OB3362F 4 Channels High Performance LED Driver FEATURES 6V to 30V Input Voltage Range 3% Matching Accuracy Between 4 LED Strings Control Current 100KHz~600KHz Operating Frequency Internal/External PWM Dimming Very Low Standby Power Programmable Over Voltage Protection Under Voltage Lockout(UVLO) Open/Short LED Protection Thermal Shutdown T High Efficiency and Compact Size APPLICATIONS LCD Monitor LCD TV Flat panel display id e The OB3362F supports external PWM dimming and internal burst dimming mode which allow flexible control of the backlight luminance. The LED current is directly modulated by external PWM duty cycle when PWM dimming mode is selected. The LED current can be adjusted by an external DC voltage when internal burst dimming mode is selected. nt i The OB3362F integrates 4 channels current balancer with up to 200mA current capability per channel and it can achieve 3% matching accuracy among LED strings. The minimum voltage of current source is regulated to as lower as 350mV, which benefits the efficiency and improves the IC thermal performance. 10V gate drive, better MOS compatibility IV The OB3362F contains a PWM boost driver which uses current mode control and fixed frequency operation. The operation frequency can be programmed by setting external resistor value at RI pin. to The OB3362F is a highly integrated and high performance LED driver that optimized for LCD backlight application. It integrates a boost driver and 4 channels of current balancer that optimized to drives multi LED arrays, and thus provides a high performance LED backlight solution with minimized BOM count. al GENERAL DESCRIPTION Co nf OB3362F is offered in 16-pin ESOP/DIP On - Br i gh t TYPICAL APPLICATION Figure1: OB3362F Typical Application Schematic ©On-Bright Electronics Confidential -1- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver Absolute Maximum Ratings Value -0.3V to 40V Vin-7V to Vin -0.3V to 40V -0.3V to 7V -20℃ ~ 85℃ 150℃ -55℃ ~150℃ 260 ℃ Parameter Vin Voltage Operating Frequency Value 6V to 30V 100KHz to 600KHz Part Number OB3362FRP OB3362FHP OB3362FHPA Note: Stresses beyond those listed under “absolute maximum Description DIP16, Pb-free in Tube ESOP16, Pb-free in Tube ESOP16, Pb-free in T&R to ratings” may cause permanent damage to the device. These T Ordering Information IV Parameter Vin Input Voltage to GND FAULT to GND LEDX to GND I/O to GND Operating Ambient Temp. TA Operating Junction Temp. TJ Min/Max Storage Temp. Tstg Lead Temp. (10 Sec) Recommended Operating Range are stress ratings only, functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure al to absolute maximum-rated conditions for extended periods On - Br i gh t Marking Information Co nf id e nt i may affect device reliability. ©On-Bright Electronics Confidential -2- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver 16 15 14 13 12 11 10 9 CMP VCC VIN GATE CS OVP LED4 LED3 ESOP16 / DIP16 IV 1 2 3 4 5 6 7 8 to ENA DIM GND RI ISET BF/ DMOD LED1 LED2 T Pin Configuration for OB3362F GND RI ISET 6 BF/DMOD 7 8 9 10 11 12 13 14 15 16 LED1 LED2 LED3 LED4 OVP CS GATE VIN VCC CMP nt i 3 4 5 id e DIM Pin Function On/off control signal input pin DC voltage or PWM signal input pin for dimming control, the DC Input voltage dimming is negative polarity Power Ground I/O Set the switching frequency by external resistor I/O Set the output current of every channels by external resistor Dimming mode selection pin • Internal bust dimming mode: connect an external capacitor I/O to ground, and the bust frequency is set by the capacitance • External PWM dimming mode: short this pin to ground. I/O LED string current input I/O LED string current input I/O LED string current input I/O LED string current input Input Over voltage protection input Input Current sense input Output Gate drive output Power Power supply I/O Internal 10V LDO output I/O Loop compensation and soft start time setting nf 2 I/O Input Co Pin Name ENA On - Br i gh t Number 1 al Terminal Assignment for OB3362F ©On-Bright Electronics Confidential -3- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver Functional Block Diagram 10V LDO UVLO T ENA VCC Drive 5V IV VIN GATE to GND CLK OSC S + - EA + CMP 350mV Control Logic nt i PWM al RI + - id e nf DIM + - Current Control LED4 gh t Co DIM 1.2V ... Dimming Control OVP 1.2V LED1 Feedback Control BF/DMOD CS ISET On - Br i Figure2: OB3362F Functional Block Diagram ©On-Bright Electronics Confidential -4- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver Electrical Characteristics VIN 6 Istandby Operating supply current LDO output Voltage VIN UVLO OFF VIN UVLO ON ENA High Voltage ENA Low Voltage VCC UVLO(OFF) UVLO(ON) VENA_H VENA_L No switching, all LEDX floating VIN> 11V 9.5 LED Current