AT1361

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:service@aimtron.com.tw 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. Descript RUN GND SW VIN FB 1 2 3 4 5 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:service@aimtron.com.tw 2 AT1361 1MHz,1A Synchronous Buck Converter Absolute Maximum Ratings:(TA=25°C) Parameter Power Supply Voltage Input Pin Voltage 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 Condition — RUN,FB SW — — — SOT-25 — — HBM MM Rated Value Min. Max. -0.3 +6.0 -0.3 VIN -0.3 VIN+0.3 1200 -35 -55 2 200 1200 1.5 200 +85 +150 Unit V V V mA mA A °C /W °C °C KV V 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 *Using X5R or X7R input capacitors. Symbol VIN TA TJ Min. 2.5 -20 - Values Typ. -+25 Max. 5.5 +85 +150 Unit Ｖ °C °C 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:service@aimtron.com.tw 3 AT1361 1MHz,1A Synchronous Buck Converter Electrical Characteristics (VIN =5V, TA=+25°C , unless otherwise noted. ) Parameter Symbol Condition Min. Values Typ. -2.3 0.1 70 0.5 0.600 0.1 0.5 -1.8 -1.0 200 0.4 0.35 ±0.1 --±0.1 Max. 5.5 --100 1 0.612 0.5 1.0 ±200 --1.2 -0.5 0.45 ±1 -0.3 ±1 Unit Input Supply Range Input Under-Voltage Lock Out threshold UVLO hysteresis Quiescent Current* Current in standby mode Feedback Voltage Feedback Voltage line-regulation Feedback Variation with Temperature Feedback current Peak Inductor Current* Maximum Output Current* Oscillator Frequency RDS(ON) of P-Channel MOSFET RDS(ON) of N-Channel MOSFET SW Leakage Current VIN VUVLO IN Rising 2.5 --- V V V µA µA V %/V % nA A A MHz KHz Ω Ω µA V V µA IS IST VFB VFB-Line FB=0.6V,ILOAD=0A Active Mode RUN=0V, VIN=5.5V --0.588 VIN =2.5V to 5.5V TA=-20°C to +85°C ---- IFB IPK IO fosc1 fosc2 RPFET RNFET ILSW VIN=5V,VOUT=3.3V VIN=5V±5%, VOUT=3.3V, L=4.7µH, TA=25°C FB=0.6V FB=0V ISW=600mA ISW=-600mA RUN=0V,SW=0V or 5V,VIN=5V 1.2 1 0.8 ----1.5 --- 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 IRUN * I PK = I O + (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:service@aimtron.com.tw 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 70 Efficiency(% VIN=3.6V VIN=4.2V 60 50 40 30 10 Load Current(mA) 100 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:service@aimtron.com.tw 5 AT1361 1MHz,1A Synchronous Buck Converter Typical characteristics : Quiescent Current vs. Input Voltage 90 85 Reference Voltage vs. Input Voltage 0.619 0.614 Quisecent Current(uA) 80 75 70 65 60 55 50 2 2.5 3 3.5 4 4.5 5 5.5 6 Reference Voltage(V) 0.609 0.604 0.599 0.594 0.589 Vout=1.2V 0.584 2 2.5 3 3.5 4 4.5 5 Vout=1.2V 5.5 6 Input Voltage(V) Input Voltage(V) Oscillator Frequency vs. Temperature 1.3 Oscillator Frequency vs. Input Voltage 1.15 1.25 1.2 Oscillator Frequency (MHz 1.15 1.1 1.05 1 0.95 0.9 0.85 Oscillator Frequency(MHz) 1.1 Load=1A 1.05 Load=0.8A 1 0.95 0.9 Vout=1.2V Load=800mA 2 2.5 3 3.5 4 4.5 5 5.5 6 0.8 0.75 0.7 -30 -20 -10 0 10 20 30 40 50 VIN=5V VOUT=3.3V 60 70 80 90 0.85 Input Voltage(V) Temperature (℃) Vout Voltage vs. Temperature 1.25 1.24 1.23 1.22 Vout Voltage vs. Temperature 1.85 1.84 1.83 1.82 Vout Voltage(V) Vout Voltage(V) 1.21 1.2 1.19 1.18 1.17 1.16 1.15 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 1.81 1.8 1.79 1.78 1.77 1.76 1.75 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Temperature (℃) 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:service@aimtron.com.tw 6 AT1361 1MHz,1A Synchronous Buck Converter Typical characteristics : Vout Voltage vs. Temperature 2.55 2.54 2.53 2.52 3.35 3.34 3.33 3.32 Vout Voltage vs. Temperature Load=0.8A Vout Voltage(V) Vout Voltage(V) 2.51 2.5 2.49 2.48 2.47 2.46 2.45 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 3.31 3.3 3.29 3.28 3.27 3.26 Load=1A VIN=5V 3.25 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Temperature (℃) Temperature (℃) Efficiency VS. Load Current 100 100 Efficiency VS. Load Current 90 90 80 80 70 70 Efficiency(%) Efficiency(% 60 60 50 50 40 VIN=2.5V,VOUT=1.2V VIN=3.6V,VOUT=1.2V 40 VIN=3.6V,VOUT=3.3V 30 30 VIN=4.2V,VOUT=1.2V 20 VIN=4.2V,VOUT=3.3V 20 VIN=5V,VOUT=1.2V L=4.7uH/SR0302 10 VIN=5V,VOUT=3.3V L=4.7uH/SR0302 10 100 Load C urre nt(mA) 1000 10 10 Load Current(mA) 100 1000 Efficiency VS. Load Current 100 90 80 70 Efficiency(% 60 50 40 VOUT=1.2V VOUT=1.8V 30 VOUT=2.5V 20 VOUT=3.3V L=4.7uH/SR0302 10 10 Load Current(mA) 100 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:service@aimtron.com.tw 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 OFF VIN=5V,VOUT=3.3V,Load=1A, Power ON EN pin ON/OFF CH1: VOUT CH2:EN CH3:SW CH4:IIN VIN=5V,VOUT=3.3V,Load=1A,EN Turn-OFF VIN=5V,VOUT=3.3V,Load=1A,EN Turn-ON 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:service@aimtron.com.tw 8 AT1361 1MHz,1A Synchronous Buck Converter Transient response CH2:VOUT CH4:IOUT VIN=5V,VOUT=3.3V,C2=100pF IOUT=0mA to1A IOUT=50mA to 1A IOUT=100mA 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:service@aimtron.com.tw 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: VO V (1 − O ) VIN VIN I RMS = I OMAX 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 23 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:service@aimtron.com.tw 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 GND R1 *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:service@aimtron.com.tw 11 AT1361 1MHz,1A Synchronous Buck Converter The Dissipation The power loss is given by: 2 2 PLOSS = I O × RDS (ON ) − P × D + I O × 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 Capacitors Surface Mount Manufacturer/Part No. TDK C3216X5R0J226M TDK C3225X5R0J46M GRM42-6X5R 106K6.3 TAIYO JMK212BJ475MG Manufacturer Website www.sumida.com www.atec-group.com Capacitance(µF) 22 47 10 4.7 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:service@aimtron.com.tw 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:service@aimtron.com.tw 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 0.037ref 0.075ref 00 100 MAX 0.057 0.006 0.051 0.020 0.008 0.122 0.118 0.069 0.022 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:service@aimtron.com.tw 14 AT1361 1MHz,1A Synchronous Buck Converter Reflow Profiles Profile Feature Sn-Pb Eutectic Assembly Large Body Small Body Pkg. thickness Pkg. thickness