RT9052 Single Channel LED Current Source Controller General Description Features The RT9052 is a low cost, single channel LED current source controller with a specific FAULT detector. The part can drive an external NPN-BJT for various applications. The RT9052 is operated with Vcc power ranging from 3.8V to 13.5V. With such a topology, it's very flexible and cost effective. z z z z z z The RT9052 comes in a small SOT-23-6 package. 3.8V to 13.5V Operation Voltage Voltage Reference 0.8V with ±2% High Accuracy FAULT Indicator with Delay Dimming Control by PWM Small Footprint Package SOT-23-6 RoHS Compliant and Halogen Free Applications z Ordering Information z RT9052 z Package Type E : SOT-23-6 Lead Plating System G : Green (Halogen Free and Pb Free) LED Backlight applications Current Source Transistor Driver Pin Configurations (TOP VIEW) Note : VCC DRI FAULT Richtek products are : ` RoHS compliant and compatible with the current require- 6 5 4 2 3 ments of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. DIM GND ISET Marking Information SOT-23-6 EU= : Product Code EU=DNN DNN : Date Code Typical Application Circuit VLED WLED RT9052 5V R1 100k 6 VCC 12V CIN 1µF DRI 5 ISET 3 4 FAULT GND 2 RB RISET 1 DIM DS9052-01 April 2011 www.richtek.com 1 RT9052 Functional Pin Description Pin No. 1 2 3 4 5 6 Pin Name Pin Function DIM GND ISET PWM Dimming Control Input. Ground. Current Setting Input. FAULT DRI VCC FAULT Signal Open Drain Output. Driver Output. Power Supply Input. Function Block Diagram VCC Reference Voltage VREF FAULT 0.9 x VREF 3ms Delay + - DIM + Driver DRI ISET GND www.richtek.com 2 DS9052-01 April 2011 RT9052 Absolute Maximum Ratings (Note 1) Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------DIM Voltage ---------------------------------------------------------------------------------------------------------------FAULT Output Voltage --------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SOT-23-6 -------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SOT-23-6, θJA -------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ----------------------------------------------------------------------------------------------------- Recommended Operating Conditions 15V 7V 7V 0.4W 250°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------DIM Voltage ---------------------------------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------------Ambient Temperature Range ------------------------------------------------------------------------------------------- 3.8V to 13.5V 0V to 5.5V −40°C to 125°C −40°C to 85°C Electrical Characteristics (VCC = 5V/12V, TA = 25°C, unless otherwise specified) Parameter Symbol Min Typ Max Unit 3.15 3.4 3.65 V 0.1 0.2 0.3 V VCC = 12V -- 0.3 0.8 mA Driver Source Current VCC = 12V, VDRI = 6V 5 -- -- mA Driver Sink Current VCC = 12V, VDRI = 6V 5 -- -- mA VCC = 12V, VDRI = 5V 0.784 0.8 0.816 V ISET Line Regulation VCC = 4.5V to 13.5V -- 3 6 mV Amplifier Voltage Gain VCC = 12V, No Load -- 70 -- dB FAULT Rising Threshold VCC = 12V 85 90 95 %VREF FAULT Hysteresis VCC = 12V -- 15 -- %VREF Sink Capability VCC = 12V @ 1mA -- 0.2 0.4 V VCC = 12V 1 3 10 ms VCC = 12V -- 15 20 μs VCC = 12V -- 0.7 1 V VCC = 12V -- 30 -- mV VCC = 12V, VDIM = 0V -- -- 5 μA UVLO Threshold Test Conditions VCC Rising UVLO Hysteresis VCC Supply Current ISET Reference Voltage Delay Time I CC VREF t DELAY Falling Delay DIM DIM Rising Threshold DIMth DIM Hysteresis Standby Current DS9052-01 April 2011 I STANDBY www.richtek.com 3 RT9052 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. θJA is measured in natural convection at TA = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. 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 4 DS9052-01 April 2011 RT9052 Typical Operating Characteristics Standby Current vs. VCC Input Voltage 1.0 VDIM = 0V 0.9 VDIM = 3V 0.9 0.8 Supply Current (mA) Standby Current (μA)1 Supply Current vs. VCC Input Voltage 1.0 0.7 0.6 0.5 0.4 0.3 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.2 0.1 0.1 0.0 0.0 3.5 5.0 6.5 8.0 9.5 11.0 12.5 14.0 3.5 5.0 DIM Threshold Voltage (V) Supply Current (mA) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 11.0 12.5 14.0 0.9 Rising 0.8 Falling 0.7 0.6 0.5 0.4 0.0 -50 -25 0 25 50 75 100 3.5 125 5.0 6.5 8.0 9.5 11.0 12.5 14.0 VCC Input Voltage (V) Temperature (°C) DIM Threshold Voltage vs. Temperature 1.0 ISET Voltage vs. VCC Input Voltage 0.820 VCC = 12V VDIM = 3V 0.815 0.9 Rising ISET Voltage (V) DIM Threshold Voltage (V) 9.5 1.0 VDIM = 3V 0.9 8.0 DIM Threshold Voltage vs. VCC Input Voltage Supply Current vs. Temperature 1.0 6.5 VCC Input Voltage (V) VCC Input Voltage (V) 0.8 Falling 0.7 0.6 0.810 0.805 0.800 0.795 0.790 0.5 0.785 0.4 0.780 -50 -25 0 25 50 Temperature (°C) DS9052-01 April 2011 75 100 125 3.5 5.0 6.5 8.0 9.5 11.0 12.5 14.0 VCC Input Voltage (V) www.richtek.com 5 RT9052 ISET Voltage vs. Temperature DRI