FAN5341UMPX - Fairchild Semiconductor Corporation

August 2010

FAN5341 • Rev. 1.0.1

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

FAN5341

Series Boost LED Driver with Integrated Schottky Diode and

Single-Wire Digital Interface

Features

 Asynchronous Boost Converter

 Internal Schottky Diode

 Up to 500mW Output Power

 Drives 3 to 5 LEDs in Series

 2.7V to 5.5V Input Voltage Range

 Single-Wire Digital Control Interface to Set LED

Brightness Levels

− 32 Linear Steps

 1.2MHz Fixed Switching Frequency

 Soft-Start Capability

 Input Under-Voltage Lockout (UVLO)

 Output Over-Voltage Protection (OVP)

 Short-Circuit Detection

 Thermal Shutdown (TSD) Protection

 Low Profile 6-lead 2.0 x 2.0 x 0.55mm UMLP Package

Applications

 Cellular Mobile Handsets

 Mobile Internet Devices

 Portable Media Players

 PDA, DSC, MP3 Players

Description

The FAN5341 is an asynchronous constant-current LED

driver capable of efficiently delivering up to 500mW to a

string of up to five LEDs in series. Optimized for small form-

factor applications, the 1.2MHz fixed switching frequency

allows the use of small chip inductors and capacitors.

The FAN5341 uses a simple single-wire digital control

interface to program the brightness levels of the LEDs in 32

linear steps by applying digital pulses.

For safety, the device features integrated over-voltage, over-

current, short-circuit detection, and thermal-shutdown

protection. In addition, input under-voltage lockout protection

is triggered if the battery voltage is too low.

The FAN5341 is available in a very low profile, small form-

factor 2mm x 2mm x 0.55mm 6-lead UMLP package that is

green and RoHS compliant.

Ordering Information

Part Number Temperature Range Package Packing

FAN5341UMPX -40 to 85°C 6-lead, 2.0 x 2.0mm UMLP Tape and Reel

FAN5341 • Rev. 1.0.1 2

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Typical Application Diagram

Figure 1. Typical Application

Block Diagram

Figure 2. Functional Block Diagram

FAN5341 • Rev. 1.0.1 3

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Pin Configuration

P1

GND

43

2

1

5

6GND

SW

FB

VOUT

VIN

EN

Figure 3. UMLP6 Package, ^Top View

Pin Definitions

Pin # Name Description

1 VOUT

Boost Output Voltage. Output of the boost regulator. Connect the LEDs to this pin. Connect COUT

(Output Capacitor) to GND.

2 VIN

Input Voltage. Connect to power source and decouple with CIN to GND.

3 EN

Enable Brightness Control. Program dimming levels by driving pin with digital pulses.

4 FB

Voltage Feedback. The boost regulator regulates this pin to 0.253V to control the LED string current.

Tie this pin to a current setting resistor (RSET) between GND and the cathode of the LED string.

5 SW

Switching node. Tie inductor L1 from VIN to SW pin.

6 GND

Ground. Tie directly to a GND plane.

FAN5341 • Rev. 1.0.1 4

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above

the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended

exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings

are stress ratings only.

Symbol Parameter Min. Max. Units

VIN VIN -0.3 6.0 V

VFB, VEN FB, EN Pins -0.3 VIN + 0.3 V

VSW SW Pin -0.3 22.0 V

VOUT VOUT Pin –0.3 22.0 V

ESD Electrostatic Discharge Protection

Level

Human Body Model per JESD22-A114 3.3 kV

Charged Device Model per JESD22-C101 2.0

TJ Junction Temperature -40 +150 °C

TSTG Storage Temperature -65 +150 °C

TL Lead Soldering Temperature, 10 Seconds +260 °C

Recommended Operating Conditions

The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating

conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding

them or designing to absolute maximum ratings.

Symbol Parameter Comments Min. Max. Units

VIN VIN Supply Voltage 2.7 5.5 V

VOUT VOUT Voltage(1) 6.2 17.5 V

IOUT VOUT Load Current 500mW Maximum Output Power 5 25 mA

TA Ambient Temperature -40 +85 °C

TJ Junction Temperature -40 +125 °C

Note:

1. Application should guarantee that minimum and maximum duty-cycle should fall between 20-85% to meet the specified

range

Thermal Properties

Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with four-layer 2s2p

boards in accordance to JEDEC standard JESD51. Special attention must be paid not to exceed junction temperature TJ(max) at a

given ambient temperature TA.

Symbol Parameter Typical Units

θJA Junction-to-Ambient Thermal Resistance, UMLP6 Package 70 °C/W

FAN5341 • Rev. 1.0.1 5

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Electrical Spec if ications

VIN = 2.7V to 5.5V and TA = -40°C to +85°C unless otherwise noted. Typical values are at TA = 25°C and VIN = 3.6V.

