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Rev. 1.0.1

Features

· High Efficiency Single Stage Power Conversion
· Wide Input Voltage Range 5V to 24V
· Back Light Lamp Ballast and Soft Dimming
· Reduce External Components
· Precision Voltage Reference Trimmed to 2%
· ZVS full-bridge topology
· Soft Start
· PWM Control at fixed frequency
· Analog and Burst Dimming Function
· Synchronizable Switching Frequency With An External

Signal

· Open Lamp Protection
· Open Lamp Regulation
· 20 Pin SSOP

Description

The FAN7310 provides all the control functions for a
series parallel resonant converter and also contains a pulse
width modulation (PWM) controller to develop a supply
voltage. Typical operating frequency range is between
30kHz and 250kHz depending on the CCFL and the
transformer's characteristics.
The FAN7310 has a patent-pending on new phase-shift
control.

20-SSOP

FAN7310

LCD Back Light Inverter Drive IC

FAN7310

Internal Block Diagram

BDIM

S_S

EA_OUT

OSCILLATOR

Error Amp.

EA_IN

6uA

max. 2V

min. 0.5V

ADIM

OUTB

OUTA

OUTC

OUTD

VIN

2.5VREF

ENA

UVLO 5V

UVLO

REF

BCT

max. 2V

min. 0.5V

OLR

1.4V

Solr

SET

CLR

UVLO

OLP

PGND

Sburst

Voltage

Reference

Internal

Bias

VIN

1.4uA

2.7V

UVLO

Output

Driver

Output

Control

Logic

AGND

S_S

Solr 105uA

Sburst 85uA

Output

Driver

SYNC

FAN7310

Pin Assignments

Pin Definitions

Name

Function Description

Name

Function Description

OLP

Open Lamp Protection

BCT

Burst Dimming Timing Capacitor

OLR

Open Lamp Regulation

Timing Resistor

ENA

Enable Input

Timing Capacitor

S_S

Soft Start

OUTD

NMOSFET Drive Output D

GND

Analog Ground

OUTC

PMOSFET Drive Output C

REF

2.5V Reference Voltage

PGND

Power Ground

ADIM

Analog Dimming Input

VIN

Supply Voltage

BDIM

Burst Dimming Input

OUTA

PMOSFET Drive Output A

EA_IN

Error Amplifier Input

OUTB

NMOSFET Drive Output B

EA_OUT

Error Amplifier Output

SYNC

Sychronization Input/Output

FAN7310

OLP

OLR

ENA

S_S

OUTC

REF

ADIM

BDIM

EA_IN EA_OUT

SYNC

OUTB

OUTA

VIN

PGND

OUTD

BCT

GND

FAN7310

Absolute Maximum Ratings

For typical values Ta=25

C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with

-25

C and 5V

Vcc

24V, unless otherwise specified.

Note:
1. Thermal resistance test board

Size: 76.2mm * 114.3mm * 1.6mm(1S0P)
JEDEC standard: JESD51-3, JESD51-7

2. Assume no ambient airflow

Characteristics

Symbol

Value

Unit

Supply Voltage

5 ~ 24

Operating Temperature Range

Topr

-25 ~ 85

Storage Temperature Range

Tstg

-65 ~ 150

Thermal Resistance Junction-Air (Note1,2)

112

C/W

Power Dissipation

1.1

FAN7310

Electrical Characteristics

For typical values Ta=25

C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with

-25

C and 5V

Vcc

24V, unless otherwise specified.

Characteristics

Symbol

Test Condition

Min.

Typ.

Max.

Unit

REFERENCE SECTION
Line Regulation

Vref

24V

2.5V Regulation Voltage

V25

2.45

2.5

2.55

OSCILLATOR SECTION(MAIN)

Oscillation Frequency

fosc

Ta = 25

C, Ct = 270pF

Rt = 18k

108

115

122

kHz

Ct = 270pF, Rt = 18k

106

115

124

CT High Voltage

Vcth

2.0

CT Low Voltage

Vctl

0.5

OSCILLATOR SECTION(BURST)
Oscillation Frequency

fosc

Ctb = 10nF, Rt=18k

195

225

255

BCT High Voltage

Vbcth

BCT Low Voltage

Vbctl

0.5

ERROR AMP SECTION
Open Loop Gain

Unit Gain Bandwidth

1.5

MHz

Feedback Output High Voltage

Veh

EA_IN = 0V

2.5

Output Sink Current

lsin

EA_OUT = 1.5V

-1

Output Source Current

lsur

EA_OUT = 1.5V

EA_IN Driving Current On OLR

Iolr

105

135

EA_IN Driving Current On Burst Dimming

Iburst

109

Feedback High Voltage On Burst Dimming

Vfbh

R(EA_IN) = 60k

Va+0.1 Va+0.4 Va+0.7

SOFT START SECTION
Soft Start Current

S_S=2V

Soft Start Clamping Voltage

Vssh

PROTECTION SECTION
Open Lamp Protection Voltage

Volp

1.75

2.25

Open Lamp Regulation Voltage

Volr

1.75

2.25

Open Lamp Protection Charging Current

Iolp

0.7

1.4

2.1

UNDER VOLTAGE LOCK OUT SECTION
Start Threshold Voltage

Vth

Start Up Current

Ist

= Vth-0.2

130

Operating Supply Current

Iop

= 12V

1.5

Stand-by Current

Isb

= 12V

200

ON/OFF SECTION
On State Input Voltage

Von

Off Stage Input Voltage

Voff

0.7

FAN7310

Electrical Characteristics

(Continued)

For typical values Ta=25

C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with

-25

C and 5V

Vcc

24V, unless otherwise specified.

