® RT8300 4-CH 150mA Constant Current LED Driver General Description Features The RT8300 is a 4-CH 150mA constant current sink LED driver capable of driving four channel constant currents with good matching ability and wide range VF variations. z 4 Constant Current Output Channels z Wide Power Supply Voltage Range : 5V to 24V Maximum Constant Current Output Voltage : 60V Low Dropout Voltage : 600mV at 120mA Output Current Constant Output Current Accuracy Between Channels : <±3% Dynamic Headroom Control (DHC) Function Constant Output Current Range : 5mA to 150mA Support 400ns Narrow PWM Pulse Fault Detection for OTP, LED Open/Short RoHS Compliant and Halogen Free The RT8300 provides four channel constant currents with less than 3% differences in output current value among the 4-CH and ICs respectively. The constant current output is adjustable from 5mA to 150mA via an external resistor (RISET). The LED brightness can also be adjusted via the PWMI pin with pulse width modulation from 0% to 100%. Thus allowing for wide VF variation. Moreover, the RT8300 provides Dynamic Headroom Control (DHC) function which can generate feedback signal to DC/DC control loop and regulate the output voltage of the RT8300. The RT8300 features LED open/short protection. If any channel has open or short condition, that particular output channel will be turned off and the FAULT pin will pull low. The RT8300 also supports Over Temperature Protection (OTP). When OTP is triggered, all output channels will be turned off and the FAULT pin will pull low. The RT8300 is available in DIP-16 (BW) and SOP-16 packages to achieve optimized solution for PCB space. Ordering Information z z z z z z z z Applications z LED Backlight Marking Information RT8300GN RichTek RT8300 GNYMDNN RT8300GN : Product Number YMDNN : Date Code RT8300GS RT8300 RT8300GS : Product Number Package Type N : DIP-16 (BW) S : SOP-16 RT8300 GSYMDNN YMDNN : Date Code Lead Plating System G : Green (Halogen Free and Pb Free) Note : 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. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8300-00 January 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8300 Pin Configurations (TOP VIEW) FB VIN PWMI 14 13 2 12 3 GND LED1 LED2 GND 4 ISET 5 10 LED4 FAULT 6 9 LED3 SLP 7 8 NC 11 GND GND PWMI VIN FB ISET FAULT SLP GND 16 2 15 3 14 4 13 5 12 6 11 7 10 8 9 GND NC LED1 LED2 LED3 LED4 NC GND SOP-16 DIP-16 (BW) Typical Application Circuit Max 150mA Max 150mA Max 150mA VIN Max 150mA VLED 60V (Max) VLED VIN VH RPH VIN CIN1 LED1 LED4 RT8300 FAULT LED Driver [1] PWMI ISET GND PWMI RISET1 FB (DHC) CIN2 RSLP1 FB LED1 LED4 SLP RT8300 FAULT LED Driver [N] PWMI ISET GND RSLP2 FB RISET2 CFB 1nF Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 SLP VIN is a registered trademark of Richtek Technology Corporation. DS8300-00 January 2012 RT8300 Functional Pin Description Pin No. Pin Name Pin Function DIP-16 (BW) SOP-16 3 3 PWMI 2 4 VIN Constant Current Output Channel Enable/Disable Input. High : Enable, Low : Disable Power Supply Input. 1 5 FB Feedback Control Voltage Output. 5 6 ISET Constant Current Set Pin. Connect to an external resistor to adjust constant current output. 6 7 FAULT Open Drain Output for Fault Detection. 7 8 SLP 4, 11, 14 1, 2, 9, 16 GND LED Short Protection Voltage Set Pin. