ON Semiconductor Confidential – NDA Required Design Note – DN06056/D Power Supply For Audio Class D Amplifier Device CS51221 Application Input Voltage Output Voltage Output Current Topology Audio 7.6-45 V 18V 8.3A Boost Table 1: CS51221 Audio Power Supply Characteristic Output Voltage Output Current Oscillator Frequency Output Voltage Ripple Load Regulation (Iout = 0.1-8.3A) Vin= 12V Line Regulation to 5V Iout = .1A) Iout = 8.3A) Size Min 18.0453 1 Typ 18.0532 Max 18.06 8.3 Unit V A kHz mVpk-pk mV/A 0.34 0.32 Height 31 % 140 150 -.693 0.28 0.25 Length 80 0.31 0.28 Width 59 Figure 1: Demonstration Board Picture Rev 1 - January, 2009 mm ON Semiconductor Confidential – NDA Required Circuit Description A boost power supply was developed for to feed 4 class D amplifiers and one auxiliary system. The design must minimize the use of through hole components, designed as small as possible on a 4 layer PCB, and only populated on the top side. The system level drawing is shown in Figure 2. The power supply is required to maintain an 18V output with input voltage variation from 7.6V to 18.4V. Above 18.4V the power supply will shutoff-minimizing losses and allow input voltage to flow to output voltage. The required voltage profile is shown in Figure 3. Figure 2: System Level Diagram of the Sony MCA ‘Audiofile’ radio 18.4 V Output Voltage pu In olt tV ag e 18.4 V 7.6V Time Figure 3: CS51221 Design Boost Curve The design has the following features: • Adjustable cycle by cycle current limiting • Overvoltage Shutoff • Undervoltage shutoff • Can be synchronized to a higher frequency • Wide operating range 7.6-18.4V operating and 18-45V nonoperating • Programmable soft start • Voltage feed forward Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Performance Information The following figures show typical performance of the evaluation board. Efficiency (%) CS51221 Visteon Boost Efficiency vs. Output Current 100 98 96 94 92 90 88 86 84 82 80 0 2 4 6 8 Output Current (A) 8V 9V 10V 11V 12V 13V 14V 15V 16V 17V 18V Figure 4: CS51221 Efficiency 8V – 18V input voltage with a 18V Output Voltage Line Regulation 18.07 Output Voltage (V) 18.065 18.06 18.055 18.05 18.045 18.04 0 2 4 6 Output Current (A) Figure 5: CS51221 Line Regulation Rev 1 - January, 2009 8 8V 9V 10V 11V 12V 13V 14V 15V 16V 17V 18V HIGH low ON Semiconductor Confidential – NDA Required Figure 6: Input and Output Ripple Voltage Vin = 8V Vout =18V Iout = 8.3A 231 mVpp Figure 7: Vin = 12V Vout =18V Iout = 8.3A 166mVpp Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 8: Vin = 16V Vout =18V Iout = 8.3A 161mVpp Figure 9: Transient Response Input Voltage = 12V output current step 1.0A to 8.0 A with 274 mV peek to peek Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 10: Soft Start Time is 5.8 ms from an Input voltage of 0V Figure 11: Soft Start Time is 5.8 ms from an Input voltage of 12V Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 12: Soft Start and Soft Stop From 12V Volts Figure 13: 8V Frequency Response 2.1 kHz and 2.4k Cross over at 71 and 54 Degrees of Phase Margin 2A Load at Full Load Right Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 14: 12V Frequency Response 1.6kHz Cross over at 80 Full Load Figure 15: 16V Frequency Response 1.5 kHz and 1.5k Cross over at 82 and 83 Degrees of Phase Margin 2A Load at Full Load Right Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Vin vs VCC & VC 13.5 Output Voltage (V) 12.5 VC_NL VCC_NL VC_3A VCC_3A 11.5 10.5 9.5 8.5 7.5 6.5 5.5 7 8 9 10 11 12 13 14 15 16 17 18 19 Input Voltage (V) Figure 16: VCC and VC vs Input Voltage Figure 17: Thermal Image of PCB at 8V 8.3A Load with a 25C ambient Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 18: Thermal Image of PCB at 12V 8.3A Load with a 25C ambient Figure 19: Thermal Image of PCB at 16V 