New Led Driver from National

[PEU]

Today I received the National Semiconductors newsletter:

New Product:
LM3557 - Step-Up Converter for White LED Applications

General Description

The LM3557 is a complete solution for white LED drive applications. With minimal external component count, no DC current leakage paths to ground, cycle-by-cycle current limit protection, and output over-voltage protection circuitry, the LM3557 offer superior performance and cost savings over standard DC/DC boost component implementations.

The LM3557 switches at a fixed-frequency of 1.25 MHz, which allows for the use of small external components. Also, the LM3557 has a wide input voltage range to take advantage of multi-cell input applications. With small external components, high fixed frequency operation, and wide input voltage range, the LM3557 is the most optimal choice for LED lighting applications.

Features
VIN Range: 2.7V-7.5V
Small External Components
1.25 MHz Constant-Switching Frequency
Output Over-Voltage Protection
Input Under-Voltage Protection
Cycle-By-Cycle Current Limit
TRUE SHUTDOWN: No DC current paths to ground during shutdown
Low Profile Package: <1 mm Height -8 Pin LLP
No External Compensation


I saw no efficiency charts in the datasheet , but it looks nice.


Pablo

 

[MrAl]

Hi Pablo,

Interesting, but not enough current for me /ubbthreads/images/graemlins/smile.gif

Take care,
Al

 

[idleprocess]

[ QUOTE ]
PEU said:
VIN Range: 2.7V-7.5V


[/ QUOTE ]

That doesn't seem like a very useful boost converter since most of the input range is greater than the Vf of most LEDs.

/ubbthreads/images/graemlins/icon3.gif

 

[milkyspit]

Well, it might reinvigorate the use of LuxV emitters in smallish flashlights! It could also drive a series array of Luxeons or even Nichia 5mm white LEDs.

 

[WildRice]

From what I looked at, it shows series LED configurations. As in cell phones. 3.6v in running 6 series Whites,is easier to controll (I guess) then 6 in parallel with resistors ...
Jeff

 

[andrewwynn]

series LEDs is to maintain even lighting... apparently current is more important than voltage for how much light an LED produces. most of these types of drivers are for 30mA types of white LEDS.. for backlighting the likes of a laptop or cellphone, very rare enough current for a lux.

-awr