 Figure 2. Schematic: Vout3 and Vout4 (built on eval board 2) Rf11 Rf12 PGOOD1 Rc1 Vin = 12V CIlim1 Cc12 Cc11 Rr1 Css1 RIlim1 32 31 30 29 28 27 26 25 Cbst1 CiV1 TRK1 FB1 COMP1 RAMP1 SS1 PGOOD1 ILIM1 BST1 EN 1 Vin = 12V 2 3 Cvin RVcco 4 Cvcc 6 Cdr Rfreq EN 5 7 8 EN1 QH1 SW1 24 U1 SYNC VIN 23 PGND1 ADP1877 VCCO DL1 VDL DL2 AGND PGND2 FREQ DH2 EN2 SW2 Rgcs1 CoV1 22 QL1 21 20 19 Rgcs2 QL2 18 10 11 12 13 Rr2 14 15 16 CoV2 Cbst2 Css2 QH2 Vin = 12V Cc22 Cc21 CiV2 CIlim2 RIlim2 Rc2 PGOOD2 Rf22 Vout3 = 3.3V L2 17 TRK2 FB2 COMP2 RAMP2 SS2 PGOOD2 ILIM2 BST2 9 Vout4 = 5V L1 DH1 Rf21 Rev. 1 | Page 4 of 15 Reference Design PRD 01135 Figure 3. Schematic: Motherboard Tracking resistors and enable jumpers are populated on the motherboard instead of the eval boards. Most of the assumed extra output capacitance is also soldered on the motherboard. Rev. 1 | Page 5 of 15 Reference Design PRD 01135 Bill of Materials Table 1. Bill of Materials, Vout1 and Vout2 (1.2V and 1.8V) (Eval board 1) Designator Part Number Manufacturer U1 ADP1877 Analog Devices 40pin LFCSP Dual Current Mode Controller 1 QH1 Si3446ADV ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QH2 Si3446ADV ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QL1 Si3446ADV ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QL2 Si3446ADV ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 L1 DO1813H-222 Coilcraft 2.2uH Unshielded Drum Core Ferrite 1 L2 CoV1 DO1813H-222 JMK212BJ106MG-T JMK212BJ106MG-T JMK212BJ106MG-T JMK212BJ106MG-T Coilcraft Taiyo Yuden Taiyo Yuden Taiyo Yuden Taiyo Yuden 2.2uH 10uF 10uF 10uF 10uF Unshielded Drum Core 0805 0805 0805 0805 Ferrite MLCC / X5R / 6.3V MLCC / X5R / 6.3V MLCC / X5R / 6.3V MLCC / X5R / 6.3V 1 3 1 2 15 CiV1 EMK212BJ106KG-T Taiyo Yuden 10uF 0805 MLCC / X5R / 16V 1 CiV2 EMK212BJ106KG-T Taiyo Yuden 10uF 0805 MLCC / X5R / 16V 1 Cvin GRM21BR71C105K Murata 1uF 0805 MLCC / X7R / 16V 1 Cbst1, Cbst2 Generic 10% Vishay 100nF 0805 2 Css1 Generic 10% Vishay 10nF 0805 Css2 Generic 10% Vishay 10nF 0805 Boost Capacitor / COG or X7R Soft Start Capacitor / COG or X7R Soft Start Capacitor / COG or X7R CIlim1 Generic 10% Vishay 33pF 0805 Current Limit Capacitor 1 CIlim2 Generic 10% Vishay 33pF 0805 Current Limit Capacitor 1 Cdr GRM185R60J105KE21 Murata 1uF 0603 MLCC / X5R / 6.3V 1 Cvcc GRM185R60J105KE21 Murata 1uF 0603 MLCC / X5R / 6.3V 1 Cc11 Generic 10% Vishay 1.5nF 0603 Compensation Capacitor - CH1 1 Cc12 Generic 10% Vishay 5pF 0603 Compensation Capacitor - CH1 1 Cc21 Generic 10% Vishay 2.2nF 0603 Compensation Capacitor - CH2 1 Cc22 Generic 10% Vishay 5pF 0603 Compensation Capacitor - CH2 1 RIlim1 Generic 1% Vishay 3.32k 0603 Current Limit Resistor 1 RIlim2 Generic 1% Vishay 2.74k 0603 Current Limit Resistor 1 Rgcs1 Generic 1% Vishay 22k 0603 Current Sense Gain Set - 6V/V 1 Rgcs2 No Pop Vishay 0603 1 Rfreq Generic 5% Vishay 97.6k 0603 Current Sense Gain Set - 12V/V Frequency Set Resistor 650kHz Rvcco Generic 10% Vishay 1 Ohm 0603 Decoupling Resistor 1 Rr1 Generic 10% Vishay 249k 0603 Vout 1 Ramp Resistor 1 Rr2 Generic 10% Vishay 432k 0603 Vout 2 Ramp Resistor 1 Rc1 Generic 10% Vishay 16.9k 0603 Compensation Resistor 1 Rc2 Generic 10% Vishay 71.5k 0603 Compensation Resistor 1 Rf11 Generic 1% Vishay 10k 0603 Feedback Resistor - CH1 1 Rf12 Generic 1% Vishay 10k 0603 Feedback Resistor - CH1 1 Rf21 Generic 1% Vishay 20k 0603 Feedback Resistor - CH2 1 Rf22 Generic 1% Vishay 10k 0603 Feedback Resistor - CH2 1 Rt11 Generic 1% Vishay 10k 0603 Voltage track Resistor - CH1 1 Rt12 Generic 1% Vishay 