RT4531WSC

® RT4531 Dual Channel 10s2p WLED Drivers General Description Features The RT4531 is a dual-channel current source with highefficiency asynchronous boost converter for backlight application. The RT4531 has built-in 1.5A/36V power MOSFET and two high current-matching capability current sink, so RT4531 can drives up 10s2p white LED. The RT4531 can allow very low voltage headroom control, therefore to improve LED strings efficiency effectively.  Input Voltage Range : 2.5V to 5.5V  Internal Soft-Start, UVLO, OTP, OCP, OVP μA Typical Shutdown Current : < 1μ 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 LED Current Accuracy ± 2% ( > 5mA) LED Current Matching ± 2% ( > 5mA) Built-in IFB1/IFB2 pin OVP, Short Protection, and Un-Use Detection      The RT4531 supports both PWM dimming and 1-wire digital dimming interface and it can realize 10 bit brightness code programming.    The RT4531 provides complete protection functions such as input Under-Voltage Lockout (UVLO), Over-Current Protection (OCP), Output Over Voltage (OVP) and OverTemperature Protection (OTP).  Ordering Information The RT4531 is available in the WL-CSP-9B 1.35x1.35 (BSC) package. RT4531 Package Type WSC : WL-CSP-9B 1.35x1.35 (BSC) Applications     Note : Smart Phones Probable Instruments Backlight for Small and Media Form Factor LCD Display with Single-cell Battery Input Richtek 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. Simplified Application Circuit L VIN C1 C3 R1 PWM Dimming RT4531 EN PWM DS4531-01 July 2016 2P10S WLEDs IFB1 IFB2 ISET GND AGND Copyright © 2016 Richtek Technology Corporation. All rights reserved. … Enable SW … VIN C2 R2 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT4531 Pin Configurations Marking Information (TOP VIEW) IFB2 33 : Product Code ISET A1 PWM B1 33W A2 A3 IFB1 B2 B3 GND C3 SW W : Date Code AGND C1 C2 VIN EN WL-CSP-9B 1.35x1.35 (BSC) Functional Pin Description 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. Copyright © 2016 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS4531-01 July 2016 RT4531 Function Block Diagram OSC UVLO VIN OTP OVP SW BL PWM/Drv DC to DC Core EN Control Logic PWM Logic GND AGND OCP PWM FB OVP ISET ISET MINFB Current Source/ FB Short Detect IFB1 IFB2 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. Copyright © 2016 Richtek Technology Corporation. All rights reserved. DS4531-01 July 2016 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. is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT4531 Absolute Maximum Ratings            (Note 1) Supply Voltage, VIN ------------------------------------------------------------------------------------------------------LED Switching Voltage, SW -------------------------------------------------------------------------------------------LED Current Source Voltage, IFB1, IFB2 ---------------------------------------------------------------------------Digital Clock Control Pin, EN, PWM --------------------------------------------------------------------------------Other Pins, ISET ---------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WL-CSP-9B 1.35x1.35 (BSC) -----------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WL-CSP-9B 1.35x1.35 (BSC), θJA -----------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) ----------------------------------------------------------------------------------------------------- Recommended Operating Conditions    −0.3V to 6V 38V −0.3V to 6V −0.3V to 6V −0.3V