AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n General Description n Features The AME5251 is a high efficiency monolithic synchronous dual buck regulator using a constant frequency, current mode architecture. Capable of delivering 1A output cur-rent each channel over a wide input voltage range from 2.5V to 5.5V, the AME5251 is ideally suited for single LiIon battery powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Under light load conditions, the AME5251 operates in a power saving mode that consumes just around 20µA of supply current, maximizing battery life in portable applications. l High Efficiency: Up to 95% l Very Low 20µA Quiescent Current l l l l l l High Efficiency in Light Load Condition 2.5V to 5.5V Input Range Adjustable Output From 0.6V to VIN Adjustable Output Voltage 1A Output Current Per Channel Low Dropout Operation: 100% Duty Cycle l No Schottky Diode Required l 1.5MHz Constant Frequency PWM Opera tion l Small DFN-12A Packages l Green Products Meet RoHS Standard 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 AME5251 is available in small DFN-12A packages. n Applications l l l l l Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. Cellular Telephones Personal Information Appliances Wireless and DSL Modems MPS Players Portable Instruments n Typical Application COUT2 VOUT2 L2 ON AME5251 VIN1 CIN2 R2 C1 R1 OFF IN2 EN2 SW2 NC2 GND FB2 FB1 GND NC1 SW1 EN1 IN1 ON VOUT1 OFF R3 CIN1 C2 R4 VIN1 L1 COUT1 Rev.A.05 1 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Function Block Diagram Constant Off-time Mode Select Slope COMP VIN 7 IN1 PWM COMP FB1 4 0.6V 0.6V VREF LOGIC 8 SW1 0.55V UVDET NMOS COMP Soft Start EN1 6 IRCOMP OSC 9 GND Constant Off-time Mode Select Slope COMP VIN 1 IN2 PWM COMP FB2 10 0.6V 0.6V VREF LOGIC 2 SW2 0.55V UVDET Soft Start EN2 12 OSC NMOS COMP IRCOMP 3 GND 2 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Pin Configuration DFN-12A (3mmx3mmx0.75mm) Top View 12 11 10 9 8 7 AME5251 1 2 3 4 5 6 AME5251-AVCxxxxxx 1. IN2 2. SW2 3. GND 4. FB1 5. NC1 6. EN1 7. IN1 8. SW1 9. GND 10. FB2 11. NC2 12. EN2 * Die Attach: Conductive Epoxy Note: Connect exposed pad (heat sink on the back) to GND. n Pin Description Pin Name NC No connection. Not internally connected. Can left floating or connected to GND. EN Enable Control Input, active high. IN Input Supply Voltage Pin. Bypass this pin with a capacitor as close to the device as possible. SW Switch Node Connection to Inductor. GND Ground. Tie directly to ground plane. FB Rev.A.05 Pin Description Output voltage Feedback input. 3 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Ordering Information AME5251 - x x x xxx xxx Output Voltage 2 Output Voltage 1 Number of Pins Package Type Pin Configuration & Special Feature Pin Configuration & Special Feature A (DFN-12A) 4 1 IN2 2. SW2 3. GND 4. FB1 5. NC1 6. EN1 7. IN1 8. SW1 9. GND 10. FB2 11. NC2 12. EN2 Package Type V: DFN Number of Pins C: 12 Output Voltage1 ADJ: Adjustable Output Voltage2 ADJ: Adjustable Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Available Opetions Part Number Marking* Output Voltage AME5251-AVCADJADJ A5251 CBLMXX VOUT1=ADJ VOUT2=ADJ Package Operating Ambient Temperature Range DFN-12A -40oC to +85oC Note: 1. The first 3 places represent product code. It is assigned by AME such as CBL . 2. A bar on top of first letter represents Green Part such as A5251. 3. The last 3 places MXX represent Marking Code. It contains M as date code in "month", XX as LN code and that is for AME internal use only. Please refer to date code rule section for detail information. 4. Please consult AME sales office or authorized Rep./Distributor for the availability of output voltage and package type. n Absolute Maximum Ratings Parameter Input Supply Voltage EN, VOUT Voltage SW Voltage ESD Classification Symbol Maximum V IN -0.3 to 6.5 V EN , VOUT -0.3 to VIN VSW -0.3 to VIN Unit V B* Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device. * HBM B: 2000V~3999V Rev.A.05 5 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Recommended Operating Conditions Parameter 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 n Thermal Information Parameter Package Die Attach Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Symbol Maximum θJC 8.5 Unit o DFN-12A Internal Power Dissipation Solder Iron (10Sec)** Conductive Epoxy C/W θJA 65 PD 1.54 W 350 o C * Measure θJC on backside center of Exposed Pad. ** MIL-STD-202G 210F 6 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Electrical Specifications VIN=3.6V, VOUT=2.5V, VFB=0.6V, L=2.2µH, CIN=4.7µF, COUT=10µF, TA=25oC, IMAX=1A unless otherwise specified. Parameter Symbol Test Condition Min Typ Max Units Input voltage VIN 2.5 5.5 V Adjustable Output Range Vout VFB VIN-0.2 V Feedback Voltage VFB For Adjustable OutputVoltage 0.588 0.612 V Feedback Pin Bias Current IFB VFB=VIN -50 50 nΑ Quiescent Current (For Adjustable Output Voltage) IQ IOUT=0mA, VFB=1V 20 40 µA 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 1.4 1.6 A EN High (Enabled the Device) VEN,HI VIN =2.5 to 5.5V 1.5 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 V 0.4 1.8 V 0.1 V o 160 Shutdown, temperature increasing C 100 EN=0V, V IN =5.0V VSW =0V or 5.0V -1 V % 1 µA Note 1. Spec. for per channel Rev.A.05 7 AME AME5251 n Detailed Description Main Control Loop AME5251 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. 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 abole 0V. Dual 1A, 1.5MHz Synchronous Step-Down Converter n Application Information The basic AME5251 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 Selecton 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 = 1 ( f )(L ) VOUT 1 − VOUT VIN 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. 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. 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 VIN −1 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. 8 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 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 + 1 8 fCOUT 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. Thermal Considerations In most applications the AME5251 does not dissipate much heat due to its high efficiency. But, in applications where the AME5251 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 AME5251 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. Output Voltage Programming The output voltage is set by an external resistive divider according to the following equation: VOUT = V REF × 1 + 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 1. 0.6V V OUT 5.5V R1 FB AME5251 R2 GND Figure 1: Setting the AME5251 Output Voltage Rev.A.05 9 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 VIN 2.5V to 5.5V 2.2µH IN SW AME5251 EN FB GND CIN 4.7µF CER 2.2µH VOUT 1.2V IN CFWD AME5251 COUT 10µF CER 150K SW GND CIN 4.7µF CER 150K FB EN VOUT 2.5V CFWD COUT 10µF CER 150K 47.3K Figure 2: 1.2V Step-Down Regulator Figure 5: 2.5V Step-Down Regulator CFWD: 22pF~220pF CFWD: 22pF~220pF VIN 3.3 to 5.5V 2.2µH IN SW AME5251 EN FB GND CIN 4.7µF CER VOUT 1.5V VIN 3.6 to 5.5V CFWD 2.2µH IN SW AME5251 EN 150K CIN 4.7µF CER 100K FB GND VOUT 3.3V CFWD 150K 33.3K Figure 3: 1.5V Step-Down Regulator Figure 6: 3.3V Step-Down Regulator CFWD: 22pF~220pF CFWD: 22pF~220pF VIN 2.5 to 5.5V 2.2µH IN SW AME5251 EN CIN 4.7µF CER FB GND COUT 10µF CER VOUT 1.6V CFWD 150K COUT 10µF CER 90K Figure 4: 1.6V Step-Down Regulator CFWD: 22pF~220pF 10 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 PCB Board Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the AME5251. 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. VIN L1 AME5251 CIN VOUT SW IN EN C1 R1 COUT FB VIN CIN L1 VOUT SW IN AME5251 EN OUT COUT NC GND Figure 7 Rev.A.05 R2 NC GND Figure 8 11 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Application Information External components selection Supplier Inductance (µ µF) Current Rating (mA) DCR (mΩ Ω) Dimensions (mm) Series TAIYO YUDEN 2.2 1480 60 3.00 x 3.00 x 1.50 NR 3015 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 Sumida 4.7 1000 135 4.50 x 3.20 x 1.55 CDRH2D14 TAIYO YUDEN 4.7 1020 120 3.00 x 3.00 x 1.50 NR 3015 GOTREND 4.7 1100 146 3.85 x 3.85 x 1.80 GTSD32 Table 1. Recommended Inductors Table 2. Recommended Capacitors for CIN and COUT 12 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Characterization Curve Efficiency vs. Output Current Efficiency vs. Output Current 100 100 Efficiency(%) Efficiency(%) 90 VIN = 2.7V 90 80 70 60 80 70 60 50 50 VOUT = 2.5V 40 0.1 VIN = 3.6V 1 COUT = 10µF L = 2.2µH 10 100 VOUT = 2.5V 40 0. 1 1000 1 COUT = 10µF L = 2.2µH 10 100 Efficiency vs. Output Current Efficiency vs. Output Current 100 100 90 90 Efficiency(%) VIN = 2.7V Efficiency(%) 80 70 60 50 VOUT = 1.5V 40 0.1 1 10 100 VIN = 3.6V 80 70 60 50 COUT = 10µF L = 2.2µH VOUT = 1.5V 40 0.1 1000 Output Current(mA) 1 COUT = 10µF L = 2.2µH 10 100 Efficiency vs. Output Current 100 100 VIN = 2.5V Efficiency(%) Efficiency(%) VIN = 5.5V 90 90 80 70 60 80 70 60 50 50 VOUT = 1.2V Rev.A.05 1000 Output Current(mA) Efficiency vs. Output Current 40 0.1 1000 Output Current(mA) Output Current(mA) 1 VOUT = 1.2V COUT = 10µF L = 2.2µH 10 100 Output Current(mA) 1000 40 0.1 1 COUT = 10µF L = 2.2µH 10 100 1000 Output Current(mA) 13 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Characterization Curve (Contd.) Reference Voltage vs. Temperature Frequency vs. Temperature 1.70 0.620 1.65 1.60 0.610 Frequency(MHz) Reference Voltage(V) 0.615 0.605 0.600 0.595 0.590 0.585 -25 0 +25 +50 +75 +100 1.50 1.45 1.40 1.35 1.30 1.25 1.20 VIN = 3.6V VIN = 3.6V 1.15 1.10 +125 -50 +50 +75 +100 +125 Output Voltage vs. Output Current 1.90 1.65 1.89 1.60 1.88 1.55 1.87 1.50 1.45 1.40 1.35 1.30 1.25 VOUT = 1.8V VIN = 3.6V 1.86 1.85 1.84 1.83 1.82 1.81 1.80 1.79 1.15 1.78 1.10 2.5 3.0 3.5 4.0 VIN(V) 4.5 5.0 5.5 1.77 100 Current Limit(A) -10 +5 300 400 500 600 700 800 900 1000 Current Limit vs. Temperature VIN = 3.3V VOUT = 1.2V -25 200 Output Current(mA) Current Limit vs. Temperature Current Limit(A) +25 Frequency vs. Supply Voltage 1.20 +20 +35 +50 +65 +80 +95 +110 +125 Temperature (oC) 14 0 Temperature (oC) 1.70 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 -25 Temperature (oC) Output Voltage(V) Frequency(MHz) 0.580 -50 1.55 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 = 3.6V VOUT = 1.2V -25 -10 +5 +20 +35 +50 +65 +80 Temperature (oC) +95 +110 +125 Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Characterization Curve (Contd.) Current Limit(A) Current Limit vs. Temperature 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 Light Load Mode output voltage ripple VIN = 5.0V VOUT = 1.2V -25 -10 +5 +20 +35 +50 +65 +80 +95 +110 +125 o Temperature ( C) VIN = 3.6V VOUT = 1.8V IOUT = 50mA 1) VSW= 5V/div 2) VOUT = 100mV/div 3) IL = 200mA/div Power Off from EN Rev.A.05 Load Step VIN = 3.6V VOUT = 1.8V IOUT = 1A VIN = 3.6V VOUT = 1.8V IOUT = 0A~1A~0A 1) EN = 2V/div 2) VOUT = 2V/div 3) IL = 500mA/div 1) VOUT= 100mV/div 2) IOUT = 500mA/div 15 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Characterization Curve (Contd.) Load Step VIN = 3.6V VOUT = 1.8V IOUT = 50mA~1A~50mA VIN = 3.6V VOUT = 1.8V IOUT = 100mA~1A~100mA 1) VOUT= 100mV/div 2) IOUT = 500mA/div 1) VOUT= 100mV/div 2) IOUT = 500mA/div Load Step 16 Load Step Power On from EN VIN = 3.6V VOUT = 1.8V IOUT = 200mA~1A~200mA VOUT = 1.2V IOUT = 1A 1) VOUT= 100mV/div 2) IOUT = 500mA/div 1) EN= 2V/div 2) VOUT = 500mV/div 3) IL = 1A/div Rev. A.05 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Date Code Rule Month Code 1: January 7: July 2: February 8: August 3: March 9: September 4: April A: October 5: May B: November 6: June C: December Marking A M X X Year xxx0 M X X xxx1 A M X X xxx2 A A M X X xxx3 A A A M X X xxx4 A A A M X X xxx5 A A A M X X xxx6 A A A M X X xxx7 A A A M X X xxx8 A A A M X X xxx9 A A A A A A A A n Tape and Reel Dimension DFN-12A (3mmx3mmx0.75mm) P PIN 1 W AME AME Carrier Tape, Number of Components Per Reel and Reel Size Rev.A.05 Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size DFN-12A (3x3x0.75mm) 12.0±0.1 mm 4.0±0.1 mm 5000pcs 330±1 mm 17 AME Dual 1A, 1.5MHz Synchronous Step-Down Converter AME5251 n Package Dimension DFN-12A (3mmx3mmx0.75mm) e D L k E1 E D1 PIN 1 IDENTIFICATION b TOP VIEW P IN 1 BOTTOM VIEW A1 A3 A REAR 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 2.450 2.650 0.096 0.104 E1 1.500 1.700 0.059 0.067 k b e L 18 MILLIMETERS 0.200MIN. 0.150 0.250 0.450TYP. 0.324 0.476 0.008MIN 0.006 0.010 0.018TYP. 0.013 0.019 Rev. A.05 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-DS5251-A.05 Corporate Headquarter AME, Inc. 8F, 12, WenHu St., Nei-Hu Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989