RT8510GQW

® RT8510 43V 4-CH LED Driver General Description Features The RT8510 is a high efficiency driver for white LEDs. It is designed for LCD panels that employ an array of LEDs as the lighting source. An integrated switch current mode boost controller drives four strings in parallel and supports up to 12 pieces of LED per string. The internal current sinks support a maximum of ±2% current mismatching for excellent brightness uniformity in each string of LED. To provide enough headroom for current sink operation the boost controller monitors the minimum voltage of feedback pins and regulates an optimized output voltage for power efficiency.  Wide Input Voltage : 4.2V to 24V  High Output Voltage : Up to 43V Adjustable Channel Current : 10mA to 40mA Channel Current Accuracy : ±3% Channel Current Matching : ±2% PWM Dimming Frequency : 120Hz to 30kHz Adjustable Switching Frequency : 500kHz to 2MHz Built-In Soft-Start Disconnects LED in Shutdown Open Current Sink Detection Adjustable Over Voltage Protection Over Temperature Protection Current Limit Protection Thin 16-Lead WQFN Package RoHS Compliant and Halogen Free             Applications   UMPC and Notebook Computer Backlight GPS, Portable DVD Backlight Pin Configuration (TOP VIEW) CH4 CH3 CH2 CH1 The RT8510 has a wide input voltage range from 4.2V to 24V and provide an adjustable 10mA to 40mA LED current. The internal 200mΩ, 43V power switch with current-mode control provides cycle-by-cycle over current protection. The RT8510 also integrates PWM dimming function for accurate LED current control. The input PWM dimming frequency can operate from 120Hz to 30kHz without inducing any inrush current through the LED or inductor. The switching frequency of the RT8510 is adjustable from 500kHz to 2MHz, allowing the user flexibility between efficiency and component size.  The RT8510 is available in a WQFN-16L 3x3 package. 16 15 14 13 RT8510 Package Type QW : WQFN-16L 3x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Z : ECO (Ecological Element with Halogen Free and Pb free) 1 12 2 11 GND 3 10 17 4 9 5 6 7 OVP PGND PGND LX 8 PWM EN VIN LX Ordering Information AGND COMP ISET RT WQFN-16L 3x3 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 © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8510 Marking Information HU= : Product Code YMDNN : Date Code HU=YM DNN Typical Application Circuit VOUT 43V MAX L 10µH VIN 4.2V to 24V CIN 10µF Chip Enable R2 10 7 VIN D1 RT8510 ROVP2 2M LX 8, 9 C2 1µF COUT 10µF 12 6 EN OVP 5 PWM 2 COMP 4 RT 3 ISET CH1 13 14 CH2 CH3 15 R3 10k C4 1nF RRT 51k C3 10nF : : : : : : : : : : 10 LED String : : ROVP1 62k 100k PWM Dimming : : : : CH4 16 PGND AGND 1 10, 11 RISET 4.75k Figure 1. General Application Circuit L 10µH VBATT 2.7V to 24V D1 CIN 10µF 7 VIN 5V Chip Enable RT8510 C2 1µF LX 8, 9 PWM Dimming R3 10k C3 10nF RRT 51k RISET 4.75k ROVP2 2M 12 6 EN OVP 5 PWM 2 COMP 4 RT 3 ISET CH1 13 14 CH2 CH3 15 COUT 10µF : : : : : : : : : : : : : : 10 LED String : : ROVP1 62k 100k C4 1nF VOUT 23V MAX (VOUT depends on DMAX) CH4 16 PGND AGND 1 10, 11 Figure 2. Low Input Voltage Application Circuit Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8510-07 December 2021 RT8510 Functional Pin Description Pin No. Pin Name 1 AGND 2 COMP 3 ISET Pin Function Analog ground of LED driver. Compensation pin for error amplifier. Connect a compensation network to ground. LED current set pin. LED current is set by the value of the resistor RISET connected from the ISET pin to ground. Do not short the ISET pin. VISET is typically 0.6V. ILED = 95 RISET Frequency adjust pin. This pin allows setting the switching frequency with a resistor to 500kHz to 2MHz. Dimming control input. 4 RT 5 PWM 6 EN Chip enable (Active High). Note that this pin is high impedance. There should be a pull low 100k resistor connected to GND when the control signal is floating. 7 VIN Power supply input. 