BP1361

BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver GENERAL DESCRIPTION APPLICATIONS The BP1361 is a continuous conduction mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the total LEDs chain voltage. With few outside components, BP1361 provides a high price performance ratio solution on the following applications: MR16 LEDs cup lighting, LEDs stage lighting, LEDs automotive lighting, LEDs solar lighting and LEDs Street lighting. The device operates from an input supply between 5V and 30V and the nominal average output current is set by an external resistor. The device provides an externally adjustable output current of up to 750mA for a single LED. Using the patent technology, the constant current of LED can be up to ± 3%. A dedicated DIM pin accepts either a DC voltage (0.5V~2.5V) dimming or a wide range of pulsed dimming. Applying a voltage of 0.3V or lower to the DIM pin turns the output off and switches the device into a low current standby state. z z z z z z Low voltage halogen replacement MR16/11 LEDs Automotive LED lighting LED stage lighting Solar LED lighting LED signal lighting LED Street lighting FEATURES z z z z z z z z z Simple low parts count Wide input voltage range: 5V to 30V Typical ±3% output current accuracy LED open-circuit protection LED short-circuit protection Up to 750mA output current Single pin on/off and brightness control using DC voltage or PWM High efficiency (up to 97%) Adjustable Constant LED Current BP1361 has a build-in power switch, based on different input voltage, BP1361 can drive several 1W or 3W LEDs. The device has the function of thermal shutdown protection and LED short/open-circuit protection. The BP1361 is available in SOT89-5 packages. TYPICAL APPLICATION CIRCUIT Figure 1. Typical Application Circuit Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 1 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver PIN ASSIGNMENT PIN DESCRIPTIONS PIN No. PIN NAMES 1 CS 2 GND Signal and power ground. Connect directly to ground plane. 3 DIM Enable switch, analog and PWM dimming input. 4 SW Switch Output. SW is the drain of the internal N-Channel MOSFET switch. 5 VIN Input Supply Pin. Must be locally bypassed. DESCRIPTION Current sense input, sampling resistant contacts between CS and VIN ORDERING INFORMATION PACKAGE SOT89-5 TEMPERATURE ORDERING PART TRANSPORT RANGE NUMBER MEDIA -40 ℃ to 85 ℃ BP1361E89E Tape and Reel Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com MARKING BP1361 Page 2 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver ABSOLUTE MAXIMUM RATINGS (Note1) SYMBOL ITEMS VALUE UNIT VIN Supply Voltage -0.3~40 V SW Drain Voltage of the internal power switch -0.3~40 V CS Current sense input (Respect to VIN) +0.3~(-6.0) V -0.3~6 V 1 A DIM ISW PDMAX Logic level dimming input Switch output current Power Dissipation (Note 2) 0.6 PTR Thermal Resistance, SOT89-5 TJ Operation Junction Temperature Range TSTG θJA Storage Temperature ESD Susceptibility (Note 3) 100 W o C /W -40 to 150 o -55 to 150 o 2 C C kV Note 1: Absolute Maximum Ratings indicate that operating beyond these ratings may damage the device. Recommended Operating Range indicates that the device is functional in that range, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Range. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 2: The maximum power dissipation must be decreasing with elevating temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA)/ θJA or the lower number given in Absolute Maximum Ratings. Note 3: Human body model, 100pF discharged through a 1.5kΩ resistor. RECOMMENDED OPERATING RANGE SYMBOL ITEMS VIN VDD Supply Voltage TOPT Operating Temperature Bright Power Semiconductor BP1361_DS_EN_V1.1 VALUE UNIT 0 ~ 30 V -40 to +85 www.bpsemi.com o C Page 3 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver ELECTRICAL CHARACTERISTICS (Note 4, 5) Unless specified otherwise, the following specifications apply for VIN=12V, TA=25 oC. SYMBOL VIN ITEMS CONDITIONS Input Voltage VUVLO VUVLO, HYS Min. Typ. 5 Max. UNIT 30 V Under voltage lock out VIN falling 4.7 V UVLO hysteresis VIN rising 100 mV Current Sense VCS Mean current sense threshold voltage VCS_HYS ICS VIN-VCS 97 Sense threshold hysteresis CS Pin Input Current VIN-VCS=50mV 100 103 mV ±15 % 8 µA Operating Frequency FSW Maximum operation frequency 1 MHz Turn Off Current IOFF Quiescent supply current with output off VDIM 115mV, the output of CS The voltage of DIM pin is divided by the internal and comparator switches low and the switch turns off. The external resistor. current flowing on the RS decreases at another rate. When (VIN-VCS) < 85mV, the switch turns on again and the mean current on the LEDs is determined by I OUT 0.085 + 0.115 = = 0.1 / Rs 2 × Rs DIM pin can be floated at normal working. When a voltage applied to DIM falls below the threshold (0.3V nom.), the output switch is turned off. The internal regulator and voltage reference remain powered during shutdown to provide the reference for the shutdown The high-side current-sensing scheme and on-board circuit. Quiescent supply current during shutdown is current-setting circuitry minimize the number of nominally 100uA. external components while delivering LEDs current with ±3% accuracy, using a 1% sense resistor. The BP1361 allows dimming with a PWM signal at the DIM