AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n General Description n Applications The AME5259A is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. Capable of delivering 1.2A output current over a wide input voltage range from 2.5V to 5.5V. Supply current with no load is 400µA and drops to<1µA in shutdown. The 2.5V to 5.5V input Voltage range makes the AME5259A ideally suited for single Li-Ion batterypowered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. PWM pulse skipping mode operation provides very low output ripple voltage for noise sensitive applications. At very light load, the AME5259A will automatically skip pulses in pulse skip mode operation to maintain output regulation. l l l l l n Typical Application n Features 2.2µH VIN IN CIN 4.7µF CER The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. The AME5259A is available in small DFN-6D, QFN-16C and SOT-25 packages. Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. Cellular Telephones Personal Information Applicances Wireless and DSL Modems MP3 Players Portable Instruments VOUT SW AME5259 A EN GND COUT 10µF CER OUT Figure 1. Fixed Output Voltage High Efficiency Step -Down Conventer VIN = 2.5V to 5.5V 2.2µH VIN IN CIN 4.7µF CER AME5259 A EN VOUT SW GND 1.8V CFWD R1 150K FB l High Efficiency: Up to 95% R2 75K COUT 10µF CER l Shutdown Mode Draws < 1µA Supply Current l 2.5V to 5.5V Input Range l Adjustable Output From 0.6V to VIN l 1.0V, 1.2V. 1.5V, 1.6V, 1.8V, 2.5V and 3.3V Fixed/Adjustable Output Voltage l 1.2A Output Current l Low dropout Operation: 100% Duty Cycle l No Schottky Diode Required l 1.5MHz Constant Frequency PWM Operation l Green Product Meet RoHS Standard Rev.A.02 VOUT=VFB (R1+R2)/R2 Figure 2. Adjustable Output Voltage 1.8V at 1000mA Step-Down Requlator C FWD: 22pF~220pF 1 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Functional Block Diagram Constant Off-time Mode Select Slope COMP VIN IN 3 PWM COMP FB/OUT 6 0.6V 0.6V VREF SW LOGIC 4 0.55V UVDET Soft Start EN 2 OSC NMOS COMP IRCOM P GND 5 Figure 3. Function Block Diagram 2 Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Pin Configuration 9 16 3 10 AME5259 A 15 2 14 1 11 13 AME5259 A 12 8 4 7 5 6 6 AME5259A-AVYxxx 1. NC 2. EN 3. IN 4. SW 5. GND 6. FB/OUT QFN-16C (3mmx3mmx0.75mm) Top View 5 DFN-6D (2mmx2mmx0.75mm) Top View 1 * Die Attach: Conductive Epoxy 2 3 4 AME5259A-AWExxx 9. IN 1. GND 10. IN 2. GND 11. IN 3. GND 12. IN 4. FB/OUT 13. SW 5. GND 14. SW 6. NC 15. SW 7. EN 16. NC 8. NC * Die Attach: Conductive Epoxy SOT-25 Top View 5 4 AME5259 A 1 2 3 AME5259A-AEVADJ 1. EN 2. GND 3. SW 4. IN 5. FB/OUT * Die Attach: Conductive Epoxy Note: Connect exposed pad (heat sink on the back) to GND. Rev.A.02 3 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Pin Description Pin Number 4 Pin Name Pin Description DFN-6D QFN-16C SOT-25 1 6, 8, 16 N/A NC No connection. Not internally connected. Can left floating or connected to GND. 2 7 1 EN Enable Control Input, active high. 3 9, 10, 11, 12 4 IN Input Supply Voltage Pin. Bypass this pin with a capacitor as close to the device as possible. 4 13, 14, 15 3 SW Switch Node Connection to Inductor. 5 1, 2, 3, 5 2 GND Ground. Tie directly to ground plane. 6 4 5 FB/OUT Output voltage Feedback input. Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Ordering Information AME5259A - x x x xxx Output Voltage Number of Pins Package Type Pin Configuration & Special Feature Pin Configuration & Special Feature A (DFN-6D) A (QFN-16C) A (SOT-25) Rev.A.02 1. NC 2. EN 3. IN 4. SW 5. GND 6. FB/OUT 1. GND 2. GND 3. GND 4. FB/OUT 5. GND 6. NC 7. EN 8. NC 9. IN 10. IN 11. IN 12. IN 13. SW 14. SW 15. SW 16. NC Package Type E: SOT-2X V: DFN W: QFN Number of Pins E: 16 V: 5 Y: 6 Output Voltage 100: 120: 150: 160: 180: 250: 330: ADJ: 1.0V 1.2V 1.5V 1.6V 1.8V 2.5V 3.3V Adjustable 1. EN 2. GND 3. SW 4. IN 5. FB/OUT 5 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Absolute Maximum Ratings Parameter Maximum Input Supply Voltage -0.3 to 6.5 EN, VOUT Voltage -0.3 to VIN SW Voltage -0.3 to VIN ESD Classification Unit V HBM 2 kV MM 200 V n Recommended Operating Conditions Parameter 6 Symbol Rating Unit Supply Voltage Voltage VIN 2.5 to 5.5 V Ambient Temperature Range TA -40 to +85 o C Junction Temperature Range TJ -40 to +125 o C Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Thermal Information Parameter Package Die Attach Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Symbol Maximum θJ C 85 o DFN-6D Conductive Epoxy θJA 160 Internal Power Dissipation PD 625 Thermal Resistance* (Junction to Case) θJ C 67 Thermal Resistance (Junction to Ambient) QFN-16C Conductive Epoxy 149 Internal Power Dissipation PD 670 Thermal Resistance* (Junction to Case) θJ C 81 Internal Power Dissipation Solder Iron (10Sec)** Conductive Epoxy θJA 260 PD 400 350 C/W mW o SOT-25 C/W mW o θJA Thermal Resistance (Junction to Ambient) Unit C/W mW o C * Measure θJC on backside center of Exposed Pad. ** MIL-STD-202G 210F Rev.A.02 7 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Electrical Specifications VIN=3.6V, VOUT=2.5V, VFB=0.6V, L=2.2µH, CIN=4.7µF, COUT=10µF, TA=25oC, IMAX=1.2A unless otherwise specified. Parameter Input voltage Test Condition VIN VIN=2.5 to 5.5V, in PWM mode For Fixed Output Voltage Min Typ Max Units 2.5 5.5 V -3 3 % VFB VIN-0.2 V 0.612 V 50 nA Output Voltage Accuracy ∆VOUT Adjustable Output Range Vout Feedback Voltage VFB For Adjustable OutputVoltage 0.588 Feedback Pin Bias Current IFB VFB=VIN -50 Quiescent Current IQ IOUT=0mA, VFB=1V 0.4 0.5 mA Shutdown Current ISHDN VEN=GND 0.1 1 µA Switch Frequency fOSC 1.5 1.8 MHz 1.2 0.6 High-side Switch On-Resistance RDS,ON, LHI ISW=200mA, VIN=3.6V 0.28 Ω Low-side Switch On-Resistance RDS,ON, LO ISW=200mA, VIN=3.6V 0.25 Ω Switch Current Limit ISW,CL VIN=2.5 to 5.5V 1.6 A EN High (Enabled the Device) VEN,HI VIN=2.5 to 5.5V EN Low (Shutdown the Device) VEN,LO VIN=2.5 to 5.5V Input Undervoltage Lockout VUVLO rising edge Input Undervoltage Lockout Hysteresis VUVLO,HYST Thermal Shutdown Temperature OTP Maximum Duty Cycle DMAX SW Leakage Current 8 Symbol 1.5 V 0.4 Shutdown, temperature increasing 1.8 V 0.1 V o 160 -1 C % 100 EN=0V, VIN=5.0V VSW=0V or 5.0V V 1 µA Rev. A.02 AME AME5259A n Detailed Description Main Control Loop AME5259A uses a constant frequency, current mode step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are intermal. During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when the current comparator resets the RS latch. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current starts to reverse as indicated by the current reversal comparator IRCMP. Pulse Skipping Mode Operation At light loads, the inductor current may reach zero or reverse on each pulse. The bottom MOSFET is turned off by the current reversal comparator, IRCMP, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator. Short-Circuit Protection When the output is shorted to ground, the frequency of the oscillator is reduced to about 180KHz. This frequency foldback ensures that the inductor current hsa more time do decay, thereby preventing runaway. The oscillator’ s frequency will progressively increase to 1.5MHz when VFB or VOUT rises above 0V. Dropout Operation As the input supply voltage decreases to a value approaching the output voltage, the duty cycle increases toward the maximum on-time. Further reduction of the supply voltage forces the main switch to remain on for more than one cycle until it reaches 100% duty cycle. The output voltage will then be determined by the input voltage minus the voltage drop across the P-channel MOSFET and the inductor. 