RT9287A-FQGQW

Preliminary RT9287A Boost Converter for WLED Power with Dual LDO General Description The RT9287A is an integrated solution for WLED and camera power. It contains a boost converter with internal schottky diode to provide WLED power and Dual LDO for the power of camera image sensor. In the section of boost converter, RT9287A's optimized operation frequency can meet the requirement of small LC filters value and low operation current with high efficiency. Internal soft start function can reduce the inrush current. The initial current of WLED is set by the external resistor RSET. The feedback voltage is 250mV. In the section of DLDO, RT9287A is a dual channel, low noise, and low dropout regulator sourcing up to 300mA at each channel. The part offers 2% accuracy, low dropout voltage (240mV@300mA), and low ground current, only 27μA per LDO. The shutdown current is near zero current, which is suitable for battery-power devices. Other features include current limiting, over temperature, output short circuit protection. The part is short circuit thermal folded back protected. RT9287A lowers its OTP trip point from 165°C to 110°C when output short circuit occurs (VOUT < 0.4V) providing maximum safety to end users. RT9287A is available in a WDFN-12L 3x3 package. Features Boost Converter VIN Operating Range : 2.7V to 5.5V Up to 85% Efficiency 22V Internal Power N-MOSFET 1MHz Switching Frequency Built-in Diode Digital Dimming with Zero-Inrush Input UVLO Protection Output Over Voltage Protection Internal Soft Start and Compensation Dual LDO Wide Operating Voltage Ranges : 2.7V to 5.5V Low-Noise for RF Application No Noise Bypass Capacitor Required Fast Response in Line/Load Transient TTL-Logic-Controlled Shutdown Input Low Temperature Coefficient Dual LDO Outputs (300mA/300mA) Ultra-Low Quiescent Current 27μA/LDO High Output Accuracy 2% Short Circuit Protection Thermal Shutdown Protection Current Limit Protection Short Circuit Thermal Folded Back Protection RoHS Compliant and 100% Lead (Pb)-Free Ordering Information RT9287APackage Type QW : WDFN-12L 3x3 (W-Type) Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) LDO Output Voltage : VOUT1/VOUT2 MG : 2.8V/1.8V FQ : 1.5V/3.1V Applications Cellular Phones WLED Driver PDAs and Smart Phones Probable Instruments Pin Configurations (TOP VIEW) VIN EN1 EN2 LX PGND VOUT 1 2 3 4 5 6 12 11 10 9 8 7 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. GND VLDO1 VLDO2 AGND FB VDD ENB WDFN-12L 3x3 DS9287A-00 July 2007 www.richtek.com 1 RT9287A Marking Information Preliminary For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail. Typical Application Circuit L1 10uH to 22uH V IN RT9287A 4 V IN 1 C IN 1uF 7 Chip Enable Chip Enable 2 3 LX VIN VDD VOUT 8 6 C1 1uF C2 0.22uF to 1uF 9 12 C OUT1 1uF C OUT2 1uF V LDO1 V LDO2 R SET 12.5 ENB EN1 EN2 AGND 10 FB VLDO1 VLDO2 11 PGND 5 Functional Pin Description Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 Pin Name VIN E N1 EN2 LX PGND VOUT ENB VDD FB AGND VLDO2 VLDO1 LDO Power Input Voltage. Enable pin for LDO channel 1. Enable pin for LDO channel 2. Boost LX Pin. Connect this Pin to an inductor. Minimize the track area to reduce EMI. Power Ground. Boost Output Voltage pin. The pin internally connects to OVP diode to limit output voltage while LEDs are disconnected. Boost Chip Enable (Active High). Note that this pin has an internal pull-down resistance around 300k Ω. Boost Supply Input Voltage Pin. Bypass 1 μF capacitor to GND to reduce the input Ripple. Boost Feedback Pin. Series connecting a resistor between WLED and ground as a current sense. Sense the current feedback voltage to set the current rating. Analog Ground. LDO Channel 2 Output Voltage. LDO Channel 1 Output Voltage. Exposed pad should