8.3A Load with a 25C ambient Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 20: Thermal Image of PCB at 12V 4.15A Load with a 25C ambient Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Schematic Figure 24: CS51221 Schematic Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Table 2 : CS51221 Bill of Materials Designator C5 C2 C8 C12 C6 C4 C20 C10 C11 C24 C16 C3 C21 C23 C22 Quantity 1 2 1 1 1 1 1 1 1 1 1 2 1 Value 330n 0.1uF 1.8nF 1nF 1uF 1uF 4.7nF 82nF 1.2n 1.2nF 1nF 1uF 4.7uF Tolerance 20% 20% 10% 10% 10% 20% ±10% 10% 5% 10% 10% 10% ±10% FootPrint 805 603 603 603 603 603 603 603 805 1206 1206 1206 1210 Manufacturer AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation AVX Corporation Manufacturer Part Number 0805ZC334JAT2A 06033C104MAT2A 0603ZC272KAT2A 0603ZC102KA72A 06036D105KAT2A 06033D105MAT2A 06031C472KAT2A 0603ZC184KAT2A 08056A122JAT2A 12061A122KAT2A 12061C102KAT2A 12065C105KAT2A 12105C475KAT2A 1 Description Ceramic Chip Capacitor 10V Ceramic Chip Capacitor 25V Ceramic Chip Capacitor 10V Ceramic Chip Capacitor 50V Ceramic Chip Capacitor 6.3V Ceramic Chip Capacitor 25V Ceramic Chip Capacitor 100V Ceramic Chip Capacitor 10V Ceramic Chip Capacitor 6.3V Ceramic Chip Capacitor 100V Ceramic Chip Capacitor 100V Ceramic Chip Capacitor 50V Ceramic Chip Capacitor 50V Enhanced Voltage Mode PWM Controller U1 C7 C13-15 C9 C17-19 D1 Q5 Z1 U2-3 R5 R14 R3 R20 R9 R21 R7 R2 R1 R23 3V Ref NA SOIC 16 ON Semiconductor CS51221 8 1 1 1 2 1 1 1 1 1 1 1 1 2 Electrolytic Capacitor Schottky Power Rectifier General Purpose NPN Transistor Zener Diode N MOSFET 8.1mOhm SMT Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor 680uF 30A 45V 40V 200mA 14V 60V 50A 49.9k 1.02k 1.58k 1k 20R0 27.4k 28.5k 3.09k 41.2k 20% NA NA ±5% NA 1% ±1.0% ±1.0% ±1.0% ±1.0% ±1.0% ±1.0% ±1.0% ±1.0% 12.5X25 TO-220 SOT-23 SOD-123 DPAK 1206 603 603 603 603 603 603 603 603 United Chemicon ON Semiconductor ON Semiconductor ON Semiconductor Infineon Vishay Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale EKZE500ELL681MK30S MBR30L45CTG MMBT3904TT1G MMSZ5244BT1G IPB081N06L3G CRCW120649K9FKEA CRCW06031K02FKEA CRCW06031K58FKEA CRCW060310K0FKEA CRCW060320R0FKEA CRCW060327K4FKEA CRCW06033K01FKEA CRCW06033K09FKEA CRCW060341K2FKEA Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Table 2 : CS51221 Bill of Materials Designator R13 R26 R25 R8 R12 R11 R15 R10 R6 R4 Quantity 1 1 1 2 2 1 1 1 Description SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor SMD Resistor Value 49.9k 6.04k 8.2k 0R0 10R0 4.99k 8.06K 5mOhm Tolerance ±1.0% ±1.0% ±1.0% ±5.0% ±5.0% ±1.0% ±1.0% ±1.0% L2 1 SMT Inductor 0.17mOhm .1 uH 10% L1 1 SMT Inductor 33 uH 10% Rev 1 - January, 2009 FootPrint 603 603 603 1206 1206 1206 1206 4527 7.5mmX 7.6mm 27.94mmX 27.9mm Manufacturer Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Vishay / Dale Manufacturer Part Number CRCW060349K9FKEA CRCW06036K04FKEA CRCW06038K20FKEA CRCW12060000Z0EA CRCW120610R0FKEA CRCW12064K99FKEA CRCW12068K06FKEA WSR55L00F Coilcraft SLC7649S-101KL_ Coilcraft SER2918H-103 ON Semiconductor Confidential – NDA Required Figure 25: Layout Top Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 26: Layout Inner Top Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 27: Layout Inner Bottom Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Figure 28: Layout Bottom Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required High Current Reverse Polarity Protection The boost converter input current at low line is over 21 A creating large losses when standard reverse polarity protection is used. The power loss when using a schottkey diode capable of 30A are as follows: PDIODE = IV ⎯Solve ⎯ ⎯→ 21A * 0.7V = 14.7W Solve PMOSFET = I 2 R ⎯⎯ ⎯→ PMOSFET 2W =R= = 4.5mΩ 2 21A 2 I Since the MOSFET will be mostly on the user need only consider the RDSon