WD3124DB Datasheet PDF

WD3124DB - Will Semiconductor

Part Number WD3124DB
Description 1000mA Buck/Boost Charge Pump Flash LED Driver
Manufacturers Will Semiconductor 
Logo Will Semiconductor Logo 
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WD3124DB datasheet
WD3124DB pdf, equivalent, schematic
Pin configuration (Top view)
Pin descriptions
Input voltage for the charge pump. Decouple with 4.7μF or 10μF ceramic
capacitor close to the pins of the IC.
Positive input for the external flying capacitor. Connect a ceramic 1μF
capacitor close to the pins of the IC.
Negative input for the external flying capacitor. Connect a ceramic 1μF
capacitor close to the pins of the IC.
Logic input to toggle operation between FLASH and TORCH mode. In
TORCH mode FB is regulated to the internal 50mV reference. In FLASH
mode FB reference voltage can be adjusted by changing the resistor from
RSET pin to ground. Choose the external current sense resistor (RSENSE) based
on desired current in TORCH mode and Flash mode.
Shutdown control input. Connect to VIN for normal operation, connect to
ground for shutdown. For normal operation, suggest connecting to VIN only
after the VIN has settled if the VIN ramping up is slow.
Connect a resistor from this pin to ground. When in FLASH mode (FLASH =
High) this resistor sets the current regulation point according to the following:
VFB =(1.38V / RSET)x10.2kΩ
Feedback input for the current control loop. Connect directly to the current
sense resistor.
Internal ground pin. Control circuitry returns current to this pin.
Power ground pin. Flying capacitor current returns through this pin.
Charge Pump Output Voltage. Decouple with an external capacitor. At least
1μF is recommended. If Higher value capacitor is used, output ripple is
Will Semiconductor Ltd.
2 Dec, 2014 - Rev. 1.1
WD3124DB transistor, diode fet, igbt, scr
Application Information
Over Temperature Protection
When the temperature of WD3124DB rises above
150, the over temperature protection circuitry
turns off the output switches to prevent damage to
the device. If the temperature drops back down
below 135, the part automatically recovers and
executes a soft start cycle.
Over Voltage Protection
The WD3124DB has over voltage protection. If the
output voltage rises above the 5.5V threshold, the
over voltage protection shuts off all of the output
switches to prevent the output voltage from rising
further. When the output decreases below 5.3V, the
device resumes normal operation.
Over Current Protection
The over current protection circuitry monitors the
average current out of the VOUT pin. If the average
output current exceeds approximately 1.5Amp, then
the over current protection circuitry shuts off the
output switches to protect the chip.
Brightness Control Using PWM
Dimming control can be achieved by applying a
PWM control signal to the EN pin. The brightness of
the white LEDs is controlled by increasing and
decreasing the duty cycle of the PWM signal. While
the operating frequency range of the PWM control is
from 60Hz to 700Hz, the recommended maximum
brightness frequency range of the PWM signal is
from 60Hz to 200Hz. A repetition rate of at least
60Hz is required to prevent flicker.
Component Selection
The WD3124DB charge pump circuit requires 3
capacitors (recommended values): 4.7μF input,
4.7μF output and 1μF flying capacitors. For the input
capacitor, a larger value of 10μF will help reduce
input voltage ripple for applications sensitive to
ripple on the battery voltage. All the capacitors
should be surface mount ceramic for low lead
inductance necessary at the 2.2MHz switching
Will Semiconductor Ltd.
frequency of the WD3124DB and to obtain low ESR,
which improves bypassing on the input and output
and improves output voltage drive by reducing
output resistance. Ceramic capacitors with X5R or
X7R temperature grade are recommended for most
applications. A selection of recommended
capacitors included in below table:
Part Number
Capacitance CapacitorSize
0402/X5R/0.5mm 0.03
0603/X5R/0.9mm 0.02
0805/X5R/1.35mm 0.02
0402/X5R/0.55mm 0.03
0603/X5R/0.9mm 0.02
0805/X5R/1.35mm 0.02
The input and output capacitors should be located
as close to the VIN and VOUT pins as possible to
obtain best bypassing, and the returns should be
connected directly to the PGND pin or to the thermal
pad ground located under the WD3124DB. The
flying capacitor should be located as close to the C1
and C2 pins as possible. To obtain lower output
ripple, the COUT value can be increased from 1μF to
2.2μF or 4.7μF with a corresponding decrease in
output ripple. For output currents of 500mA to
1000mA, the recommended CF flying capacitor
value of 1μF should be used.
Resistor Selection
The sense resistor RSENSE is determined by the
value needed in the Torch mode for the desired
output current by the equation:
RSENSE = VFB/ IOUT where VFB = 50mV (Torch Mode).
Once the RSENSE resistor has been selected for
Torch mode, the VFB voltage can be selected for
Flash mode using the following equation:
VFB = IOUT × RSENSE (Flash Mode) where IOUT is for
Flash Mode.
Next, the RSET resistor can be selected for Flash
mode using the following equation:
RSET = (1.38V/VFB)x10.2kΩ(Flash Mode)
For an example of 200mA Torch mode and 600mA
Flash mode, the values RSENSE = 0.25Ω, VFB =
9 Dec, 2014 - Rev. 1.1

Information Total 13 Pages
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