RT8003 600mA, 2MHz, High-Efficiency Synchronous Buck PWM Converter General Description Features The RT8003 is a high-efficiency synchronous buck PWM converter with integrated P-Channel and N-Channel power MOSFET switches. Capable of delivering 600mA output current over a wide input voltage range of 2.4V to 5.5V, the RT8003 is ideally suited for portable applications powered by a single Li-Ion battery or by 3-cell NiMH/NiCd batteries. The device operates at 2MHz PWM switching fixed frequency, can use smaller CIN, COUT capacitor and inductor. l l l l l l l l The RT8003 integrates two low RDS(ON) 230mΩ and 180mΩ of high and low side switching MOSFETs to reduce board space, as only resistors and capacitors along with one inductor are required externally for operation. The RT8003 has adjustable output range down to 0.5V. The other features include internal soft-start, chip enable, over temperature and over current protections. It is available in a space-saving VDFN-10L 3x3 package. l Ordering Information l RT8003 l l l l l l Applications Package Type QV : VDFN-10L 3x3 (V-Type) l Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) l Note : Richtek products are : l l Battery-Powered Equipments Low Power CPU and DSP Supplies Digital Cameras and Hard Disks Protable Instruments and Notebook Computers Celluar Phones, PDAs, and Handheld PCs USB-Based DSL Modems and Other Network Interface Cards Pin Configurations RoHS compliant and compatible with the current require- (TOP VIEW) ments of IPC/JEDEC J-STD-020. } Suitable for use in SnPb or Pb-free soldering processes. Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. DS8003-08 March 2011 LX VDD NC NC EN 1 10 2 9 3 GND 4 5 8 7 11 9 } l 2.4V to 5.5V Input Voltage Range Adjustable Output from 0.5V to VIN Guaranteed 600mA Output Current Accurate Reference : 0.5V (±1.5%) Up to 90% Conversion Efficiency Typical Quiescent Current : 200µA Integrated Low RDS(ON) High- and Low Side Power MOSFET Switches : 230mΩ and 180mΩ Current Mode PWM Operation Fixed Frequency : 2MHz 100% Maximum Duty Cycle for Lowest Dropout Internal Soft-Start No Schottky Diode Required Over Temperature and Over Current Protection Small 10-Lead VDFN 3x3 Package RoHS Compliant and 100% Lead (Pb)-Free GND GND GND COMP FB VDFN-10L 3x3 www.richtek.com 1 RT8003 Typical Application Circuit V IN 2.4V to 4.2V C IN 1uF Chip Enable 2 VDD 5 7 C COMP 10nF LX EN 1 L OUT 2.2uH RT8003 R1 10k 6 COMP FB GND 8, 9, 10, Exposed Pad (11) R2 7.15k V OUT 1.2V/600mA C OUT 1uF Recommended component selection for Typical Application Circuit. VOUT (V) V IN (V) CIN (µF) COUT (µF) LOUT (µH) R1 (kΩ) R2 (kΩ) CCOMP (nF) 0.5 2.4 to 3.3 1 1/2.2 2.2/1 10 Open 10 1 2.4 to 3.6 1 1/2.2 2.2/1 10 10 10 1.2 2.4 to 4.2 1 1/2.2 2.2/1 10 7.15 10 1.8 2.4 to 5.5 1 1/2.2 2.2/1 10 3.83 10 2.5 3.3 to 5.5 1 1/2.2 2.2/1 10 2.49 10 3.3 4.2 to 5.5 1 1/2.2 2.2/1 10 1.78 10 Suggested Inductors Component Series Supplier ABC SR0302 Sumida CDRH2D14 TDK VLP4612 Inductance ESR Current Rating Dimensions (µH) (mΩ) (mA) (mm) 1 60 2100 2.2 90 1650 2.2 94 1000 1 110 1500 2.5 170 1100 3x2.8x2.5 3.2x3.2x1.55 4.6x3.4x1.2 Suggested Capacitors For CIN and COUT Component Supplier TDK Panasonic TAIYO YUDEN www.richtek.com 2 Part No. Capacitance (uF) Case Size C1608X5R1A105M 1 0603 C1608X5R1A225M 2.2 0603 ECJ1VB0J105M 1 0603 ECJ1VB0J225M 2.2 0603 JMK107BJ105M 1 0603 JMK107BJ225M 2.2 0603 DS8003-08 March 2011 RT8003 Functional Pin Description Pin No. Pin Name Pin Function 1 LX Internal Power MOSFET Switches Output. Connect this pin to the inductor. 2 VDD Power Input Supply. Input voltage which supplies current to the output pin. Connect this pin with a low-ESR capacitor to GND 3, 4 NC No Internal Connection 5 EN Chip Enable (Active High). Logic low shuts down the converter. Floating this pin is forbidden. 