® RT9276 Synchronous Boost Converter with Voltage Detector General Description Features The RT9276 is a synchronous boost converter, which is based on a fixed frequency Pulse-Width-Modulation (PWM) controller using a synchronous rectifier to obtain maximum efficiency. The converter provides a power supply solution for products powered by a variety of batteries such as single cell, dual cell alkaline, NiMH and NiCd battery. At light load currents, the converter enters power save mode to maintain a high efficiency over a wide load current range. z True Load Disconnection During Shutdown z Internal Synchronous Rectifier Up to 96% Efficiency Current Mode PWM Operation with Internal Compensation Low Start-Up Voltage Low Quiescent Current Internal Soft-Start Control Low Battery Comparator Low EMI Converter (Anti-Ringing) Power Save Mode for Improved Efficiency at Light Load Current Over Current Protection Short Circuit Protection Over Temperature Protection Over Voltage Protection Small WDFN-10L 3x3 Package RoHS Compliant and Halogen Free The output voltage can be programmed by an external resistor divider, or fixed at a certain voltage. Moreover, the converter can be disabled to minimize battery drain. During shutdown, the load is completely disconnected from the battery. The maximum peak current in the boost switch is limited to 2A for current limit. z z z z z z z z z z z z For the RT9276, a low-EMI mode is implemented to reduce ringing of the inductor phase pin when the converter enters discontinuous conduction mode. Moreover, a voltage detector is built-in in the chip for low battery detection. Ordering Information ) z Applications z z All One-Cell, Two-Cell and Three-Cell Alkaline, NiCd, NiMH and Single-Cell Li Batteries Hand-Held Devices WLED Flash Light Package Type QW : WDFN-10L 3x3 (W-Type) z Lead Plating System G : Green (Halogen Free and Pb Free) Pin Configurations (TOP VIEW) Boost VOUT Default : Adjustable 33 : 3.3V 50 : 5.0V EN VOUT FB/NC LBO GND 1 2 3 4 5 GND RT9276(- z 11 10 9 8 7 6 PGND LX PGOOD LBI VBAT Note : WDFN-10L 3x3 Richtek products are : ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Marking Information EW= : Product Code Suitable for use in SnPb or Pb-free soldering processes. EW=YM DNN Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS9276-02 July 2013 YMDNN : Date Code is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9276 Typical Application Circuit L VBAT CIN RT9276 2 9 LX VOUT 6 VBAT VOUT R3 COUT FB 3 R1 7 R2 10 PGND Chip Enable R5 R6 R4 LBI LBO 4 8 PGOOD 1 EN GND LBO PGOOD 5, Exposed Pad (11) Figure 1. Adjustable Output Voltage Boost Converter with Voltage Detector L VBAT CIN RT9276 2 9 LX VOUT 6 VBAT 7 Chip Enable R3 COUT LBO 4 R1 R2 VOUT R4 LBI 10 PGND PGOOD 1 EN 8 PGOOD NC 3 GND 5, Exposed Pad (11) Figure 2. Fixed Output Voltage Boost Converter with Voltage Detector Functional Pin Description Pin No. Pin Name Pin Function 1 EN Chip Enable (Active High). 2 VOUT Boost Output. 3 FB / NC Feedback Input for Adjustable Output Voltage Version / No Internal Connection for Fixed Output Voltage Version. 4 LBO Voltage Detector Output. 5 GND Ground. 6 VBAT Battery Supply Input. 7 LBI Voltage Detector Input. 8 PGOOD Power Good Indicator. 9 LX Switching Node. Connect this pin to an inductor. 10 PGND Power Ground. 