8, 9 10, 11 12 13, 14, 15, 16 LX Switching pin of boost converter. PGND Power ground of boost converter. OVP Sense input for over voltage protection. The detecting threshold is 1.2V. CH1 to CH 4 Current sink for LED. Leave the pin unconnected, if not used. 17 (Exposed Pad) GND The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Functional Block Diagram OVP LX EN VIN + 1.2 - RT OSC S Q R Q Regulator OCP OTP PWM Controller + PGND + EA - COMP 0.4V LED Detection PWM 4 CH1 CH2 CH3 CH4 + + - - + : : + 0.6V - - ISET AGND Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8510 Absolute Maximum Ratings          (Note 1) Supply Input Voltage to GND ------------------------------------------------------------------------------------------EN, PWM, ISET, COMP, RT to GND --------------------------------------------------------------------------------LX, OVP, CH1, CH2, CH3, CH4 to GND ----------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C WQFN-16L 3x3 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------------WQFN-16L 3x3, θJC -----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM -------------------------------------------------------------------------------------------------------------------------MM ---------------------------------------------------------------------------------------------------------------------------- Recommended Operating Conditions    −0.3V to 26.5V −0.3V to 26.5V −0.3V to 48V 1.471W 68°C/W 7.5°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 4.2V to 24V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 4.5V, TA = 25°C unless otherwise specified) Parameter Symbol VIN Quiescent Current IQ VIN Shutdown Current ISHDN VIN Under Voltage Lockout UVLO Test Conditions Min Typ Max VCOMP = 0V, no switching 0.7 1 1.5 VCOMP = 2V, switching 1.6 2 3 VIN = 4.5V, EN = 0V 0.01 -- 10 Rising 2.07 2.3 2.53 Falling 1.98 2.2 2.42 2 -- -- -- -- 0.8 Unit mA A V Control Input EN Threshold Voltage Logic-High VIH PWM Threshold Logic-High VIH Voltage Logic-Low VIL Logic-Low VIL VIN = 4.2V to 24V V 1.5 VIN = 4.2V to 24V 0.6 PWM Dimming Frequency f PWM 120 -- 30k Hz EN, PWM Leakage Current ILKG 2 -- 6 A EN Shutdown Delay tEN RRT = 51k 28 32 36 ms RRT = 25k 1.65 1.94 2.23 RRT = 51k 0.94 1.1 1.27 RRT = 102k 0.48 0.57 0.66 Boost Converter Switching Frequency fOSC Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 MHz is a registered trademark of Richtek Technology Corporation. DS8510-07 December 2021 RT8510 Parameter Symbol Test Conditions LX On Resistance (N-MOSFET) RDS(ON)_N VIN > 4.5V Minimum ON Time tMON Maximum Duty DMAX LX Current Limit ILIM VCOMP = 2V, switching Min Typ Max Unit 0.18 0.25 0.33  59 90 121 ns 85 90 95 % 1.5 2 2.7 A -2 -- 2 % 3 % LED Current Programming LED Current Matching ILEDM LED Current Accuracy ILEDA ISET Pin Voltage VISET LED Current ICHx 2V > CHx > 0.4V calculating (I(MAX)  I(AVG)) / I(AVG) x 100%, RISET = 4.75k 2V > CHx > 0.4V calculating (ICH  ISET) / ISET x 100%, RISET = 4.75k 2V > CHx > 0.4V, RISET = 4.75k -3 0.56 0.6 0.64 V 19.4 20 20.6 mA Fault Protection OVP Threshold VOVP 1.16 1.2 1.24 V OVP Fail Threshold VOVPF 33 55 77 mV 145 160 175 °C Thermal Shutdown Temperature TSD LED Pin Under Voltage Threshold VLSD No connection 18 60 100 mV Regulated VCHx VCHx Highest LED string voltage, RISET = 4.75k 0.3 0.4 0.5 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 under natural convection (still air) at TA = 25°C with the component mounted on a high effectivethermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design; not subject to production testing. Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8510 Typical Operating Characteristics LED Current vs. Input Voltage Efficiency vs. Input Voltage 26 100 90 24 LED Current (mA) Efficiency (%) 80 70 60 50 40 30 20 22 20 CH1 CH2 CH3 CH4 18 16 10 fOSC = 1MHz 10 x 4 LEDs, fOSC = 1MHz 14 0 4 8 12 16 20 4 24 9 14 LED Current vs. Temperature 24 VISET vs. Temperature 26 0.70 24 0.65 22 0.60 VISET (V) LED Current (mA) 19 Input Voltage (V) Input Voltage (V) 20 0.55 18 0.50 16 0.45 VIN = 12V, fOSC = 1MHz VIN = 12V, fOSC = 1MHz 0.40 14 -50 -25 0 25 50 75 100 -50 125 -25 0 Temperature (°C) 25 50 75 100 125 Temperature (°C) VISET vs. Input Voltage LED Current vs. PWM Duty Cycle 90 0.8 80 LED Current (mA) VISET (V) 0.7 0.6 0.5 70 60 50 PWM = 30kHz PWM = 10kHz PWM = 1kHz PWM = 120Hz 40 30 20 0.4 10 fOSC = 1MHz 0.3 10 x 4 LEDs, fOSC = 1MHz 0 4 8 12 16 20 Input Voltage (V) Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 24 0 10 20 30 40 50 60 70 80 90 100 Duty Cycle (%) is a registered trademark of Richtek Technology Corporation. DS8510-07 December 2021 RT8510 OVP Threshold vs. Input Voltage Switch Off Current vs. Temperature 1.5 Switch Off Current (mA) 1.5 OVP Threshold (V) 1.4 1.3 1.2 1.1 1.3 1.1 0.9 0.7 fOSC = 1MHz, VIN = 4.5V fOSC = 1MHz 0.5 1.0 4 8 12 16 20 -50 24 Input Voltage (V) VIN (2V/Div) IOUT (50mA/Div) IOUT (50mA/Div) Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 25 50 75 100 125 Line Transient Response VIN (5V/Div) Time (50ms/Div) 0 Temperature (°C) Line Transient Response VIN = 11V to 14V, fOSC = 1MHz -25 VIN = 4.5V to 5.5V, fOSC = 1MHz Time (50ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8510 Application Information The RT8510 is a general purpose 4-CH LED driver capable of delivering an adjustable 10 to 40mA LED current. The CLK IC is a current mode boost converter integrated with a 43V/2A power switch and can cover a wide VIN range from Output of PWM Comparator 4.2V to 24V. The switching frequency is adjustable by an PWM external resistor from 500kHz to 2MHz. The part Pulse integrates built-in soft start, with PWM dimming control; moreover, it provides over voltage, over temperature and current limiting protection features. Soft-Start The RT8510 equips a built-in soft-start feature to prevent high inrush current during start-up. The soft-start function prevents excessive input current and input voltage droop during power on state. Compensation The control loop can be compensates by adjusting the external components connected to the COMP pin. The COMP pin is the output of the internal error amplifier. The compensation capacitors, C3 and C4, will adjust the integrator zero and pole respectively to maintain stability. Moreover, the resistor, R3, will adjust the frequency integrator gain for fast transient response. T2 T1 Normal Operation T4 T3 Normal Operation Pulse Skipped Normal Operation Figure 3. Pulse Skip Mode Setting and Regulation of LED Current The LED current can be calculated by the following equation : ILED  95 RISET where RISET is the resistor between the ISET pin and GND. This setting is the reference for the LED current at channel 1-4 and represents the sensed LED current for each string. The DC/DC converter regulates the LED current according to RISET. Power Sequence LED Driver is without power sequence concern. Figure 4, Figure 5 and Figure 6 are different power sequences respectively. There is no concern in the above condition. Switching Frequency The LED driver switching frequency is able to adjusted as the following equation : 51k fOSC  (MHz) RRT LED Connection The RT8510 equips 4-CH LED divers with each channel supporting up to 12 LEDs. The LED strings are connected from the output of the boost converter to pins 13, 14, 15 and 16 respectively. If one of the LED channel is not used, the LED pin should be opened directly. VIN VOUT EN 1ms PWM Power On Mode 1 Figure 4 Light Load Mode When the input voltage is close to the output voltage, VOUT ripple will increase. The VOUT should be set at higher than 1.2 x VIN. If duty pulse is close to minimum on-time and smaller than 120ns, the duty pulse will be skipped. Figure 3 shows the timing diagram with skipped pulse. Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS8510-07 December 2021 RT8510 Over Voltage Protection VIN The RT8510 integrates over voltage protection (OVP) function. When the voltage at the OVP pin reaches the threshold voltage, the internal switch will be turned off. The internal switch will be turned on again once the voltage at OVP pin drops below its threshold voltage. VOUT EN PWM Power Off Mode 1-1 VIN The OVP threshold voltage is adjustable and can be clamped at a certain voltage level and it can be calculated by the following equation :  R  VOUT(OVP)  VOVP   1  OVP2  ROVP1   VOUT where VOVP = 1.2V (typ.). EN PWM Power Off Mode 1-2 Figure 5 ROVP1 and ROVP2 are the resistors in the voltage divider connected to the OVP pin. If at least one string is in normal operation, the controller will automatically ignore the open strings and continue to regulate the current for the strings in normal operation. It is suggested to use 2MΩ for ROVP2 to reduce loading effect. Current Limit Protection VIN UVLO VOUT EN 1ms PWM Power On Mode 2 The RT8510 can limit the peak current to achieve over current protection. The RT8510 senses the inductor current during the “ON” period that flows through the LX pin. The duty cycle depends on the current signal and internal slope compensation in comparison with the error signal. The internal switch will be turned off when the current signal is larger than the internal slope compensation. In the “OFF” period, the inductor current will be decreased until the internal switch is turned on by the oscillator. VIN UVLO VOUT EN PWM Power On Mode 2 Figure 6 Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 Brightness Control The RT8510 brightness dimming control is determined by the signal on the PWM pin with a suggested PWM frequency range from 120Hz to 30kHz. However, the LED current cannot be 100% proportional to duty cycle especially for high frequency and low duty ratio because of physical limitation caused by inductor rising time. Please refer to Table 1 and Figure 7. is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8510 Table 1. Dimming Frequency (Hz) 120 < f PWM  500 500 < f PWM  1k Duty (Min.) 0.2% 0.4% Duty (Max.) 100% 100% 0.8% 1.5% 3% 10% 100% 100% 100% 100% 1k < f PWM  2k 2k < f PWM  5k 5k < f PWM  10k 10k < fPWM  30k Note : The minimum duty in Table 1 is based on the application circuit and does not consider the deviation of current linearity. LED Current vs. PWM Duty Cycle 90 The boost converter operates in DCM over the entire input voltage range when the inductor value is below this value L. When inductance greater is than L, the converter operates in CCM at the minimum input voltage and may be discontinuous at higher voltages. The inductor must be selected with a saturated current rating that is greater than the peak current provided by the following equation : IPEAK  80 LED Current (mA) where VOUT is the maximum output voltage, VIN is the minimum input voltage, fOSC is the operating frequency and IOUT is the total current from all LED strings. 70 VOUT  IOUT VIN  D  T  2L   VIN where η is the efficiency of the power converter and T is the operating period. 60 50 PWM = 30kHz PWM = 10kHz PWM = 1kHz PWM = 120Hz 40 30 20 10 VIN = 12V, VPWM = 0V to 3V 0 0 10 20 30 40 50 60 70 80 90 100 Duty Cycle (%) Figure 7 Diode Selection Schottky diodes are recommended for most applications because of their fast recovery time and low forward voltage. The power dissipation, reverse voltage rating and pulsating peak current are the important parameters for Schottky diode selection. Make sure that the diode's peak current rating exceeds IPEAK and reverse voltage rating exceeds the maximum output voltage. Output Capacitor Selection Over Temperature Protection The RT8510 has over temperature protection function to prevent the IC from overheating due to excessive power dissipation. The OTP function will shutdown the IC when junction temperature exceeds 160°C . Inductor Selection The value of the inductance L can be approximated by the following equation, where the transition is from discontinuous conduction mode (DCM) to continuous conduction mode (CCM) : L D  (1  D)2  VOUT 2  fOSC  IOUT The duty cycle can be calculated according to the following equation : V  VIN D  OUT VOUT Copyright © 2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 The input capacitor reduces current spikes from the input supply and minimizes