Regulation ISET Voltage LEDX Current VISET ILED nf Current Matching 1 Co 10 5.4 5.2 1.5 0.96 uA mA 10.5 570 170 1.25 RSET=20k ohm 1.2 180 nt i CLoad = 2nF CLoad = 2nF 140 220 10 40 20 170 ILED = 90mA - VLEDX LEDX Regulation Voltage 1 V V V V V KHz 90 id e VOSC Dmax TON_MIN/TLEB Vlimited VH_GATE TRising TFalling al RSET=115K ohm RSET=374K ohm FOSC OSC Voltage Maximum Duty Cycle Minimum On Time/LEB Time CS Current Limit Voltage Gate High Level Gate Rising Time Gate Falling Time V 3 Boost Converter OSC frequency 30 ENA=0V IVCC Units IV Standby current Max to Operating Input Voltage Typ. T VIN=12V, ENA=5V, ISET=60kohm to ground, TA=25℃, if not otherwise noted. Parameter Symbol Condition Min 270 V % ns mV V nS nS V mA 3 % 350 mV Low Frequency Oscillator for Burst Mode Dimming Burst frequency gh t Triangular waveform CBF/DMOD=2.2nF high CBF/DMOD=2.2nF low CBF/DMOD=2.2nF 1.2 1.6 2 - 0.2 - V - 100 % 2.2 KHz V External LPWM Dimming Control Br i External LPWM duty 0 high BF/DMOD=0V 2.0 low BF/DMOD=0V V 0.8 V On - External LPWM Logic input level BF/DMOD=0V ©On-Bright Electronics Confidential -5- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver PROTECTION OVP Over Voltage Threshold VOVP_OV Rising Edge 1.2 V 75 mV 200 mV LEDX Over Voltage Threshold VLEDX_OV 5 5.5 6 V LED open protection threshold 200 mV Thermal Shutdown threshold TOTP 165 ℃ Thermal Shutdown Hysteresis 20 ℃ V VIN=12V, V -V 5.1 V VFAULT Clamp voltage to VIN FAULT IN FAULT VFAULT pull down current IFAULT 60 uA Note: 1 Matching is defined as the difference of the maximum to minimum current divided by two times of the average currents of all channels. System Startup Normal operation VOVP_UV I LED _ MAX − I LED _ MIN 2 ⋅ I LED _ avg × 100% On - Br i gh t Co nf id e nt i al Δ= to IV T OVP UVLO threshold (normal) ©On-Bright Electronics Confidential -6- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver load changes. The slope-compensation signal is added to the current-sense signal to improve the stability at high duty cycles. The OB3362F has a gate driver which can provide 10V high level voltage (when VCC=10V), this can greatly extend the select range of external power MOSFET as well as increase the overall system efficiency. At light loads, the OB3362F automatically skips some pulses to improve efficiency and also prevent overcharging the output capacitor. In the pulse-skipping mode, the inductor current ramps up for a minimum on-time (typical 140ns), then deliver the stored energy to the output. The switch remains off until another pulse is needed to boost the output voltage. IV to nt i al LED Current Sources Maintaining uniform LED brightness and dimming capability are critical for LCD backlighting applications. The OB3362F is equipped with 4 matched current sources. These specialized current sources are accurate to within 3%. All LED full-scale currents are identical by setting through the resistor at ISET pin (18mA < ILED < 200mA). I LED = 3000 × id e General Operation The OB3362F LED driver is designed for LCD backlight system applications. It incorporates a fixed frequency, current mode boost converter, a 10V regulator specially to power the gate driver, dimming control circuits and 4 channels current sources which regulate the current of LED array made up by 4 LED strings. When enabled, the converter boosts the output voltage to provide sufficient headroom for the current sources to regulate their respective string current. OB3362F features programmable operation frequency (100KHz to 600KHz) by setting the resistor on RI pin which allows the trade-off between the external components and the efficiency. Internal burst and external PWM dimming modes are provided to offer the flexible dimming control. OB3362F offers comprehensive protection features to protect the system in various fault conditions. The open/short LED string protection ensures that one or more LED strings fail do not cause overall LED array out of function. The cycle-by-cycle current limit function limits the maximum current flowing through the external power MOSFET. The over temperature protection ensures that the system will not run into condition of thermal runaway and blow up. The principle of operation can be understood by referring to the block diagram. T Function Description nf The minimum voltage drop across each current source is approximately 350mV. The low voltage drop helps to reduce the dissipation while maintaining sufficient compliance to control the LED current within the required tolerances. If any one channel out of the total 4 channels is not used, the relative LEDX pin should be connected to a voltage that higher than 5.5V to disable this channel, the LEDX voltage must lower than 40V to prevent IC be damaged. All LEDX pins in use are measured and the lowest voltage is extracted and fed into the step-up converter’s error amplifier to regulate the step-up converter’s output voltage. Br i gh t Co Internal 10V Regulator VCC and UVLO The OB3362F includes an internal switching mode regulator which is specially used to power the gate driver. When the VIN is great than 10V, the regulator generates a 10V supply. If VIN smaller than 10V, the output of regulator can follow VIN voltage until VIN drop below the UVLO voltage threshold. The OB3362F also has an internal 5V regulator to power the rest analog and logic circuitry. The OB3362F have Under Voltage Lockout (UVLO) function. The chip is disabled when the Vin is below the UVLO threshold (typically 5.2V) and the hysteresis of UVLO is nearly 200mV. On - Frequency Setting The internal oscillator frequency is set by the resistor on at RI pin as shown in the equation. High frequency operation optimizes the regulator for small component size at the expense of efficiency due to increased switching losses. While low frequency operation offers the better overall efficiency, but requires larger components and more PCB area. 67850 FOSC = RRI (kΩ) Fixed-Frequency Boost converter A fixed-frequency, current mode, boost converter is built in and it automatically chooses the lowest active LEDX voltage to regulate the output voltage. The resulting error signal is amplified and compared to the internal sensing current signal plus the slope compensation to determine the on-time of the switching MOSFET. The error amplifier sources or sinks the current to the COMP pin to adjust the required inductor current as the ©On-Bright Electronics 1.2V RSET Confidential -7- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver IV Figure3: Duty cycle of positive internal burst vs DIM voltage nt i al to LED String Open Protection The open LED string protection is achieved by OVP. When one or more strings are open, the respective LEDX pins are discharged to ground. Since the lowest LEDX is selected to be the input of the error amplifier of the boost converter, as a result, the output voltage will be charging until it exceeds OVP threshold. If the voltage level at the corresponding LEDX pin is less than 200mV while OVP happens, then the LED string open is recognized and the controller will mark off the open string. Once the mark-off operation completes, the remaining LED strings will force the output voltage back into tight regulation. The strings will keep the mark-off information until the system shuts down. The IC shuts down the boost converter if all strings in use are open. nf id e Dimming Control Two commonly used PWM dimming modes, internal burst mode dimming and external burst (PWM) dimming, are supported without any additional external components. Different dimming modes are selected by BF/DMOD pin. The LED brightness is determined by the control signal at DIM pin. External PWM burst dimming mode is selected by shorting BF/DMOD pin to ground. OB3362F accepts an external PWM signal to DIM pin with a swing voltage of 0V to a level greater than 2.2V. The LED brightness is controlled by the duty cycle of the external PWM signal. The burst frequency is equal to PWM frequency. Internal PWM burst mode dimming mode is obtained by connecting a capacitor from the BF/DMOD pin to ground. A low frequency triangular waveform generator is formed by the capacitor and internal circuit of the IC. Duty cycle so as to LED brightness is controlled by the analog signal at DIM pin. The burst mode dimming frequency Fburst is set by the following equation: 3.5uF ( Hz ) Fburst = C BF _ DMOD A DC voltage ranging from 0.2V to 2.2V at DIM pin corresponds to a LED brightness of approximately 0% to 100%, as shown in Figure 3. T Startup When ENA is active high, the OB3362F checks the topology connection first. The control signal at FAULT pin turns on the external PMOS slowly, the chip monitors the OVP pin to see if the Schottky diode (boost diode) is connected or the boost output is short to GND, if the voltage at OVP pin is lower than 75mV, the output will be disabled and the external PMOS is turned off. The OB3362F will also check other faults (UVLO, OCP and OTP), if there is no fault, then the boost converter will boost up the output with the internal soft start. Br i gh t Co LED String Short Protection The OB3362F will determine if the short strings happened by monitoring the voltage level at LEDX pin. If one or more strings are shorted, the respective LEDX pins will be pulled up to the boost output and suffer high voltage stress. If the voltage on the LEDX pin exceeds the preset threshold level (5.5V), then the string shorting condition is detected. Moreover, if this