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 10, 9, 12, 13 11 to 14 8 10, 15 LED4 to LED1 NC Constant Current Sink Output. No Internal Connection. Function Block Diagram LED1 LED2 LED3 LED4 VIN ISET PWMI DHC Function IOUT Regulator Open/Short Detection Constant Current Control Circuit with PWM Control FB FAULT Thermal Protection GND SLP Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8300-00 January 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8300 Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------Output Voltage LED1 to LED4 -----------------------------------------------------------------------------------------FB, PWMI, FAULT, ISET to GND --------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C DIP-16 (BW) ----------------------------------------------------------------------------------------------------------------SOP-16 ----------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) DIP-16 (BW), θJA ----------------------------------------------------------------------------------------------------------SOP-16, θJA ----------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------Junction Temperature -----------------------------------------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------------------- Recommended Operating Conditions z z z −0.3V to 32V −0.3V to 70V −0.3V to 28V 2.5W 1.176W 40°C/W 85°C/W 260°C 150°C −65°C to 150°C (Note 3) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------- 5V to 24V Junction Temperature Range --------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range --------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 24V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max VIN Rising -- 3.6 -- VIN Falling -- 3.1 -- -- -- 60 V 116.4 120 123.6 mA -- ±0.5 ±3 % -- ±0.1 ±0.5 %/V μA Under Voltage Lockout Threshold VUVLO Output Voltage VLEDx LED1 to LED4, all CHs off LED Current Accuracy ILEDX2 VLEDX = 0.6V, RISET = 900Ω LED Current Matching dI LEDX2 Output Current vs. Output Voltage Regulation %/dVLEDX Output Current of SLP ISLP VSLP = 0.43V to 2V -- 16 -- VSLPH VLEDX = 14V -- 2 -- VSLPL VLEDX = 3.03V -- 0.43 -- VOLP VLEDx -- 50 -- Logic-High VPWMIH TA = −40°C to 85°C 2 -- -- Logic-Low VPWMIL TA = −40°C to 85°C -- -- 0.8 VFBH IFBH = 50μA -- 3.3 -- VFBL IFBL = 1mA -- 0.2 -- SLP Pin Voltage Open LED Protection (OLP) Voltage PWMI Input Voltage Feedback Voltage ILEDX = 120mA, VLEDX = 0.6V, RISET = 900Ω VLEDX within 0.5V and 3V, RISET = 900Ω Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 Unit V V mV V is a registered trademark of Richtek Technology Corporation. DS8300-00 January 2012 RT8300 Parameter Symbol Test Conditions Min Typ Max Unit I FBH VFB = 3.3V -- 50 -- μA I FBL -- 1 -- mA I OH VFB = 0.2V VLEDx = 50V, all CHs off, PWMI = Low -- --- 0.5 μA TOTP Junction Temperature -- 140 -- °C ΔTOTP Junction Temperature -- 50 -- °C Supply Current I DD(ON) RISET = 3.6kΩ, PWMI = High -- 3 5 mA Shutdown Current I SHDN Shutdown -- 6 20 μA FB Pin Output Current Output Leakage Current Thermal Protection Temperature Thermal Protection Temperature Hysteresis Low to High PWMI to LEDx Transition Propagation High to Low Delay Time Transition Shutdown Delay Time t PLH 0.1 t PHL 0.05 0.1 0.4 t SHDN -- 32 -- ms Power On Reset Time t RESET -- 256 -- μs Soft-Start Time t SS -- 128 -- ms Fault Blanking Time t FB -- 32 -- ms PWMI High Blanking Time t RB -- 4 -- μs Fault Detection Time tF -- 2 -- μs PWM = 100% 0.3 0.6 μs 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. The device is not guaranteed to function outside its operating conditions. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8300-00 January 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8300 Typical Operating Characteristics Supply Current vs. Input Voltage Shutdown Current vs. Input Voltage 4.0 7 Shut down Current (μA)1 Supply Current (mA) 3.5 3.0 2.5 2.0 1.5 6 5 4 3 PWMI = High, RISET = 3.6kΩ 1.0 2 5 9 13 17 21 25 5 9 Input Voltage (V) LED Current vs. Input Voltage 17 21 25 Low Dropout Voltage vs. LED Current 1.0 Low Dropout Voltage (V) 130 124 LED Current (mA) 13 Input Voltage (V) LED1 LED2 LED3 LED4 118 112 106 0.8 0.6 0.4 0.2 VLEDx = 0.6V, RISET = 900Ω 0.0 100 5 VIN (20V/Div) PWMI (5V/Div) FB (5V/Div) 9 13 17 21 70 90 110 130 Input Voltage (V) LED Current (mA) Power On Sequence Power Off Sequence 150 VIN (20V/Div) PWMI (5V/Div) FB (5V/Div) tSS = 128ms I LED (1A/Div) I LED (1A/Div) VIN = 24V, PWM = 100% Time (50ms/Div) Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 50 25 VIN = 24V, PWM = 100% Time (50ms/Div) is a registered trademark of Richtek Technology Corporation. DS8300-00 January 2012 RT8300 Application Information The RT8300 is a 4-CH LED current source controller with an internal N-MOSFET driver. The RT8300 regulates the lowest voltage of the LED strings and generates a feedback control signal to a primary controller to regulate the LED current. Each LED channel current is accurately matched and controlled by sensing an internal resistor in series with the MOSFET. All channels' LED brightness can be precisely controlled by applying a PWM signal to the PWMI pin. The RT8300 also features several protections including Short LED Protection (SLP), Open LED Protection (OLP), and Over Temperature Protection (OTP). Dynamic Headroom Control Function LED Current Setting R3 (MIN) = Each channel's LED current can be calculated by following equation : ILED ≅ 108 RISET Where RISET is the resistor between the ISET pin and GND. This setting is the reference for the LED current at the LED pin and represents the sensed LED current for each string. The RT8300 brightness dimming control is decided by the signal on the PWMI pin. Refer to the following figure. The minimum dimming duty can be as low as 1% for the 200Hz frequency. LED Current vs. PWM Duty LED Current (mA) 100 80 60 40 20 PWM = 200Hz 0 20 V - 0.2 VOUT (MAX) = VOUT (Default) +R1( REF ) R3 V - 3.3 VOUT (MIN) = VOUT (Default) +R1( REF ) R3 VFB - VREF IFB(typ.) Where VOUT is converter output voltage, VREF is converter reference voltage and typical IFB is 50μA. The connection is shown as the following figure. VOUT R1 R3 30 40 50 60 70 80 VFB 0.2V to 3.3V R2 Figure 2 Power On and Power Off Sequence 120 10 VOUT (Default) = VREF (1+ R1 ) R2 Converter VREF Brightness Control 0 The Dynamic Headroom Control (DHC) function is used to generate feedback signal to primary DC/DC control loop and regulate the LED current of the RT8300. This function can improve IC's thermal performance and efficiency. The R1, R2 and R3 selection is shown in below equation : 90 PWM Duty (%) 100 When power converter output voltage and VIN are both ready. PWMI pulled high will enable the RT8300, and IC will check channel unused or not in first period (256μs).The unused channel is needed to short to GND or FAULT will be turned on. The second period is 128ms soft start time, the RT8300 feedback voltage is 3.3V in this period. Then, IC gets into the fault blanking time (32ms) when PWM duty is 100% since fault blanking counter depends on the PWM on period. After the third period, fault function will turn on. About power off sequence, IC will shut down after 32ms when PWMI pin is pulled low. The power on and power off sequence are shown as the following figure. Figure 1 Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8300-00 January 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8300 channels are re-enabled when the junction temperature cools down by approximately 50°C. Power On VIN PWMI SS start VFB = 3.3V FAULT Blanking ~32ms ~128ms IC reset (checking unused Chs) ~256µs Status ILED Open LED Protection Normal If the VLEDx is < 50mV after a fault blanking period, the counter will be triggered when PWM is high. Moreover, there is a 4μs blanking time on every