10k 0603 Voltage track Resistor - CH1 1 Rt21 Generic 1% Vishay 20k 0603 Voltage track Resistor - CH2 1 Rt22 Generic 1% Vishay 10k 0603 Voltage track Resistor - CH2 1 CoV2 Value Package Comment Rev. 1 | Page 6 of 15 Quantity 1 1 1 Reference Design Table 2. PRD 01135 Bill of Materials, Vout3 and Vout4 (3.3V and 5.0V) Designator Part Number U1 ADP1877 Manufacturer Analog Devices 40pin LFCSP Dual Current Mode Controller 1 QH1 NTGS3446G ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QH2 NTGS3446G ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QL1 NTGS3446G ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 QL2 NTGS3446G ON-Semi SOT23-6 Single 60mOhm 20V N-FET 1 L1 MSS1048-682 Coilcraft 6.8uH Shielded Drum Core Ferrite 1 L2 CoV1 MSS1048-682 JMK212BJ106MG-T JMK212BJ106MG-T 6CE100KX JMK212BJ106MG-T GRM31CR60J107ME GRM31CR60J226K 35CE10KX Coilcraft Taiyo Yuden Taiyo Yuden Sanyo Taiyo Yuden Murata Murata Sanyo 6.8uH 10uF 10uF 100uF 10uF 100uF 22uF 10uF Shielded Drum Core 0805 0805 6.3x6mm SMT 0805 1206 1206 5x6mm SMT Ferrite MLCC / X5R / 6.3V MLCC / X5R / 6.3V Aluminum Electrolytic MLCC / X5R / 6.3V MLCC / X5R / 6.3V MLCC / X5R / 6.3V Aluminum Electrolytic 1 1 2 3 1 2 1 4 CiV1 EMK212BJ106KG-T Taiyo Yuden 10uF 0805 MLCC / X5R / 16V 1 CiV2 EMK212BJ106KG-T Taiyo Yuden 10uF 0805 MLCC / X5R / 16V 1 Cvin Cbst1, Cbst2 GRM21BR71C105K Murata 1uF 0805 MLCC / X7R / 16V 1 Generic 10% Vishay 100nF 0805 Boost Capacitor / COG or X7R 2 Css1 Generic 10% Vishay 100nF 0805 Soft Start Capacitor / COG or X7R 1 Css2 Generic 10% Vishay 10nF 0805 Soft Start Capacitor / COG or X7R 1 CIlim1 Generic 10% Vishay 33pF 0805 Current Limit Capacitor 1 CIlim2 Generic 10% Vishay 33pF 0805 Current Limit Capacitor 1 Cdr GRM185R60J105KE21 Murata 1uF 0603 MLCC / X5R / 6.3V 1 Cvcc GRM185R60J105KE21 Murata 1uF 0603 MLCC / X5R / 6.3V 1 Cc11 Generic 10% Vishay 68pF 0603 Compensation Capacitor - CH1 1 Cc12 Generic 10% Vishay 5pF 0603 Compensation Capacitor - CH1 1 Cc21 Generic 10% Vishay 220pF 0603 Compensation Capacitor - CH2 1 Cc22 Generic 10% Vishay 5pF 0603 Compensation Capacitor - CH2 1 RIlim1 Generic 1% Vishay 3.32k 0603 Current Limit Resistor 1 RIlim2 Generic 1% Vishay 3.01k 0603 Current Limit Resistor 1 Rgcs1 Generic 1% Vishay 22k 0603 Current Sense Gain Set - 6V/V 1 Rgcs2 No Pop Vishay 0603 Current Sense Gain Set - 12V/V 1 Rfreq Generic 5% Vishay 61.9k 0603 Frequency Set Resistor – 1MHz 1 Rvcco Generic 10% Vishay 1 Ohm 0603 Decoupling Resistor 1 Rr1 Generic 10% Vishay 1.00M 0603 Vout 1 Ramp Resistor 1 Rr2 Generic 10% Vishay 750k 0603 Vout 2 Ramp Resistor 1 Rc1 Generic 10% Vishay 26.1k 0603 Compensation Resistor 1 Rc2 Generic 10% Vishay 249k 0603 Compensation Resistor 1 Rf11 Generic 1% Vishay 11.0k 0603 Feedback Resistor - CH1 1 Rf12 Generic 1% Vishay 1.50k 0603 Feedback Resistor - CH1 1 Rf21 Generic 1% Vishay 10k 0603 Feedback Resistor - CH2 1 Rf22 Generic 1% Vishay 2.21k 0603 Feedback Resistor - CH2 1 CoV2 Value Package BOM items in bold are assumed additional system capacitance. Rev. 1 | Page 7 of 15 Comment Quantity Reference Design PRD 01135 NOTES Reference designators shown on the schematic but not listed on the Bill of Materials are place holders for possible design adjustments (snubbers, additional decoupling capacitors and clamp diodes). These components should be put in the layout, but not populated unless after testing it is deemed necessary. If a different number, or different type of output capacitors are used on the switching outputs the loop compensation components