YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 1
Description
The YB1517 is a Current-mode PWM step-up
DC-DC converter. It can drive up to 18V at 3.0V
input and 30V at 5.0V input. The 1 MHz switching
frequency allows it to work with tiny external
components, therefore minimize the footprint and
cost in space consideration products.
One of the major applications for YB1517 is in the dc
to dc converter and OLED power supply and TFT
panel power supply.
When using YB1517 for white LED driving, it is not
recommended to control LED brightness by applying
a PWM signal to the CTRL pin, because the built-in
soft-start circuit might interfere the start-up operation
of YB1517 and cause lower brightness. It operates
as current source to drive up to 5 white LEDs in
series at 3.0V input and up to 8 white LEDs at 5.0V
input. 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.
YB1517 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
Features
• 900 KHz current-mode PWM converter
• Built-in internal switch
• Adjustable output voltage up to 30V
• 2.7V to 16V input range
• <1uA shutdown current
• Internal Soft Start
• Drives up to 5 white LEDs
• Tiny Inductor and Capacitors allowed
• Small 5-Lead SOT-23 package
• 220mV Low Reference Voltage
Applications
• LCD Display Module
• White LED Backlighting
• PDAs, GPS terminals
• Digital Cameras
• Cellular Phone
• Electronic Books
• Portable Applications
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 2
Pin Configuration
Pin Description
Table 1
Ordering Information
Table 2
Pin NAME Description
1 SW
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.
2 GND Ground Pin. Connect directly to local ground plane.
3 FB
Feedback Pin. Reference voltage is 220mV. When connecting
LEDs and a resistor at this pin, LED current is determined by
the resistance and CTRL voltage.
4 CTRL
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
5 VIN Input Supply Pin. Bypass this pin with a capacitor as close to
the device as possible
Order Number Supplied as Package Marking
YB1517ST25 3000 units Tape & Reel Y58 F
Figure 3 : YB1517 Pin Configuration
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 3
Absolute Maximum Ratings
VIN .................................................................................20V
SW Voltage ....................................................................35V
FB Voltage .......................................................................5V
CTRL Voltage...................................................................5V
Maximum Junction Temp,TJ (not 2) ............................150°C
Lead Temperature (Soldering 10 sec).........................250°C
Thermal Resistance (SOT-25, θJA) .......................250℃/W
Internal Power Disspation (SOT-25, PD)......................0.4W
Electricity Characteristics
Table 3
Recommended Operating Conditions
Operating Temperature (note 3) .........................-40°C~85°C
Supply Voltage .................................................... 2.7 V~16V
SW Voltage ....................................................................30V
ESD Susceptibility (HBM).............................................. 2KV
ESD Susceptibility (MM)...............................................200V
Symbol Function Parameter Test Conditions Min Typ Max Units
Vin Input Voltage Range 2.7 16 V
Not Switching VFB = 0.5V 1.2 1.5 1.7 mA
IQ
(Quiescent
Current) Shutdown CTRL = 0V 0.3 1 uA
VFB Feedback Voltage
Iout=20mA,Vout = 6V
Circuit of Figure 2 210 220 230 mV
100% duty cycle 850 900 1000 mA
ICL Switch Current Limit
40% duty cycle 400 mA
IB FB Pin Bias Current VFB=220mV 1 uA
FRSW Switching Frequency 850 900 950 KHz
DTMX Maximum Duty Cycle 85 %
DTMN Minimum duty cycle 20 25 %
VSAT Switch Vcesat At Isw = 200mA 180 mV
ILKG Switch Leakage Current Ctrl = 0.5V 1 μA
Full On 1.7 V
VCTL VCTRL for Full LED
current Full Off 0.3 V
ICTL CTRL Pin Bias Current Ctrl = 2V 40 μA
OVP Over Voltage Protection 34 V
θJA Thermal Resistance 220 °C/W
Note:
Absolute maximum ratings are limits beyond which damage to the device may occur. The maximum
allowable, power dissipation at any ambient temperature is calculated using: PD(MAX)= [TJ(max)-TA]/θJA .
(TA=25°C, Vin=3.3V, L=22uH, Cin=1uF, Cout=4.7uF unless otherwise noted)
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 4
Typical Characteristics
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 5
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 6
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 7
Functional Block
Operation
The YB1517 uses a constant frequency,
current mode control scheme to regulate
the output voltage. 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.
Application Information
Soft Start and Current Limit
The internal soft start circuit minimizes the
inrush current during turning on YB1517.
The maximum switch current is limited to
about 900 mA by the chip.
Over Voltage Protection
The YB1517 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
YB1517 will then switch to a high duty
cycle resulting in a high output voltage,
which may cause SW pin voltage to
exceed its maximum 34V rating. The
YB1517 will shutdown automatically until
Figure 3: YB1517 Block Diagram
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 8
input condition changes to bring it out of
the shutdown mode.
Inductor Selection
A 22uH inductor is recommended for most
applications to the dc to dc converter and
OLED supply and TFT panel power supply .
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 4.7uF capacitor is sufficient for most
applications. For additional bypassing, a
100nF ceramic capacitor can 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.
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 9
Figure 4 : Typical Application Circuit
Figure 5 : TFT Panel Power Application Circuit
YB1517
Step-up DC-DC Converter & White LED Driver
YB1517 MRev.1.0 www.yobon.com.tw 10
Package Description
All the contains in this datasheet are not assuming any responsibility for use of any
circuitry described no circuit patent license are implied and Yobon reserves the right at
any time without notice to change said circuitry and specifications.
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that is always welcome and with our appreciations.
