RY3730

RY3730 1.2MHz, 30V Output, Step-Up WLED Driver Features • • • • • 2.5V to 5.5V Input Voltage Drivers up to 8 Series WLEDs Low 250mV Feedback Voltage 1.2MHz Fixed Switching Frequency Internal 1.6A Switch Current Limit • • • • • Internal Compensation Thermal Shutdown Over Voltage Protection Dimming with wide Frequency Range Available in a 6-pin SOT-23 package • PDA LED back light Applications • • Camera Flash White LED Digital still cameras General Description The Y3730 is a step-up converter designed for driving up to 8 Series white LED's from a single cell Lithium Ion battery. Its low 250mV feedback voltage reduces power loss and improves efficiency. Optimized operation frequency can meet the requirement of small LC filters value and low operation current with high efficiency. Internal soft start function can reduce the inrush current. Tiny package type provides the best solution for PCB space saving and total BOM cost. Typical Application Circuit L1 VIN VOUT D1 8·WLED VIN SW RY3730 Dimming CIN COUT OVP EN/PWM GND FB R1 Figure1. Basic Application Circuit Email: support@rychip.com ©RYCHIP Semiconductor Inc. 7 http://www.rychip.com Page 1 / RY3730 1.2MHz, 30V Output, Step-Up WLED Driver Package and Pin Description TOP VIEW LX 1 6 IN GND 2 5 OVP FB 3 4 EN SOT23-6 Top Marking: KDYLL (device code: KD, Y=year code, LL= lot number code) Pin Name Function 1 LX Power Switch Output. LX is the drain of the internal MOSFET switch. Connect the power inductor and output rectifier to LX. LX can swing between GND and 30V. 2 GND 3 FB Feedback Input. The FB voltage is 0.25V. Connect a resistor divider to FB. 4 EN Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns it off. When not used, connect EN to the input supply for automatic startup. 5 OVP Over Voltage Input. OV measures the output voltage for open circuit protection. Connect OV to the output at the top of the LED string. 6 IN Ground Pin Input Supply Pin. Must be locally bypassed. Order Information Marking Part No. Model Description Package MOQ KDYLL 70390004 RY3730 RY3730 WLED Driver, 2.5-5.5V, 8 Series WLED Driver, 1.2MHz, SOT23-6 SOT23-6 3000PCS Email: support@rychip.com ©RYCHIP Semiconductor Inc. 7 http://www.rychip.com Page 2 / RY3730 1.2MHz, 30V Output, Step-Up WLED Driver Absolute Maximum Ratings Parameter Absolute Maximum Ratings Unit VIN, VEN VSW All Other Pins -0.3 to 6 -0.3 to 30 -0.3 to 6 V V V Continuous Power Dissipation(TA=+25℃) 0.6 W Junction Temperature Operating Temperature Range Lead Temperature Storage Temperature Thermal ResistanceθJA Thermal ResistanceθJC 150 -40 to 85 260 -65 to 150 250 130 °C Parameter Recommended Unit Supply Voltage VIN Output Voltage VOUT Operating Junction Temp.(TJ) 2.5 to 5.5 VIN to 30 -40 to 125 V V °C °C °C °C /W °C /W Recommended Operating Conditions Electrical Characteristics Parameter Symbol Test Conditions Supply Current(Shutdown) Quiescent Current SW Leakage SW On Resistance Operating Input Voltage Current Limit Oscillator Frequency Maximum Duty Cycle Feedback Voltage FB Input Bias Current EN Threshold IIN VEN=0V VFB=0.2V,switch VSW = 20V OVP Threshold Vovp Thermal Shutdown Email: support@rychip.com ©RYCHIP Semiconductor Inc. 7 Min Typ Max Unit 0.1 0.15 1 0.3 1 650 5.5 µA mA µA mΩ V A MHz % mV nA V 400 2.5 ILIMIT fSW DMAX VFB VIN= 4V,Duty cycle=50% 237 -50 VEN OVP Threshold 1.6 1.2 90 250 -10 1 263 35 V 160 °C http://www.rychip.com Page 3 / RY3730 1.2MHz, 30V Output, Step-Up WLED Driver Typical Performance Characteristics Note (1): Performance waveforms are tested on the evaluation board. Note (2): VIN = 5V, 5 WLEDs, unless otherwise noted. Efficiency vs Input Voltage Steady State Operation Enable Startup VIN = 5V VIN = 5V, 5 WLEDs VIN = 5V, 5 WLEDs Enable Shutdown Start Up into Open Load VIN = 5V, 5 WLEDs VIN = 5V PWM Dimming VIN = 5V, 5 WLEDs, f=200HZ Output Current vs PWM Dimming Duty f=200HZ Email: support@rychip.com ©RYCHIP Semiconductor Inc. 7 http://www.rychip.com Page 4 / RY3730 1.2MHz, 30V Output, Step-Up WLED Driver Application information Setting the LED Current The LED current is controlled by the feedback resistor, R1, in Table 1. The current through the LEDs is given by the equation 250mV/R1. Table 1 shows the selection of resistors for a given LED current. ILED (mA) R1 (Ω) 1 250 5 50 10 25 15 16.7 20 12.5 Table 1—ILED vs. R1 R1=0.25 / ILED ILED is average LED current. Dimming Control a. Using a PWM Signal to EN Pin For controlling the LED brightness, the RY3730 can perform the dimming control by applying a PWM signal to EN pin. The internal soft start and the wide range dimming frequency can eliminate inrush current and audio noise when dimming. The average LED current is proportional to the PWM signal duty cycle. The magnitude of the PWM signal should be higher than the maximum enable voltage of EN pin, in order to let the dimming control perform correctly for preventing the flicker issue, the suqqested PWM frequency is ≥1kHz or ≤200Hz. b. Using a DC Voltage Using a variable DC voltage to adjust the brightness is a popular method in some applications. According to the Superposition Theorem, as the DC voltage increases, the voltage contributed to VFB increases and the voltage drop on R2 decreases, i.e. the LED current decreases. For example, if the VDC range is from 0V to 2.8V, the selection of resistors sets dimming control of LED current from 20mA to 0mA. c. Using a Filtered PWM signal Another common application is using a filtered PWM signal as an adjustable DC voltage for LED dimming control. A filtered PWM signal acts as the DC voltage to regulate the output current. In this circuit, the output ripple depends on the frequency of PWM signal. For smaller output voltage ripple (