1.2A, 1.5MHz Synchronous Step-Down Converter n Application Information The basic AME5259A application circuit is shown in Typical Application Circuit. External component selection is determined by the maximum load current and begins with the selection of the inductor value and followed by CIN and COUT. Inductor Selection For a given input and output voltage, the inductor value and operating frequency determine the ripple current. The ripple current DIL increases with higher VIN and decreases with higher inductance. ∆I L = V 1 × VOUT (1 − OUT ) VIN f ×L A reasonable starting point for setting ripple current is ∆IL=0.4(lmax). The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. For better efficiency, choose a low DC-resistance inductor. CIN and COUT Selection The input capacitance, CIN is needed to filter the trapezoidal current at the source of the top MOSFET. To prevent large voltage transients, a low ESR input capacitorsized for the maximum RMS current must be used. The maximum RMS capacitor current is given by: I RMS = I OUT ( MAX ) × VOUT VIN × −1 VIN VOUT This formula has a maximum at VIN=2VOUT, where IRMS=IOUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. Note that the capacitor manufacturer ripple current ratings are often based on 2000 hours of life. This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. The selection of COUT is determined by the effective series resistance(ESR) that is required to minimize voltage ripple and load step transients. The output ripple, VOUT, is determined by: ∆VOUT ≅ ∆I L ESR + Rev.A.02 1 8 fCOUT 9 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Detailed Description Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. However, care must be taken when these capacitors are used at the input and output. When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be mistaken as loop instability. At worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at VIN large enough to damage the part. Output Voltage Programming The output voltage is set by an external resistive divider according to the following equation : VOUT = VREF ⋅ (1 + Thermal Considerations In most applications the AME5259A does not dissipate much heat due to its high efficiency. But, in applications where the AME5259A is running at high ambient temperature with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maximum junction temperature of the part. If the junction temperature reaches approximately 160OC, both power switches will be turned off and the SW node will become high impedance. To avoid the AME5259A from exceeding the maximum junction temperature, the user will need to do some thermal analysis. The goal of the thermal analysis is to determine whether the power dissipated exceeds the maximum junction temperature of the part. The temperature rise is given by: TR = ( PD)(θ JA ) Where PD is the power dissipated by the regulator and θJA is the thermal resistance from the junction of the die to the ambient temperature. R1 ) R2 Where VREF equals to 0.6V typical. The resistive divider allows the FB pin to sense a fraction of the output voltage as shown in Figure 4. 