to 6V 1.22W 81.5°C/W 150°C 260°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 2.5V to 5.5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 3.6V, CIN = 2.2μF, COUT = 1μF, L = 4.7μH, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Power Supply UVLO VUVLO VIN falls -- 2.2 2.3 V UVLO Hysteresis Voltage VUVLO VIN rises after UVLO 30 50 200 mV VIN Supply Current IQ EN = High, Non-switching -- 1.2 -- mA VIN Shutdown Current ISHDN VIN = 5V -- 1 -- A Thermal Shutdown TSD -- 150 -- C -- 15 -- C IFBx = 20mA 2 -- 2 % IFBx = 20mA -- 1 2 % IFBx = 500A IFBx = 20mA, measured on IFBx pin which has a lower voltage. -- 1 -- % 200 300 430 mV 0.88 1 1.12 MHz Thermal Shutdown Hysteresis Back Light LED Accuracy of Back Light Output Current 1/2 AIBL1, 2 Matching of Output Current MIBL BLED Sense Voltage 1/2 VDSBL Back Light Switching Frequency f blosc Copyright © 2016 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS4531-01 July 2016 RT4531 Parameter Symbol Test Conditions Min Typ Max Unit Maximum Duty Cycle DMAX 90 95 -- % Back Light N-MOSFET Ron RDS(ON)_BLN 100 270 400 m Back Light Current Limit ILIM_BL After 5ms in soft-start 1.15 1.5 1.85 A Back Light Over Voltage Protection VBLOVP Close loop, VIN = 3.6V 35.5 36.5 37.5 V IFBx Pin Over Voltage Threshold VIFBXOVP Measure on IFBx pin -- 5 -- V One Wire Detection Delay tes_delay 300 -- -- s One Wire Detection Time tes_det 400 -- -- s One Wire Detection Window tes_win Measure from En low to high En pin low time in detection window Measure from En low to high, Fblosc = 1MHz -- 1 -- ms tstart 3 -- -- s tEOS 3 -- -- s Logic Control Start Time of Program Stream End Time of Program Stream High Time Low Bit tH_LB Logic 0 2 -- 180 s Low Time Low Bit tL_LB Logic 0 2x tH_LB -- 360 s High Time High Bit tH_HB Logic 1 2x tL_HB -- 360 s Low Time High Bit tL_HB Logic 1 2 -- 180 s Logic-Low VEN_L -- -- 0.4 Logic-High VEN_H 1.4 -- -- Logic-Low VPWM_L -- -- 0.4 Logic-High VPWM_H 1.4 -- -- EN Pull Low Resistor REN 280 400 520 k PWM Pull Low Resistor RPWM 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 EN Input Voltage PWM Input Voltage V V 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. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2016 Richtek Technology Corporation. All rights reserved. DS4531-01 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT4531 Typical Application Circuit L 4.7µH VIN 2.5V to 5.5V C1 1µF R1 10 C3 1µF / 50V C2 … … EN B1 PWM PWM Dimming C3 RT4531 C1 Enable SW VIN C2 1µF 2P10S WLEDs A3 IFB1 A2 IFB2 ISET A1 GND AGND R2 63.4k B2 B3 Timing Diagram Timing Diagram1 for 1-wire Continuous Coding PWM Tstart Tes_delay Tes_det >300µs >400µs Tes_win Tstart Addr8 Addr7 =H =L D1 = L EOS Addr8 =L 3~360µs 2x tL_HB Programming Code1 Programming Code2 Timing Diagram2 for Shutdown and then Reprogram PWM EN Detection Window Programming Code Copyright © 2016 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 > 2.5ms Shutdown Detection Window Programming Code is a registered trademark of Richtek Technology Corporation. DS4531-01 July 2016 RT4531 Typical Operating Characteristics Efficiency vs. Input Voltage 100 95 90 Efficiency(%) Efficiency (%) Efficiency vs. Output Current 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 85 80 ILED = 20mA ILED = 10mA 75 70 65 60 55 VIN = 3.6V, VOUT = 31V, 10s2p, 20mA/string VOUT = 31V, 10s2p 50 0 0 0 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 2.5 3 3.5 Output Current (A) Dimming Linearity 5 5.5 1.3 Switching