RT9263

Preliminary RT9263 High Efficiency, Low Supply Current, Step-up DC/DC Converter General Description The RT9263 is a compact, high efficient, step-up DC/DC converter with an adaptive current mode PWM control loop, providing a stable and high efficient operation over a wide range of load currents. It operates in both continuous and discontinuous current modes in stable waveforms without external compensation. The low start-up input voltage below 1V makes RT9263 suitable for 1 to 4 battery cell applications providing up to 400mA output current. The 550KHz high switching rate minimized the size of external components. Besides, the 17µA low quiescent current together with high efficiency maintains long battery lifetime. Features 1.0V Low Start-up Input Voltage High Supply Capability to Deliver 3.3V 100mA with 1V Input Voltage 17µA Quiescent (Switch-off) Supply Current 90% Efficiency 550KHz Fixed Switching Rate Providing Flexibility for Using Internal and External Power Switches SOT89-5 Package Applications PDA Portable Instrument DSC Ordering Information RT9263 Package type X5 : SOT89-5 Operating temperature range C: Commercial standard C : Chip enable control E : Driver for external power devices Pin Configurations Part Number RT9263CCX5 (Plastic SOT89-5) Pin Configurations TOP VIEW 5 4 1 2 3 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. CE VDD FB LX GND EXT VDD FB LX GND RT9263ECX5 (Plastic SOT89-5) TOP VIEW 5 4 Typical Application Circuit 1 2 3 VIN + 100pF VDD CE RT9263CCX5 LX GND FB R2 980K D1 1N5819 C2 1µF + R1 1.6M L1 4.7µH 100µF 3.3V VOUT1 C1 100µF Fig. 1 RT9263CCX5 Typical Application for Portable Instruments below 400mA DS9263-00 November 2001 www.richtek-ic.com.tw 1 RT9263 Preliminary VIN + 100pF VDD R1 1.6M Q1 NMOS R2 980K L1 4.7µH D1 1N5819 C2 1µF + 100µF 3.3V VOUT1 RT9263ECX5 GND LX EXT FB C1 100µF Fig. 2 0.4A ~ 1A Output Current Application Rm 0.05~0.1Ω Fig. 3 High Voltage Application (Rm should be added when IL > 100mA) R2 C2 200K 1µF Fig.4 High Voltage Application with Shutdown Control www.richtek-ic.com.tw 2 + Chip Enable + 3.3/5V VIN L1 100µF 10µH Q1 NMOS 0.1µF D1 VDD RT9263CCX5 LX CE GND FB R1 2.2M + + 3.3/5V VIN L1 100µF VDD EXT RT9263ECX5 LX GND FB 10µH Q1 NMOS 0.1µF D1 R1 2.2M R2 C2 200K 1µF 15V VOUT1 C1 100µF 15V VOUT1 C1 100µF DS9263-00 November 2001 Preliminary Function Block Diagram RT9263 VDD _ FB 1.25V RT9263CCX5 LX L oop Control Circuit Q1 NMOS R1 + CE GND VDD RT9263ECX5 EXT LX 1.25V DS9263-00 November 2001 _ + FB L oop Control Circuit Q1 NMOS R1 GND www.richtek-ic.com.tw 3 RT9263 Pin Description Pin No. RT9263CCX5 RT9263ECX5 -1 2 3 4 5 1 -2 3 4 5 Pin Name EXT CE VDD FB LX GND Preliminary Pin Function Output pin for driving external NMOS or NPN When driving an NPN, a resistor should be added for limiting base Chip enable RT9263CCX5 gets into shutdown mode when CE pin set to low. Input positive power pin of RT9263 Feedback input pin Internal reference voltage for the error amplifier is 1.25V. Pin for switching Ground Absolute Maximum Ratings Supply Voltage LX Pin Switch Voltage Other I/O Pin Voltages LX Pin Switch Current EXT Pin Driver Current Power Dissipation, PD @ TA = 25°C SOT89-5 • Package Thermal Resistance SOT89-5, θJA Operating Junction Temperature Storage Temperature Range 300°C/W 150°C -65°C ~ +150°C 0.5W -0.3V to 6V -0.3V to (VDD + 0.8V) -0.3V to (VDD + 0.3V) 2.5A 30mA www.richtek-ic.com.tw DS9263-00 November 2001 4 Preliminary Electrical Characteristics (VIN = 1.5V, VDD set to 3.3V, Load Current = 0, TA = 25°C, unless otherwise specified) Parameter Start-UP Voltage Operating VDD Range No Load Current I (VIN) Switch-off Current I (VDD) Shutdown Current I (VIN) Feedback Reference Voltage Switching Rate Maximum Duty LX ON Resistance Current Limit Setting EXT ON Resistance to VDD EXT ON Resistance to GND Line Regulation Load Regulation CE Pin Trip Level Temperature Stability for FB, LFB, LBI Thermal Shutdown Thermal Shutdown Hysterises TS TSD ∆TSD ∆VLINE ∆VLOAD ILIMIT Symbol VST VDD INO LOAD IOFF VREF FS DMAX Test Conditions IL = 1mA Start-up to IDD1 > 250µA VIN = 1.5V, VOUT = 3.3V CE Pin = 0V, VIN = 4.5V Close Loop, VDD = 3.3V VDD = 3.3V VDD = 3.3V VDD = 3.3V VDD = 3.3V VDD = 3.3V VDD = 3.3V VIN = 1.5 ~ 2.5V, IL = 1mA VIN = 2.5V, IL = 1 ~ 100mA VDD = 3.3V Guaranteed by Design Guaranteed by Design Guaranteed by Design Min -0.8 ---1.225 --------0.2 ---Typ 0.98 -47 17 0.1 1.25 550 92 0.25 2 40 30 10 0.25 0.8 50 165 10 RT9263 Max 1.05 6 --1 1.275 --------1.4 ---Units V V µA µA µA V KHz % Ω A Ω Ω mV/V mV/mA V ppm/°C °C °C ISWITCH OFF VIN = 6V DS9263-00 November 2001 www.richtek-ic.com.tw 5 RT9263 Typical Operating Charateristics Efficiency Preliminary Efficiency VOUT= 5.0V; TA = 25°C VOUT = 3.3V ; TA = 25°C No Load Current 90 80 70 60 140 No Load Current TA = 25°C VOUT = 3.3V 120 100 TA = 25°C VOUT = 5.0V IDD ( µ A) IDD ( µ A) Refer to Application Circuit Fig.1 1 1.2 1.5 2 2.5 3 50 40 30 20 10 0 80 60 40 20 0 1 Refer to Application Circuit Fig.1 1.2 1.5 2 2.5 3 4 Input Voltage (V) Input Voltage (V) Start Up Voltage 1.4 Start Up Voltage 1.25 1.20 1.15 TA = 25°C 1.3 VOUT = 3.3V Input Voltage (V) 1.2 1.1 1.0 0.9 TA = 25°C VOUT= 5.0V Input Voltage (V) Refer to Application Circuit Fig.1 1.10 1.05 1.00 0.95 0.90 0.85 0.8 0 20 40 60 80 100 0.80 0 Refer to Application Circuit Fig.1 ILOAD (mA) ILOAD (mA) in constant resistance load 25 50 75 100 ILOAD (mA) ILOAD (mA) in constant resistance load www.richtek-ic.com.tw DS9263-00 November 2001 6 Preliminary Application Note Output Voltage Setting Referring to application circuits Fig.1 to Fig.4, the output voltage of the switching regulator (VOUT1) can be set with Eq.1. R1 VOUT1 = (1 + ) × 1.25 V R2 Feedback Loop Design Referring to application circuits Fig.1 to Fig.4, The selection of R1 and R2 based on the trade-off between quiescent current consumption and interference immunity is stated below: • Follow Eq.1 • Higher R reduces the quiescent current (Path current = 1.25V/R2), however resistors beyond 5MΩ 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. • A proper value of feed forward capacitor parallel with R1 on Fig.1 to Fig.4 can improve the noise immunity of the feedback loops, especially in an improper layout. An empirical suggestion is around 100pF ~ 1nF for feedback resistors of MΩ, and 10nF ~ 0.1µF for feedback resistors of tens to hundreds KΩ. 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 pins. Layout Guide Prober Parasitics _ Q + RT9263 PRECAUTION 1: Improper probing to FB pin will cause fluctuation at VOUT1. It may damage RT9263 and system chips because VOUT1 may drastically rise Eq.1 to an over-rated level due to unexpected interference or parasitics being added to FB pin. PRECAUTION 2: Disconnecting R1 or short circuit across R2 may also cause similar IC damage as described in precaution 1. PRECAUTION 3: When large R values were used in feedback loops, any leakage in FB node may also cause VOUT1 voltage fluctuation, and IC damage. To be especially highlight here is when the air moisture frozen and re-melt on the circuit board may cause several µA leakage between IC or component pins. So, when large R values are used in feedback loops, post coating, or some other moisture-preventing processes are recommended. VOUT1 R1 FB Pin R2 • A full GND plane without gap break. • VOUT1 to GND noise bypass – Short and wide connection for C2 to Pin2 and Pin5. • VIN to GND noise bypass – Add a 100µF 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. DS9263-00 November 2001 www.richtek-ic.com.tw 7 RT9263 Package Information Preliminary D D1 A H C B C1 e e A b b1 b Symbol A b B b1 C C1 D D1 e H Dimensions In Millimeters Min 1.400 0.360 2.400 0.406 -0.800 4.400 -1.400 0.380 Max 1.600 0.520 2.600 0.533 4.250 -4.600 1.700 1.600 0.430 Dimensions In Inches Min 0.055 0.014 0.094 0.016 -0.031 0.173 -0.055 0.014 Max 0.063 0.020 0.102 0.021 0.167 -0.181 0.067 0.063 0.017 5-Lead SOT-89 Surface Mount www.richtek-ic.com.tw DS9263-00 November 2001 8 Preliminary RT9263 DS9263-00 November 2001 www.richtek-ic.com.tw 9 RT9263 Preliminary RICHTEK TECHNOLOGY CORP. Headquarter 6F, No. 35, Hsintai Road, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5510047 Fax: (8863)5537749 RICHTEK TECHNOLOGY CORP. Taipei Office (Marketing) 8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek-ic.com.tw www.richtek-ic.com.tw DS9263-00 November 2001 10