Demo Note for the A8580 Evaluation Board 4.0V IN – 40V IN , 3.3V OUT, 2.5A, 425KHz Asynchronous Buck Regulator with Low IQ PFM Mode Page 1 of 13 December 18th, 2012 GENERAL SPECIFICATIONS Specification Absolute Maximum Input Voltage Operating Input Voltage Range V IN START Threshold, V IN rising V IN STOP Threshold, V IN falling Output Voltage (FB: 47K/147K, ±1%) Steady-State Output Current (12V IN ) Pulse-by-pulse Current Limit @ 30% duty PWM/PFMn Input Min –0.3 4.0 3.6 3.2 3.175 − 3.12 –0.3 Nom − 12 3.8 3.4 3.302 2.5 3.69 − Max 40 35 4.0 3.6 3.434 − 4.25 5.5 Units Volts Volts Volts Volts Volts A A Volts OPERATING INSTRUCTIONS Input Power Connection: Connect a 12V power supply from V IN to GND that is capable of at least 2.5A. Once operational, V IN can fall as low as 3.4V TYP (3.6V MAX ) before the A8580 is reset. PWM/PFMn Input and DIP switch SW1 (SLEEPn): Connect an external voltage to the PWM/PFMn input and set SW1 (SLEEPn) to control the A8580’s operating mode. The following table summarizes the A8580’s operating modes based on SW1 (SLEEPn) and the PWM/PFMn input. Also, PWM/PFMn may be used to synchronize the A8580 PWM switching frequency by applying a square wave above 510KHz. SW1 (SLEEPn) PWM/PFMn Operating Mode OFF (SLEEPn<0.5V) N/A Low current SLEEP mode, no output voltage ON (SLEEPn>2.1V) < 0.8V > 2.6V CLK signal Low IQ PFM mode, supports up to 500mA TYP Normal PWM mode at 425KHz, supports up to 2.5A Normal PWM mode, synchronized to external CLK Note: Set SW1 to the “OFF” position before driving the SLEEPn test point by a pulse generator or an external power supply. Note: Continuously applying more than 5.5V to the PWM/PFMn pin may damage the A8580. Output Load Connections: Connect a load from V OUT to GND. The steady-state load current can be as high as 2.5A. Pulseby-pulse current limit and/or thermal shutdown will occur if the load is greater than 3.7A. Page 2 of 13 December 18th, 2012 DEMO BOARD PICTURE PWM/PFMn Input > 2.6V for PWM < 0.8V for PFM SW1 (SLEEPn) MODIFYING THE DEMO BOARD TO PRODUCE V OUT > 5.5V If the demo board is modified to produce more than 5.5Vout two changes must be made: 1) Jumper J1 must be set to the “lower” position (shown below) so the on-board 3.3V LDO (U2) will deliver the BIAS voltage to the A8580. 2) Diode D2 must be rotated 90° clockwise so it is “in circuit” and the 3.3V LDO (U2) will operate. If U2 is operational, the Low IQ current of the EVB will increase. Rotate D2 90° so it connects to this pad Move J1 to the “lower” position Page 3 of 13 December 18th, 2012 DEMO BOARD SCHEMATIC Default jumper position BIAS BIAS VOUT 3.3V C53 100nF 16V 0603 C52 Empty J1 16V 0603 5 4 C1 4.7uF 16V 1206 U2 LP2992IM5-3.3 C2 4.7uF 16V 1206 C3 4.7uF 16V 1206 C4 Empty xxV 16 or 18mm 2 Cx 10nF D2 B140 SOD123 1 3 O In Bp En GND GND BEAD1 0 ohms CB CIN5 47 or 33uF 4.7uF 50V 50V 8mm 1210 CIN5a 0.47uF 100V 0805 CIN5b 47nF 50V 0603 VIN_FILT CIN4 4.7uF 50V 1210 CIN3 4.7uF 50V 1210 CIN2 0.47uF 100V 0805 