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| Preliminary RT9275 Tiny Package, High Efficiency, Step-Up DC/DC Converter General Description The RT9275 is a compact, high efficiency, and low voltage step-up DC/DC converter with an Adaptive Current Mode PWM control loop, includes an error amplifier, ramp generator, comparator, switch pass element and driver in which providing a stable and high efficient operation over a wide range of load currents. The low start-up input voltage below 1V makes RT9275 suitable for 1 to 4 battery cells applications. Both internal 2.5A switch and driver for driving external power devices (NMOS or NPN) are provided. It is incorporating with softstart function, Under Voltage protection function. RT9275 is available in SOT-23-6 package. Features 1V Low Start-up Input Voltage at 1mA Load Zero Shutdown Mode Supply Current 90% Efficiency 400kHz Switching Frequency Providing Flexibility for Using Internal and External Power Switches Build Soft-Start function internally Under-Voltage Protection Small SOT-23-6 Package RoHS Compliant and 100% Lead (Pb)-Free Applications PDA DSC LCD Panel RF-Tags MP3 Portable Instrument Wireless Equipment Ordering Information RT9275 Package Type E : SOT-23-6 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) Pin Configurations (TOP VIEW) FB 6 1 EN VDD 5 2 LX 4 3 Note : RichTek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating. Marking Information For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail. EXT GND SOT-23-6 Note : There is no pin1 indicator on top mark for SOT-23-6 type, and pin 1 will be lower left pin when reading top mark from left to right. DS9275-06 March 2007 www.richtek.com 1 RT9275 Typical Application Circuit L1 4.7 uH VIN C3 10uF Preliminary D1 FS1J2E VOUT C2 1uF 3.3V/5V C4 R1 2M/3M + VDD EN EXT RT9275 GND LX FB 6.8pF/ 3.3pF C1 10uF/20uF R2 980k/1M Functional Pin Description Pin No. 1 2 3 4 5 6 Pin Name EN EXT GND LX VDD FB Pin Function Chip Enable (Active High) Output pin for driving external NMOS Ground Pin for switching Input positive power pin of RT9275 Feedback input pin. Internal reference voltage for the error amplifier is 1.25V. Function Block Diagram VDD FB Bandgap/ Soft Start V REF Under Voltage Protection EXT LX + Loop Control Circuit VDD Over Voltage Protection Function Suspend EN Over Temp. Detector GND www.richtek.com 2 DS9275-06 March 2007 Preliminary Absolute Maximum Ratings (Note 1) RT9275 Supply Voltage --------------------------------------------------------------------------------------------------------- 7V LX Pin Switch Voltage ------------------------------------------------------------------------------------------------ -0.3V to 7V Other I/O Pin Voltages ----------------------------------------------------------------------------------------------- -0.3V to 7V LX Pin Switch Current ------------------------------------------------------------------------------------------------ 2.5A EXT Pin Driver Current ------------------------------------------------------------------------------------------------ 200mA Power Dissipation, PD @ TA = 25C SOT-23-6 --------------------------------------------------------------------------------------------------------------- 0.4W Package Thermal Resistance (Note 3) SOT-23-6, JA ---------------------------------------------------------------------------------------------------------- 250C/W Junction Temperature ------------------------------------------------------------------------------------------------- 150C Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260C Storage Temperature Range ---------------------------------------------------------------------------------------- -65C to +150C