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June 2013

FL7701

Smart LED Lamp Driver IC with PFC Function

Features

 Digitally Implemented Active PFC Function

(No Additional Circuit Necessary for High PF)

 Built-in HV Supplying Circuit: Self Biasing

 Application Input Range: 80 VAC ~ 308 VAC

 AOCP Function with Auto-Restart Mode

 Built-in Over-Temperature Protection Function

 Cycle-by-Cycle Current Limit

 Current-Sense Pin Open Protection

 Low Operating Current: 0.85 mA (Typical)

 Under-Voltage Lockout with 5 V Hysteresis

 Programmable Oscillation Frequency

 Programmable LED Current

 Analog Dimming Function

 Soft-Start Function

 Precise Internal Reference: ±3%

Applications

 LED Lamp for Decorative Lighting

 LED Lamp for Low-Power Lighting

Description

The FL7701 LED lamp driver is a simple IC with PFC

function. The special “adopted digital” technique of the

IC can automatically detect input voltage condition and

send an internal reference signal for achieving high

power factor. When AC input is applied to the IC, PFC

function is automatically enabled. Otherwise, when DC

input is applied to the IC, PFC function is automatically

disabled. The FL7701 does not need a bulk capacitor

(electrolytic capacitor) for supply rail stability, which can

significantly affect to LED lamp system.

Related Resources

 Evaluation Board: FEBFL7701_L30U003A

Ordering Information

Part Number

Operating

Temperature Range

FL7701MX

-40°C to +125°C

Package

Packing Method

8-Lead, Small Outline Integrated Circuit (SOIC),

JEDEC MS-012, .150-inch Narrow Body

Tape & Reel

© 2011 Fairchild Semiconductor Corporation

FL7701 • Rev. 1.0.4

www.fairchildsemi.com

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. Unit

VCC IC Supply Voltage

HV High Voltage Sensing

20 V

500 V

IO+/IO-

VADIM

VRT

VCS

TA

TJ

TSTG

θJA

PD

ESD

Peak Drive Output Current (Sourcing / Sinking)

Analog Dimming

RT Pin Voltage

Allowable Current Sensing Detection Voltage

Operating Ambient Temperature Range

Operating Junction Temperature

Storage Temperature Range

Thermal Resistance Junction-Air(1,2)

Power Dissipation

Human Body Model, JESD22-A114

Electrostatic Discharge Capability

Charged Device Model, JESD22-C101

-40

-40

-65

250

5

5

5

+125

+150

+150

135

660

2000

1000

mA

V

V

V

C

C

C

C/W

mW

V

Notes:

1. Thermal resistance test board. Size: 76.2 mm x 114.3 mm x 1.6 mm (1S0P); JEDEC standard: JESD51-2, JESD51-

3.

2. Assume no ambient airflow.

© 2011 Fairchild Semiconductor Corporation

FL7701 • Rev. 1.0.4

4

www.fairchildsemi.com

4. Dimming Function

The FL7701 uses the ADIM pin for analog or 0 V to

10 V dimming by using a resistive divider. The peak

voltage of internal reference, which is DAC_OUT signal

in Figure 5, is changed by the VADIM level, as shown in

Figure 7, and has different peak level according to the

operating mode.

VDAC _ OUT

0.5V

0.365V

AC mode

DC mode

0.5V

3.5V

VADIM

Figure 7. VADIM vs. VDAC_OUT(peak)

5. Inductor Design

The FL7701 prefixed internal duty ratio range is below

50%, or around 400 ns, from timing point of view. The

range is dependent on the input voltage and LED

numbers in its string.

Minimum duty is calculated as:

Dmin

 n Vf

 Vin(max)

where:

η is efficiency of system;

VIN(max) is maximum input voltage;

Vf is forward drop voltage of LED; and

n is LED number in series connection.

(1)

Current Limit

Average

LED Current

ton toff

Dmin 1-Dmin

(a) DCM Mode

Current peak at LED average

current maximum point

(ILED(ave.peak))

DCM

Current peak at LED current

maximum point (ILED(peak))

Average

LED Current (ILED(ave))

0.5∆i

∆i

0.5∆i

DCM

CCM

Current min at LED current

maximum point (ILED(min))

Dmin

ton toff

1-Dmin

(b) CCM Mode

Figure 8. DCM and CCM Operation

In DCM Mode, inductance is:

Lm



n V f  (1  Dmin )

f s   irip

[H ]

(2)

If the peak current is fixed at 350 mApk, the formula for

the peak current is:

I LED(ave. peak)



 icon



 irip

2

[A]

(3)

In FL7701, the LED RMS current determines the

inductance parameter. To drive for CCM Mode, define

LED RMS current first, as:

[A]I  I 2LED(rms)

LED(ave. peak)

(4)

Substituting Equation (2) for Equation (4), the

inductance of inductor is obtained.

VIN

Vbridge

ZCD

DAC

VLED

Vdrain

Π 2Π 3Π

Bridge Diode

Output Voltage

Input Voltage

Peak

Vdd Charging

Voltage

Input Voltage

Peak

4Πt

t

t

t

t

ILED Input Voltage

Peak

t

t

IFRD

IMOSFET

t

Iinput

t

t

T/2 = 1/(Input Frequency * 2)

T = 1/Input Ferquency

Figure 9. Typical Performance Characteristics

© 2011 Fairchild Semiconductor Corporation

FL7701 • Rev. 1.0.4

7

www.fairchildsemi.com

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