Datenblatt-pdf.com


WD3148 Schematic ( PDF Datasheet ) - WillSEMI

Teilenummer WD3148
Beschreibung White LED Driver
Hersteller WillSEMI
Logo WillSEMI Logo 




Gesamt 17 Seiten
WD3148 Datasheet, Funktion
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






WD3148 Datasheet, Funktion
WD3148
Typical Characteristics
(Ta=25oC, VIN=3.6V, VEN=VIN, CIN=COUT=1μF, 10 LEDs, unless otherwise noted)
100 100
90 90
80
70
60
50
0
L=22uH,10LEDs
VIN=3.0V
VIN=3.6V
VIN=4.2V
VIN=5.0V
2 4 6 8 10 12 14 16 18 20
Output Current (mA)
Efficiency vs. Output Current
80
70
60
50
0
L=22uH 6x2LEDs
V =3.0V
IN
V =3.6V
IN
V =4.2V
IN
V =5.0V
IN
4 8 12 16 20 24 28 32 36 40
Output Current (mA)
Efficiency vs. Output Current
21.0
20.5
20.0
VIN=3.0V
19.5
VIN=3.6V
VIN=4.2V
19.0
VIN=5.0V
-50 -30 -10 10 30 50 70 90
Temperature (oC)
LED Current vs. Temperature
21.0
20.5
20.0
19.5
10LEDs
19.0
2.5
3.0 3.5 4.0 4.5 5.0 5.5
Input Voltage (V)
LED Current vs. Supply Voltage
0.70
0.65
0.60
VIN=3.0V
VIN=3.6V
VIN=4.2V
VIN=5.0V
0.55
0.50
-50 -30 -10 10 30 50 70 90
Temperature (oC)
Frequency vs. Temperature
0.70
0.65
0.60
0.55
0.50
2.5
3.0 3.5 4.0 4.5 5.0 5.5
Supply Voltage (V)
Frequency vs. Supply Voltage
Will Semiconductor Ltd.
6 Apr 12, 2016 - Rev. 1.0

6 Page









WD3148 pdf, datenblatt
converter
Ilim = over current limit
η = efficiency
Inductor Selection
The selection of the inductor affects steady state
operation as well as transient behavior and loop
stability. These factors make it the most important
component in power regulator design. There are
three important inductor specifications, inductor
value, DC resistance and saturation current.
Considering inductor value alone is not enough.
The inductor value determines the inductor ripple
current. Choose an inductor that can handle the
necessary peak current without saturating,
according to half of the peak-to-peak ripple current
given by Equation 3, pause the inductor DC current
given by:
ut × ut
C×
(5)
Inductor values can have ±20% tolerance with no
current bias. When the inductor current approaches
saturation level, its inductance can decrease 20% to
35% from the 0A value depending on how the
inductor vendor defines saturation current. Using an
inductor with a smaller inductance value forces
discontinuous PWM when the inductor current
ramps down to zero before the end of each
switching cycle. This reduces the boost converters
maximum output current, causes large input voltage
ripple and reduces efficiency. Large inductance
value provides much more output current and higher
conversion efficiency. For these reasons, a 10μH to
22μH inductor value range is recommended. A
22μH inductor optimized the efficiency for most
application while maintaining low inductor peak to
peak ripple. When recommending inductor value,
the factory has considered 40% and +20%
tolerance from its nominal value.
WD3148
Schottky Diode Selection
The rectifier diode supplies current path to the
inductor when the internal MOSFET is off. Use a
schottky with low forward voltage to reduce losses.
The diode should be rated for a reverse blocking
voltage greater than the output voltage used. The
average current rating must be greater than the
maximum load current expected, and the peak
current rating must be greater than the peak
inductor current.
Diode the following requirements:
Low forward voltage
High switching speed : 50ns max.
Reverse voltage
Rated current
: VOUT + VF or more
: IPK or more
Compensation Capacitor Selection
The compensation capacitor CCOMP, connected from
COMP pin to GND, is used to stabilize the feedback
loop of the WD3148. A 220nF ceramic capacitor for
CCOMP is suitable for most applications.
Input and Output Capacitor Selection
The output capacitor is mainly selected to meet the
requirements for the output ripple and loop stability.
This ripple voltage is related to the capacitor’s
capacitance and its equivalent series resistance
(ESR). Assuming a capacitor with zero ESR, the
minimum capacitance needed for a given ripple can
be calculated by
C ut
ut ut
ut × s × r e
(6)
Where, Vripple = peak-to-peak output ripple. The
additional output ripple component caused by ESR
is calculated using:
r eR
ut ×
R
(7)
Due to its low ESR, Vripple_ESR can be neglected for
Will Semiconductor Ltd.
12 Apr 12, 2016 - Rev. 1.0

12 Page





SeitenGesamt 17 Seiten
PDF Download[ WD3148 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
WD3148White LED DriverWillSEMI
WillSEMI

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche