AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n General Description The AME5253 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. Capable of delivering 1A output current over a wide input voltage range from 2.5V to 5.5V, the AME5253 is ideally suited for single Li-Ion battery powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Under light load conditions, the AME5253 operates in a power saving mode that consumes just around 20µA of supply current, maximizing battery life in portable applications. 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 AME5253 is available in SOT-25 packages. Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. n Applications l l l l l Cellular Telephones Personal Information Appliances Wireless and DSL Modems MP3 Players Portable Instruments n Typical Application VIN = 2.5V to 5.5V VIN IN CIN 4.7µF CER 2.2µH VOUT SW AME5253 EN GND CFWD R1 150K FB R2 75K 1.8V 1000mA COUT 10µF CER VOUT=VFB (R1+R2)/R2 Figure 1. 1.8V at 1000mA Step-Down Requlator CFWD: 22pF~220pF n Features l l l l l l l l l l l Rev.A.04 High Efficiency: Up to 95% Very Low 20µA Quiescent Current High efficiency in light load condition 2.5V to 5.5V Input Range Adjustable Output From 0.6V to VIN 1A Output Current Low Dropout Operation: 100% Duty Cycle No Schottky Diode Required 1.5MHz Constant Frequency PWM Operation SOT-25 Packages All AME’ s Lead Free Product Meet RoHS Standard 1 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Function Block Diagram Constant Off-time Mode Select Slope COMP VIN IN 3 PWM COMP FB 6 0.6V 0.6V VREF SW LOGIC 4 0.55V UVDET Soft Start EN 2 NMOS COMP IRCOMP OSC GND 5 Figure 2. Founction Block Diagram 2 Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Pin Configuration SOT-25 Top View 5 AME5253-AEVADJ 1. EN 2. GND 3. SW 4. IN 5. FB 4 AME5253 1 2 3 Die Attach: Conductive Epoxy n Pin Description Pin Number Pin Name Pin Description 1 EN No connection. Not internally connected. Can left floating or connected to GND. 2 GND Ground. Tie directly to ground plane. 3 SW Switch Node Connection to Inductor. 4 IN Input Supply Voltage Pin. Bypass this pin with a capacitor as close to the device as possible. 5 FB Output voltage Feedback input. Rev.A.04 3 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Ordering Information AME5253 - x x x xxx Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration Package Type Number of Pins 1. EN 2. GND 3. SW 4. IN 5. FB E: SOT-2X V: 5 A (SOT-25) 4 Output Voltage ADJ: Adjustable Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Absolute Maximum Ratings Parameter Symbol Maximum VIN -0.3 to 6.5 VEN, VOUT -0.3 to VIN VSW -0.3 to VIN Input Supply Voltage EN, VOUT Voltage SW Voltage Unit V B* ESD Classification Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device. * HBM B: 2000V~3999V 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 θJ C 81 Unit o SOT-25 Internal Power Dissipation Solder Iron (10Sec)** Conductive Epoxy θJA 260 PD 400 350 C/W mW o C * Measure θJC on backside center of Exposed Pad. ** MIL-STD-202G 210F Rev.A.04 5 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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 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 0.588 0.612 V Feedback Pin Bias Current IFB VFB=VIN 50 nA Quiescent Current IQ IOUT=0mA, VFB=1V 20 35 µA Shutdown Current ISHDN VEN=GND 0.1 1 µA Switch Frequency fOSC 1.5 1.8 MHz 0.6 -50 1.2 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 6 Symbol V 0.4 Shutdown, temperature increasing 1.8 V 0.1 V o 160 100 EN=0V, VIN=5.0V VSW =0V or 5.0V -1 V C % 1 µA Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Detailed Description Main Control Loop AME5253 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 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. n Application Information The basic AME5253 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 = 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. 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 V IN 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. Rev.A.04 7 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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. Output Voltage Programming Thermal Considerations In most applications the AME5253 does not dissipate much heat due to its high efficiency. But, in applications where the AME5253 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 AME5253 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. 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 3. 0.6V ≤ V OUT ≤ 5.5V R1 FB AME5253 R2 GND Figure 3. Setting the AME 5253 Output Voltage 8 Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 VIN 2.5V to 5.5V 2.2µH IN SW AME5253 EN FB GND CIN 4.7µF CER VOUT 1.2V V IN 2.7V to 5.5V C OUT 10µF CER C FWD IN SW AME5253 EN FB GND CIN 4.7µF CER SW EN CIN 4.7µF CER FB GND IN SW FB GND V OUT 3.3V C FWD AME5253 CIN 4.7µF CER C OUT 10µF CER 150K 33.3K Figure 8: 3.3V Step-Down Regulator C FWD: 22pF~220pF VOUT 1.6V C FWD AME5253 150K 2.2µH EN Figure 5: 1.5V Step-Down Regulator C FWD: 22pF~220pF IN FB 47.3K V IN 3.6V to 5.5V C OUT 10µF CER 150K 2.2µH C OUT 10µF CER Figure 7: 2.5V Step-Down Regulator CFWD : 22pF~220pF VOUT 1.5V C FWD V OUT 2.5V CFWD GND CIN 4.7µF CER 100 K VIN 2.5V to 5.5V SW AME5253 Figure 4: 1.2V Step-Down Regulator C FWD: 22pF~220pF 2.2µH IN EN 150K 150 K VIN 3.3V to 5.5V 2.2µH C OUT 10µF CER 150K 90K Figure 6: 1.6V Step-Down Regulator C FWD: 22pF~220pF Rev.A.04 9 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the AME5253. These items are also illustrated graphically in Figures 9. 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 IN SW C FWD AME5253 EN CIN FB GND C OUT R2 R1 CFWD : 22pF~220 pF 10 VOUT Figure 9: AME5253 Adjustable Voltage Regulator Layout Diagram Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Application Information External components selection Supplier Inductance (µ H) Current Rating (mA) DCR (m 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 Rev.A.04 11 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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 12 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) Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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 Output Voltage vs. Output Current 1.90 1.89 1.60 1.88 1.55 1.87 1.50 1.45 1.40 1.35 1.30 1.25 1.20 +125 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 1.65 +20 +35 +50 +65 +80 +95 +110 +125 Temperature (oC) Rev.A.04 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 13 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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 14 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 Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Characterization Curve (Contd.) Load Step 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 Rev.A.04 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 15 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 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 SOT-25 P0 W AME AME PIN 1 P Carrier Tape, Number of Components Per Reel and Reel Size 16 Package Carrier Width (W) Pitch (P) Pitch (P0) Part Per Full Reel Reel Size SOT-25 8.0±0.1 mm 4.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm Rev. A.04 AME 1A, 1.5MHz Synchronous Step-Down Converter AME5253 n Package Dimension SOT-25 Top View Side View D E H L PIN 1 S1 e A1 A Front View b 2.40 BSC 1.00 BSC 0.70 BSC 0.95 BSC Note: 1. Lead pattern unit description: BSC: Basic. Represents theoretical exact dimension or dimension target. 2. Dimensions in Millimeters. 3. General tolerance 0.05mm unless otherwise specified. 0.95 BSC 1.90 BSC Rev.A.04 17 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. , August 2014 Document: 1283-DS5253-A.04 Corporate Headquarter AME, Inc. 2F, 302 Rui-Guang Road, Nei-Hu District Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989