6 FB Switcher Feedback Voltage. This pin is the inverting input of the error amplifier. FB senses the switcher output through an external resistor divider network. FB regulation voltage is 0.5V. 7 COMP Compensation Input. This pin is the output of the internal error amplifier. Connect an external capacitor to compensate the regulator controlled loop. GND Ties the pin directly to the cathode terminal of CIN and C OUT and ground plane with the lowest impedance. Signal and Common Ground (The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation). The GND pad area should be as large as possible and using many vias to conduct the heat into the buried GND plate of PCB layer. All small-signal, compensation and feedback components should connect to this pin. 8, 9, 10, 11 (Exposed Pad) Function Block Diagram EN Shutdown Control VDD Slope Compensation Oscillator Current Limit Detector - PWM Comparator COMP VREF FB + Error Amplifier - + Over Temperature Detector Control Logic Current Sense Driver LX Zero Detector GND DS8003-08 March 2011 www.richtek.com 3 RT8003 Absolute Maximum Ratings (Note 1) Supply Voltage ---------------------------------------------------------------------------------------------------−0.3V to 6V LX Voltage --------------------------------------------------------------------------------------------------------- −0.3V to (VDD + 0.3V) l Power Dissipation, PD @ TA = 25°C VDFN-10L 3x3 ----------------------------------------------------------------------------------------------------1.923W l Package Thermal Resistance (Note 2) VDFN-10L 3x3, θJA -----------------------------------------------------------------------------------------------52°C/W l Junction Temperature -------------------------------------------------------------------------------------------150°C l Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------260°C l Storage Temperature Range ----------------------------------------------------------------------------------- −65°C to 150°C l ESD Susceptibility (Note 3) HBM (Human Body Mode) -------------------------------------------------------------------------------------2kV MM (Machine Mode) --------------------------------------------------------------------------------------------200V l l (Note 4) Recommended Operating Conditions l l l l Supply Voltage ---------------------------------------------------------------------------------------------------2.4V to 5.5V Enable Input Voltage, VEN -------------------------------------------------------------------------------------0V to 5.5V Ambient Temperature Range ---------------------------------------------------------------------------------- −40°C to 85°C Junction Temperature Range ----------------------------------------------------------------------------------0°C to 125°C Electrical Characteristics (VDD = 3.3V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Supply Current Quiescent Current IQ VEN = 3.3V, VFB = VREF + 0.15V, IOUT = 0mA 90 200 400 µA Shutdown Current I SHDN VEN = 0V -- 0.01 1 µA V REF 0.4925 0.5 0.5075 V Switching Frequency Range f OSC 1.7 2.0 2.3 MHz Maximum Duty Cycle DC 100 -- -- % Reference Reference Voltage Oscillator VDD = VOUT Output Voltage Line R egulation VDD = 2.4V to 5.5V, ILOAD = 100mA -- -- +1.5 % Load Regulation 10mA < ILOAD < 600mA -- -- +1.5 % Power Switches RDS(ON) of P-Channel MOSFET RP_FET VDD = 3.3V, IL X = 300mA 100 230 600 mΩ RDS(ON) of N-Channel MOSFET RN_FET VDD = 3.3V, IL X = −300mA 100 180 600 mΩ Current Limit ILIMIT VDD = 3.3V, V FB = V REF - 0.15V 1.6 2 2.4 A To be continued www.richtek.com 4 DS8003-08 March 2011 RT8003 Parameter Symbol Test Conditions Min Typ Max -- -- 0.4 1.5 -- -- Unit Logic Input EN Threshold Logic-Low Voltage VIL VDD = 2.4V to 5.5V, Shutdown Logic-High Voltage VIH VDD = 2.4V to 5.5V, Enable V Protection Thermal Shutdown Temperature TSD -- 180 -- °C Thermal Shutdown Hysteresis ∆TSD -- 20 -- °C 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. θJA is measured in the natural convection at TA = 25°C on a high effective thermal conductivity test board of JEDEC 51-7 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. DS8003-08 March 2011 www.richtek.com 5 RT8003 Typical Operating Characteristics Output Voltage Deviation vs. Output Current Output Voltage Deviation vs. Temperature 0.40% 0.4 0.00% 0 Output Voltage Deviation (%) Output Voltage Deviation (%) 0.10% 0.1 -0.10% -0.1 -0.20% -0.2 -0.30% -0.3 -0.40% -0.4 -0.50% -0.5 -0.60% -0.6 -0.70% -0.7 0.20% 0.2 0.00% 0 -0.20% -0.2 -0.40% -0.4 -0.60% -0.6 -0.80% -0.8 -1.00% -1.0 -1.20% -1.2 -1.40% -1.4 -1.60% -1.6 -1.80% -1.8 0 100 200 300 400 500 600 700 800 -50 -25 0 Output Current (mA) 100% 100 Efficiency vs. Output Current 100 125 150 90% 90 80 80% 80% 80 70% 70 70% 70 60% 60 50% 50 40% 40 30% 30 60% 60 50% 50 40% 40 30% 30 20% 20 20% 20 10% 10 10% 10 0% 0 0% 0 10 100 1000 VIN = 3.3V, VOUT = 1.2V, IOUT = 200mA -50 -25 0 25 50 75 100 125 150 Temperature (°C) Output Current (mA) Frequency vs. Input Voltage Frequency vs. Temperature 2.15 2.05 2.1 2.00 Frequency (MHz)1 Frequency (MHz) 75 Efficiency vs. Temperature 100% 100 VIN = 3.3V, VOUT = 1.2V 1 50 Temperature (°C) Efficiency (%) Efficiency (%) 90% 90 25 2.05 2 1.95 1.95 1.90 1.85 1.80 1.9 1.85 1.75 2.5 3 3.5 4 4.5 Input Voltage(V) www.richtek.com 6 5 5.5 -50 -25 0 25 50 75 100 125 Temperature DS8003-08 March 2011 RT8003 Quiescent Current vs. Input Voltage 300 Quiescent Current vs. Temperature 250 VFB = 0.65V Quiescent Current (μA) Quiescent Current (μA) 250 200 150 100 50 VIN = 3.3V, VFB = 0.65V 200 150 100 50 0 0 2.5 3 3.5 4 4.5 5 -50 5.5 -25 0 Input Voltage(V) VREF vs. Temperature 75 100 125 5 5.5 VREF vs. Input Voltage 0.52 0.515 0.515 0.51 0.51 0.505 V REF (V) V REF (V) 50 Temperature (°C) 0.52 0.5 0.495 0.49 0.505 0.5 0.495 0.49 0.485 0.485 0.48 -50 -25 0 25 50 75 100 125 0.48 2.5 Temperature (°C) 3 3.5 4 4.5 Input Voltage (V) Current Limit vs. Input Voltage Load Transient Response 3 VIN = 3.3V, VOUT = 1.2V IOUT = 50mA to 600mA 2.5 Current Limit (A) 25 2 Output Voltage (50mV/Div) Load Current (200mA/Div) 1.5 1 0.5 0 2.5 3 3.5 4 4.5 Input Voltage (V) DS8003-08 March 2011 5 5.5 Time (250μs/Div) www.richtek.com 7 RT8003 Steady State Steady State VIN = 3.3V, VOUT = 1.2V, IOUT = 0mA, COUT = 1uF Output Voltage VIN = 3.3V, VOUT = 1.2V, IOUT = 600mA, COUT = 1uF Output Voltage (10mV/Div) (10mV/Div) (1V/Div) VLX VLX (1V/Div) Time (25μs/Div) Time (250ns/Div) Soft Start Function Output Voltage VEN Input Current (500mV/Div) (2V/Div) (200mA/Div) VIN = 3.3V, VOUT = 1.2V, IOUT = 600mA Time (500μs/Div) www.richtek.com 8 DS8003-08 March 2011 RT8003 Application Information RT8003 is a Pulse-Width-Modulated (PWM) step-down DC/DC converter. Capable of delivering 600mA output current over a wide input voltage range from 2.4V to 5.5V. The RT8003 is ideally suited for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources within the range such as cellular phones, PDAs and handy terminals. PSM Operation Consequently, the converter will enter pulse-skipping mode (PSM) during extreme light load condition or when modulation index (VOUT /VIN) is extreme low. This could reduce switching loss and further increase power conversion efficiency. Over Current Protection Chip Enable/Disable and Soft-Start Four operational modes are available: PWM, PSM, LowDrop-Out and shut down modes. Pulling EN pin lower than 0.4V shuts down the RT8003 and reduces its quiescent current to 1µA. Pulling EN pin higher than 1.5V enables the RT8003 and initiates the soft-start cycle. RT8003 has internal soft-start that can reduce the Inrush Current during the rising of Output Voltage. The RT8003 continuously monitors the inductor current by sensing the voltage across the P-MOSFET when it turns on. When the inductor current is higher than current limit threshold (1.8A typical), OCP activates and forces the P-MOSFET turning off to limit inductor current cycle by cycle. But it will shut down when the VOUT trip the UV protection. Output Voltage Setting and Feedback Network PWM Operation During normal operation, the RT8003 regulates output voltage by switching at a constant frequency transferring the power to the load in each cycle by PWM. The RT8003 uses a slope-compensated, current-mode PWM controller capable of achieving 100% duty cycle. At each rising edge of the internal oscillator, the Control Logic cell sends a PWM ON signal to the Driver cell to turn on internal PMOSFET. This allows current to ramp up through the inductor to the load, and stores energy in a magnetic field. The switch remains on until either the current-limit is tripped or the PWM