Symbol Parameter Conditions Min. Typ. Max. Units

Power Supplies

ISD Shutdown Supply Current EN = GND, VIN = 3.6V 0.30 0.75 μA

VUVLO Under-Voltage Lockout

Threshold

VIN Rising 2.10 2.35 2.60 V

VIN Falling 1.90 2.15 2.40

VUVHYST Under-Voltage Lockout

Hysteresis 250 mV

EN: Enable Pin

VIH HIGH-Level Input Voltage 1.2 V

VIL LOW-Level Input Voltage 0.4 V

REN EN Pull-Down Resistance 200 300 400 kΩ

TLO EN Low Time for Dimming VIN = 3.6V; See Figure 14 0.5 300 µs

THI Time Delay Between Steps VIN = 3.6V; See Figure 14 0.5 µs

TSD EN Low, Shutdown Pulse Width VIN = 3.6V; from Falling Edge of EN 1

ms

Feedback and Reference

VFB Feedback Voltage ILED = 20mA from -40°C to +85°C,

2.7V ≤ VIN ≤ 5.5V 240 253 266 mV

IFB Feedback Input Current VFB = 253mV 0.1 1.0 μA

Power Outputs

RDS(ON)_Q1 Boost Switch On-Resistance VIN = 3.6V, ISW = 100mA 600 mΩ

VIN = 2.7V, ISW = 100mA 650

ISW(OFF) SW Node Leakage(1) EN = 0, VIN = VSW = VOUT = 5.5V,

VLED = 0 0.1 2.0

μA

ILIM-PK Boost Switch Peak Current Limit VIN = 3.6V 750 mA

Oscillator

fSW Boost Regulator Switching

Frequency 1.0 1.2 1.4 MHz

Output and Protection

VOVP

Boost Output Over-Voltage

Protection 18.0 18.9 21.0 V

OVP Hysteresis 0.8

VTLSC VOUT Short Circuit Detection

Threshold VOUT Falling V

IN – 1.4 V

VTHSC VOUT Short Circuit Detection

Threshold VOUT Rising VIN – 1.2 V

DMAX Maximum Boost Duty Cycle(2,3) 85

%

DMIN Minimum Boost Duty Cycle(2,3) 20

TTSD Thermal Shutdown 150 °C

THYS Thermal Shutdown Hysteresis 35 °C

Notes:

1. SW leakage current includes the leakage current of 2 internal switches; SW to GND and SW to VOUT.

2. Not tested in production and guaranteed by design.

3. Application should guarantee that minimum and maximum duty cycle should fall between 20-85% to meet the specified

range.

FAN5341 • Rev. 1.0.1 6

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Electrical Spec if ications

Figure 4. 5 LEDs: Efficiency vs. LED Current

vs. Input Voltage Figure 5. 5 LEDs: Efficiency vs. LED Current

vs. Input Voltage

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

2.7 3 3.3 3.6 3.9 4.2

Input Voltage (V)

Delta Feedba ck Vo ltage (mV )

-40°C

+25°C

+85°C

Figure 6. 4 LEDs: Efficiency vs. LED Current

vs. Input Voltage

Figure 7. Delta of VFB Over Input Voltage and

Temperature for 4 LEDs with L=10µH and

COUT=1.0µF at ILED=25mA

Figure 8. 3 LEDs: Efficiency vs. LED Current

vs. Input Voltage Figure 9. Over-Voltage Protection vs. Input Voltage

17.0

17.5

18.0

18.5

19.0

19.5

20.0

2.7 3 3.3 3.6 3.9 4.2

Input Voltage (V)

OVP (V)

4 LEDs

L = 10µH

COUT = 1.0µF

ILED = 25mA

50

60

70

80

90

5 10152025

LED Curr ent ( m A)

Eff ici ency (%)

VIN=2.8V

VIN=3.6V

VIN=4.2V

3 LEDs

L = 10µH

COUT = 1.0µF

ILED = 25mA

50

60

70

80

90

510152025

LE D Curre n t (mA)

Efficiency (%)

VIN=2.7V

VIN=3.6V

VIN=4.2V

4 LEDs

L = 10µH

COUT = 1.0µF

ILED = 25mA

50

60

70

80

90

510152025

LED Current (m A)

Eff i ci enc y ( % )

VIN=2.8V

VIN=3.6V

VIN=4.2V

5 LEDs

L = 4.7µH

COUT = 1.0µF

ILED = 25mA

50

60

70

80

90

5 10152025

LE D Cur rent (m A)

Efficiency (%)

VIN=2.7V

VIN=3.6V

VIN=4.2V

5 LEDs

L = 10µH

COUT = 1.0µF

ILED = 25mA

FAN5341 • Rev. 1.0.1 7

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Electrical Spec if ications

Figure 10. Line Transient Response for 4 LEDs at

VIN=3.6V ± 0.6V with L=10µH, COUT=1.0µF and

ILED=25mA

Figure 11. FAN5341 Dimming Operation at VIN=3.6V for 4

LEDs with L=10µH, COUT=1.0µF and ILED=25mA

Figure 12. Startup Waveform for Switch Voltage, Inductor

Current, VFB and EN for 4 LEDs at VIN=3.6V±

0.6V with L=10µH, COUT=1.0µF and ILED=25mA

Figure 13.Stead

y

-State Waveform for VOUT, Switch Voltage

and Inductor Current for 4 LEDs at VIN=3.6V ±

0.6V with L=10µH, COUT=1.0µF and ILED=25mA

FAN5341 • Rev. 1.0.1 8

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Circuit Description

Overview

The FAN5341 is an inductive current-mode boost serial

LED driver that achieves LED current regulation by

maintaining 0.253V across the RSET resistor. The current

through the LED string (ILED) is therefore given by:

SET

LED R

I253.0

= (1)

The voltage VOUT is determined by the sum of the forward

voltages across each LED, plus the voltage across RSET,

which is always 253mV.