be soldered to PCB board and connected to GND. Pin Function Exposed Pad GND www.richtek.com 2 DS9287A-00 July 2007 Preliminary Function Block Diagram Current Sense RT9287A 1.0MHz OSC Slope Compensation OCP OVP PWM Logic LX VOUT VDD UVLO /PGOOD Timer Dimming Controller Shutdown and Logic Control V REF + + - ENB FB EN1 V REF Soft-Start /Clamping PGND VIN - + MOS Driver VLDO1 Current-Limit and Thermal Protection AGND Error Amplifier EN2 Shutdown and Logic Control V REF - + MOS Driver VLDO2 Current-Limit and Thermal Protection AGND Error Amplifier DS9287A-00 July 2007 www.richtek.com 3 RT9287A Absolute Maximum Ratings Preliminary (Note 1) −0.3V to 6V −0.3V to 22V −0.3V to 21V −0.3V to 6V 0.606W 165°C/W 8.2°C/W 150°C 260°C −65°C to 150°C 2kV 200V Supply Input Voltage, VIN, VDD ----------------------------------------------------------------------------------------LX Input Voltage ----------------------------------------------------------------------------------------------------------Output Voltage, VOUT ----------------------------------------------------------------------------------------------------The Other Pins ------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WDFN-12L 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 4) WDFN-12L 3x3, θJA ------------------------------------------------------------------------------------------------------WDFN-12L 3x3, θJC ------------------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 2) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions (Note 3) Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VDD = 3.7V, FREQ left floating, VIN = VOUT + 1V, VEN = VIN, CIN = COUT = 1μA, TA = 25°C, unless otherwise specified) Parameter Boost System Supply Input Operation voltage Range Under Voltage Lock Out Quiescent Current Supply Current Shutdown Current Line Regulation Oscillator Operation Frequency Maximum Duty Cycle Reference Voltage Feedback Reference Voltage Diode Forward Voltage Symbol Test Condition Min Typ Max Units VDD VUVLO IQ IIN ISHDN VFB = 1.5V, No switch VFB = 0V, Switch VENB < 0.4V VDD2 = 3V to 4.3V 2.7 1.7 ----- -2 300 -2 -- 5.5 2.3 450 2 5 3 V V μA mA μA % fOSC -85 1 90 --- MHz % VREF 0.237 0.25 0.263 V VFW IFW = 100mA -- 0.9 -- V To be continued www.richtek.com 4 DS9287A-00 July 2007 Preliminary Parameter M OSFET O n Resistance of MOSFET P rotection O VP Threshold O CP Control Interface E NB Threshold Logic-Low Voltage Logic-High Voltage VIL VIH TLO THI TSHDN VIN (Note 5) VDROP VOUT ΔV ΔVLINE ΔVLOAD ILIM IQ ISHDN VIH VIL TSD ΔTSD f = 100Hz P SRR ILOAD = 1 0mA PSRR P SRR ILOAD = 1 50mA f = 1kHz f = 10kHz f = 100Hz f = 1kHz f = 10kHz IOUT = 1mA VIN = ( V OUT + 0.3V) to 5.5V or VIN > 2 .7V, whichever is larger 1mA < IOUT < 300mA RLOAD = 1 Ω VEN1, 2 > 1.5V VEN1, 2 < 0.4V VIN = 2 .7V to 5.5V, Power On VIN = 2 .7V to 5.5V, Shutdown R efer to Figure 1 R efer to Figure 1 R efer to Figure 1 -1.4 0.5 0.5 1 -----VOV P --20 400 RDS(ON) 0.5 0.9 Symbol Test Condition Min Typ RT9287A M ax Units -- Ω --- V mA 0.4 -300 --- V V μs μs ms E NB Low Time for Dimming Delay Between Steps Time S hut Down Delay Time Dual LDO Input Voltage Dropout Voltage V OUT A ccuracy Line Regulation Load Regulation Current Limit Q uiescent Current S hutdown Current E N1,2 T hreshold O utput Voltage TC Thermal Shutdown Thermal Shutdown Hysteresis O utput Voltage Range VIN = 2 .7V to 5.5V IOUT = 300mA 2.7 -1.2 −2 --3 30 --1.5 ----------- -240 ----450 58 ---100 170 40 − 65 − 60 − 50 − 65 − 50 − 50 5.5 330 3.6 +2 0.2 0.6 700 80 1 -0.4 ---------- V mV V % %/V % mA μA μA V V ppm/°C °C °C dB dB dB dB dB dB DS9287A-00 July 2007 www.richtek.com 5 RT9287A Preliminary 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. The device is not guaranteed to function outside