AT1361 1MHz,1A Synchronous Buck Converter Features • High efficiency (95%) possible • No Schottky Diode Required • 1A Output Current at 5V input 3.3V output • Oscillation frequency 1.0MHz • Built-in ON/OFF Function • Built-in Short Circuit Protection • Low Dropout Operation: 100% Duty Cycle • Stand-by current max. 1µA • Input voltage: 2.5V ~5.5V Applications • Power Supply for portable devices General Description The AT1361 provides complete control for a DC/DC converter optimized for high-performance microprocessor applications. It is operated on current mode architecture for excellent line and load transient response. 1MHz operation frequency is allowing the use of small surface mount inductor and capacitor. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. The AT1361 is a family of low-noise synchronous step-down DC/DC converters that is ideally suited for systems powered from a 1-cell Li-ion battery or from a 3-cell to 4-cell NiCd, NiMH, or alkaline battery. It can also be used to USB-Based power system. Block Diagram Aimtron reserves the right without notice to change this circuitry and specifications. 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 1 AT1361 1MHz,1A Synchronous Buck Converter Pin Configuration Ordering Information Part number AT1361X_GRE Package SOT-25, Green ▲▲▲▲▲ Marking : Date Code with one bottom line *For more marking information, contact our sales representative directly Pin Description Symbol Pin No. RUN GND SW VIN FB 1 2 3 4 5 Descript ON/OFF Control Power ground Switch Node Connection to Inductor Power Supply Output Feedback 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 2 AT1361 1MHz,1A Synchronous Buck Converter Absolute Maximum Ratings:(TA=25°C) Parameter Condition Power Supply Voltage Input Pin Voltage Rated Value Min. Max. -0.3 +6.0 -0.3 VIN -0.3 VIN+0.3 1200 — RUN,FB SW — P-Channel Switch Source Current (DC) N-Channel Switch Sink Current (DC) Peak SW Sink and Source Current Thermal Resistance from Junction to Ambient θJA Operating temperature TA Storage temperature ESD Susceptibility *2 Unit V V V mA — - 1200 mA — SOT-25 - 1.5 200 A °C /W — — HBM MM -35 -55 +85 +150 °C °C KV V 2 200 1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2. Device are ESD sensitive. Handling precaution recommended. The Human Body model is a 100pF capacitor discharged through a 1.5KΩ resistor into each pin. Recommended Operating Conditions (TA=+25°C) Parameter Power supply voltage Operating temperature* Operating junction temperature Symbol VIN TA TJ Values Min. 2.5 -20 - Typ. -+25 - Unit Max. 5.5 +85 +150 Ｖ °C °C *Using X5R or X7R input capacitors. 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 3 AT1361 1MHz,1A Synchronous Buck Converter Electrical Characteristics (VIN =5V, TA=+25°C , unless otherwise noted. ) Parameter Input Supply Range Input Under-Voltage Lock Out threshold UVLO hysteresis Symbol VIN VUVLO Quiescent Current* IS Current in standby mode IST Feedback Voltage VFB Feedback Voltage line-regulation VFB-Line Feedback current IFB Peak Inductor Current* IPK Maximum Output Current* IO RDS(ON) of P-Channel MOSFET RDS(ON) of N-Channel MOSFET SW Leakage Current IN Rising FB=0.6V,ILOAD=0A Active Mode RUN=0V, VIN=5.5V VIN =2.5V to 5.5V TA=-20°C