CIN1 47nF 50V 0603 COMP SS CP 15pF 0603 RZ 26.1K CZ 470pF 0603 FSET CSS 22nF 0603 1 2 5 13 9 3 8 VREG12 RFSET 60.4K 4 6 R4 4.99M COMP SS FSET VREG RFB1 147K 10 FB CO2 22uF 16V 1210 CO3 Empty 16V 1210 CO4 CO4a 0.47uF 47nF 100V 50V 0805 0603 CO5 Empty 16V 1210 CO6 Empty 16V 8mm CO7 Empty 16V 8mm CO8 Empty 16V 8mm BODE Empty CFB RFB2 47K SW SLEEP PWM/PFM CO1 22uF 16V 1210 16 BOOT BIAS SW1 PWM/PFM GND GND VOUT D1 SS2P4 CBOOT 47nF 0603 CVREG 1uF 0603 SLEEP VIN_FILT VIN VIN LO 8.2uH 7.6mm x 7.6mm DR72-8R2-R A8580_LP SW SW SW 15 14 SW BIAS VIN 11 VIN RPU 10K Rsnub 6.81 NPOR 7 POR TP4 GND 10pF 0603 Csnub 330pF 0603 TP3 GND TP1 GND TP2 GND R6 10K 0 A8580 Evaluation PCB 12.0Vin / 3.3Vout: RFB1 = 147K, RFB2 = 47K Note: CB is an optional, bulk, electrolytic capacitor for general supply filtering DEMO BOARD BILL-OF-MATERIALS REFERENCE DESIGNATORS FOOTPRINT QTY. MANUFACTURER N/A 1 Allegro MicroSystems eTSSOP-16 1 Allegro MicroSystems A8580 SOT23-5 0603 0603 0603 0603 0603 1206 0603 0805 1 1 2 1 1 1 1 1 1 National Semi LP2992IM5-3.3 Digikey LP2992IM5-3.3CT-ND 1206 0603 3 1 Capacitor, Electrolytic, 33µF or 47µF, 50V, <0.5Ω, -40°C to 125°C Thru Hole 8mm x 11.5mm 1 Nichicon Nichicon Nichicon UBW1H330MPD UBT1H330MPD UBT1H470MPD DigiKey Mouser Mouser UBW1H330MPD-ND 647-UBT1H330MPD 647-UBT1H470MPD CIN1, CIN5b, CO4a, CBOOT Capacitor, Ceramic, 47nF, 50V, 10%, X7R, -55°C to 125°C 0603 4 Murata GRM188R71H473KA61D Digikey 490-3287-1-ND CIN2, CIN5a, CO4 Capacitor, Ceramic, 0.47uF, 100V, 10%, X7R, 55°C to 125°C 0805 3 Murata GRM21BR72A474KA73L Digikey 490-3326-1-ND TDK C3225X7R1H475K C3225X7R1H475M Digikey 445-7726-1-ND 445-7727-1-ND TDK C3225X7R1C226K Digikey 445-3945-2-ND Digikey Mouser SS2P4-M3/84AGICT-ND 625-SS2P4-M3/84A Digikey Mouser Digikey Mouser B140HWDICT-ND 621-B140HW-7 283-3644-1-ND 704-DRA74-8R2-R 5010K-ND DESCRIPTION PCB A8580 PCB for eTSSOP16, Rev 0.1 U1 A8580, 2A Buck Regulator U2 R4 R6, RPU RFB1 RFB2 RFSET Rsnub RZ BEAD1 Regulator, LDO, 3.3V/250mA Resistor, 4.99MΩ, 1/10W, 1% Resistor, 10KΩ, 1/10W, 1% Resistor, 147KΩ, 1/10W, 1% Resistor, 47KΩ, 1/10W, 1% Resistor, 60.4KΩ, 1/10W, 1% Resistor, 6.81Ω, 1/4W, 1% Resistor, 26.1KΩ, 1/10W, 1% Resistor, 0Ω, 0805 C1, C2, C3 C53 Capacitor, Ceramic, 4.7µF, 16V, X7R Capacitor, Ceramic, 100nF, 25V, X7R CB MANUFACTURER P/N SOURCE PURCHASE P/N 4pcb.com CIN3, CIN4, CIN5 Capacitor, Ceramic, 4.7µF, 50V, X7R 1210 3 CFB CO1, CO2 Csnub CSS CVREG CZ CP Capacitor, Ceramic, 10pF, 50V, COG Capacitor, Ceramic, 22µF, 16V, X7R Capacitor, Ceramic, 330pF, 50V, X7R Capacitor, Ceramic, 22nF, 50V, X7R Capacitor, Ceramic, 1µF, 50V, X7R Capacitor, Ceramic, 560pF, 50V, X7R Capacitor, Ceramic, 15pF, 50V, C0G 0603 1210 0603 0603 0603 0603 0603 1 2 1 1 1 1 1 Cx Capacitor, Ceramic, 10nF, 50V, X7R 0603 1 BODE, C4, C52, CIN4, CO3, CO4, CO5, CO6, CO7, CO8 Empty Various 0 D1 Schottky Diode, 40V, 2A SMP 1 Vishay SS2P4-M3/84A D2 Schottky Diode, 40V, 1A, SOD123 SOD123 1 Diodes, Inc Diodes, Inc B140HW-7 B140HW-7 7.6mm x 7.6mm 4.35mm thick 