input. A logic level below 0.3V at DIM forces BP1361 to turn off the LEDs and the logic level at DIM must be at least 2.5V to turn on the full LEDs current. The frequency of PWM dimming ranges from 100Hz to Bright Power Semiconductor BP1361_DS_EN_V1.1 Additionally, to ensure the reliability, the BP1361 is built with a thermal shutdown (TSD) protection and can link a NTC closing to LEDs by the pin DIM. As a result, the BP1361 can detect the temperature of LEDs and change the LEDs current to protect LEDs, (The detail is in the following application notes.) www.bpsemi.com Page 5 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver APPLICATION NOTES Setting nominal average output current with external resistor RS The nominal average output current in the LEDs is determined by the value of the external current sense resistor (RS) connected between VIN and CS and is given by: I OUT = 0.1 / Rs ( Rs ≥ 0.12Ω) This equation is valid when DIM pin is floating or applied with a voltage higher than 2.5V (must be less than 5V). Actually, RS sets the maximum average current which can be adjusted to a less one by dimming. Output current adjustment by external DC control voltage The DIM pin can be driven by an external dc voltage (VDIM), as shown, to adjust the output current to a value below the nominal average value defined by 0.1/RS. (2.5V ≤ V DIM ≤ 5V ) Output current adjustment by PWM control A Pulse Width Modulated (PWM) signal with duty cycle PWM can be applied to the DIM pin, as shown below, to adjust the output current to a value below the nominal average value set by resistor RS: I OUT = 0.1 × D Rs (0 ≤ D ≤ 100%,2.5V < V pulse < 5V ) If the high voltage is below 2.5V, I OUT = (V pulse − 0.5) × 0.1 × D 2 × Rs (0 ≤ D ≤ 100%,0.5V < V pulse < 2.5V ) PWM dimming provides reduced brightness by modulating the LEDs forward current between 0% to 100%. The LEDs brightness is controlled by adjusting the relative ratios of the on time to the off time. For example, a 25% pulse width can set LEDs average current to 25% of the nominal value defined by 0.1/Rs. To ensure this switching process between on and off state is invisible by human eyes, the switching frequency must be greater than 120 Hz. The advantage of PWM dimming is that the forward current is always constant; therefore the LEDs color does not vary with brightness as it does with analog dimming. Pulsing the current provides precise brightness control while preserving the color purity. The dimming frequency of BP1361 can be as high as 20 kHz. Shutdown mode Taking the DIM pin to a voltage below 0.3V will turn off the output and the supply current will fall to a low standby level of 100μA nominal. The average output current is given by: (0.5V ≤ V DIM ≤ 2.5V ) Soft-start An external capacitor from the DIM pin to ground will provide additional soft-start delay on DIM pin, so LED current will increase slowly and soft-start can be done. Normally, the relation of soft-start time and capacitance is approximately 150us/nF. Note that 100% brightness setting current equaling Inherent open-circuit and short-circuit LED to I OUT = 0.1 / Rs , which corresponds to VDIM: protection If the connection to the LEDs is open-circuited, I OUT = 0.1 × (V DIM − 0.5) 2 × Rs Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 6 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver BP1361 will operate in safely low power mode. If LEDs is short-circuited, BP1361 will operate in the safe mode with low frequency current limiting protection. Bypass Capacitor selection A low ESR capacitor should be used for input decoupling. The larger ESR value will lead to the lower efficient. This capacitor has to support the relatively high peak current to the coil and smooth the current ripple on the input supply. The minimum value of 2.2uF is acceptable in the case of DC input source. For the rectified AC input or low voltage input, the bypass capacitor should be 220uF and the tantalum capacitor is recommended. The input capacitor should be placed as close as possible to the input pin. For guarantee the stability over temperature and voltage, capacitors with X7R, X5R, or better dielectric are recommended. Inductor selection Recommended inductor value for the BP1361 is 47uH. The inductor saturation current must be 30% ~ 50% higher than the output current. Diode selection To maximize efficiency and performance, the Diode should be Schottky diode with a fast recovery, low forward voltage, low capacitance and low current leakage. The current and voltage ability depend on the application. Note that diode should have 30% design buffer for stable and reliable operation. It is very important to consider the reverse leakage of the diode when operating above 85°C. Excess leakage current will increase the power dissipation of system. The rectifier diode, rectifying AC12V, must use low forward voltage Schottky diode to reduce diode dissipation. Reducing output ripple Peak to peak ripple current in the LEDs can be reduced, if required, by shunting a capacitor across the LEDs: A value of 1uF will reduce the supply ripple current by a factor three approximately. Lower ripple can be achieved with higher capacitor values. Note that the capacitor will not affect operating frequency or efficiency, but it will increase start-up delay and change the