YOBON YB1522ST25

YB1522
Step-up DC-DC Converter White LED Driver
Description
Features
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.
„ Built-in Internal Switch
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.
„ 5” ~ 7” LCD Display Module
„ 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
„ White LED Backlighting
„ Car TV
„ Handheld and PDA
„ Electronic Books
„ Digital Photo Frame
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.
Typical Application Circuit
Figure 1: Typical Application Circuit
YB1522 Rev.1.0
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YB1522
Step-up DC-DC Converter White LED Driver
Pin Configuration
SW
1
GND
2
FB
3
5
VIN
4
CTRL
SOT23-5
Figure 2: Pin Configuration
Pin Description
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 100mV. Connect LEDs and a
resistor at this pin. LED current is determined by the resistance and
CTRL voltage.
Shutdown Pin and Dimming Control Pin.
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.
Input Supply Pin. Bypass this pin with a capacitor as close to the
device as possible.
Ordering Information
Order Number
Package Type
Supplied As
Package Marking
YB1522ST25
SOT23-5
3000 units Tape & Reel
Please contact sales
representative
YB1522 Rev.1.0
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2
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
Input Voltage Range
VIN
Not Switching
IQ
Shutdown
Test Conditions
TYP
MAX
Units
16
V
1.5
1.7
mA
0.3
1
uA
110
mV
3
VFB = 0.3V
1.2
CTRL = 0V
IOUT = 20mA,VOUT = 12.5V
Circuit of Figure 1
90
100
85% duty cycle
620
650
mA
450
mA
Feedback Voltage
VFB
Switch Current Limit
ICL
FB Pin Bias Current
IB
Switching Frequency
FSW
Maximum Duty Cycle
DMAX
Minimum Duty Cycle
DMIN
Switch Vcesat
VSAT
At ISW = 200mA
Switch Leakage Current
ILKG
CTRL = 0.3V
VCTRL for Full LED Current
VCTL
CTRL Pin Bias Current
ICTL
Over Voltage Protection
Over Thermal Protection
Thermal Resistance
MIN
40% duty cycle
VFB = 100mV
900
930
20
Full On
1
uA
960
KHz
85
%
25
%
180
mV
1
μA
1.7
V
0.3
Full Off
V
40
μA
OVP
30
V
OTP
160
°C
θJA
220
°C/W
CTRL = 2V
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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3
YB1522
Step-up DC-DC Converter White LED Driver
Typical Performance Characteristics
C1=1uF/16V
C2=10uF/16V
L1=33uH/CD43
R1=0.71Ω
Output Waveform
Output Ripple
Vin & Efficiency
Vin & Iout
95%
180
160
85%
Iout (mA)
Efficiency (%)
90%
80%
75%
70%
140
120
100
65%
80
60%
2.5
3
3.5
4
4.5
5
5.5
6
2.5
YB1522 Rev.1.0
3
3.5
4
4.5
5
5.5
6
Vin (V)
Vin (V)
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YB1522
Step-up DC-DC Converter White LED Driver
C1=1uF/16V
C2=10uF/16V
L1=33uH/CD43
R1=0.62Ω
Output Waveform
Output Ripple
Vin & Iout
Vin & Efficiency
88%
250
86%
200
Iout(mA)
Efficiency (%)
84%
82%
80%
78%
150
100
50
76%
74%
0
72%
2.5
2.5
3
3.5
4
4.5
5
5.5
6
3
3.5
4
4.5
5
5.5
6
Vin(V)
Vin(V)
YB1522 Rev.1.0
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YB1522
Step-up DC-DC Converter White LED Driver
C1=1uF/16V
C2=10uF/16V
L1=33uH/CD43
R1=0.55Ω
Output Waveform
Output Ripple
Vin & Efficiency
Vin & Iout
80%
200
180
76%
Iout(mA)
Efficiency (%)
78%
74%
72%
160
140
70%
120
68%
100
66%
80
2.5
3
3.5
4
4.5
5
5.5
6
Vin(V)
YB1522 Rev.1.0
2.5
3
3.5
4
4.5
5
5.5
6
Vin (V)
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YB1522
Step-up DC-DC Converter White LED Driver
C1=1uF/16V
C2=10uF/16V
L1=33uH/CD43
R1=0.5Ω
Output Waveform
Output Ripple
Vin & Efficiency
Vin & Iout
72%
250
200
68%
Iout (mA)
Efficiency (%)
70%
66%
64%
150
100
62%
50
60%
0
58%
2.5
3
3.5
4
4.5
5
5.5
6
2.5
Vin (V)
YB1522 Rev.1.0
3
3.5
4
4.5
5
5.5
6
Vin (V)
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YB1522
Step-up DC-DC Converter White LED Driver
Typical Performance Characteristics
Supply Current (Vctrl = 0V)
Supply Current (Vctrl = Vin)
1
6
0.8
5
4
0.6
uA
mA 3
0.4
2
0.2
1
0
0
2
3
4
5
6
7
8
9
2
3
4
5
V
7
8
9
250
300
350
400
8
9
Vcesat
Switching Frequency
250
932.2
932
200
Vcesat ( mV)
931.8
931.6
Khz
6
V
931.4
931.2
150
100
50
931
0
930.8
2
3
4
5
6
7
8
50
9
100
150
200
Switching Current ( mA)
Vin(V)
Switch Leakage Current
CTRL Pin Bias Current
0.5
60
0.4
50
40
0.3
uA
uA 30
0.2
20
0.1
10
0
0
2
3
4
5
6
7
8
9
3
4
5
6
7
Vin(V)
Vin (V)
YB1522 Rev.1.0
2
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YB1522
Step-up DC-DC Converter White LED Driver
Function Block
Figure 3: YB1522 Block Diagram
Operation
Application Information
The YB1522 uses a constant frequency,
current mode control scheme to regulate
the output LED current. Its operation can
be understood by referring to the block
diagram in Figure 3. At the start of each
oscillator cycle, a voltage proportional to
the switch current is added to a ramp
output and the resulting sum is fed into the
positive terminal of the PWM comparator
(comparator-1). When this voltage exceeds
the level of the comparator negative input,
the peak current has been reached, and
the SR latch (in Control Logic) is reset and
turns off the power switch. The voltage at
the negative input of the comparator comes
from the output of the error amplifier. The
error amplifier sets the correct peak current
level to keep the output in regulation. If the
error amplifier’s output increases, more
current is delivered to the output; if it
decreases, less current is delivered.