ESD Susceptibility (Note 2) HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V Electrical Characteristics (VIN = 1.5V, VOUT = VDD = 3.3V, TA = 25C, unless otherwise specified) Parameter Start-UP Voltage Operating VDD Range No Load Current I (VIN) (Note 4) Continuous Switching Current Switch-off Current I (VDD) Shutdown Current I (VIN) Feedback Reference Voltage Output Voltage Temperature Coefficient (refer to VFB) Switching Frequency Symbol VST VDD INO LOAD ISWITCH Test Conditions IL = 1mA VDD pin voltage VIN = 1.5V, VOUT = 3.3V VIN = EN = 3.3V, VFB = GND Min -2 -0.2 --1.225 -300 Typ 0.9 -160 0.3 50 0.01 1.25 50 400 0.3 Max 1.0 6 200 0.5 75 1 1.275 -500 Units V V A mA A A V ppm/C kHz %/C ISWITCH OFF VIN = 6V IOFF VREF Ts FS EN = 0V, VIN = 4.5V Close Loop, VDD = 3.3V TA = -40C to 85C VDD = 3.3V TA = -40C to 85C VDD = 3.3V VDD = 3.3V ILIM VDD = 3.3V VDD = 3.3V VDD = 3.3V VLINE VLOAD VDD = 3.5 ~ 6V, IL = 1mA VIN = 2.5V, IL = 1 ~ 100mA Frequency Temperature Coefficient f Maximum Duty LX ON Resistance Current Limit Setting (Note 5) EXT ON Resistance to VDD EXT ON Resistance to GND Line Regulation (refer to VFB) Load Regulation (Note 6) VDD Over Voltage Protection EN Pin Trip Level DMAX 85 -1.5 ----6.3 90 0.3 2.0 5 5 1.5 0.25 6.8 0.8 -1.1 2.5 8.5 8.5 10 -7.3 1.2 % A mV/V mV/mA V V VDD = 3.3V 0.4 To be continued DS9275-06 March 2007 www.richtek.com 3 RT9275 Parameter Soft Start time Under Voltage Protection - Threshold Voltage Thermal Shutdown Thermal Shutdown Hysterises TSS Preliminary Symbol Test Conditions Min 3.0 0.75 --Typ 6.0 0.85 165 10 Max 12 0.95 --Units ms V C C VTH-UVP TSD TSD Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. 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 remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. JA is measured in the natural convection at T A = 25C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 4. No Load Current is highly dependent on practical system design and component selection that cannot be covered by production testing. Typical No Load Current is verified by typical application circuit with recommended components. No Load Current performance is guaranteed by Switch Off Current and Continuous Switching Current. Note 5. Current Limit is guaranteed by design at TA = 25C. Note 6. Load Regulation is not tested at production due to practical instrument limitation. Load Regulation performance is dominantly dependent on DC loop gain and LX ON Resistance that are guaranteed by "Line Regulation" and "LX ON Resistance" tests in production. www.richtek.com 4 DS9275-06 March 2007 Preliminary Typical Operating Characteristics Frequency vs. Temperature 500 450 400 RT9275 Feedback vs. Temperature 1.252 Frequency (kHz) 1.25 300 250 200 150 100 50 0 -20 -10 0 10 20 30 40 50 60 70 80 90 Feedback (V) 350 1.248 1.246 VIN = 2V, VOUT = 3.3V, ILOAD = 60mA 1.244 VIN = 2V, VOUT = 3.3V, ILOAD = 60mA -20 0 20 40 60 80 Temperature (C) Temperature (C) Current Limit vs. Temperature 2.6 2.4 2.2 2 Efficiency vs. Output Current 95 90 85 Current Limit (A) 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 -20 -10 0 10 20 30 40 50 60 70 80 90 Efficiency (%) 1.8 80 75 70 65 60 55 VIN VIN VIN VIN VIN = = = = = 3.0V 2.5V 2.0V 1.5V 1.0V VIN = 2V, VOUT = VDD = 3.3V VOUT = 3.3V, TA = 25C 50 1 10 100 1000 Temperature (C) Output Current (mA) Efficiency vs. Output Current 100 95 90 Output Voltage vs. Output Current 3.32 3.31 Output Voltage (V) Efficiency (%) 85 80 75 70 65 60 55 50 1 10 100 1000 3.3 3.29 3.28 3.27 3.26 VIN VIN VIN VIN VIN VIN VIN VOUT = 5V, TA = 25C = = = = = = = 4.5V 4.0V 3.5V 3.0V 2.5V 2.0V 1.5V VIN VIN VIN VIN VIN = = = = = 3.0V 2.5V 2.0V 1.5V 1.0V VOUT = 3.3V 3.25 1 10 100 1000 Output Current (mA) Output Current (mA) DS9275-06 March 2007 www.richtek.com 5 RT9275 Preliminary Output Voltage vs. Output Current 4.98 4.97 LX & Output Ripple VIN = 1V, VOUT = 3.3V @ 10mA 4 Output Voltage (V) 4.95 4.94 4.93 4.92 4.91 LX (V) VOUT = 5.0V VIN VIN VIN VIN VIN VIN VIN 10 4.96 2 0 = = = = = = = 4.5V 4.0V 3.5V 3.0V 2.5V 2.0V 1.5V 100 1000 Output Ripple (mV) 10 0 -10 4.9 1 Time (1s/Div) Output Current (mA) LX & Output Ripple VIN = 1V, VOUT = 3.3V @ 100mA 4 4 LX & Output Ripple VIN = 1.5V, VOUT = 3.3V @ 10mA LX (V) LX (V) Output Ripple (mV) 2 0 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 Time (1s/Div) Time (1s/Div) LX & Output Ripple VIN = 1.5V, VOUT = 3.3V @ 100mA 4 4 LX & Output Ripple VIN = 2V, VOUT = 3.3V @ 10mA LX (V) LX (V) Output Ripple (mV) 2 0 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 Time (1s/Div) Time (1s/Div) www.richtek.com 6 DS9275-06 March 2007 Preliminary RT9275 LX & Output Ripple VIN = 2.5V, VOUT = 3.3V @ 10mA 4 LX & Output Ripple VIN = 2V, VOUT = 3.3V @ 100mA 4 LX (V) 0 LX (V) Output Ripple (mV) 2 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 Time (1s/Div) Time (1s/Div) LX & Output Ripple 6 VIN = 2.5V, VOUT = 3.3V @ 100mA 4 4 LX & Output Ripple VIN = 3V, VOUT = 3.3V @ 10mA LX (V) 0 LX (V) Output Ripple (mV) 2 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 Time (1s/Div) Time (5s/Div) LX & Output Ripple 6 VIN = 3V, VOUT = 3.3V @ 100mA 4 4 6 LX & Output Ripple LX (V) 0 LX (V) Output Ripple (mV) 2 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 VIN = 1.5V, VOUT = 5V @ 10mA Time (1s/Div) Time (1s/Div) DS9275-06 March 2007 www.richtek.com 7 RT9275 LX & Output Ripple Preliminary LX & Output Ripple 6 4 6 4 LX (V) 0 LX (V) Output Ripple (mV) VIN = 1.5V, VOUT = 5V @ 100mA 2 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 VIN = 2V, VOUT = 5V @ 10mA Time (1s/Div) Time (1s/Div) LX & Output Ripple 6 4 6 4 LX & Output Ripple LX (V) LX (V) Output Ripple (mV) 2 0 2 0 Output Ripple (mV) 10 0 -10 VIN = 2V, VOUT = 5V @ 150mA 10 0 -10 VIN = 2.5V, VOUT = 5V @ 10mA Time (1s/Div) Time (1s/Div) LX & Output Ripple 6 4 6 4 LX & Output Ripple LX (V) 0 VIN = 2.5V, VOUT = 5V @ 200mA 10 0 -10 LX (V) Output Ripple (mV) 2 2 0 Output Ripple (mV) 10 0 -10 VIN = 3V, VOUT = 5V @ 10mA Time (1s/Div) Time (5s/Div) www.richtek.com 8 DS9275-06 March 2007 Preliminary RT9275 LX & Output Ripple 6 4 LX & Output Ripple 6 4 LX (V) LX (V) Output Ripple (mV) VIN = 3V, VOUT = 5V @ 250mA 2 0 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 VIN = 3.5V, VOUT = 5V @ 10mA Time (1s/Div) Time (5s/Div) LX & Output Ripple 6 4 LX & Output Ripple 6 4 LX (V) LX (V) Output Ripple (mV) VIN = 3.5V, VOUT = 5V @ 250mA 2 0 2 0 Output Ripple (mV) 10 0 -10 10 0 -10 VIN = 4V, VOUT = 5V @ 10mA Time (1s/Div) Time (5s/Div) LX & Output Ripple 6 4 6 4 LX & Output Ripple LX (V) 0 VIN = 4V, VOUT = 5V @ 250mA 10 0 -10 LX (V) Output Ripple (mV) 2 2 0 Output Ripple (mV) 10 0 -10 VIN = 4.5V, VOUT = 5V @ 10mA Time (1s/Div) Time (10s/Div) DS9275-06 March 2007 www.richtek.com 9 RT9275 LX & Output Ripple 6 4 Preliminary Load Transient Respones Output Voltage (mV) Output Current (mA) 20 0 -20 LX (V) Output Ripple (mV) 2 0 10 0 -10 VIN = 4.5V, VOUT = 5V @ 250mA 40 20 0 VIN = 1V, VOUT = 3.3V, IOUT = 10mA to 50mA Time (1s/Div) Time (100s/Div) Load Transient Respones Output Voltage (mV) 50 0 -50 Load Transient Respones Output Voltage (mV) VIN = 2V, VOUT = 3.3V, IOUT = 10mA to 100mA 50 0 -50 Output Current (mA) 100 50 0 VIN = 1.5V, VOUT = 3.3V, IOUT = 10mA to 100mA Output Current (mA) 100 50 0 Time (100s/Div) Time (100s/Div) Load Transient Respones Output Voltage (mV) 50 0 -50 Load Transient Respones Output Voltage (mV) VIN = 3V, VOUT = 3.3V, IOUT = 10mA to 100mA 50 0 -50 VIN = 2.5V, VOUT = 3.3V, IOUT = 10mA to 100mA Output Current (mA) 100 50 0 Output Current (mA) 100 50 0 Time (100s/Div) Time (100s/Div) www.richtek.com 10 DS9275-06 March 2007 Preliminary RT9275 Load Transient Respones Load Transient Respones Output Voltage (mV) 50 0 -50 Output Voltage (mV) VIN = 1.5V, VOUT = 5V, IOUT = 10mA to 50mA VIN = 2V, VOUT = 5V, IOUT = 10mA to 100mA 50 0 -50 Output Current (mA) 40 20 0 Output Current (mA) 100 50 0 Time (100s/Div) Time (100s/Div) Load Transient Respones Output Voltage (mV) Output Voltage (mV) VIN = 2.5V, VOUT = 5V, IOUT = 10mA to 100mA 50 0 -50 50 0 -50 Load Transient Respones VIN = 3V, VOUT = 5V, IOUT = 10mA to 100mA Output Current (mA) Output Current (mA) 100 50 0 100 50 0 Time (100s/Div) Time (100s/Div) Load Transient Respones Output Voltage (mV) Output Voltage (mV) VIN = 3.5V, VOUT = 5V, IOUT = 10mA to 100mA 50 0 -50 50 0 -50 Load Transient Respones VIN = 4V, VOUT = 5V, IOUT = 10mA to 100mA Output Current (mA) Output Current (mA) 100 50 0 100 50 0 Time (100s/Div) Time (100s/Div) DS9275-06 March 2007 www.richtek.com 11 RT9275 Load Transient Respones Output Voltage (mV) Preliminary VIN = 4.5V, VOUT = 5V, IOUT = 10mA to 100mA 50 0 -50 Output Current (mA) 100 50 0 Time (100s/Div) www.richtek.com 12 DS9275-06 March 2007 Preliminary Application Information Output Voltage Setting Referring to Typical Application Circuits, the output voltage of the switching regulator (VOUT) can be set with Equation (1). VOUT = ( 1+ R1 R2 ) x 1.25V RT9275 Layout Guide A full GND plane without gap break. VDD to GND noise bypass - Short and wide connection for the 1F MLCC capacitor between Pin5 and Pin3. VIN to GND noise bypass - Add a capacitor close to L1 inductor, when VIN is not an idea voltage source. Minimized FB node copper area and keep far away from noise sources. Minimized parasitic capacitance connecting to LX and EXT nodes, which may cause additional switching loss. Board Layout Example (2-Layer Board) (Refer to Typical Application Circuit for the board) (1) Feedback Loop Design Referring to Typical Application Circuits. The selection of R1 and R2 based on the trade-off between quiescent current consumption and interference immunity is stated below: Follow Equation (1) Higher R reduces the quiescent current (Path current = 1.25V/R2), however resistors beyond 5M are not recommended. Lower R gives better noise immunity, and is less sensitive to interference, layout parasitics, FB node leakage, and improper probing to FB pins. VOUT R1 FB Pin _ Q + R2 Prober Parasitics A proper value of feed forward capacitor parallel with R1 can improve the noise immunity of the feedback loops, especially in an improper layout. An empirical suggestion is 1 = 10 to 20kHz 2R1C4 For applications without standby or suspend modes, lower values of R1 and R2 are preferred. For applications concerning the current consumption in standby or suspend modes, the higher values of R1 and R2 are needed. Such "high impedance feedback loops" are sensitive to any interference, which require careful layout and avoid any interference, e.g. probing to FB pin. - Top Layer - - Bottom Layer DS9275-06 March 2007 www.richtek.com 13 RT9275 Outline Dimension Preliminary H D L C B b A A1 e Symbol A A1 B b C D e H L Dimensions In Millimeters Min 0.889 0.000 1.397 0.250 2.591 2.692 0.838 0.080 0.300 Max 1.295 0.152 1.803 0.560 2.997 3.009 1.041 0.254 0.610 Dimensions In Inches Min 0.031 0.000 0.055 0.010 0.102 0.106 0.033 0.003 0.012 Max 0.051 0.006 0.071 0.022 0.118 0.122 0.041 0.010 0.024 SOT-23-6 Surface Mount Package Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com www.richtek.com 14 DS9275-06 March 2007 |
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