YB1508

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YB1508P - YB1508P
YB1508 - YB1508

YB1508
Step-up DC-DC Converter White Driver Description
YB1508 step-up DC-DC converter, acting current source drive white LEDs series. Series connecting LEDs provides identical currents resulting uniform brightness eliminating need ballast resistors. light intensity these LEDs proportional current passing through them. Additional features include output over voltage protection prevent device damage faulty open circuit caused abnormal conditions, one-pin shutdown multiple methods dimming control. YB1508 switches fixed frequency 1MHz, allowing tiny external components input noise ripple. control brightness, current pulsed applying (pulse width modulated) signal with frequency range 100Hz 50KHz CTRL pin. YB1508 available profile 5-lead SOT-23 package.
2.7V input range Adjustable output voltage Built internal switch Inherently matched current Fixed frequency 1MHz operation Open protection profile 5-Lead SOT-23 package High efficiency: over 3.6V input voltage Drives white LEDs
Applications
Display Module OLED panel/sub-panel White Backlighting Digital Camera Cellular Phone Portable Application
Typical Application Circuit
Figure 1Typical Application Circuit YB1508 MRev1.4 WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver Description
Figure 2YB1508 SOT23-5
Designator
Table
Name CTRL
Description
Switching Pin. This collector internal power switch. Connect inductor diode. Minimize metal trace area connected this reduce EMI. Ground Pin. Connect directly local ground plane. Feedback Pin. Reference voltage 200mV. Connect LEDs resistor this pin. current determined resistance CTRL voltage. Shutdown Dimming Control pin. VCTRL 1.8V generates full-scale current VCTRL 0.4V chip Switching from 0.4V 2.0V, duty cycle controls current Input Supply Pin. Bypass this with capacitor close device possible.
Ordering Information
Table
Order Number High YB1508 YB1508P
Package Type SOT23-5 SOT23-5
Supplied 3000 units Tape Reel 3000 units Tape Reel
Package Marking Y58P
YB1508 MRev1.4
WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver Absolute Maximum Ratings
voltage other pins Maximum Junction Temp,Tj Lead Temperature (Soldering
sec)
Thermal Resistance
Electricity Characteristics
Table 3(TA=25°C, Vin=3.3V Cin=1uF Cout=4.7uF unless otherwise noted)
Function Parameter Input Voltage Range Feedback Voltage Bias current Supply current Switching Frequency Maximum Duty Cycle Minimum duty cycle Switch Vcesat Switch Current Limit Switch Leakage Current VCTRL Full current CTRL Bias Current Chip turn delay Over Voltage Protection YB1508 YB1508P Ctrl
Conditions Iout =20mA, Vout 12.5V Circuit figure (L=22uH Cout =4.7uF) ohms 0.3V CTRL
Units
200mA duty cycle Ctrl 0.3V
YB1508 MRev1.4
WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver Functional Block Diagram
Figure Block Diagram
Application Information
Operation operation YB1508 understood referring block diagram Figure voltage proportional switch current added ramp output resulting into positive terminal comparator. When this voltage exceeds level comparator negative input, peak current been reached, latch reset turns power switch. voltage negative input comparator comes from output error amplifier. error amplifier sets correct peak current level keep output regulation. error amplifier's output increases, more current delivered output; decreases, less current delivered.
small size high efficiency major concerns, inductor should have core losses 1MHz (copper wire resistance).
Capacitor Selection
small size ceramic capacitors makes them ideal YB1508 applications. types recommended because they retain their capacitance over wider voltage temperature ranges than other types.
Diode selection
maintain high efficiency, average current rating schottky diode should larger than peak inductor current, IPK. Schottky diode with forward drop fast switching speeds ideal increasing efficiency portable applications. reverse breakdown voltage schottky diode must larger than output voltage.
Inductor Selection
22uH inductor recommended most YB1508 applications. Although
YB1508 MRev1.4
WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver
Inrush Current maximum switch current limited about chip. Typically, this large current will occur about 40us during start larger Cout will increase duration high current. However, when first connected, even larger current flow into Cout. This occurs when open circuit Cout voltage changes from microseconds. Because duration this large current short, will usually cause problems. Current Dimming Control current reduced pulse width modulating CTRL voltage from 0.4V 1.8V. Using mode, current controlled from 100%. Open Circuit Protection YB1508 internal open-circuit protection circuit. When LEDs disconnected from circuit fail open, YB1508 will then shutdown until goes CTRL goes lower than 0.4V. Different maximum Vout requested from YoBon. Board Layout Consideration maximize efficiency, rise fall times switch should made short possible. Proper layout high frequency switching path important prevent electromagnetic interference (EMI) problems. Place COUT close VOUT pin. ground plane under switching regulator needed minimize interplane coupling. addition, feedback resistor should tied directly without other connection ensure clean, noise-free connection.
Figure Dimming Control Using Voltage
Figure Dimming Control Using Filtered Signal
YB1508 MRev1.4
WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver
Figure Li-Ion White LEDs Application Circuit
Figure Li-Ion Three White LEDs Application Circuit
Figure Four White LEDs Application Circuit
YB1508 MRev1.4
WWW.YOBON.COM.TW
YB1508
Step-up DC-DC Converter White Driver SOT-25 Package Information
contents this datasheet assuming responsibility circuitry described, circuit patent license implied Yobon reserves right time without notice change said circuitry specifications.
YB1508 MRev1.4
WWW.YOBON.COM.TW

YB1508

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