comparator signals for the output in regulation. After the switch is turned off, the inductor releases the magnetic energy and forces current through the N-MOSFET synchronous rectifier to the output-filter capacitor and load. The output-filter capacitor stores charge The output voltage can be set from VREF to VIN by a voltage divider as: the internal VREF is 0.5V with 1.5% accuracy. In practical application, keep R1 = 10kΩ respectively and choose appropriate R2 according to the required output voltage. Inductor Selection The output inductor is suggested as the table of suggested inductors for optimal performance. Make sure that the inductor will not saturate over the operation conditions including temperature range, input voltage range, and maximum output current. If possible, choose an inductor with rated current higher than 2A so that it will not saturate even under short circuit condition. Input Capacitor Selection turns off and allows the converter entering discontinuous conduction mode when the inductor current decreases to The input capacitor can filter the input peak current and noise at input voltage source. The capacitor with low ESR (effective series resistance) provides the small drop voltage to stabilize the input voltage during the transient loading. For input capacitor selection, the ceramic capacitors larger than 1µF is recommend. The capacitor must conform to the RMS current requirement. The maximum RMS ripple current is calculated as : zero. The zero current detection on threshold is about 80mA.This reduces conduction loss and increase power IRMS = IOUT(MAX) when the inductor current is above the average output current and releases charge when the inductor current is below the average current to smooth the output voltage across the load. A Zero Detector monitors inductor current by sensing v oltage drop across the N-MOSFET synchronous rectifier when it turns on. The N-MOSFET conversion efficiency at light load condition. DS8003-08 March 2011 VOUT (VIN - VOUT) VIN www.richtek.com 9 RT8003 L1 Output Capacitor Selection The capacitor’ s ESR determines the output ripple voltage and the initial voltage drop following a high slew-rate transient’ s edge. Typically, if the ESR requirement is satisfied, the capacitance is adequate to filtering. The output ripple voltage can be calculated as: ∆VOUT = ∆IC (ESR + VOUT LX VIN R4 C1 VDD RT8003 EN R1 FB C3 COMP C2 GND R2 1 ) 8 x COUT x fOSC Where f OSC = operating frequency, COUT = output capacitance and ∆IC = ∆IL = ripple current in the inductor. Figure 1 The ceramic capacitor with low ESR value provides the low output ripple and low size profile. Connect a 1µF/2.2µF ceramic capacitor at output terminal for good performance and place the input and output capacitors as close as possible to the device. Layout Considerations Follow the PCB layout guidelines for optimal performance of RT8003. 1. For the main current paths as indicated in bold lines in Figure 1, keep their traces short and wide. 2. Put the input capacitor as close as possible to the device pins (VDD and GND). Figure 2. Top Layer 3. LX node is with high frequency voltage swing and should be kept small area. Keep analog components away from LX node to prevent stray capacitive noise pick-up. 4. Connect feedback network behind the output capacitors. Keep the loop area small. Place the feedback components near the RT8003. 5.Connect all analog grounds to a command node and then connect the command node to the power ground behind the output capacitors. 6. An example of 2-layer PCB layout is shown in Figure 2 to Figure 3 for reference. www.richtek.com 10 Figure 3. Bottom Layer DS8003-08 March 2011 RT8003 Outline Dimension D2 D L E E2 SEE DETAIL A 1 e b 2 1 2 1 A A1 A3 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.800 1.000 0.031 0.039 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 2.950 3.050 0.116 0.120 D2 2.300 2.650 0.091 0.104 E 2.950 3.050 0.116 0.120 E2 1.500 1.750 0.059 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 V-Type 10L DFN 3x3 Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. DS8003-08 March 2011 www.richtek.com 11