to +85°C Feedback Variation with Temperature Oscillator Frequency Condition VIN=5V,VOUT=3.3V * I PK = I O + Unit Min. Typ. Max. 2.5 -- 5.5 V -- 2.3 -- V -- 0.1 -- V -- 70 100 µA -- 0.5 1 µA 0.588 0.600 0.612 V -- 0.1 0.5 %/V -- 0.5 1.0 % -- -- ±200 nA 1.2 1.8 -- A 1 -- -- A fosc1 VIN=5V±5%, VOUT=3.3V, L=4.7µH, TA=25°C FB=0.6V 0.8 1.0 1.2 MHz fosc2 FB=0V -- 200 -- KHz ISW=600mA -- 0.4 0.5 Ω ISW=-600mA -- 0.35 0.45 Ω RUN=0V,SW=0V or 5V,VIN=5V -- ±0.1 ±1 µA 1.5 -- -- V -- -- 0.3 V -- ±0.1 ±1 µA RPFET RNFET ILSW RUN High-Level Input VIN =2.5V to 5.5V VRUN＿H Voltage RUN Low-Level Input VIN =2.5V to 5.5V VRUN＿L Voltage RUN leakage Current Values IRUN (V − VOUT ) × t ON ∆I = I O + IN 2 2× L 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 4 AT1361 1MHz,1A Synchronous Buck Converter Typical Application Circuit L1:Sumida CDRH4D28-4R7 Figure 1 .Adjustable Voltage Regulator Efficiency VS. Load Current 90 80 VIN=2.8V Efficiency(% 70 VIN=3.6V VIN=4.2V 60 50 40 30 10 100 Load Current(mA) L1:Sumida CDRH4D28-4R7 Figure 2 .Buck-Boost Regulator 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 5 AT1361 1MHz,1A Synchronous Buck Converter Typical characteristics : Reference Voltage vs. Input Voltage 90 0.619 85 0.614 Reference Voltage(V) Quisecent Current(uA) Quiescent Current vs. Input Voltage 80 75 70 65 60 0.609 0.604 0.599 0.594 0.589 55 Vout=1.2V Vout=1.2V 0.584 50 2 2.5 3 3.5 4 4.5 5 5.5 2 6 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage(V) Input Voltage(V) Oscillator Frequency vs. Temperature 1.3 Oscillator Frequency vs. Input Voltage 1.25 1.2 Oscillator Frequency (MHz Oscillator Frequency(MHz) 1.15 1.1 1.05 1 0.95 1.15 Load=1A 1.1 1.05 Load=0.8A 1 0.95 0.9 0.85 0.9 0.8 Vout=1.2V Load=800mA VIN=5V 0.75 VOUT=3.3V 0.85 2 2.5 3 3.5 4 4.5 5 5.5 6 0.7 -30 -20 -10 0 10 Input Voltage(V) 30 40 50 60 70 80 90 Vout Voltage vs. Temperature Vout Voltage vs. Temperature 1.25 1.85 1.24 1.84 1.23 1.83 1.22 1.82 Vout Voltage(V) Vout Voltage(V) 20 Temperature (℃) 1.21 1.2 1.19 1.81 1.8 1.79 1.18 1.78 1.17 1.77 1.16 1.76 1.75 1.15 -30 -20 -10 0 10 20 30 40 50 Temperature (℃) 60 70 80 90 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Temperature (℃) 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 6 AT1361 1MHz,1A Synchronous Buck Converter Typical characteristics : Vout Voltage vs. Temperature 2.55 3.35 2.54 3.34 2.53 3.33 2.52 3.32 Vout Voltage(V) Vout Voltage(V) Vout Voltage vs. Temperature 2.51 2.5 2.49 Load=0.8A Load=1A 3.31 3.3 3.29 2.48 3.28 2.47 3.27 2.46 3.26 2.45 3.25 VIN=5V -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -30 -20 -10 Temperature (℃) 10 20 30 40 50 60 70 80 90 Temperature (℃) Efficiency VS. Load Current Efficiency VS. Load Current 100 90 90 80 80 70 70 Efficiency(%) 100 Efficiency(% 0 60 50 VIN=2.5V,VOUT=1.2V 40 60 50 40 VIN=3.6V,VOUT=3.3V VIN=3.6V,VOUT=1.2V 30 30 VIN=4.2V,VOUT=3.3V VIN=4.2V,VOUT=1.2V 20 20 VIN=5V,VOUT=1.2V L=4.7uH/SR0302 VIN=5V,VOUT=3.3V L=4.7uH/SR0302 10 10 10 100 10 1000 Load Current(mA) 100 Load C urre nt(mA) 1000 Efficiency VS. Load Current 100 90 80 Efficiency(% 70 60 50 VOUT=1.2V 40 VOUT=1.8V 30 VOUT=2.5V 20 VOUT=3.3V L=4.7uH/SR0302 10 10 100 Load Current(mA) 1000 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 7 AT1361 1MHz,1A