Source Current vs. DRI Voltage 0.820 55 0.815 53 DRI Source Current (mA) ISET Voltage (V) 0.810 0.805 0.800 0.795 0.790 0.785 0.780 0.775 0.770 0.765 -50 -25 0 25 50 75 100 49 47 45 43 41 39 37 VCC = 12V 0.760 51 VCC = 12V, VISET 0.6V, VDIM = 3V 35 125 0 1 2 Temperature (°C) 4 5 6 7 DRI Voltage (V) DRI Source Current vs. Temperature DRI Sink Current vs. DRI Voltage 25 70 60 DRI Sink Current (mA) DRI Source Current (mA) 3 50 40 30 20 20 15 10 5 10 VCC = 12V, VISET 0.6V, VDRI = 6V 0 -50 -25 0 25 50 75 100 VCC = 12V, VISET = 1V, VDIM = 3V 0 0 125 1 2 3 4 5 6 7 DRI Voltage (V) Temperature (°C) DIM PWM Dimming LED Current vs. PWM Duty 180 8LEDs 160 LED Current (mA) VDIM (5V/Div) VISET (500mV/Div) VLED (2V/Div) I LED (100mA/Div) 140 120 100 80 60 40 VCC = 12V, RISET = 5.1Ω, VLED = 3V VCC = 12V, RISET = 5.1Ω, VDIM = 0 to 5V/250Hz 20 0 Time (1ms/Div) 0 10 20 30 40 50 60 70 80 90 100 PWM Duty (%) www.richtek.com 6 DS9052-01 April 2011 RT9052 Application Information The RT9052 is a low cost single channel LED current source controller with a specific FAULT indicating scheme. This device can drive an external NPN-BJT for various applications. The RT9052 is operated with VCC power ranging from 3.8V to 13.5V. With such a topology, it is very flexible and cost effective. Capacitors Selection Careful selection of the external capacitors for the RT9052 is necessary to maintain high stability and performance. A capacitor ≥ 1μF must be connected between VCC and ground to improve supply voltage stability for proper operation. The RT9052 has a FAULT function with delay. The FAULT output is an open drain output. Connect a 100kΩ pull up resistor to external 5V source to obtain an output voltage. When the ISET voltage reaches 90% of normal value, FAULT will become active and be pulled high by external circuits with a typical 3ms delay. LED Current Setting The RT9052 includes a 0.8V reference voltage for easy setting of the LED current source. As shown in application circuit, the LED current is easily set via an RISET resistor. ILED Thermal Considerations 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 FAULT Function 0.8 (V) = RISET (Ω) selection, the following criteria Should be considered : DC current gain hFE , threshold voltage VBE, collectoremitter voltage V CE, maximum collector current IC package thermal resistance θ(JA). ( A) PWM Dimming Operation For controlling the LED brightness, the RT9052 can perform dimming control by applying a PWM signal to the DIM pin. The average LED current is proportional to the PWM signal duty cycle. Note that the magnitude of the PWM signal needs to be higher than the maximum dimming voltage of the DIM pin, in order to have correct dimming control. where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJAis the junction to ambient thermal resistance. For recommended operating condition specifications of the RT9052, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θ JA , is layout dependent. For SOT-23-6 packages, the thermal resistance, θ JA, is 250°C/W on a standard JEDEC 51-3 single-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : PD(MAX) = (125°C − 25°C) / (250°C/W) = 0.400W for SOT-23-6 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. For the RT9052 package, the derating curve in Figure 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. NPN Transistor Selection The RT9052 drives the NPN transistor via the DRI pin (source Base current IB ). When making an NPN transistor DS9052-01 April 2011 www.richtek.com 7 RT9052 Maximum Power Dissipation (W)1 0.45 Layout Consideration Single-Layer PCB 0.40 There are three critical layout considerations. 0.35 ` 0.30 0.25 The current setting resistor should be located as close as possible to the RT9052 to avoid inducing any noise. ` The input capacitor have to put at near the IC for improved 0.20 performance. 0.15 ` The pass element operating under high power situation 0.10 may raise the junction temperature above the package thermal resistance limit. (copper area can be added to improve power dissipation.) 0.05 0.00 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve for RT9052 Package Place CIN near the IC for improved performance VLED WLED DRI DIM RB ISET node copper area should be minimized and kept far away from noise sources CIN 6 VCC VCC GND 2 5 DRI ISET 3 4 FAULT RISET GND 5V R1 The GND plane should be connected to a strong ground plane for heat sinking and noise protection. Figure 2. PCB Layout Guide www.richtek.com 8 DS9052-01 April 2011 RT9052 Outline Dimension H D L C B b A A1 e Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.889 1.295 0.031 0.051 A1 0.000 0.152 0.000 0.006 B 1.397 1.803 0.055 0.071 b 0.250 0.560 0.010 0.022 C 2.591 2.997 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 SOT-23-6 Surface Mount Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. DS9052-01 April 2011 www.richtek.com 9