as the switching losses can be negated. The final consideration is to determine how the MOSFET might be turned on when appropriate and turned off when the voltage is reversed. Figure 29 shows one solution for the low side reverse polarity protection Figure 29: Low Side Reverse Polarity Protection and Simulated Results Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Current Sharing of Parallel MOSFETS Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required Efficiency Calculator An efficiency calculator was constructed for boost converter applications to predict the effect of component changes on system efficiency and to aid the designer in making critical design tradeoffs. The user should enter all of the information they know about the design then change parameters like RDSon and frequency to gauge the system sensitivity to the parameter. Figure 30 Shows the predicted efficiency of the design at 140kHz. The efficiency can also be predicted for the 375 kHz, 417kHz, and 500kHz . 95% 95% 94% 94% 93% 93% 92% 92% 91% 91% 90% 90% 89% 89% 88% 88% 87% 87% 86% 86% 85% 85% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Figure 30: Predicted Efficiency of Design at 140 kHz Left 375 kHz Blue = 8V, Green = 12V, Red = 18V 95% 95% 94% 94% 93% 93% 92% 92% 91% 91% 90% 90% 89% 89% 88% 88% 87% 87% 86% 86% 85% 85% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 Figure 30: Predicted Efficiency of Design at 417 kHz Left 500 kHz Blue = 8V, Green = 12V, Red = 18V Rev 1 - January, 2009 9 ON Semiconductor Confidential – NDA Required The on resistance of the MOSFET makes a large impact at low line on the system level efficiency. The charts below compare the Fairchild FDD13AN06A0CT with the On Semiconductor NTB45N06LT4G which has similar gate charge characteristics, and the NTB75N06G which has similar RDSon. The Infineon IPB081N06L3G can also be used for higher efficiency. 95% 95% 94% 94% 93% 93% 92% 92% 91% 91% 90% 90% 89% 89% 88% 88% 87% 87% 86% 86% 85% 85% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Figure 30: Predicted Efficiency of Design at 140 kHz FDD13AN06A0CT Left and NTB45N06LT4G right Blue = 8V, Green = 12V, Red = 18V 95% 95% 94% 94% 93% 93% 92% 92% 91% 91% 90% 90% 89% 89% 88% 88% 87% 87% 86% 86% 85% 85% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Figure 31: Predicted Efficiency of Design at 140 kHz FDD13AN06A0CT Left and NTB75N06G right Blue = 8V, Green = 12V, Red = 18V Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required When calculating the component values for the worst case it is important to find to local ambient temperature. One way to predict the local temperature of components is to use linear super position as discussed in [1]. Using linear super position one can take a series of measurements of a PCB temperature shown in Figure 32 when major power component are made to dissipate a know power. The temperatures are then recorded and coefficients are calculated to determine the influence of all components running simultaneously at a given area of interest shown in Figure 33 . Once the data is collected the only remaining information needed is the power dissipation of each component. Figure 32: Steady State Thermal Image Captures on Individual Component Heating Rev 1 - January, 2009 ON Semiconductor Confidential – NDA Required A Temperature vs Load B C 200 D E Area Temperature (C) 180 160 F G 140 H I 120 J K 100 L M 80 60 N O 40 P Q 20 0 0 1 2 3 4 5 6 Output Current (A) 7 8 9 R S T U Figure 33: Area of Interest Selected for Temperature Evaluation and Calculated Thermal Data 1 © 2009 ON Semiconductor. Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its products at any time, without notice. Design note created by Tim Kaske and Bryan McCoy, e-mail: [email protected] ; [email protected] Rev 1 - January, 2009