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Technical content
Features
Input Voltage Range : 2.5V to 5.5V Internal Soft-Start, UVLO, OTP, OCP, OVP Typical Shutdown Current : < 1μμμμμA 1MHz Switching Frequency Drives Up to 10 WLEDs in Two Strings Independent PWM Dimming and 1-Wire Dimming Control PWM Dimming Frequency from 20k to 100kHz Up to 10 Bit Dimming Resolution Built-in IFB1/IFB2 pin OVP, Short Protection, and Un-Use Detection RT4531 Package Type WSC : WL-CSP-9B 1.35x1.35 (BSC) SW ISET GND RT4531 VIN EN L VIN IFB1 Enable 2P10S WLEDs IFB2PWM AGND R1C1 PWM Dimming
www.richtek.com DS4531-01 July 2016 ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Functional Pin Description WL-CSP-9B 1.35x1.35 (BSC) (TOP VIEW) Pin Configuration s Marking Information 33W 33 : Product Code W : Date Code ISET EN IFB1 GND SW PWM IFB2VIN AGND A1 A2 A3 B3B1 C1 C2 C3 Pin No. Pin Name Pin Function A1 ISET Full-Scale LED Current Set Pin. Connecting a resistor to the pin programs the full-scale LED current. A2 IFB2 Single Output 2 for Backlight LED. A3 IFB1 Single Output 1 for Backlight LED. B1 PWM Enable Control, and PWM Dimming Signal Input. B2 AGND Analog Ground. B3 GND Power Ground. C1 EN Enable Control, and 1-Wire Dimming Signal Input. C2 VIN Supply Input Pin. C3 SW Switch Node of Boost Converter.
DS4531-01 July 2016 www.richtek.com ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Function Block Diagram Operation The RT4531 is a high efficiency solution with 10S2P string for backlight applications. The RT4531 optimizes the feedback regulation voltage to provide high efficiency and also keep high current matching. The RT4531 can receive either the 1-wire dimming at EN pin or PWM dimming at PWM pin for brightness dimming. If the 1-wire dimming is selected, the PWM pin should be kept high; If the PWM dimming is selected, the EN pin should be kept high. OCP Protection The RT4531 features a 1.5A OCP. The driver provides cycle-by-cycle current limit function to control the current on power switch. The boost switch turns off when the inductor current reaches this current threshold and it remains off until the beginning of the next switching cycle. This protects the RT4531 and external component under overload conditions. OTP Protection The OTP function will disable boost and current source when the junction temperature exceeds 150 °C. Then restart to soft-start when the junction temperature is smaller than 135°C. OVP Protection The OVP function monitors the SW pin's voltage. Once it exceeds OVP threshold = 36.5V twice, the boost and current source will be latched off. Until PWM or EN go high from low again, the latch state will be released. 1-wire Brightness Dimming The RT4531 is built-in a 10-bit resolution brightness control. The EN pin features a simple 1-wire interface to allow digital brightness control. If the 1-wire dimming is needed, signals of a specific pattern should be input detection window into EN pin; Otherwise, PWM pin need to be enabled.(refer to Timing Diagram1 for Continuous Coding).The Register Program and register map give an overview of the protocol used by RT4531. PWM Brightness Dimming Besides programmable built-in 1-wire backlight LED current control, the RT4531 features a built-in PWM dimming current control by PWM pin, offering a linear current dimming by external clock source. In order to guarantee the PWM dimming resolution, recommending PWM dimming frequency have to be operated at range of 20kHz to 100kHz. Control LogicEN Current Source/ FB Short Detect IFB1 IFB2 SW BL PWM/Drv GND UVLOVIN OCP OSC MINFB PWM Logic DC to DC Core ISET PWM ISET FB OVP OTP OVP AGND
www.richtek.com DS4531-01 July 2016 ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.