Frequency (MHz)1 0.020 0.018 Output Current (mA) 4.5 Switching Frequency vs. Input Voltage 0.022 ILED1 ILED2 0.016 0.014 0.012 0.010 0.008 0.006 0.004 0.002 1.2 1.1 1.0 0.9 0.8 VIN = 3.6V 0.000 0.7 0 20 40 60 80 100 2.5 3 3.5 Dimming Duty Cycle (%) 4 4.5 5 5.5 Input Voltage (V) Switching Frequency vs. Temperature Sense Voltage vs. Output Current 1.13 0.315 1.08 0.314 Sense Voltage (V) Switching Frequency (MHz)1 4 Input Voltage(V) 1.03 0.98 0.93 0.313 0.312 0.311 0.88 0.310 -50 -25 0 25 50 75 100 Temperature (°C) Copyright © 2016 Richtek Technology Corporation. All rights reserved. DS4531-01 July 2016 125 0 2.5 5 7.5 10 12.5 15 17.5 20 Output Current (mA) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT4531 Application Information Register Program 1-Wire Interface (Device Address 0x2F) MSB LSB MSB LSB MSB LSB MSB Addr Addr Addr Addr Addr Addr Addr Addr Start D16 D15 D14 D13 D12 D11 D10 8 7 6 5 4 3 2 1 Address Data3 Data2 LSB D9 D8 D7 D6 D5 D4 D3 D2 D1 EOS Data1 Register Map Bit Label Reset Description D16 Ramp Up 0 D15 Ramp Up 0 D14 Ramp Up 1 D13 Ramp Down 0 D12 Ramp Down 0 D11 Ramp Down 1 D10 ILED 0 MSB = sDAC D9 ILED 0 sDAC D8 ILED 0 sDAC D7 ILED 0 sDAC D6 ILED 0 sDAC D5 ILED 0 sDAC D4 ILED 0 sDAC D3 ILED 0 sDAC D2 ILED 0 sDAC D1 ILED 0 LSB = sDAC [000] = 4s, [001] = 8s, [010] = 16s,[011] = 64s, [100] = 256s, [101] = 1.024ms, [110] = 2.048ms, [111] = 4.096ms [000] = 4s, [001] = 8s, [010] = 16s, [011] = 64s, [100] = 256s, [101] = 1.024ms, [110] = 2.048ms, [111] = 4.096ms   Copyright © 2016 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS4531-01 July 2016 RT4531 Protection Actions EN High Source Current to FBx Soft-Start/ Normal Operation N SW > OVP for > 8cycles in 10msec Y Latch Off FBx < 30mV For 600µs? N Soft-Start /Normal Operation Y Y X = 2? Latch Off N FBx Turned Off Soft-Start/Normal Operation Copyright © 2016 Richtek Technology Corporation. All rights reserved. DS4531-01 July 2016 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT4531 LED Current Setting The dual channels of the RT4531 can provide up to 20 mA current each. No matter either 1-wire Brightness Dimming or PWM Brightness Dimming is selected, the full-scale current (current when dimming duty cycle is 100%) of each channel should be programmed by an external resistor RISET at ISET pin according to Equation 1. IFB V  ISET  KISET RISET IFBX  IFB  DAC code 1024 (2) Where : IFB : the full-scale LED current set by the RISET at ISET pin. Code : the 10-bit DAC code D1~D10 programmed by 1wire interface. To enter 1-wire dimming mode, the following digital pattern on the EN pin must be recognized by the IC when the IC starts from the shutdown mode. (1) Where : VISET = 1V, 1. Pull the EN pin high to enable the RT4531 and start the detection window for digital dimming. KISET = 1268 2. After the digital dimming detection delay time (T - Brightness Control es_delay, >300μs), drive the EN low for more than the detection time (T-es_det, >400μs). a. 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.By the 1-wire Brightness Dimming, a master can program the 10-bit code D1(LSB) to D10(MSB) to any of 1024 steps with a single command. The programmed value will be stored in an internal register and set the dual-channel current according to Equation 2. The code will be reset to default value when the IC is shut down or disabled. VIN 2.5V to 5.5V 3. Pull the EN pin high after the detection time (>400μs) and before the detection window (Tes_win,