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YB1522
Step-up DC-DC Converter White LED Driver
Description
The YB1522 is a step-up DC-DC converter;
with wide input voltage range from 3V to
16V, which operates as current source to
drive up to 3S7P to 3S10P (VIN at 3V to
5V). 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. The YB1522
switches at a fixed frequency of ~930KHz,
allowing the use of tiny, low profile
inductors and capacitors to minimize
footprint and cost in space consideration
applications.
The YB1522 can drive up to 3S10P white
LEDs from a single Li-Ion battery. At
automotive (5V/12V) applications with
higher conversion efficiency. 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 1KHz to the CTRL pin.
YB1522 has integrated Latched Over
Voltage Protection that prevents damage to
the device in case of a high impedance
output due to faulty LED or open circuit
caused by abnormal conditions.
Features
„ Built-in Internal Switch
„ 3V to 16V Input Range
„ <1uA Shutdown Current
„ High Efficiency
„ Internal Soft Start
„ Drives up to 3S7P to 3S10P White
LEDs(VIN at 3.5V to 5V)
„ Over Voltage Protection 30V
„ Small 5-Lead SOT-23 Package
„ Analog and PWM Dimming Control
„ 100mV Low Reference Voltage
Applications
„ 5” ~ 7” LCD Display Module
„ White LED Backlighting
„ Car TV
„ Handheld and PDA
„ Electronic Books
„ Digital Photo Frame
Typical Application Circuit
YB1522 Rev.1.0
Figure 1: Typical Application Circuit
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YB1522
Step-up DC-DC Converter White LED Driver
Pin Configuration
SW 1
5 VIN
GND 2
FB 3
4 CTRL
SOT23-5
Figure 2: Pin Configuration
Pin Description
Table 1
Pin NAME
Description
Switching Pin. This is the collector of the internal NPN power switch.
1 SW Connect to inductor and diode. Minimize the metal trace area
connected to this pin to reduce EMI.
2 GND Ground Pin. Connect directly to local ground plane.
Feedback Pin. Reference voltage is 100mV. Connect LEDs and a
3 FB resistor at this pin. LED current is determined by the resistance and
CTRL voltage.
Shutdown Pin and Dimming Control Pin.
4
CTRL
VCTRL > 1.8V generates full-scale LED current.
VCTRL < 0.4V chip is off.
Switching from 0.4V to 2.0V, PWM duty cycle controls the LED current.
5
VIN
Input Supply Pin. Bypass this pin with a capacitor as close to the
device as possible.
Ordering Information
Order Number Package Type
YB1522ST25
SOT23-5
Supplied As
3000 units Tape & Reel
Package Marking
Please contact sales
representative
YB1522 Rev.1.0
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YB1522
Step-up DC-DC Converter White LED Driver
Absolute Maximum Ratings
Recommended Operating Conditions
VIN .......................................................... 20V
SW Voltage .............................................32V
FB Voltage ................................................5V
CTRL Voltage............................................5V
Maximum Junction Temp, TJ ............... 150°C
Lead Temperature (Soldering 10 sec).......300°C
Operating Temperature......... -40°C to 85°C
Supply Voltage............................... 3V~16V
SW Voltage...........................................20V
Electrical Characteristics
Table 2 (VIN = 3.3V, CIN = 1uF, COUT = 10μF, TA=25°C, unless otherwise noted.)
Description
Symbol
Test Conditions
MIN TYP
MAX Units
Input Voltage Range
VIN
3 16 V
Not Switching
IQ VFB = 0.3V
1.2 1.5 1.7 mA
Shutdown
CTRL = 0V
0.3 1 uA
Feedback Voltage
VFB
IOUT = 20mA,VOUT = 12.5V
Circuit of Figure 1
90
100 110
mV
Switch Current Limit
85% duty cycle
ICL
40% duty cycle
620 650
450
mA
mA
FB Pin Bias Current
Switching Frequency
IB VFB = 100mV
FSW
1 uA
900 930 960 KHz
Maximum Duty Cycle
DMAX
85 %
Minimum Duty Cycle
DMIN
20 25 %
Switch Vcesat
Switch Leakage Current
VSAT
ILKG
At ISW = 200mA
CTRL = 0.3V
180 mV
1 μA
VCTRL for Full LED Current
VCTL
Full On
Full Off
1.7 V
0.3 V
CTRL Pin Bias Current
ICTL CTRL = 2V
40 μA
Over Voltage Protection
OVP
30 V
Over Thermal Protection
OTP
160 °C
Thermal Resistance
θJA
220 °C/W
Note :
Absolute maximum ratings are limits beyond which damage to the device may occur.
The maximum allowable power dissipation is a function of maximum function temperature, TJ(MAX), the junction
to ambient thermal resistance, θJA , and the ambient temperature. The maximum allowable, power dissipation
at any ambient temperature is calculated using: PD(MAX)= [TJ(MAX)-TA]/θJA . Exceeding the maximum allowable
power dissipation will cause excessive die temperature. All limits at temperature extremes are guaranteed via
correlation using standard statistical methods.
YB1522 Rev.1.0
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