LTC3453 LINER [Linear Technology], LTC3453 Datasheet - Page 11

• Manufacturer Part Number: LTC3453
• Description: Synchronous Buck-Boost High Power White LED Driver
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
PACKAGE DESCRIPTIO
Unused Outputs
If fewer than 4 LED pins are to be used, unused LEDx pins
should be connected to V
current source outputs are not being used and shuts off
the corresponding output currents to save power. A small
trickle current (~30µA) is still applied to unused outputs to
detect if a white LED is later switched in and also to
distinguish unused outputs from used outputs during
startup.
LED Failure Modes
If an individual LED fails as a short circuit, the current
source biasing it is shut off to save power. This is the same
4.35 ± 0.05
2.90 ± 0.05
U
2.15 ± 0.05
(4 SIDES)
OUT
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
U
. The LTC3453 senses which
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
ON THE TOP AND BOTTOM OF PACKAGE
PIN 1
TOP MARK
(NOTE 6)
W
4.00 ± 0.10
U
(4 SIDES)
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
U
0.65 BSC
0.30 ±0.05
0.72 ±0.05
PACKAGE OUTLINE
UF Package
0.75 ± 0.05
operation as described previously (if the output were
initially designated unused at power-up by connecting its
LEDx pin to V
If an individual LED fails as an open circuit, the control loop
will initially attempt to regulate off of its current source
feedback signal, since it will appear to be the one requiring
the largest forward voltage drop to run at its programmed
current. This will drive V
LED will never accept its programmed current, V
be voltage-limited by means of a secondary control loop.
The LTC3453 limits V
other LEDs will still remain biased at the correct pro-
grammed current but the overall circuit efficiency will
decrease.
0.200 REF
0.00 – 0.05
2.15 ± 0.10
(4-SIDES)
R = 0.115
BOTTOM VIEW—EXPOSED PAD
OUT
TYP
). Efficiency is not materially affected.
15
OUT
OUT
16
to 4.5V in this failure mode. The
0.65 BSC
higher. As the open circuited
0.30 ± 0.05
0.55 ± 0.20
1
2
(UF16) QFN 1004
PIN 1 NOTCH R = 0.20 TYP
OR 0.35 × 45° CHAMFER
LTC3453
OUT
11
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