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YB1508
Step-up DC-DC Converter , White LED Driver
Description
Features
The YB1508 is a step-up DC-DC converter,
acting as current source to drive up to 8
white LEDs in series. Series connecting of
the LEDs provides identical LED currents
resulting in uniform brightness and
eliminating the need for ballast resistors.
The light intensity of these LEDs is
proportional to the current passing through
them. Additional features include output over
voltage protection to prevent device damage
due to faulty LED or open circuit caused by
abnormal conditions, and one-pin shutdown
and multiple methods of dimming control.
The YB1508 switches at a fixed frequency of
1MHz, allowing the use of tiny external
components and low input noise and ripple.
To control LED brightness, the LED current
can be pulsed by applying a PWM (pulse
width modulated) signal with a frequency
range of 100Hz to 50KHz to the CTRL pin.
The YB1508 is available in a low profile 5-lead
SOT-23 package.
Typical Application Circuit
„ 2.7V to 9V input range
„ Adjustable output voltage up to 40V
„ Built in internal switch
„ Inherently matched LED current
„ Fixed frequency of 1MHz PWM
operation
„ Open LED protection
„ Low profile 5-Lead SOT-23 package
„ High efficiency: over 80% at 3.6V
input voltage
„ Drives up to 8 white LEDs
Applications
„ LCD Display Module
„ OLED panel/sub-panel
„ White LED Backlighting
„ Digital Camera
„ Cellular Phone
„ Portable Application
YB1508 MRev1.4
Figure 1Typical Application Circuit
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Pin Description
YB1508
Step-up DC-DC Converter , White LED Driver
Figure 2YB1508 SOT23-5
Pin Designator
Table 1 :
Pin Name
1 SW
2 GND
3 FB
4 CTRL
5 VIN
Description
Switching Pin. This is the collector of the internal NPN power switch. Connect to
inductor and diode. Minimize the metal trace area connected to this pin to reduce
EMI.
Ground Pin. Connect directly to local ground plane.
Feedback Pin. Reference voltage is 200mV. Connect LEDs and a resistor at this
pin. LED current is determined by the resistance and CTRL voltage.
Shutdown Pin and Dimming Control pin.
A. VCTRL > 1.8V generates full-scale LED current
B. VCTRL < 0.4V chip is off
C. Switching from 0.4V to 2.0V, PWM duty cycle controls the LED current
Input Supply Pin. Bypass this pin with a capacitor as close to the device as
possible.
Ordering Information
Table 2:
Order Number
High Ovp YB1508
Low Ovp YB1508P
Package Type
SOT23-5
SOT23-5
Supplied as
3000 units Tape & Reel
3000 units Tape & Reel
Package Marking
Y58
Y58P
YB1508 MRev1.4
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YB1508
Step-up DC-DC Converter , White LED Driver
Absolute Maximum Ratings
SW voltage
All other pins
40V
10V
Maximum Junction Temp,Tj
Lead Temperature (Soldering 10
sec)
Thermal Resistance
150 °C
300 °C
195 °C
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
FB Pin Bias current
Supply current
Switching Frequency
Maximum Duty Cycle
Minimum duty cycle
Switch Vcesat
Switch Current Limit
Switch Leakage Current
VCTRL for Full LED current
CTRL Pin Bias Current
Chip turn off delay
Over Voltage Protection
Conditions
Iout =20mA, Vout = 12.5V
Circuit of figure 1. (L=22uH
Cout =4.7uF)
Rfb = 10 ohms
Vfb = 0.3V
CTRL = 0V
At Isw = 200mA
40% duty cycle
Ctrl = 0.3V
Ctrl = 2V
YB1508
YB1508P
Min
2.7
180
2
0.7
20
1.6
Typ
200
10
3.5
1
0.8
25
200
250
1
1.7
20
36
21
Max
9
Units
V
220 mV
20 μA
mA
μA
1.3 MHz
93 %
35 %
mV
mA
μA
1.8 V
μA
30 μS
V
YB1508 MRev1.4
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