Electrical Characteristics
Recommended Operating Conditions (Note 4) (VIN = 3.6V, CIN = 2.2μF, COUT = 1μF, L = 4.7μH, TA = 25°C, unless otherwise specified) Absolute Maximum Ratings (Note 1) Power Dissipation, PD @ TA = 25°C Package Thermal Resistance (Note 2) ESD Susceptibility (Note 3) Parameter Symbol Test Conditions Min Typ Max Unit Power Supply UVLO V UVLO VIN falls -- 2.2 2.3 V UVLO Hysteresis Voltage VUVLO VIN rises after UVLO 30 50 200 mV VIN Supply Current I Q EN = High, Non-switching -- 1.2 -- mA VIN Shutdown Current I SHDN V IN = 5V -- 1 -- A Thermal Shutdown T SD -- 150 -- C Thermal Shutdown Hysteresis -- 15 -- C Back Light LED Accuracy of Back Light Output Current 1/2 AIBL1, 2 I FBx = 20mA 2 -- 2 % Matching of Output Current MIBL IFBx = 20mA -- 1 2 % BLED Sense Voltage 1/2 VDSBL IFBx = 20mA, measured on IFBx pin which has a lower voltage. 200 300 430 mV Back Light Switching Frequency fblosc 0.88 1 1.12 MHz
DS4531-01 July 2016 www.richtek.com ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Parameter Symbol Test Conditions Min Typ Max Unit Maximum Duty Cycle D MAX 90 95 -- % Back Light N-MOSFET Ron R DS(ON)_BLN 100 270 400 m Back Light Current Limit I LIM_BL After 5ms in soft-start 1.15 1.5 1.85 A Back Light Over Voltage Protection VBLOVP Close loop, V IN = 3.6V 35.5 36.5 37.5 V IFBx Pin Over Voltage Threshold VIFBXOVP Measure on IFBx pin -- 5 -- V Logic Control One Wire Detection Delay tes_delay Measure from En low to high 300 -- -- s One Wire Detection Time tes_det En pin low time in detection window 400 -- -- s One Wire Detection Window tes_win Measure from En low to high, Fblosc = 1MHz -- 1 -- ms Start Time of Program Stream tstart 3 -- -- s End Time of Program Stream tEOS 3 -- -- s High Time Low Bit t H_LB Logic 0 2 -- 180 s Low Time Low Bit t L_LB Logic 0 2 x tH_LB -- 360 s High Time High Bit t H_HB Logic 1 2 x tL_HB -- 360 s Low Time High Bit t L_HB Logic 1 2 -- 180 s EN Input Voltage Logic-Low V EN_L -- -- 0.4 V Logic-High V EN_H 1.4 -- -- PWM Input Voltage Logic-Low V PWM_L -- -- 0.4 V Logic-High V PWM_H 1.4 -- -- EN Pull Low Resistor R EN 280 400 520 k PWM Pull Low Resistor R PWM 280 400 520 k PWM Logic Low Width to Shutdown TSD_PWM PWM pin high to low, then shutdown 20 -- -- ms EN Logic Low Width to Shutdown TDS_EN EN pin high to low, then shutdown 2.5 -- -- ms 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. θ JA is measured at T A = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.
www.richtek.com DS4531-01 July 2016 ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Typical Application Circuit Timing Diagram Timing Diagram1 for 1-wire Continuous Coding Timing Diagram2 for Shutdown and then Reprogram PWM Detection Window Programming Code > 2.5ms Shutdown Detection Window Programming CodeEN PWM EN Tes_delay Tes_det >300µs >400µs Tes_win <1.23ms Tstart Addr8 = H Addr7 = L tH_LB < 2x tH_HB tL_LB > 2x tL_HB D1 = L EOS 3~360µs Detection Window Programming Code1 Programming Code2 Tstart Addr8 = L SW ISET GND RT4531 VIN EN 1µF L 4.7µH 1µF / 50V VIN C3C2 IFB1 A3Enable 2P10S WLEDs 2.5V to 5.5V IFB2 A2PWMB1 AGND 101µF 63.4k PWM Dimming
DS4531-01 July 2016 www.richtek.com ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Typical Operating Characteristics Switching Frequency vs. Input Voltage 0.7 0.8 0.9 1.0 1.1 1.2 1.3 2.5 3 3.5 4 4.5 5 5.5 Input Voltage (V) Switching Frequency (MHz) 1 Switching Frequency vs. Temperature 0.88 0.93 0.98 1.03 1.08 1.13 -50 -25 0 25 50 75 100 125 Temperature (°C) Switching Frequency (MHz) 1 Sense Voltage vs. Output Current 0.310 0.311 0.312 0.313 0.314 0.315 0 2.5 5 7.5 10 12.5 15 17.5 20 Output Current (mA) Sense Voltage (V) Dimming Linearity 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022 0 2 04 06 08 0 1 0 0 Dimming Duty Cycle (%) Output Current (mA) VIN = 3.6V ILED1 ILED2 Efficiency vs. Output Current Output Current (A) Efficiency (%) VIN = 3.6V, V OUT = 31V, 10s2p, 20mA/string Efficiency vs. Input Voltage 100 2.5 3 3.5 4 4.5 5 5.5 Input Voltage(V) Efficiency(%) VOUT = 31V, 10s2p ILED = 20mA ILED = 10mA
www.richtek.com DS4531-01 July 2016 ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation.