noise injection to the converter. For most applications, a 10μF ceramic capacitor is sufficient. A value higher or lower may be used depending on the noise level from the input supply and the input current to the converter. For lower output voltage ripple, a low ESR ceramic capacitor is recommended. The output voltage ripple consists of two components: one is the pulsating output ripple current flowing through the ESR, and the other is VRIPPLE  VRIPPLE_ESR  VRIPPLE_C V  VIN1  I  IPEAK  RESR  PEAK  AVDD  COUT1  VAVDD  f   is a registered trademark of Richtek Technology Corporation. DS8510-07 December 2021 RT8510 Thermal Considerations Layout Considerations The junction temperature should never exceed the absolute maximum junction temperature TJ(MAX), listed under Absolute Maximum Ratings, to avoid permanent damage to the device. The maximum allowable power dissipation depends on the thermal resistance of the IC package, the PCB layout, the rate of surrounding airflow, and the difference between the junction and ambient temperatures. The maximum power dissipation can be calculated using the following formula : PCB layout is very important for designing switching power converter circuits. The following layout guides should be strictly followed for best performance of the RT8510. The power components, L1, D1, CIN, COUT must be placed as close as possible to reduce current loop. The PCB trace between power components must be as short and wide as possible.  Place L1 and D1as close as possible to LX pin . The trace should be as short and wide as possible.  The compensation circuit should be kept away from the power loops and should be shielded with a ground trace to prevent any noise coupling. Place the compensation components as close as possible to COMP pin.  The exposed pad of the chip should be connected to ground plane for thermal consideration. For continuous operation, the maximum operating junction temperature indicated under Recommended Operating Conditions is 125°C. The junction-to-ambient thermal resistance, θJA, is highly package dependent. For a WQFN-16L 3x3, the thermal resistance, θJA, is 68°°C/W on a standard JEDEC 51-7 high effective-thermalconductivity four-layer test board. The maximum power dissipation at TA = 25°C can be calculated as below : PD(MAX) = (125°C − 25°C) / (68°C/W) = 1.471W for a WQFN-16L 3x3 package. The compensation circuit should be kept away from the power loops and should be shielded with a ground trace to prevent any noise coupling. 16 15 14 13 GND C3 R3 C4 AGND COMP ISET RT 1 12 2 Maximum Power Dissipation (W) 1.60 11 GND 3 10 17 4 6 7 9 OVP PGND PGND LX D1 VOUT 8 PWM EN VIN LX 5 The maximum power dissipation depends on the operating ambient temperature for the fixed TJ(MAX) and the thermal resistance, θJA. The derating curves in Figure 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Place the power components as close as possible. The traces should be wide and short especially for the highcurrent loop. L1 CIN R2 COUT C2 GND + where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction-to-ambient thermal resistance. CH4 CH3 CH2 CH1 PD(MAX) = (TJ(MAX) − TA) / θJA  VIN GND Figure 9. PCB Layout Guide Four-Layer PCB 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 25 50 75 100 125 Ambient Temperature (°C) Figure 8. Derating Curve of Maximum Power Dissipation Copyright © 2021 Richtek Technology Corporation. All rights reserved. DS8510-07 December 2021 is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT8510 Outline Dimension D SEE DETAIL A D2 L 1 E E2 e b A A1 1 1 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options A3 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 2.950 3.050 0.116 0.120 D2 1.300 1.750 0.051 0.069 E 2.950 3.050 0.116 0.120 E2 1.300 1.750 0.051 0.069 e L 0.500 0.350 0.020 0.450 0.014 0.018 W-Type 16L QFN 3x3 Package 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 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. www.richtek.com 12 DS8510-07 December 2021