its operating conditions. Note 4. θ JA i s measured in the natural convection at T A = 25 °C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. The case point of θJC is on the expose pad for the QFN package. Note 5. The dropout voltage is defined as VIN -VOUT, which is measured when VOUT is VOUT(NORMAL) − 100mV. www.richtek.com 6 DS9287A-00 July 2007 Preliminary Typical Operating Characteristics Boost Efficiency vs. Input Voltage 86 84 82 RT9287A Boost Efficiency vs. Load Current 90 L = 22μH 80 L = 22μH Efficiency (%) Efficiency (%) 80 78 76 74 L = 10μH 70 L = 10μH 60 VOUT = 15V, ILOAD = 20mA 72 3 3.5 4 4.5 5 5.5 50 0 VIN = 3.7V, VOUT = 15V 10 20 30 40 50 60 Input Voltage (V) Load Current (mA) Boost OVP vs. Input Voltage 20.02 20.01 20.00 253.8 253.6 Boost Feedback Voltage vs. Input Voltage Feedback Voltage (mV) 253.4 253.2 253.0 252.8 252.6 252.4 252.2 252.0 OVP (V) 19.99 19.98 19.97 19.96 2.5 3 3.5 4 4.5 5 5.5 VOUT = 15V, ILOAD = 1mA 2.5 3 3.5 4 4.5 5 5.5 Input Voltage (V) Boost Feedback Voltage vs. Temperature 253.2 253.0 252.8 252.6 252.4 252.2 252.0 254.0 253.5 Input Voltage (V) Boost Feedback Voltage vs. Load Current VIN = 3.7V, VOUT = 15V Feedback Voltage (mV) Feedback Voltage (mV) VIN = 3.7V, VOUT = 15V, ILOAD = 10mA -40 -20 0 20 40 60 80 253.0 252.5 252.0 251.5 251.0 250.5 0 10 20 30 40 50 Temperature (°C) Load Current (mA) DS9287A-00 July 2007 www.richtek.com 7 RT9287A Boost Dimming Operation Preliminary Boost Normal Operation VEN (1V/Div) VIN (50mV/Div) VOUT (50mV/Div) I LED (10mA/Div) VLX (10V/Div) VIN = 3.7V, 4WLED VIN = 3.7V, 4WLED, ILED = 20mA, L = 10μH Time (1ms/Div) Time (500ns/Div) LDO1 Output Voltage vs. Temperature 2.90 LDO2 Output Voltage vs. Temperature 1.90 Output Voltage (V) Output Voltage (V) VIN = VEN1 = 4.3V 2.85 1.85 2.80 1.80 2.75 1.75 VIN = VEN2 = 4.3V 1.70 25 50 75 100 125 2.70 -50 -25 0 -50 -25 0 25 50 75 100 125 Temperature (°C) Temperature (°C) LDO Quiescent Current vs. Temperature 70 LDO1 Dropout Voltage vs. Load Current 350 300 Quiescent Current (uA) 85°C 25°C -40°C Dropout Voltage (V) VIN = VEN1 = VEN2 = 4.3V 65 250 200 150 100 50 60 55 50 -50 -25 0 25 50 75 100 125 0 0 50 100 150 200 250 300 Temperature (°C) Load Current (mA) www.richtek.com 8 DS9287A-00 July 2007 Preliminary RT9287A LDO Line Transient Response LDO PSRR 0 -10 -20 -30 VIN 4.8 (V) ILOAD = 10mA ILOAD = 100mA 3.8 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 10 0.01 100 0.1 ILOAD = 0mA VOUT1 (20mV/Div) VOUT2 (20mV/Div) VIN = VEN1 = VEN2 = 3.3V ± 0.1V 1000 1 10000 10 100000 100 1000000 1000 Both ILOAD = 1mA, VIN = 3.8V to 4.8V Time (250μs/Div) Frequency (Hz) Frequency (kHz) LDO Line Transient Response VIN 4.8 (V) 3.8 LDO Load Transient Response IOUT (100mA/Div) VOUT1 (20mV/Div) VOUT2 (20mV/Div) Both ILOAD = 10mA, VIN = 3.8V to 4.8V ILOAD = 10mA to 100mA, VIN = VEN = 4.3V VOUT1 (20mV/Div) VOUT2 (20mV/Div) Time (250μs/Div) Time (250μs/Div) LDO Load Transient Response LDO Power On from EN IOUT (200mA/Div) VOUT1 (100mV/Div) VOUT2 (100mV/Div) ILOAD = 10mA to 350mA, VIN = VEN = 4.3V VEN (2V/Div) VOUT1 (2V/Div) VOUT2 (2V/Div) Both ILOAD = 100mA, VIN = 5V Time (250μs/Div) Time (10μs/Div) DS9287A-00 July 2007 www.richtek.com 9 RT9287A LDO Power Off from EN Preliminary Cross Talk VEN (2V/Div) VOUT1 (2V/Div) VOUT2 (2V/Div) I Boost (10mA/Div) VOUT1 (50mV/Div) VOUT2 (50mV/Div) Both ILOAD = 100mA, VIN = 5V VIN = VEN = 4.3V Time (250μs/Div) Time (250μs/Div) www.richtek.com 10 DS9287A-00 July 2007 Preliminary Application Information Boost Converter LED Current Control As shown in Figure 1, the RT9287A regulates the LED current by setting the current sense resistor (RSET) connected between FB pin and ground. The reference voltage of FB pin is 0.25V in typical. The LED current (ILED) can be