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PDF WD3148 Datasheet ( Hoja de datos )

Número de pieza WD3148
Descripción White LED Driver
Fabricantes WillSEMI 
Logotipo WillSEMI Logotipo

Total 17 Páginas
		
WD3148 Hoja de datos, Descripción, Manual
WD3148
White LED Driver with PWM Brightness Control
in Tiny Package
WD3148
Http://www.sh-willsemi.com
With a 40-V rated integrated power switch MOSFET,
the WD3148 is a boost converter that drives up to 10
White LEDs in series. The WD3148 operates at
600kHz fixed switching frequency to reduce output
ripple, improve conversion efficiency, and allows for
the use of small external components.
FB 1
COMP 2
GND 3
6 VIN
5 EN
4 LX
The default Full-Scale White LED current is set by an
external sensor resistor with regulated 200mV
feedback voltage, as shown in typical application.
During operation, the LED current can be controlled
using the Pulse Width Modulation (PWM) signal
applied on the EN pin, through which the PWM
Duty-Cycle determines the feedback reference voltage
and then the White LED current. In PWM mode, the
WD3148 does not burst the LED current; therefore, it
does not generate audible noises on the ceramic
output capacitor. For maximum protection, the device
features integrated open LED protection that disables
the WD3148 to prevent the output voltage from
exceeding the absolute maximum ratings during open
LED conditions.
The WD3148 is available in a PCB space saving DFN
2mm x 2mm-6L Package with bottom thermal pad.
Standard product is Pb-free and Halogen-free.
DFN 2mm x 2mm-6L
Pin configuration (Top view)
3148
Y
W
Marking
= Device Code
= Year Code
= Week Code
Order information
Features
2.7V~5.5V Input voltage range
38V Open LED Protection
200mV Reference Voltage
600kHz Switching frequency
Up to 91% Efficiency
PWM Brightness Control
PWM Dimming Duty ranges from 0.3% to 100%
Built-in Soft-Start and Over-Current limit
Device
Package
Shipping
WD3148D-6/TR DFN-2x2-6L 3000/Reel&Tape
Applications
Smart Phones
Tablets
Portable games
Will Semiconductor Ltd.
1 Apr 12, 2016 - Rev. 1.0

1 page

WD3148 pdf
WD3148
Electronics Characteristics (Ta=25oC, VIN=3.6V, VEN=VIN, CIN=COUT=1μF, unless otherwise noted)
Parameter
Symbol
Supply Current
Operation Voltage Range
VIN
Under Voltage Lockout
VUVLO
UVLO Hysteresis
VUVLO-HYS
Quiescent Current
IQ
Supply Current
IS
Shutdown Current
ISD
Enable and Reference Control
EN Threshold Voltage
EN Pull-down Resistance
EN Shutdown Pulse Width
VENL
VENH
REN
tOFF
Voltage and Current Control
Feedback Reference
VREF
Feedback Input Bias Current
Operation Frequency
Maximum Duty Cycle
PWM Dimming Clock Rate
PWM Dimming Duty Cycle
Power Switch
On Resistance
N-channel Leakage Current
OC and OLP
Current Limit
Open LED Protection
Threshold
Thermal Shutdown
Thermal Shutdown
Temperature
TSD Hysteresis
IFB
fOSC
DMAX
RON
ILN_NFET
ILIM
VOLP
TSD
TSD-HYS
Test Conditions
VIN Rising
No Switching
Switching
VEN < 0.4V
EN High to Low
100% Full Scale
1% Dimming
0.3% Dimming
Recommended
Recommended
VIN=3.6V, 100mA
VLX=40V, TA=25ºC
LED Open,
Measured on LX
Min
2.7
1.8
0
1.5
2.5
190
2.4
500
92
5
0.3
0.68
36
Typ Max Unit
-- 5.5 V
2.2 2.5 V
0.1 V
0.4 1 mA
1 2 mA
1 μA
0.4 V
VIN V
1 M
ms
200 210 mV
3.6 mV
1.5 mV
1 μA
600 700 kHz
95 %
100 KHz
100 %
0.4
1 μA
0.85
38 40
A
V
160 °C
30 °C
Will Semiconductor Ltd.
5 Apr 12, 2016 - Rev. 1.0

5 Page

WD3148 arduino
As shown in Figure 1, the IC chops up the internal
200mV reference voltage at the duty cycle of the
PWM signal. The pulse signal is then filtered by an
internal low pass filter. The output of the filter is
connected to the error amplifier as the reference
voltage for the FB pin regulation. Therefore,
although a PWM signal is used for brightness
dimming, only the WLED DC current is modulated,
which is often referred as analog dimming.This
eliminates the audible noise which often occurs
when the LED current is pulsed in replica of the
frequency and duty cycle of PWM control. Unlike
other scheme which filters the PWM signal for
analog dimming, WD3148 regulation voltage is
independent of the PWM logic voltage level which
often has large variations.
WD3148
An internal thermal shutdown turns off the device
when the typical junction temperature of 160°C is
exceeded. The device is released from shutdown
automatically when the junction temperature
decreases by 30°C.
Application Information
Maximum Output Current
The overcurrent limit in a boost converter limits the
maximum input current and thus maximum input
power for a given input voltage. Maximum output
power is less than maximum input power due to
power conversion losses. Therefore, the current
limit setting, input voltage, output voltage and
efficiency can all change maximum current output.
The current limit clamps the peak inductor current;
therefore, the ripple has to be subtracted to derive
maximum DC current. The ripple current is a
function of switching frequency, inductor value and
duty cycle. The following equations take into
account of all the above factors for maximum output
current calculation.
Figure 1. Block Diagram of Programmable FB
Voltage Using PWM Signal
For optimum performance, use the PWM dimming
frequency in the range of 5kHz to 100kHz. And the
recommended minimum PWM Duty Cycle is 1% for
stable LED driving and no blind dimming.
Under-Voltage Lockout
An under-voltage lockout prevents operation of the
device at input voltages below typical 2.2V. When
the input voltage is below the under voltage
threshold, the device is shut down and the internal
switch FET is turned off. If the input voltage rises by
under voltage lockout hysteresis, the IC restarts.
Thermal Shutdown
××
ut
(3)
Where
IP = inductor peak to peak ripple
L = inductor value
Vf = Schottky diode forward voltage
Fs = switching frequency
Vout = output voltage of the boost converter. It is
equal to the sum of VFB and the voltage drop across
LEDs.
××
ut
ut
(4)
Where
Iout_max = maximum output current of the boost
Will Semiconductor Ltd.
11 Apr 12, 2016 - Rev. 1.0

11 Page


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