may need adjustment. The assumed additional output caps are listed in bold type in the BOM. FETs and other components with quantities greater than 1 are connected in parallel with the other FETs / components of the same reference designator. Paralleled FETs should be placed physically close together and have large power planes connecting all the drains together and large power planes connecting all the sources together. Gate drive resistors may be used if there is concern about possible paralleling issues. Ground symbols with multiple parallel lines (not the triangle symbol) designator should be connected together with one small plane and tied to the power ground plane (triangle symbol) at one point near the IC. Each IC should have its own signal ground pour. The PGND1 and PGND2 pins should be connected directly to the source of the lowside MOSFET for that channel with short wide traces. They should not connect into the main ground plane except at the MOSFET sources. Except for the feedback resistors (Rfxx), E24 values may be substituted for the E96 values specified. The feedback resistors need to be as specified. Rev. 1 | Page 8 of 15 Reference Design PRD 01135 GRAPHS Figure 4. Vout1 (1.2V) Efficiency 1.2V Efficiency 85.00% 80.00% Efficiency 75.00% 70.00% Vin max Vin nom Vin min 65.00% 60.00% 55.00% 50.00% 0 0.5 1 1.5 2 2.5 Current A Figure 5. Vout2 (1.8V) Efficiency 1.8V Efficiency 90.00% 85.00% 80.00% Efficiency 75.00% Vin max 70.00% Vin nom Vin min 65.00% 60.00% 55.00% 50.00% 0 0.2 0.4 0.6 0.8 1 1.2 Current Rev. 1 | Page 9 of 15 1.4 1.6 1.8 2 Reference Design PRD 01135 Figure 6. Vout3 (3.3V) Efficiency 3.3V Efficiency 85.00% 80.00% Efficiency 75.00% 70.00% Vin max Vin nom Vin min 65.00% 60.00% 55.00% 50.00% 0 0.2 0.4 0.6 0.8 1 1.2 Current Figure 7. Vout4 (5.0V) Efficiency 5V Efficiency 95.00% 90.00% 85.00% Efficiency 80.00% Vin max 75.00% Vin nom 70.00% Vin min 65.00% 60.00% 55.00% 50.00% 0 0.5 1 1.5 Current (A) Rev. 1 | Page 10 of 15 2 2.5 Reference Design PRD 01135 Figure 8. Figure 9. Enable Waveforms Disable Waveforms (full load) Rev. 1 | Page 11 of 15 Reference Design PRD 01135 Figure 10. Figure 11. Ripple Waveforms (full load) Vout1 and Vout2 Transient Response (50% step) Rev. 1 | Page 12 of 15 Reference Design Figure 12. PRD 01135 Vout3 and Vout4 Transient Response (50% step), Vin=12.0V Note: At higher input voltages, depending on the load, the two channels of the 3.3V and 5V outputs may have duty cycles that would require both outputs to switch simultaneously. The ADP1877 delays one of the outputs so that it can measure the current in the low side fet during a quiet period. This causes some additional transient response that resembles a beat frequency on the ripple. It is not instability and is well-bounded. It resembles voltage drop in the ground plane due to the load change. Here is an example (50% step, Vin=13.2V). Note the extra transition in the center, not due to the load transient. Rev. 1 | Page 13 of 15 Reference Design PRD 01135 PERFORMANCE DATA Table 3. Vout1/2 Temperature Rise over Ambient Component Vinnom Units U1 21.4 degC L1 29.3 degC QH1 19.4 degC QL1 25.2 degC L2 QH2 28.5 18.5 degC degC QL2 20.2 degC Table 4. Vout3/4 Temperature Rise over Ambient Component Vinnom Units U1 L1 25.5 19.8 degC degC QH1 28.3 degC QL1 37.7 degC L2 QH2 17.1 25.7 degC degC QL2 35.4 degC Rev. 1 | Page 14 of 15 Reference Design PRD 01135 ©2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. Error! Unknown document property name. Rev. 1 | Page 15 of 15