calculated by the following Equation. ILED = VREF / RSET (1) RT9287A (3) VOUT = RA x {(FB/RB) + (FB-GPIO)/RGPIO} + FB As GPIO = 0V, VOUT = RA x {(0.25/RB) + (0.25/RGPIO)} + 0.25 As GPIO = 2.8V, VOUT = RA x {(0.25/RB) + (0.25-2.8)/RGPIO} + 0.25 As GPIO = 1.8V, VOUT = RA x {(0.25/RB) + (0.25-1.8)/RGPIO} + 0.25 For Efficiency Consideration set RA = 990kΩ. (4) (5) (6) In order to have an accurate LED current, a precision resistor is preferred (1% is recommended). V IN 2.7V to 5.5V L1 10uH to 22uH RT9287A LX Chip Enable EN PGND VDD VOUT FB C1 1uF V FB = 0 .25V R SET Figure 1. Application for Driving 3 series WLEDs Inductor Selection The recommended value of the inductor is from 10μH to 22μH for 4 to 5 WLEDs applications. For 3WLEDs, the recommended value of the inductor is from 4.7μH to 22μH. Small size and better efficiency are the major concerns for portable devices, just as RT9287A's application for mobile phone. The inductor should have low core loss at 1MHz and low DCR for better efficiency. The inductor saturation current rating should be considered to cover the inductor peak current. Output Voltage Control For fixed output voltage application, the output voltage can be adjusted by the divider circuit on FB pin. Figure2 shows a 2-level voltage control circuit for OLED application. The output voltage can be calculated by the following equations. Table 1 is the recommended resistance for different conditions. Table 1. Suggested Resistance for Output Voltage Control RB RGPIO RA Conditions (kΩ) ( kΩ ) ( kΩ ) Case A : Normal Voltage = 16V (GPIO = 0V) 1100 18 495 Dimming Voltage = 12V (GPIO = 1.8V) Case B : Normal Voltage = 16V (GPIO = 0V) 1200 19.5 840 Dimming Voltage = 12V (GPIO = 2.8V) V IN GPIO VDD VOUT RA R GPIO OLED RT9287A LX V EN ENB FB RB PGND Figure 2. Application Circuit for 2-level Output Voltage Control Dual LDO Like any low-dropout regulator, the external capacitors used with the RT9287A must be carefully selected for regulator stability and performance. Using a capacitor whose value is > 1μF on the LDO input and the amount of capacitance can be increased without limit. The input capacitor must be located a distance of not more than 0.5 inch from the input pin of the IC and returned to a clean analog ground. Any high quality ceramic or tantalum capacitor can be www.richtek.com 11 DS9287A-00 July 2007 RT9287A Preliminary VOUT Short to GND used for this part. The capacitor with larger value and lower ESR (equivalent series resistance) provides better PSRR and line-transient response. The output capacitor must meet both requirements for minimum amount of capacitance and ESR in all applications. The LDO is designed specifically to work with low ESR ceramic output capacitor in space-saving and performance consideration. Using a ceramic capacitor whose value is at least 1μF with ESR is > 20mΩ on the LDO output ensures stability. The LDO still works well with other kinds of output capacitor due to the wide stable ESR range. Figure 3 shows the curves of allowable ESR range as a function of load current for various output capacitor values. Output capacitor of larger capacitance can reduce noise and improve load transient response, stability, and PSRR. The output capacitor should be located not more than 0.5 inch from the VOUT pin of the LDO and returned to a clean analog ground. VOUT 0.4V IOUT TSD 170 °C 110 °C OTP Trip Point 110 °C IC Temperature 80 °C Figure 4. Short Circuit Thermal Folded Back Protection when Output Short Circuit Occurs (Patent) Thermal Considerations The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junctions to ambient. The maximum power dissipation can be calculated by following formula : PD(MAX) = ( TJ(MAX) - TA ) / θJA Region of Stable COUT ESR vs. Load Current 