rising part of PWM. When the counter accumulates to 2μs, only this open channel will be off but not latched. The FAULT will be turned on and pulled low. The time of startup depends on VOUT Power Off VIN PWMI Status Shutdown Delay ~32ms Shutdown Short LED Protection ILED Figure 3 Over Temperature The RT8300 has an Over Temperature Protection function to prevent excessive power dissipation from overheating the device. The OTP will disable all channels if the junction temperature exceeds 140°C and sends a fault signal. The If the voltage of VLEDx is >112 x 10-6 x RSLP (7 x VSLP) after fault blanking period, the counter will be triggered when PWM is high. Moreover, there is a 4μs blanking time on every rising part of PWM. When the counter accumulates to 2μs, this short channel will be off and latched. The FAULT pin will be pulled low. The fault state can only be released by PWM off after 32ms. The operation and protection flow is shown as the following figure. VIN and PWMI Power On Start (RESET) Disable this Channel Un-used Status of Channel is VLEDX Floating? (Un-used channel need short to GND) Soft-Start Function and ILED Turn-On (128ms) Over Temperature Protection ? Tj >140°C Follow the Normal Flow PWMI = low after 32ms or VIN < UVLO SLP: Fault pulled low, only this channel off and latch OLP: Fault pulled low, only this channel off and non-latch VFB = 3.3V OLP = SLP = L Fault Blacking Time VFB = 0.2V to 3.3V (32ms) OLP = SLP = L Tj <90°C Auto-recovery Turn-Off All Channel FLT Pulled Low Normal Operation TF < 2µs TF > 2µs Open / Short Detection Time LED Short / Open Protection ? Figure 4 Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS8300-00 January 2012 RT8300 For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications of the RT8300, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θJA, is layout dependent. For DIP-16 Maximum Power Dissipation (W)1 Thermal Considerations 2.6 2.4 Four-Layer PCB DIP-16 (BW) 2.2 2.0 1.8 1.6 1.4 1.2 1.0 SOP-16 0.8 0.6 0.4 0.2 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curves for the RT8300 Packages (BW) package, the thermal resistance, θJA, is 40°C/W on a standard JEDEC 51-7 four-layer thermal test board. For SOP-16 packages, the thermal resistance, θJA, is 85°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 : P D(MAX) = (125°C − 25°C) / (40°C/W) = 2.5W for DIP-16 (BW) package PD(MAX) = (125°C − 25°C) / (85°C/W) = 1.176W for SOP-16 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. For the RT8300 packages, the derating curves in Figure 5 allow the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2012 Richtek Technology Corporation. All rights reserved. DS8300-00 January 2012 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8300 Outline Dimension Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 3.700 4.320 0.146 0.170 A1 0.381 0.710 0.015 0.028 A2 3.200 3.600 0.126 0.142 b 0.360 0.560 0.014 0.022 b1 1.143 1.778 0.045 0.070 b2 2.920 3.100 0.115 0.122 c 0.204 0.360 0.008 0.014 D 18.80 19.30 0.740 0.760 E 6.200 6.600 0.244 0.260 E1 7.320 7.920 0.288 0.312 E2 8.350 9.250 0.329 0.364 L 0.100 2.540 e 3.000 3.600 0.118 0.142 16-Lead DIP (BW) Plastic Package Copyright © 2012 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS8300-00 January 2012 RT8300 H A M B J F C I D Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 9.804 10.008 0.386 0.394 B 3.810 3.988 0.150 0.157 C 1.346 1.753 0.053 0.069 D 0.330 0.508 0.013 0.020 F 1.194 1.346 0.047 0.053 H 0.178 0.254 0.007 0.010 I 0.102 0.254 0.004 0.010 J 5.791 6.198 0.228 0.244 M 0.406 1.270 0.016 0.050 16–Lead SOP Plastic 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. DS8300-00 January 2012 www.richtek.com 11