Application Information
1-Wire Interface (Device Address 0x2F) Register Map Bit Label Reset Description D16 Ramp Up<2> 0 [101] = 1.024ms, [110] = 2.048ms, [111] = 4.096ms D15 Ramp Up<1> 0 D14 Ramp Up<0> 1 D13 Ramp Down<2> 0 [101] = 1.024ms, [110] = 2.048ms, [111] = 4.096ms D12 Ramp Down<1> 0 D11 Ramp Down<0> 1 D10 ILED<9> 0 MSB = sDAC<9> D9 ILED<8> 0 sDAC<8> D8 ILED<7> 0 sDAC<7> D7 ILED<6> 0 sDAC<6> D6 ILED<5> 0 sDAC<5> D5 ILED<4> 0 sDAC<4> D4 ILED<3> 0 sDAC<3> D3 ILED<2> 0 sDAC<2> D2 ILED<1> 0 sDAC<1> D1 ILED<0> 0 LSB = sDAC<0> Start Addr Addr Addr Addr Addr Addr Addr Addr
1 D9 D8 D7 D6 D5 D4 D3 D2 D1 EOS
DS4531-01 July 2016 www.richtek.com ©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Protection Actions Soft-Start/ Normal Operation SW > OVP for > 8cycles in 10msec Latch Off Y N EN High Source Current to FBx FBx < 30mV For 600µs? FBx Turned Off Y N X = 2? Y Latch Off N Soft-Start /Normal Operation Soft-Start/Normal Operation
©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. RISET at ISET pin according to Equation 1. the IC is shut down or disabled. starts from the shutdown mode.
- Pull the EN pin high to enable the RT4531 and start the
detection window for digital dimming.
- After the digital dimming detection delay time (T
detection time (T-es_det, >400μs).
- Pull the EN pin high after the detection time (>400μs)
Figure 1. RT4531 1-wire Dimming Typical Application
©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. current is regulated to full-scale according to Equation 1. Figure 2. RT4531 PWM Dimming Typical Application remains off until the beginning of the next switching cycle. and it would not be trigger OVP. detected from the PWM signals.
©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Figure 3. Derating Curve of Maximum Power Dissipation and temperature difference between junction to ambient. the junction to ambient thermal resistance. ambient temperature on the maximum power allowed. guidelines must be strictly followed. strong ground plane for heat sinking and noise protection. voltage swing. It should be kept at a small area. line that avoid the PWM signal couple to ISET.
©Copyright 2016 Richtek Technology Corporation. All rights reserved. is a registered trademark of Ric htek Technology Corporation. Table 1. Recommended Components for Typical Application Circuit Figure 4. PCB Layout Guide area should be minimized for reducing EMI. the PWM signal couple to ISET.
www.richtek.com DS4531-01 July 2016 Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st 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 furnish ed 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 infringeme nts 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 R ichtek or its subsidiaries. Outline Dimension Symbol Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 0.500 0.600 0.020 0.024 A1 0.170 0.230 0.007 0.009 b 0.240 0.300 0.009 0.012 D 1.300 1.400 0.051 0.055 D1 0.800 0.031 E 1.300 1.400 0.051 0.055 E1 0.800 0.031 e 0.400 0.016 WL-CSP-9B 1.35x1.35 (BSC)