Synchronous Buck Converter Typical characteristics : Power ON/OFF CH1: VOUT CH2: VIN CH3:SW CH4:IIN VIN=5V,VOUT=3.3V,Load=1A, Power ON VIN=5V,VOUT=3.3V,Load=1A,Power OFF EN pin ON/OFF CH1: VOUT CH2:EN CH3:SW CH4:IIN VIN=5V,VOUT=3.3V,Load=1A,EN Turn-ON VIN=5V,VOUT=3.3V,Load=1A,EN Turn-OFF 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 8 AT1361 1MHz,1A Synchronous Buck Converter Transient response CH2:VOUT CH4:IOUT VIN=5V,VOUT=3.3V,C2=100pF IOUT=0mA to1A IOUT=100mA to 1A IOUT=50mA to 1A IOUT=200mA to1A Ripple noise ◎VIN=5V,VOUT=3.3V,Load=0A ◎VIN=5V,VOUT=3.3V,Load=1A 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 9 AT1361 1MHz,1A Synchronous Buck Converter Application Information Short Circuit Protection Function The AT1361 has short circuit protection(see the Electrical Characteristics frequency item). When the output is shorted to ground, the frequency of the oscillator is reduced to about 200KHz. This frequency foldback ensures that the inductor current has more time to decay. It will prevent the inductor current and internal P-MOSFET current runaway to damage the device. The frequency will return to the normal values when the short circuit condition is removed and the feedback voltage reaches 0.6V. Capacitor Selection In continuous mode, the source current of the top MOSFET is square wave of duty cycle. The Primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the AT1361. A load step at the output can induce ringing at the input VIN. This ringing can couple to the output and be mistaken as loop instability. The oscillation can be improved by add the capacitance of the input capacitor. A typical value is 4.7~22µF ceramic (X5R or X7R), POSCAP or Aluminum Polymer. These capacitors will provide good high frequency bypassing and their low ESR will reduce resistive losses for higher efficiency. The input capacitor RMS current varies with the input voltage and the output voltage. The equation for the maximum RMS current in the input capacitor is: I RMS = I OMAX VO V (1 − O ) VIN VIN The output capacitor depends on the suitable ripple voltage. Low ripple voltage corresponds to lower effective series resistance (ESR). The output ripple voltage is determined by: ∆VOUT ≅ ∆I L ( ESR + 1 ) 8 fC OUT The output capacitor RMS ripple current is given by: I RMS = 1 VOUT × (VIN − VOUT ) L × f × VIN 2 3 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 10 AT1361 1MHz,1A Synchronous Buck Converter When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. Inductor Selection The inductor is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple current. Always consider the losses associated with the DCR and its effect on the total converter efficiency when selecting an inductor. The inductor is selected to limit the ripple current to some predetermined value, typically 20~40% of the full load current at the maximum input voltage. The formula of inductance value is as below: ∆I L = 0.2 ~ 0.4 × I OUT ( MAX ) L= VOUT f × ∆I L ⎛ VOUT ⎜⎜1 − VIN ⎝ ⎞ ⎟⎟ ⎠ Adjustable Output Voltage The AT1361 appears a 0.6V reference voltage at FB pin. The output voltage is set by a resistive divider which is according to the following formula: 0.6V=VOUT=5.5V R2 FB VOUT R2 = 0.6V × (1 + ) R1 R1 GND *R1=150KΩ for stability consideration. 