LTC3215EDD Ver la hoja de datos (PDF) - Linear Technology
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LTC3215EDD Datasheet PDF : 14 Pages
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LTC3215
OPERATION
Mode Switching
The LTC3215 will automatically switch from 1x mode to
1.5x mode, and subsequently from 1.5x mode to 2x mode
whenever a dropout condition is detected at the ILED pin.
The part will wait approximately 2ms before switching
to the next mode. This delay allows the LED to warm up
and reduce its forward voltage which may remove the
dropout condition.
In order to reset the part back into 1x mode, the LTC3215
must be brought into shutdown (EN = LOW). Immediately
after the part has been brought to shutdown, it may be
enabled into the 1x mode via the EN pin. An internal com-
parator will not allow the main switches to connect VIN
and CPO in 1x mode until the voltage at the CPO pin has
decayed to less than or equal to the voltage at the VIN pin.
2.2µF
2.2µF
2.2µF
2.2µF
2.9V TO 4.4V
µP
VIO
2.2µF
ON/OFF
C1+ C1– C2+ C2–
VIN
CPO
LTC3215
ILED
EN
ILED*
VIO
R2
TORCH/FLASH
ISET
R1
*ITORCH = [(1.22V/R1) – ((VIO – 1.22V)/R2)] • 3270
IFLASH = [(1.22V/(R1 • R2/(R1 + R2))] • 3270
3215 F02a
(2a)
4.7µF
2.9V TO 4.4V
2.2µF
C1+ C1– C2+ C2–
VIN
CPO
LTC3215
ILED
EN
PWM
ISET
9.31k 1k
1%
9.31k
1%
3215 F02b
1µF
(2b)
Figure 2
4.7µF
3215fc
8
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