Characteristics

Symbol

Test Condition

Min.

Typ.

Max.

Unit

OUTPUT SECTION
PMOS Gate High Voltage

Vpdhv

= 12V

Vcc

PMOS Gate Low Voltage

Vphlv

= 12V

Vcc-10.5 Vcc-8.5 Vcc-6

NMOS Gate Drive Volgate

Vndhv

= 12V

8.5

10.5

NMOS Gate Drive Volgate

Vndhv

= 12V

PMOS Gate Voltage With UVLO
Activated

Vpuv

= Vth-0.2

Vcc-0.3

NMOS Gate Voltage With UVLO
Activated

Vnuv

= Vth-0.2

0.3

Rising Time

= 12V

200

500

Falling Time

= 12V

200

500

MAX./MIN OVERLAP
Min. Overlap between diagonal
switches

fosc=100KHz

Max. Overlap betwwen diagonal
switches

fosc=100KHz

100

DELAY TIME
PDR_A/NDR_B

Rt=18k

450

PDR_C/NDR_D

Rt=18k

450

FAN7310

Function Description

UVLO : The under voltage lockout circuit guarantees
stable operation of the IC's control circuit by stopping
and starting it as a function of the Vin value. The UVLO
circuit turns on the control circuit when Vin exceeds 5V.
When Vin is lower than 5V, the IC's standby current is
less than 200uA.

ENA : Applying the voltage higer than 2V to ENA pin
enables the operation of the IC. Applying to the voltage
lower than 0.7V to ENA pin will disable the operation of
the inverter.

Soft start :The soft start function is provided that S_S
pin is connected through a capacitor to GND. A soft
start circuit ensures a gradual increase in the input and
output power. The capacitor connected to S_S pin
determines the rate of rise of the duty ratio. It is
charged by a current source of 6uA.

Main oscillator : Timing capacitor CT are charged by
the reference current source, formed by the timing
resistor Rt whose voltage is regulated at 1.25V. The
sawtooth waveform charges up to 2V. Once reached,
capacitors begin discharging down to 0.5V. Next timing
capacitors start charging again and a new switching
cycle begins. The main frequency can be programmed
with adjusting the values of Rt and CT. The main fre-
quency can be calculated as below.

Burst oscillator & burst dimming :Timing capacitor
BCT are charged by the reference current source,
formed by the timing resistor Rt whose voltage is regu-
lated at 1.25V. The sawtooth waveform charges up to
2V. Once reached, capacitors begin discharging down
to 0.5V. Next timing capacitors start charging again and
a new switching cycle begins. The burst dimming fre-
quency can be programmed with adjusting the values
of Rt and BCT. The burst dimming frequency can be
calculated as below.

The burst dimming frequency should be greater than
120Hz to avoid visible flicker.

To compare the input of BDIM pin with the 0.5~2V trian-
gular wave of burst oscillator makes the PWM pulse for
burst dimming. The PWM pulse controls EA_OUT's
voltage by summing 85uA into EA_IN pin.

fop =

32 RT CT

-------------------------------

fburst =

3.75

64 RT BCT

-----------------------------------

FAN7310

Open lamp regulation & open lamp protection : It is
necessary to suspend power stage operation if an open
lamp occurs, because the power stage has high gain.
When a voltage higher than 2V is applied to the OLR
pin, the part enters the regulation mode and controls
EA_OUT voltage to limit the lamp voltage by summing
105uA into the feedback node. At the same time, the
OLP capacitor, connected to the OLP pin, is charged by
the 1.4uA internal current source. Once reached to 2V,
IC enters shut down where all the output is high.

SYNC: This pin is used as the frequency synchroniza-
tion. The switching frequency can be synchronized with
an external control signal.

OUTPUT DRIVES: The four output drives are designed

so that switches A and B, C and D never turn on

simultaneously. The OUTA-OUTB pair is intended to

drive one half-bridge in the external power stage. The

OUTC-OUTD pair will drive the other half-bridge.

FAN7310

Typical Application Circuit

330k

OUTD

C6 1u

C28

10n

IC1 FAN7310

S_S

GND

REF

OLR

ENA

BDIM

OLP

VIN

OUTA

PGND

OUTB

SYNC

OUTC

ADIM

EA_IN

EA_OUT

OUTD

BCT

OLP1

R15

OUTB

C4 6.8n

CCFL

REF

C21
10n

OLR

10u

4.7n

VCC

D11

D1N4148

OLP1

BAV99

R26

10k

C25

100u

R5 27k

C19

2.2n

R9
8.2k

100k

D1N4148

OLP

FDS8958A

OLR

R24

10k

R16

1.5k

C1 1u

FDS8958A

R22

10k

C10

15p

DIM(0~3.3V)

C26

C14
20n

C27

REF

R14

100k

OUTA

100k

R3
20k

R25

10k

C16

2.2n

OUTC

56k

BAV99

22k

KST2222

C22

ENA

TX1

C5 220p

FAN7310

10/6/04 0.0m 001

Stock#DSxxxxxxxx

2004 Fairchild Semiconductor Corporation

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which, (a) are intended for surgical implant into the body,

or (b) support or sustain life, and (c) whose failure to

perform when properly used in accordance with
instructions for use provided in the labeling, can be

reasonably expected to result in a significant injury of the

user.

2. A critical component in any component of a life support

device or system whose failure to perform can be

reasonably expected to cause the failure of the life support

device or system, or to affect its safety or effectiveness.

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PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY
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Ordering Information

Product number

Package

Operating Temperature

FAN7310G

20-SSOP

-25

C ~ 85

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