11 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS9276-02 July 2013 RT9276 Function Block Diagram PGOOD VOUT Determine Higher Voltage Soft-Start Control EN OCP, OTP, OVP VREF1 EA FB VBAT Logic UGATE Control Back Gate Control LX PWM LGATE Current Sense GND Internal Compensation PGND LBO VREF2 + - LBI Figure 3. Adjustable Voltage Regulator PGOOD VOUT Determine Higher Voltage Soft-Start Control EN VREF1 OCP, OTP, OVP VOUT VBAT Logic UGATE Control Back Gate Control LX EA LGATE PWM Current Sense PGND GND LBO Internal Compensation VREF2 + - LBI Figure 4. Fixed Voltage Regulator Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS9276-02 July 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9276 Absolute Maximum Ratings z z z z z z z z z z z z (Note 1) Supply Input Voltage, VBAT ---------------------------------------------------------------------------------------------Boost Output Voltage, VOUT -------------------------------------------------------------------------------------------Switch Output Voltage, LX ---------------------------------------------------------------------------------------------<10ns -----------------------------------------------------------------------------------------------------------------------Digital Input Voltage, EN, LBI -----------------------------------------------------------------------------------------Digital Output Voltage, LBO, PGOOD -------------------------------------------------------------------------------Others Pin ------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions z z z −0.3V to 6V −0.3V to 6.5V −0.3V to 6.5V −2V to 7.5V −0.3V to 6V −0.3V to 6V −0.3V to 6V 1.429W 70°C/W 8.2°C/W 150°C 260°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage Range, VBAT ------------------------------------------------------------------------------------- 1.2V to 5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VBAT ≥ 2.5V or VBAT = VOUT + 0.7V, VEN = VBAT, CIN = 10μF, COUT = 22μF, TA = 25°C, unless otherwise specified) Parameter Pre-charge Current Symbol Test Conditions Min Typ Max Unit IPre-chg VIN = 5V -- 100 -- mA VBAT ILOAD = 1mA -- 1.2 -- V 0.8 -- 5 V -- -- 5 V 0.49 0.5 0.51 V −3 -- 3 % 0.96 1.2 1.44 MHz -- 90 -- % DC/DC Stage Minimum Start-Up Input Voltage Input Voltage Range After Start-Up VBAT Output Voltage Range VOUT Feedback Reference Voltage VFB For Adjustable Output Voltage Output Voltage Accuracy ΔVOUT For Fixed Output Voltage Switching Frequency fLX Maximum Duty Cycle DMAX Non-Switching Quiescent Current IQ,NS No Switching -- 100 -- μA Shutdown Current ISHDN VEN = 0, VBAT = 1.2V -- 2 5 μA Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS9276-02 July 2013 RT9276 Parameter Symbol Test Conditions Min Typ Max Unit Protection Over-Temperature Protection T OTP -- 170 -- °C Over-Temperature Hysteresis T OTP_Hys -- 40 -- °C Over-Current Protection IOCP 1.6 2 2.4 A Over-Voltage Protection VOVP 5.4 -- 6 V VOUT = 3.3V -- 220 -- VOUT = 5V -- 200 -- VOUT = 3.3V -- 260 -- VOUT = 5V -- 240 -- VOUT = 3.3V Power MOSFET N-MOSFET ON-Resistance RDS(ON)_N P-MOSFET ON-Resistance RDS(ON)_P mΩ mΩ Enable Control EN Threshold Voltage Logic-High VIH Rising 0.8 -- -- Logic-Low VIL Falling -- -- 0.2 0.49 0.5 0.51 V -- 10 -- mV -- 15 -- Ω V Voltage Detector LBI Voltage Threshold VLBI_Rising LBI Voltage Hysteresis VLBI_Hys LBO Output Impedance RON_LBO VLBI = 0V, VOUT = 3.3V Note 1. Stresses beyond those listed “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 may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS9276-02 July 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9276 Typical Operating Characteristics μF, COUT = 22μ μF, L = 4.7μ μH, unless otherwise specified. CIN = 10μ Efficiency vs. Load Current Efficiency vs. Load Current 100 100 90 90 80 VIN = 3V VIN = 2.4V VIN = 1.8V VIN = 1.2V VIN = 0.9V 70 60 50 40 Efficiency (%) Efficiency (%) 80 30 20 10 70 VIN = 4.2V VIN = 3.6V VIN = 3V VIN = 2.4V VIN = 1.8V 60 50 40 30 20 10 VOUT = 3.3V 0 0.001 0.01 0.1 VOUT = 5V 0 0.001 1 0.01 Load Current (A) 100 90 90 80 IOUT = 100mA IOUT = 10mA Efficiency (%) Efficiency (%) 80 60 IOUT = 200mA 50 40 30 20 10 IOUT = 100mA IOUT = 10mA 70 60 50 40 30 20 10 VOUT= 3.3V VOUT = 5V 0 0 0.9 1.4 1.9 2.4 2.9 3.4 0.9 1.4 Input Voltage (V) 5.2 3.35 5.1 Output Voltage (V) 3.30 VIN = 3V VIN = 2.4V VIN = 1.8V VIN = 1.2V VIN = 0.9V 3.20 3.15 2.4 2.9 3.4 3.9 4.4 4.9 Output Voltage vs. Load Current 3.40 3.25 