LM3570SD ,Low Noise White LED Driver SystemFeaturesn 2.7V to 5.5V Input VoltageTheLM3570deviceprovidesacompleteLEDdriversolutionfor wireless h ..
LM3578 ,Switching RegulatorElectrical Characteristics=These specifications apply for 2V ≤ V ≤ 40V (2.2V ≤ V ≤ 40V for T ≤ −25˚ ..
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LM3578AM ,Switching RegulatorElectrical Characteristics (Continued)=These specifications apply for 2V ≤ V ≤ 40V (2.2V ≤ V ≤ 40V ..
LM3578AM ,Switching RegulatorElectrical Characteristics (Continued)=These specifications apply for 2V ≤ V ≤ 40V (2.2V ≤ V ≤ 40V ..
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LM3570SD
Low Noise White LED Driver System
LM3570
Low Noise White LED Driver System
General DescriptionThe LM3570 device providesa complete LED driver solution
for wireless handsets and other portable devices usinga
display and keypad. With three constant current sources,up three white LEDs canbe usedfor display lighting with
excellent current matching (0.3% typ.). The regulated 4.35V
output voltageis perfectfor driving auxiliary keypad LEDsin
voltage mode.
The LM3570 utilizesa high efficiency 3/2 CMOS charge-
pump witha pre-regulation loop that minimizes conducted
noiseon the input.It acceptsan input voltage range from
2.7Vto 5.5V and maintainsa constant current determinedby
the current throughan external RSET resistor.
The device suppliesupto 80mAof total load currentto
accommodate any combinationofupto three white LEDs,
and additional current from VOUT. The switching frequencyis
setat 500kHz. (typ.)to keepthe conducted noise spectrum
away from sensitive frequencies within portableRF devices. applyinga pulse width modulated (PWM) signalto the
PWM pin, the user has the abilityto independently control
the brightnessofthe regulated current source outputs with-
out shutting down the regulated output voltage.
Features 2.7Vto 5.5V Input Voltage Regulated Output Voltage (VOUT= 4.35V) RegulatedIDx with ±0.3% matching between constant
current outputs High Efficiency3/2 Boost function Drives one, two,or three white LEDs withno bias
resistor losses Drives auxiliary keypad LEDSin voltage mode Upto 80mA total output current Active-High Enable Active-High PWM Control Pinfor independent controlof
current sources Very small solution size 1µA(max) shutdown current 500kHz switching frequency (typ.) Linear regulation generates predictable noise spectrum LLP-14 package: 4.0mmX 3.0mmX 0.8mm
Applications Portable devices using whiteor blue LEDs with display
and backlightor frontlight 1-Cell LiIon battery-operated equipment including PDAs,
hand-held PCs and cellular phones
Typical Application CircuitJuly 2004
LM3570
Low
Noise
White
LED
Driver
System