condition continues for greater than 8192 clock cycles, the respective string is marked off and its current regulation is disabled. Once the string is marked off, it is disconnected from the output voltage regulation loop of the boost converter. The marked-off strings will be shut down completely until the system restarts. Duty = (V DIM − 0.2) ×100% for 0.2V ≤ VDIM ≤ 2.2V 2 On - Table 2. Dimming mode selection Function Internal Burst External LPWM Pin Connection BF/DMOD DIM Polarity Capacitor 0.2V-2.2V Positive <0.1V PWM Positive ©On-Bright Electronics Confidential -8- Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver pulse current. It must be as small as possible； Use wide and short trace for connecting the boost switching components（inductor (L1), external MOSFET (Q1), output diode (D1),and output capacitor(C2) ）. 2) Connect a separate signal ground trace to AGND pin, a separate power ground trace to PGND pin, and then tie them together at input GND pin. 3) Place the Vcc filter capacitor (C3), R3 (RI resistor), C7 (CMP capacitor), C6 (BF/DMOD capacitor), and R4 (ISET resistor) as close to the IC as possible 4) The IC(ESOP16) exposed pad is internally connected to AGND pin ,OB3362F have a good thermal path to ambient to dissipate heat by connecting this pad to AGND trace T Thermal Shutdown The OB3362F includes a thermal protection circuit. When the junction temperature exceeds 165°C (typical), the controller and current sources shut down and do not restart until the junction temperature drops below 145°C (typical). Layout Consideration nt i al to IV Careful attention must be paid to the PCB board layout and components placement. Proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. Using the following guidelines for good PCB layout: 1) The loop of L1→D1→C2→GND and L1→Q1→GND is flowing with high frequency id e L1 Co C2 AGND On - Br i gh t PGND R R R C R444C C666 R333R D1 nf Q1 C C C C777 C333C ©On-Bright Electronics Confidential -9- Preliminary Datasheet OB_DOC_DS_3362F00 ©On-Bright Electronics Confidential - 10 - nf Co id e nt i VIN: 10-30V DIM: 0V, Max. Brightness; 5V, Min. Brightness (for internal burst mode dimming) ENA: Disable, 0-0.8V; Enable, 2-5V LOAD: ILED/channel = 180 mA/channel, 10 LEDs/channel, gh t Br i On - al to IV T 4 Channels High Performance LED Driver OB3362F Reference Application Circuit Figure4：OB3362F Reference Application Schematic Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver gh t Co nf id e nt i al to IV T Package Mechanical Data: Symbol On - Br i A A1 A2 B B1 C D E E1 e L E2 ©On-Bright Electronics Dimensions In Millimeters Min Max 3.710 5.334 0.381 2.921 4.953 0.380 0.570 1.524 (BSC) 0.200 0.360 18.800 20.230 6.096 7.112 7.320 8.255 2.540 (BSC) 2.920 3.810 7.620 10.922 Confidential - 11 - Dimensions In Inches Min Max 0.146 0.210(0.181) 0.015(0.020) 0.115 0.195(0.150) 0.015 0.022 0.060 (BSC) 0.008 0.014 0.740 0.800 0.240 0.280 0.288 0.312 0.100 (BSC) 0.115 0.150 0.300 0.430 Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver 16-Pin Plastic ESOP nt i al to IV T 5.1.10 Co nf id e WITH PLATING Dimensions In Millimeters gh t Symbol On - Br i A A1 A2 b c D E E1 e L θ ©On-Bright Electronics Min 1.35 0.02 1.35 0.38 0.20 9.86 5.80 3.80 Max 1.70 0.12 1.55 0.47 0.25 10.06 6.20 4.00 Dimensions In Inches Min 0.053 0.001 0.053 0.015 0.008 0.388 0.228 0.150 1.27(BSC) 0.45 0º Max 0.067 0.005 0.061 0.019 0.010 0.396 0.244 0.157 0.050(BSC) 0.80 8º Confidential - 12 - 0.018 0º 0.031 8º Preliminary Datasheet OB_DOC_DS_3362F00 OB3362F 4 Channels High Performance LED Driver Important Notice Right to make changes IV T On-Bright Electronics Corp. reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. Warranty information to On-Bright Electronics Corp. warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with its standard warranty. Testing and other quality control techniques are used to the extent it deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. al On-Bright Electronics Corp. assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using On-Bright’s components, data sheet and application notes. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. nt i Life support id e On-Bright Electronics Corp.’s products are not designed to be used as components in devices intended to support or sustain human life. On-bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in medical applications. Military On - Br i gh t Co nf On-Bright Electronics Corp.’s products are not designed for use in military applications. On-Bright Electronics Corp. will not be held liable for any damages or claims resulting from the use of its products in military applications. ©On-Bright Electronics Confidential - 13 - Preliminary Datasheet OB_DOC_DS_3362F00