0.6V VOUT 5.5V R1 FB AME5259 A R2 GND Figure 4. Setting the AME 5259A Output Voltage 10 Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A VIN 2.5V to 5.5V 2.2µH IN SW AME5259A EN CIN 4.7µF CER FB GND V OUT 1.2V C FWD C OUT 10µF CER 150 K 150 K 2.2µH IN SW AME5259A EN CIN 4.7µF CER FB GND V OUT 1.5V CFWD IN SW AME5259A EN CIN 4.7µF CER FB GND SW AME5259A EN VIN 3.3V to 5.5V C OUT 10µF CER 150 K 100 K 2.2µH IN FB GND V OUT 2.5V C OUT 10µF CER CFWD 150 K 47.3K Figure 8. 2.5V Step-Down Regulator C FWD: 22pF~220 pF 2.2µH IN SW AME5259A EN CIN 4.7µF CER FB GND V OUT 3.3V CFWD C OUT 10µF CER 150 K 33.3K Figure 9. 3.3V Step-Down Regulator C FWD: 22pF~220 pF Figure 6. 1.5V Step-Down Regulator C FWD: 22pF~220 pF VIN 2.5V to 5.5V 2.2µH CIN 4.7µF CER Figure 5. 1.2V Step-Down Regulator C FWD: 22pF~220 pF VIN 3.5V to 5.5V VIN 2.7V to 5.5V V OUT 1.6V C FWD C OUT 10µF CER 150 K 90K Figure 7. 1.6V Step-Down Regulator C FWD: 22pF~220 pF Rev.A.02 11 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the AME5259A. These items are also illustrated graphically in Figures 10 and Figures 11 . Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide. 2. Does the VFB pin connect directly to the feedback resistors? The resistive divider R2/R1 must be connected between the (+) plate of COUT and ground. 3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs. 4. Keep the switching node, SW, away from the sensitive VFB node. 5. Keep the (-) plates of CIN and COUT as close as possible. L1 VIN IN C1 AME5259A CIN VOUT SW EN R1 VOUT SW IN AME5259A CIN COUT FB L1 VIN EN OUT COUT NC R2 GND AME5259A AME5259A NC 1 6 VOUT EN 2 5 GND L1 VIN 3 GND NC 4 Output capacitor must be near AME 5259 A NC 1 6 FB EN 2 5 GND VIN SW 3 4 SW C OUT C OU T C IN CIN must be placed between VDD and GND as closer as possible SW should be connected to Inductor by wide and short trace, keep sensitive components away from this trace Figure 10. AME5259A Adjustable Voltage Regulator Layout Diagram 12 Output capacitor must be near AME5259A L1 C IN CIN must be placed between VDD and GND as closer as possible SW should be connected to Inductor by wide and short trace, keep sensitive components away from this trace C1 R1 R2 Figure 11. AME5259A Fixed Voltage Regulator Layout Diagram Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Application Information Supplier Inductance (µ µH) Current Rating (mA) DCR (mΩ Ω) Dimensions (mm) Series TAIYO YUDEN 2.2 1480 60 3.00 x 3.00 x 1.50 NR3015 GOTREND 2.2 1500 58 3.85 x 3.85 x 1.80 GTSD32 Sumida 2.2 1500 75 4.50 x 3.20 x 1.55 CDRH2D14 Table 1. Recommended Inductors Rev.A.02 13 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Characterization Curve Efficiency vs. Output Current Efficiency vs. Output Current 100 100 VIN = 2.7V 90 Efficiency (%) Efficiency (%) 90 80 70 60 80 70 60 50 50 VOUT = 2.5V 40 0.1 V IN = 3.6V 1 COUT = 10µF L = 2.2µH 10 100 VOUT = 2.5V 40 0.1 1200 1 COUT = 10µF L = 2.2µH 10 100 Output Current (mA) Output Current (mA) Efficiency vs. Output Current Efficiency vs. Output Current 1200 100 90 VIN = 2.7V Efficiency (%) Efficiency (%) 90 80 70 60 50 70 60 50 V OUT = 1.5V 40 0.1 VIN = 3.6V 80 1 COUT = 10µF L = 2.2µH 10 100 VOUT = 1.5V 40 0.1 1200 Output Current (mA) Efficiency vs. Output Current 1 COUT = 10µF L = 2.2µH 10 100 Output Current (mA) 1200 Efficiency vs. Output Current 100 VIN = 2.5V Efficiency (%) Efficiency (%) 80 70 60 VOUT = 1.2V 70 60 1 VOUT = 1.2V COUT = 10µF L = 2.2µH 10 100 Output Current (mA) 14 80 50 50 40 0.1 VIN = 5.5V 90 90 1200 40 0.1 1 COUT = 10µF L = 2.2µH 10 100 1200 Output Current (mA) Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Characterization