1.9 Input Voltage (V) Output Voltage vs. Load Current Output Voltage (V) 1 Efficiency vs. Input Voltage Efficiency vs. Input Voltage 100 70 0.1 Load Current (A) 3.10 5.0 VIN = 4.2V VIN = 3.6V VIN = 3V VIN = 2.4V VIN = 1.8V VIN = 1.2V VIN = 0.9V 4.9 4.8 4.7 4.6 3.05 VOUT = 3.3V 3.00 0.001 0.01 0.1 Load Current (A) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 1 VOUT = 5V 4.5 0.001 0.01 0.1 1 Load Current (A) is a registered trademark of Richtek Technology Corporation. DS9276-02 July 2013 RT9276 Switching Output Voltage vs. Input Voltage 6.0 Output Voltage (V) 5.5 5.0 VIN (1V/Div) VOUT (50mV/Div) IOUT= 10mA IOUT= 100mA 4.5 4.0 VLX (5V/Div) 3.5 3.0 ILX (500mA/Div) 2.5 VOUT = 5V VBAT = 1.2V, VOUT = 3.3V, ILOAD = 100mA 2.0 0.9 1.4 1.9 2.4 2.9 3.4 3.9 4.4 Time (250ns/Div) 4.9 Input Voltage (V) Load Transient Response Switching VIN (2V/Div) VOUT (100mV/Div) VIN (2V/Div) VOUT (50mV/Div) VLX (5V/Div) ILX (500mA/Div) IOUT (100mA/Div) VBAT = 2.4V, VOUT = 3.3V, ILOAD = 100mA to 200mA VBAT = 2.4V, VOUT = 3.3V, ILOAD = 200mA Time (500μs/Div) Time (250ns/Div) Line Transient Response Switching Frequency vs. Temperature Switching Frequency (kHz) 1300 VIN (2V/Div) VOUT (100mV/Div) IOUT (100mA/Div) 1250 1200 1150 1100 1050 VIN = 1.8V VIN = 2.4V 1000 950 VBAT = 1.8V to 2.4V, VOUT = 3.3V, ILOAD = 100mA VOUT = 3.3V 900 Time (500μs/Div) -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS9276-02 July 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9276 Voltage Detector Response FB Reference Voltage vs. Temperature 0.55 FB Reference Voltage (V) 0.54 0.53 0.52 0.51 0.50 VIN = 1.8V VIN = 2.4V 0.49 LBO (2V/Div) 0.48 0.47 0.46 LBI (500mV/Div) VBAT = 1.8V, VOUT = 5V, RLBO = 200kΩ VOUT = 3.3V 0.45 -40 -25 -10 5 20 35 50 65 80 95 110 125 Time (1ms/Div) Temperature (°C) Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS9276-02 July 2013 RT9276 Application Information The RT9276 integrates a high efficiency synchronous stepup DC-DC converter and a low battery detector. To fully utilize its advantages, peripheral components should be appropriately selected. The following information provides detailed description of application. Inductor Selection For a better efficiency in high switching frequency converter, the inductor selection has to use a proper core material such as ferrite core to reduce the core loss and choose low ESR wire to reduce copper loss. The most important point is to prevent core saturation when handling the maximum peak current. Using a shielded inductor can minimize radiated noise in sensitive applications. The maximum peak inductor current is the maximum input current plus half of the inductor ripple current. The calculated peak current has to be smaller than the current limitation in the electrical characteristics. A typical setting of the inductor ripple current is 20% to 40% of the maximum input current. If the selection is 40% 1 IPK = IIN(MAX) + IRIPPLE = 1.2 × IIN(MAX) 2 ⎡ IOUT(MAX) × VOUT ⎤ = 1.2 × ⎢ ⎥ ⎣ η × VBAT(MIN) ⎦ The minimum inductance value is derived from the following equation : L= η × IIN(MIN)2 × [ VOUT − VBAT(MIN) ] 0.4 × IOUT(MAX) × VOUT 2 × fLX Depending on the application, the recommended inductor value is between 2.2μH and 10μH. Input Capacitor Selection For better input bypassing, low-ESR ceramic capacitors are recommended for performance. A 10μF input capacitor is sufficient for most applications. For a lower output power requirement application, this value can be decreased one is the pulsating output ripple current which flows through the ESR, and the other is the capacitive ripple caused by charging and discharging. VRIPPLE = VRIPPLE(ESR) + VRIPPLE(C) ≅ IPEAK × RESR + IPEAK ⎡ VOUT − VBAT ⎤ COUT ⎢⎣ VOUT × fLX ⎥⎦ Output Voltage Setting Referring to application circuit (Figure 1), the output voltage of the switching regulator (VOUT) can be set with below equation : ⎛ R3 ⎞ VOUT = ⎜ 1 + ⎟ × VFB ⎝ R4 ⎠ where VFB = 0.5V (typ.) When the input voltage is larger than output setting voltage 370mV (typ.) the RT9276 will be in pre-charge mode. During pre-charge phase, the synchronous P-MOSFET is turned on until the output capacitor is charged to a value close to the input voltage minus 0.2V. Then the converter is followed by PWM operation. The adaptive precharge current increases linearly to overcome the loading current in the pre-charge phase. If the loading current is larger than pre-charge current, the RT9276 will be in precharge mode until loading current is removed or reduced. Low Battery Voltage Detector The low battery voltage detector is designed to monitor the battery voltage and to generate an error flag when the battery voltage drops below a user-set threshold voltage. The function is active only when the device is enabled. When the device is disabled, the LBO pin is in high impedance. The LBI threshold voltage is 0.5V typically, with 10mV hysteresis voltage. If the low-battery detection circuit is not used, the LBI pin should be connected to GND (or to VBAT) and the LBO pin can be left unconnected. Do not let the LBI pin floating. Thermal Considerations Output Capacitor Selection For lower output voltage ripple, low ESR ceramic capacitors are recommended. The tantalum capacitors can be used as well, but their ESR is bigger than ceramic capacitors. The output voltage ripple consists of two components: Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS9276-02 July 2013 For continuous operation, do not exceed absolute maximum operation junction temperature. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9276 The maximum power dissipation can be calculated by following formula : PD(MAX) = (TJ(MAX) − TA) / θJA Layout Consideration For best performance of the RT9276, the following layout guidelines must be strictly followed : where T J(MAX) is the maximum operation junction temperature, TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. ` Input and Output capacitors should be placed close to the IC and connected to ground plane to reduce noise coupling. For recommended operating conditions specification, the maximum junction temperature is 125°C. The junction to ambient thermal resistance θJA is layout dependent. For WDFN-10L 3x3 package, the thermal resistance θJA is 70°C/W on a standard JEDEC 51-7 four- layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : ` The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. ` Keep the main current traces as short and wide as possible. ` Place the feedback components as close as possible to the IC and keep away from the noisy devices. The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. The Figure 5 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W) 1.6 Four-Layer PCB 1.4 Cin and Cout should be placed close to the IC and connected to ground plane to reduce noise coupling. CIN V BAT COUT 10 PGND EN 1 L FB node copper 9 LX VOUT 2 R3 area should be 3 8 PGOOD FB/NC VOUT minimized and 7 LBI LBO 4 R4 11 5 6 kept far away from VBAT GND noise sources (LX pin) GND The GND and Exposed Pad should be connected to a strong ground plane for heat sinking and noise protection. GND PD(MAX) = (125°C − 25°C) / (70°C/W) = 1.429W for WDFN-10L 3x3 packages Figure 6. PCB Layout Guide 1.2 WDFN-10L 3x3 1.0 0.8 0.6 0.4 0.2 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curve of Maximum Power Dissipation Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS9276-02 July 2013 RT9276 Outline Dimension D2 D L E E2 1 e SEE DETAIL A 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 0.700 0.800 0.028 0.031 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 W-Type 10L DFN 3x3 Package Richtek Technology Corporation 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. DS9276-02 July 2013 www.richtek.com 11