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 11 AT1361 1MHz,1A Synchronous Buck Converter The Dissipation The power loss is given by: PLOSS = I O2 × RDS (ON ) − P × D + I O2 × R DS ( ON ) − N × (1 − D) + 1 × VIN × I O × (t r + t f ) × f s 2 1 + × VD × I O × (t r + t f ) × f s + VIN × I Q 2 TJ ( MAX ) = T A + θ JA × PLOSS Inductance(µH) 4.7 4.7 Inductors Surface Mount Manufacturer/Part No. Sumida CDRH4D28-4R7 ABC SH40284R7YSB Manufacturer Website www.sumida.com www.atec-group.com Capacitance(µF) 22 47 10 4.7 Capacitors Surface Mount Manufacturer/Part No. TDK C3216X5R0J226M TDK C3225X5R0J46M GRM42-6X5R 106K6.3 TAIYO JMK212BJ475MG Manufacturer Website www.tdk.com www.tdk.com www.murata.com www.t-yuden.com 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 12 AT1361 1MHz,1A Synchronous Buck Converter PC Board Layout 1. The most critical aspect of the layout is the placement of the input capacitor C1. It must be placed as close as possible to the AT1361 to reduce the input ripple voltage. 2. Power loops on the input and output of the converter should be laid out with the shortest and widest traces possible. The longer and narrower the trace, the higher resistance and inductance it will have. The length of traces in series with the capacitors increases its ESR and ESL and reduces their effectiveness at high frequency. 3. The FB pin should connect to feedback resistors directly. And the route should be away from the noise source, such as inductor of SW line. 4. Grounding all components at the same point may effectively reduce the occurrence of loop. 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 13 AT1361 1MHz,1A Synchronous Buck Converter Package Outline :SOT-25 SYMBOL A A1 A2 b C D E E1 L e e1 r INCHES MIN 0.035 0.000 0.035 0.010 0.003 0.110 0.102 0.059 0.014 MAX 0.057 0.006 0.051 0.020 0.008 0.122 0.118 0.069 0.022 0.037ref 0.075ref 00 100 MILLIMETERS MIN MAX 0.90 1.45 0.00 0.15 0.90 1.30 0.25 0.50 0.08 0.20 2.80 3.10 2.60 3.00 1.50 1.75 0.35 0.55 0.95ref 1.90ref 00 100 NOTES - - 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 14 AT1361 1MHz,1A Synchronous Buck Converter Reflow Profiles Profile Feature Sn-Pb Eutectic Assembly Large Body Small Body Pkg. thickness Pkg. thickness <2.5mm or Pkg. ≥2.5mm or Pkg. 3 volume ≥350mm3 volume <350mm Average ramp-up rate (TL to TP) Preheat -Temperature Min(Tsmin) -Temperature Max (Tsmax) -Time (min to max)(ts) Tsmax to TL -Ramp-up Rate Time maintained above: -Temperature (TL) -Time (tL) Peak Temperature(TP) Time within 5°C of actual Peak Temperature (tP) Ramp-down Rate Time 25°C to Peak Temperature 3°C/second max. Pb-Free Assembly Large Body Small Body Pkg. thickness Pkg. thickness ≥2.5mm or Pkg. ≥2.5mm or Pkg. volume ≥350mm3 volume ≥350mm3 3°C/second max. 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds 3°C/second max. 183°C 60-150 seconds 217°C 60-150 seconds 225+0/-5°C 10-30 seconds 240+0/-5°C 10-30 seconds 6°C/second max. 6 minutes max. 245+0/-5°C 10-30 seconds 250+0/-5°C 20-40 seconds 3°C/second max. 8 minutes max. *All temperatures refer to topside of the package, measured on the package body surface. 7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 1/11/2008 REV:1.0 Email:[email protected] 15