Curve (Contd.) Reference Voltage vs. Temperature Frequency vs. Temperature 1.70 1.65 0.615 1.60 Frequency (MHz) Reference Voltage (V) 0.620 0.610 0.605 0.600 0.595 0.590 0.585 0.580 -25 0 +25 +50 +75 +100 1.50 1.45 1.40 1.35 1.30 1.25 1.20 VIN = 3.6V -50 1.55 VIN = 3.6V 1.15 1.10 +125 -50 -25 0 +50 +75 +100 +125 Temperature ( C) Temperature ( C) Frequency vs. Supply Voltage Output Voltage vs. Output Current 1.70 1.90 1.65 1.89 1.60 1.88 Output Voltage (V) Frequency (MHz) +25 o o 1.55 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 VOUT = 1.8V VIN = 3.6V 1.87 1.86 1.85 1.84 1.83 1.82 1.81 1.80 1.79 1.78 1.10 2.5 3.0 3.5 4.0 4.5 5.0 5.5 1.77 100 200 300 400 500 600 700 800 900 1200 Output Current (mA) VIN(V) Current Limit (A) Current Limit vs. Temperature Rev.A.02 3.0 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 -40 VIN = 5.0V VOUT = 1.2V -25 -10 +5 +20 +35 +50 +65 +80 Temperature (oC) +95 +110 +125 15 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Tape and Reel Dimension DFN-6D (2mmx2mmx0.75mm) P PIN 1 W AME AME Carrier Tape, Number of Components Per Reel and Reel Size Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size DFN-6D (2x2x0.75mm) 8.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm QFN-16C (3mmx3mmx0.75mm) P PIN 1 W AME AME Carrier Tape, Number of Components Per Reel and Reel Size 16 Package Carrier W idth (W) Pitch (P) Part Per Full Reel Reel Size QFN-16C (3x3x0.75mm) 12.0±0.1 mm 4.0±0.1 mm 3000pcs 330±1 mm Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Tape and Reel Dimension (Contd.) SOT-25 P W AME AME PIN 1 Carrier Tape, Number of Components Per Reel and Reel Size Rev.A.02 Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size SOT-25 8.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm 17 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Package Dimension DFN-6D (2mmx2mmx0.75mm) e b D E L E1 PIN 1 IDENTIFICATION D1 TOP VIEW BOTTOM VIEW SYMBOLS A G1 REAR VIEW G INCHES MIN MAX MIN MAX A 0.700 0.800 0.028 0.031 D 1.900 2.100 0.075 0.083 E 1.900 2.100 0.075 0.083 e 18 MILLIMETERS 0.650 TYP 0.026 TYP D1 1.100 1.650 0.043 0.065 E1 0.600 1.050 0.024 0.041 b 0.180 0.350 0.007 0.014 L 0.200 0.450 0.008 0.018 G 0.178 0.228 0.007 0.009 G1 0.000 0.050 0.000 0.002 Rev. A.02 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Package Dimension QFN-16C (3mmx3mmx0.75mm) e b E1 E k L D D1 PIN 1 IDENTIFICATION Bottom View A3 A A1 Top View Real View SYMBOLS INCHES MIN MAX MIN MAX A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.203REF. 0.008REF. D 2.924 3.076 0.115 0.121 E 2.924 3.076 0.115 0.121 D1 1.600 1.800 0.063 0.071 E1 1.600 1.800 0.063 0.071 k b e L Rev.A.02 MILLIMETERS 0.200MIN. 0.180 0.280 0.500TYP. 0.324 0.476 0.008MIN. 0.007 0.011 0.020TYP. 0.013 0.019 19 AME 1.2A, 1.5MHz Synchronous Step-Down Converter AME5259A n Package Dimension SOT-25 Top View Side View D E H L PIN 1 S1 e A1 A Front View b n Lead Pattern 2.40 BSC 1.00 BSC 0.70 BSC Note: 1. Lead pattern unit description: 0.95 BSC 0.95 BSC 1.90 BSC 20 BSC: Basic. Represents theoretical exact dimension or dimension target. 2. Dimensions in Millimeters. 3. General tolerance +0.05mm unless otherwise specified. Rev. A.02 www.ame.com.tw E-Mail: [email protected] Life Support Policy: These products of AME, Inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of AME, Inc. AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. AME, Inc. , January 2014 Document: 1283-DS5259A-A.02 Corporate Headquarter AME, Inc. 8F, 12, WenHu St., Nei-Hu Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989