Driving Five LEDs in Series

FAN5341 can drive five LEDs in series but, the forward

voltage (VF) of the LED MUST be less than 3.5V such that it

remains under the over-voltage specification of 18.9V.

UVLO and Soft-Start

If EN has been low for more than 1ms, the IC may initiate a

“cold start” soft-start cycle when EN rises, provided VIN is

above the UVLO threshold.

Digital Inte rfa c e

The FAN5341 implements a single-wire digital interface to

program the LED brightness to one of thirty-two (32) levels

spaced in linear steps. With this single-wire solution, the

FAN5341 does not require the system processor to

constantly supply a signal to it to drive the LEDs.

Digital Dimming Control

The FAN5341 starts driving the LEDs at the maximum

brightness level. After startup, the control logic is ready to

accept programming pulses to decrease the brightness

level by the number of positive edges applied to the EN pin.

Figure 14 shows the digital pulse dimming control.

Over-Current and Short-Circuit Detection

The boost regulator employs a cycle-by-cycle peak inductor

current limit of ~750mA.

Over-Voltage / Open-Circuit Protection

If the LED string is an open circuit, FB remains at 0V and

the output voltag continues to increase in the absence of an

over-voltage protection (OVP) circuit. The FAN5341’s OVP

circuit disables the boost regulator when VOUT exceeds

18.9V and continues to keep the regulator off until VOUT

drops below 18.1V.

Thermal Shutdown

When the die temperature exceeds 150°C, a reset occurs

and remains in effect until the die cools to 125°C, at which

time, the circuit is allowed to begin the soft-start sequence.

Figure 14. Digital Pulse-Dimming Control Diagram

FAN5341 • Rev. 1.0.1 9

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Application Information

Inductor & Output Capacitor Selection

# of LEDs Inductor (L) Part Number Manufacturer Min COUT Part Number Manufacturer

3, 4, 5

10.0µH

LQH43MN100K03 Murata

1.00µF CV105X5R105K25AT AVX/Kyocera

NLCV32T-100K-PFR TDK

VLF3010AT-100MR49-1 TDK

4.7µH

LQH43MN4R7K03 Murata

1.00µF CV105X5R105K25AT AVX/Kyocera

NLCV32T-4R7M-PFR TDK

LPF2010T-4R7M ABCO

Table 1. Recommended External Components

Component Placement and PCB Recomendations

Figure 15. Recommended Component Placement

Input Capacitance

In a typical application, the input and output capacitors

should be placed as close to the IC as possible; no

additional capacitance is needed to ensure proper

functionality. However, in a testing environment, where the

FAN5341 is typically powered by a power supply with

relatively long cables, an additional input capacitor (10µF)

may be needed to ensure stable functioning. This capacitor

should be placed close to where the power supply cables

attach to the FAN5341 evaluation board.

PCB Recommendations

 The inductor can be connected to VIN with vias through

another layer if needed.

 The feedback pin should be connected back to the IC on

a sub-layer.

FAN5341 • Rev. 1.0.1 10

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface

Physical Dimensions

SIDE VIEW

NOTES:

A. PACKAGE CONFORMS TO JEDEC MO-229

EXCEPT WHERE NOTED.

B. DIMENSIONS ARE IN MILLIMETERS.

C. DIMENSIONS AND TOLERANCES PER

ASME Y14.5M, 1994.

D. LANDPATTERN RECOMMENDATION IS BASED

ON FSC DESIGN ONLY.

E. DRAWING FILENAME: MKT-UMLP06Erev2.

BOTTOM VIEW

TOP VIEW

RECOMMENDED LAND PATTERN

13

64

2X

0.05

0.00

0.55 MAX

0.10 C

0.08 C

(0.15)

C

SEATING

PLANE

2.0

0.70

0.80

1.35

1.45

PIN1

IDENT

0.10 C A B

0.05 C 6X

6X

0.10 C

PIN1

IDENT

A

B

0.35

0.25

0.35

0.25

0.65

1.45

0.80

0.50

0.35 0.65

6X

1.80

A

(0.25)

Figure 16. 6-Lead Molded Leadless Package (UMLP)

Package drawings are provided as a service to customers consideri ng Fairchild components. Drawings may change in any manner without

notice. Pleas e note the revision and/or date on the drawing and contact a Fairchild Semiconduct or represent ative to verify or obtain the most

recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers

Fairchild products.

Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:

http://www.fairchildsemi.com/packaging/.

FAN5341 • Rev. 1.0.1 11

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface