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PDF WD3148 Datasheet ( Hoja de datos )

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

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
WD3148
Operation Information
Operation
The WD3148 is a high efficiency, high output
voltage boost converter in a small package size.
The device is ideal for driving white LED in series.
The serial LED connection provides even
illumination by sourcing the same output current
through all LEDs, eliminating the need for expensive
factory calibration. The device integrates 40V/0.8A
switch FET and operates in pulse width modulation
(PWM) with 600KHz fixed switching frequency. For
operation see the block diagram. The duty cycle of
the converter is set by the error amplifier output and
the current signal applied to the PWM control
comparator. The control architecture is based on
traditional current-mode control; therefore, slope
compensation is added to the current signal to allow
stable operation for duty cycles larger than 50%.
The feedback loop regulates the FB pin to a low
reference voltage (200mV typical), reducing the
power dissipation in the current sense resistor.
Soft Start-up
The WD3148 Build-in Soft-Start function limits the
inrush current while the device turn-on.
Open LED Protection
Open LED protection circuitry prevents IC damage
as the result of white LED disconnection. The
WD3148 monitors the voltage at the LX pin and FB
pin during each switching cycle. The circuitry turns
off the switch FET and shuts down the IC when both
of the following conditions persist for 4 switching
clock cycles: (1) the LX voltage exceeds the VOVP
threshold and (2) the FB voltage is less than half of
regulation voltage. Then, the WD3148 turns off the
power switch FET and shuts down IC until EN or
power supply is recycled to enable IC.
Shutdown
The WD3148 enters shutdown mode when the EN
voltage is logic low for more than 2.5ms. During
shutdown, the input supply current for the device is
less than 1μA (max). Although the internal FET
does not switch in shutdown, there is still a DC
current path between the input and the LEDs
through the inductor and Schottky diode. The
minimum forward voltage of the LED array must
exceed the maximum input voltage to ensure that
the LEDs remain off in shutdown. However, in the
typical application with two or more LEDs, the
forward voltage is large enough to reverse bias the
Schottky and keep leakage current low.
Current Program
The FB voltage is regulated by a low 0.2V reference
voltage. The LED current is programmed externally
using a current-sense resistor in series with the LED
string. The value of the RSET is calculated using
Equation 1:
(1)
Where
ILED = output current of LEDs
VFB = regulated voltage of FB
RSET = current sense resistor
The output current tolerance depends on the FB
accuracy and the current sensor resistor accuracy.
PWM Brightness Dimming
When the EN pin is constantly high, the FB voltage
is regulated to 200mV typically. However, the EN
pin allows a PWM signal to reduce this regulation
voltage; therefore, it achieves LED brightness
dimming. The relationship between the duty cycle
and FB voltage is given by Equation 2.
Duty × mv
(2)
Where
Duty = Duty Cycle of the PWM signal
200mV = Internal Reference Voltage
Will Semiconductor Ltd.
10 Apr 12, 2016 - Rev. 1.0

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