1. FAN5340: Synchronous Constant-Current. Series Boost LED Driver with
FAN5340: Synchronous Constant-Current Series Boost LED Driver with Integrated Load Disconnect
Product Presentation

2. Overview
There has been a proliferation of small TFT LCD displays being used in portable electronics today
These LCDs require white LEDs to backlight it in order to display that images on it
White LEDs can be driven in series of parallel
LED drivers must not only provide excellent efficiency performance to prolong operation of the portable device but also provide a good visual experience
Small form factor for the LED driver and the solution itself are also important factors since space is at a premium

3. Introduction
FAN5340 is a synchronous constant-current series boost LED driver with load disconnect that drives 2 to 4 white LEDs
Compact and cost effective solution that provides superior performance
Up to 85% efficiency
Excellent LED Current Linearity
Integrated Load Disconnect
Small form factor: WLCSP-8, 1.57mm x 1.57mm
Driving the LEDs in series provides one excellent benefit – it ensures that all LEDs will have equal brightness

4. FAN5340 Synchronous Constant-Current Series Boost LED Driver
Reduces
Start-up Transients and Audible Interference
Features
Synchronous Operation
Up to 85% Efficiency
500mW Output Power
Drives 2 to 4 40mA
Integrated Disconnect Load
Lower Audible Noise
Saves Power during PWM Dimming
Excellent PWM Linearity
1.2MHz Switching Frequency
Output Over-Voltage Protection
Pkg: WLCSP-8 & 3x3mm MLP
Status
Mobile Handsets
MP3 Players
Mobile Internet Devices
Rugged Handheld PCs
Portable Medical Equipment

5. FAN5340 Efficiency
4 LEDs in Series
3 LEDs in Series

6. FAN5340: LED Current Linearity
FAN5340 dims the LEDs through PWM dimming at 300Hz to 1kHz
To achieve linear LED current especially at low brightness levels, duty cycle is <5% and requires a low PWM frequency i.e. 300Hz
The graph on the left shows LED current linearity over the full range while the one on the right is for duty cycle <2%

7. FAN5340: Load Disconnect FAN5340 integrates true load disconnect
It provides 2 benefits:
Prevents leakage current to LEDs from input when FAN5340 is OFF
Reduces audible noise generated by COUT capacitor
Large voltage ripples on this capacitor causes audible noise by mechanical deformation in the ferroelectric compounds

8. FAN5340 Features & Benefits
High Efficiency
Up to 85% peak efficiency to minimize power consumption in portable products
Serial Driver
Drives LEDs in series to enable equal level of brightness for all LEDs
No need for current matching between channels
Load Disconnect
Prevents reverse leakage current by disconnecting LEDs when FAN5340 is OFF to reduce current
Reduces audible noise in COUT capacitor
LED Current Linearity
Linear relationship between LED current and duty cycle (full range including low duty cycle)
Uniform dimming especially at low LED current
Small Form Factor
Saves PCB space in portable products
WLCSP-8 package occupies <2.5mm2

9. FAN FAN5640
Keypad
Lighting
LCD
Backlight

10. Pricing & Availability
Fairchild Part Number
Package
Unit 1ku
Availability
FAN5340UCX
WLCSP-8
$0.75
Now
FAN5340MPX
MLP-8
$0.79
August 2010

11. Technical Materials FAN5340 Datasheet
FAN5340 Product Overview
Evaluation Boards
Request via Sales Center
Samples

12. Marketing & Apps Contacts
Marketing Contact
Wayne Seto
Applications Support
Mark Barycza