100 Region of Stable C OUT ESR ((Ω)) Region of Stable C OUT ESR Ω VIN = 5V, CIN = COUT1 = COUT2 = 1uF/X7R 10 Unstable Range 1 0.1 Stable Range Where T J(MAX) i s the maximum operating ction temperature, TA is the ambient temperature and the θJA is the junction to ambient thermal resistance. For recommended operating conditions specification of the T9287A, where TJ(MAX) is the maximum junction temperature of the die and TA is the maximum ambient temperature. The junction to ambient thermal resistance JA is layout dependent. For WDFN-12L 3x3 packages, the thermal resistance JA is 60 oC/W on the standard JEDEC 51-7 four-layers thermal test board. The maximum power dissipation at TA = 25°C can be calculated by following formula: PD(MAX) = ( 120°C − 25°C ) / (60°C/W) = 1.667W for WDFN12L 3x3 packages The maximum power dissipation depends on operating ambient temperature for fixed TJ(MAX) and thermal resistance JA. For RT9287A packages, the Figure 5 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. DS9287A-00 July 2007 0.01 Simulation Verify 0.001 0 50 100 150 200 250 300 Load Current (mA) Figure 3. Stable Cout ESR Range Thermal protection limits power dissipation in LDO. When the operating junction temperature exceeds a certain temperature, the OTP circuit starts the thermal shutdown function and turns the pass element off. The pass element turns on again after the junction temperature is cooled down. The RT9287A lowers its OTP trip level from 170°C to 110°C when output short circuit occurs (VOUT < 0.4V) as shown in Figure 4. It reduces operating junction temperature and provides maximum safety to customer while output short circuit occurring. www.richtek.com 12 Preliminary 1.8 RT9287A Maximum Power Dissipation (W) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curves for RT9287A Packages Layout Guide The exposed pad and GND should be connected to a strong ground plane for heat sinking and noise prevention. Traces should be kept as short as possible. LX node copper area should be minimized for reducing EMI. The Dual LDO input capacitor C1 must be located a distance of not more than 0.5 inch from the VDD1 pin and returned to ground plane. The Boost input capacitor C2 should be placed as closed as possible to Pin 7. The Dual LDO output capacitor C3 and C4 must be located a distance of not more than 0.5 inch from the VLDO1 and VLDO2 pin and returned to ground plane. FB node copper area should be minimized and keep far away from noise sources (LX). Feedback resistance R2 should be placed as closed as possible to Pin 5. The input capacitor must be located a distance of not more than 0.5 inch from the VIN Pin. C1 C4 The output capacitors C3 and C4 should be located not more than 0.5 inch from the VOUT pin of the LDO. FB node copper area should be minimized and keep far away from noise sources (L X ). RSET and R1 should be placed as close as RT9287A. R SET VIN EN1 EN2 L1 LX PGND VOUT 1 2 3 4 5 6 12 11 10 9 8 VLDO1 VLDO2 AGND FB VDD ENB C2 C3 GND C5 Grand Plane 7 The output capacitor C5 should be connected directly from Pin6 The exposed pad, PGND, and AGND should be connected to a strong ground plane for heat sinking and noise prevention. Figure 6 DS9287A-00 July 2007 www.richtek.com 13 RT9287A Outline Dimension Preliminary 2 1 2 1 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. Symbol A A1 A3 b D D2 E E2 e L Dimensions In Millimeters Min 0.700 0.000 0.175 0.150 2.950 2.300 2.950 1.400 0.450 0.350 0.450 Max 0.800 0.050 0.250 0.250 3.050 2.650 3.050 1.750 Dimensions In Inches Min 0.028 0.000 0.007 0.006 0.116 0.091 0.116 0.055 0.018 0.014 0.018 Max 0.031 0.002 0.010 0.010 0.120 0.104 0.120 0.069 W-Type 12L DFN 3x3 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 DS9287A-00 July 2007