1 Cooper Bussmann DRA74-8R2-R LO Inductor, 8.2uH, 3.17ASAT @ 25C, 40mΩ 3.3V, BIAS, COMP, FSET, NPOR, PWM/PFM, SLEEP, SS, SW, VIN, VOUT, VREG, Test Points, Red, 0.063" diameter 0.063" 12 Keystone 5010 Digikey GND Test Points, Black, 0.063" diameter 0.063" 5 Keystone 5011 Digikey 5011K-ND J1 Header, 3-pins, 0.1" spacing (Note: P/N is for a 36pin strip) 1 Sullins PEC36SAAN Digikey S1012E-36-ND SW1 Rubber Feet DIP Switch, 1 position Self stick rubber feet 1 4 C & K Components 3M SDA01H0SBR SJ-5303 (CLEAR) Digikey Digikey CKN9490CT-ND SJ5303-7-ND Page 4 of 13 SMT Clear December 18th, 2012 DEMO BOARD PERFORMANCE Efficiency vs IOUT (PWM Mode) 95 Efficiency (%) 90 85 80 8Vin 75 12Vin 16Vin 70 0 500 1000 1500 2000 2500 Iout (mA) Efficiency vs IOUT (PFM Mode) 90 80 70 Efficiency (%) 60 50 40 30 20 10 0 10 100 1000 10000 100000 Iout (µA) Page 5 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE Load Regulation vs IOUT 0.00 8Vin 12Vin Deviation from Vo at 100mA (%) 16Vin -0.10 -0.20 -0.30 -0.40 0 500 1000 1500 2000 2500 Iout (mA) Line Regulation vs VIN at 1.0A 0.50 Line Regulation(%) 0.25 0.00 -0.25 -0.50 7 8 9 10 11 12 13 14 15 16 17 18 Vin(V) Page 6 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE Bode Plot: 12V IN , 330mA Load: 0dB at 59.7KHz, PM=64.3deg, GM=11.3dB Bode Plot: 12V IN , 2.5A Load: 0dB at 66.8KHz, PM=60deg, GM=8.6dB Page 7 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE Component Temperatures: 12V IN , 3.3V OUT , 500mA Load, T AMB =25°C No Airflow (still air) Component Temperatures: 12V IN , 3.3V OUT , 2.5A Load, T AMB =25°C No Airflow (still air) Page 8 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE PWM Startup 12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1 PWM Shutdown 12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1 CH1=V OUT , CH2=COMP, CH3=SS, CH4=SLEEPn CH1=V OUT , CH2=COMP, CH3=SS, CH4=SLEEPn PWM Output Voltage Ripple 12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1, CH1=V OUT PWM Transient Response 12V IN , 1A load step up/down, PWM/PFMn=1 CH1=V OUT , CH2=COMP, CH4=IOUT Page 9 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE PWM to PFM Transition 12V IN , 470mA (7Ω) load CH1=V OUT , CH2=COMP, CH3=SW, CH4=PWM/PFMn PFM to PWM Transition 12V IN , 470mA (7Ω) load CH1=V OUT , CH2=COMP, CH3=SW, CH4=PWM/PFMn PFM Output Voltage Ripple 12V IN , 1mA (3.3KΩ) load CH1=V OUT PFM Output Voltage Ripple 12V IN , 400mA (8Ω) load CH1=V OUT Page 10 of 13 December 18th, 2012 DEMO BOARD PERFORMANCE SW Voltage at 12V IN , 100mA load, PWM/PFMn=1 CH3=SW Input Voltage Ripple at 12V IN , 2.5A load, PWM/PFMn=1 CH1=V IN Page 11 of 13 SW Voltage at 12V IN , 2.5A load, PWM/PFMn=1 CH3=SW Output Shorted, Hiccup Mode Operation, PWM/PFMn=1 CH1=V OUT , CH2=COMP, CH3=SS, CH4=I L December 18th, 2012 DEMO PCB LAYOUT Top Layer and Top Silk Layer 2 and Top Silk Page 12 of 13 December 18th, 2012 DEMO PCB LAYOUT Layer 3 and Top Silk Bottom Layer and Bottom Silk Page 13 of 13 December 18th, 2012