frequency of dimming. Operation Notation at low input voltage The internal regulator disables the internal power Bright Power Semiconductor BP1361_DS_EN_V1.1 switch until the input voltage is above the startup threshold (VUVLO+100mV). Above the threshold, the device will start to operate. However, there is an especial case that if the input voltage is above the threshold and is too close to the output voltage, then the switch duty cycle will be high and the device power dissipation will enlarge. When device operates in this case for a long time, the device will trigger thermal shutdown (See detail in section of thermal shutdown TSD). In practical application, it’s necessary to keep the potential difference between input and output. The drive to the switch is turned off when the input voltage falls below the under-voltage threshold (VUVLO). Thermal considerations When the device operates at high ambient temperatures, or drives the maximum load current, care must be taken to avoid exceeding the power limitation. The larger copper area around the chip pin is good to radiate heat. In practical application, the device mounted on a 25mm2 PCB must have 1oz copper in current density. Note that the system efficiency will decrease, if utilizing unsuitable coils or excessive parasitic output capacitance on the switch output. Thermal compensation of output current High luminance LEDs often need to be supplied with a temperature compensated current in order to maintain stable and reliable operation at all drive levels. BP1361 can use an external temperature sensing network, normally using Negative Temperature Coefficient (NTC) thermal resistors and/or diodes, mounted very close to the LEDs detecting temperature of LEDs and changing LEDs current. The output of the sensing network can be used to drive the DIM pin in order to reduce output current with increasing temperature. Thermal shutdown protection To ensure the reliability, the BP1361 is built with a thermal shutdown (TSD) protection function. The TSD protects the IC from over temperature (150℃). When the chip temperature decreases below (130℃), the IC recovers again. PCB Layout considerations Careful PCB layout is critical to achieve low switching losses and stable operation. Use a multilayer board whenever possible for better noise immunity. In order to minimize current loop noise, the input bypass capacitor should have an isolate ground plane. www.bpsemi.com Page 7 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver SW pin The SW pin of the device is a fast switching node, so PCB tracks should be kept as short as possible. Moreover, the ground pin of the device should be soldered directly to the ground plane. Coil and decoupling capacitors and current sense resistor It is particularly important to mount the coil and the input decoupling capacitor as close to the device pins as possible to minimize parasitic resistance and inductance, if not system efficiency will be degraded. Depending on PCB design, more copper tracks between coil and GND/VCC are useful for lowering interface of coil skein. It is also important to minimize any track resistance in series with current sense resistor RS, to keep the accuracy of sampling current. Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 8 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver TYPICAL PERFORMANCE CHARACTERISTICS 1) Output Current vs Input Voltage of 1W LED 400 350 300 Iout (mA) 250 200 1*1W 3*1W 5*1W 150 100 50 0 8 10 12 14 16 18 20 22 24 26 28 30 Vin (V) 2）Output Current Deviation vs Input Voltage of 1W LED 5 4 1*1W 3*1W 5*1W Iout Deviation (%) 3 2 1 0 -1 -2 -3 -4 -5 8 10 12 14 16 18 20 22 24 26 28 30 Vin (V) Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 9 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver 3）System Efficiency vs Input Voltage of 1W LED 100 95 Eff (%) 90 85 80 1*1W 3*1W 5*1W 75 70 8 10 12 14 16 18 20 22 24 26 28 30 Vin (V) 4）Output Current vs Input Voltage of 3W LED 800 750 Iout (mA) 700 650 600 1*3W 3*3W 550 500 8 10 12 14 16 18 20 22 24 26 28 30 Vin (V) Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 10 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver 5）Output Current Deviation vs Input Voltage of 3W LED 5 4 3 Deviation (%) 2 1 0 -1 -2 1*3W 3*3W -3 -4 -5 8 10 12 14 16 18 20 22 24 26 28 30 24 26 28 30 Vin (V) 6）System Efficiency vs Input Voltage of 3W LED 100 95 Eff (%) 90 85 80 1*3W 3*3W 75 70 8 10 12 14 16 18 20 22 Vin (V) Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 11 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver 7) LED Current vs Vdim 400 350 Iout (mA) 300 250 200 150 100 1*1W 50 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Vdim (V) 8) Output Current vs Dim Duty （200Hz） Duty vs Iout 800 700 1W LED 3W LED 600 Iout (mA) 500 400 300 200 100 0 0 20 40 60 80 100 Duty (%) Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 12 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver 9) Vcs vs Temperature 102.0 101.8 101.6 Vcs (mV) 101.4 101.2 101.0 100.8 100.6 100.4 100.2 100.0 -20 0 20 40 60 80 100 Temp TYPICAL APPLICATION CIRCUIT of MR16 Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 13 BP1361 30V/750mA High Dimming Ratio Constant Current LED Driver PACKAGE INFORMATION SOT89-5 Package Bright Power Semiconductor BP1361_DS_EN_V1.1 www.bpsemi.com Page 14