Soft Start and Current Limit
The internal soft start circuit minimizes the
inrush current during turning on YB1522.
The maximum switch current is limited to
about 650mA by the chip.
YB1522 Rev.1.0
LED Current and Dimming Control
The LED’s current is set by a resistor
connected at FB pin to GND using:
I LED =
100mV
RLED
The maximum LED current set initially can
be reduced by pulse width modulating the
CTRL. A better approach is to adjust the
feedback voltage for dimming control.
Either a DC level signal or a filtered PWM
signal can be used to control the LED
current as illustrated in Figure 4 and Figure
5 respectively. Using the above different
scheme, the LED current can be controlled
from 0% to 100% to its maximum value.
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YB1522
Step-up DC-DC Converter White LED Driver
VDC (V)
VFB (mV)
IOUT (mA)
Duty
IOUT (mA)
2
0
0
0%
20
1.8
2.2
0.43
20%
17.4
1.6
9.2
1.8
30%
15
1.4
19.6
3.6
40%
12.4
1.2
31.1
6
50%
10
1
43.4
8.5
60%
8
0.8
63
12.3
70%
6.4
0.6
74
14.5
80%
4.07
0.4
86.4
16.9
100%
0
0.2
96.9
19
0
102
20
PWM : 2V ; 1KHz ; Vin=3.6V
Figure 4: Dimming Control Using a DC Voltage
YB1522 Rev.1.0
Figure 5: Dimming Control Using a Filtered PWM
Signal
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YB1522
Step-up DC-DC Converter White LED Driver
Over Voltage Protection
The YB1522 has an internal over voltage
protection circuit which also acts as an
open-circuit protection. In the cases of
open circuit or the LEDs failure, the LEDs
are disconnected from the circuit, and the
feedback voltage will be zero. The YB1522
will then switch to a high duty cycle
resulting in a high output voltage, which
may cause SW pin voltage to exceed its
maximum 30V rating. The YB1522 will
shutdown automatically until input condition
changes to bring it out of the shutdown
mode.
Inductor Selection
A 33uH inductor is recommended for most
applications to drive more than 3x7 WLEDs.
Although small size and high efficiency are
major concerns, the inductor should have
low core losses at 1MHz and low DCR
(copper wire resistance).
Diode Selection
To maintain high efficiency, the average
current rating of the Schottky diode should
be large than the peak inductor current, IPK.
Schottky diode with a low forward drop and
fast switching speeds are ideal for increase
efficiency in portable application. Choose a
reverse breakdown of the Schottky diode
large than the output voltage.
Capacitor Selection
Choose low ESR capacitors for the output
to minimize output voltage ripple. Multilayer
capacitors are a good choice for this as well.
A 10uF capacitor is sufficient for 3x7
WLEDs applications. For additional
bypassing, a 100nF ceramic capacitor can
YB1522 Rev.1.0
be used to shunt high frequency ripple on
the input.
The input bypass capacitor CIN, as shown
in Figure 1, must be placed close to the IC.
This will reduce copper trace resistance
which affects input voltage ripple of the IC.
For additional input voltage filtering, a
100nF bypass capacitor can be placed in
parallel with CIN to shunt any high
frequency noise to ground. The output
capacitor, COUT, should also be placed
close to the IC. Any copper trace
connections for the COUT capacitor can
increase the series resistance, which
directly effect output voltage ripple.
The feedback network, resister R2 should
be kept close to the FB pin to minimize
copper trace connections that can inject
noise into the system. The ground
connection for the feedback resistor
network should connect directly to an
analog ground plane. The analog ground
plane should tie directly to the GND pin. If
no analog ground plane is available, the
ground connection for the feedback
network should tie directly to the GND pin.
Trace connections made to the inductor
and Schottky diode should be minimized to
reduce power dissipation and increase
overall efficiency.
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YB1522
Step-up DC-DC Converter White LED Driver
Package Information (SOT23-5)
NOTICE:
y The information described herein is subject to change without notice.
y Yobon does not assume any responsibility for use of any circuitry or applications described herein, nor
does it convey any patent license.
YB1522 Rev.1.0
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