LTC3453

11

3453fa

APPLICATIO S I FOR ATIO

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.

Unused Outputs

If fewer than 4 LED pins are to be used, unused LEDx pins

current source outputs are not being used and shuts off

the corresponding output currents to save power. A small

trickle current (~30

µA) 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

operation as described previously (if the output were

initially designated unused at power-up by connecting its

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

be voltage-limited by means of a secondary control loop.

other LEDs will still remain biased at the correct pro-

grammed current but the overall circuit efficiency will

decrease.

PACKAGE DESCRIPTIO

UF Package

16-Lead Plastic QFN (4mm

× 4mm)

(Reference LTC DWG # 05-08-1692)

4.00

± 0.10

(4 SIDES)

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

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION

ON THE TOP AND BOTTOM OF PACKAGE

PIN 1

TOP MARK

(NOTE 6)

0.55

± 0.20

16

15

1

2

BOTTOM VIEW—EXPOSED PAD

2.15

± 0.10

(4-SIDES)

0.75

± 0.05

R = 0.115

TYP

0.30

± 0.05

0.65 BSC

0.200 REF

0.00 – 0.05

(UF16) QFN 1004

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

0.72

±0.05

0.30

±0.05

0.65 BSC

2.15

± 0.05

(4 SIDES)

2.90

± 0.05

4.35

± 0.05

PACKAGE OUTLINE

PIN 1 NOTCH R = 0.20 TYP

OR 0.35

× 45° CHAMFER