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FAN7346
4-Channel LED Current Balance Controller
Features
Description
Linear Balance Control for 4-Channel LED Arrays
Wide LED String Voltage Range: 100V
Wide VCC Voltage: 10.5V to 35V
External Linear Regulation Switch: MOSFET or BJT
Internal Voltage Regulator for Feedback
Monitoring Drain-Source Voltage of External Switch
Precision Current Accuracy Trimmed to 1.5%
Supports External PWM Dimming - Positive
Supports Wide Dimming Ratio: 0.5%~100%
Adaptive Linear Regulation Method
Generate Integrated Feedback Signal for Primary
Controller (Current Feedback + PWM Dimming)
High Efficiency by Primary Side Direct Feedback
Thermal Shutdown (Auto-Recovery)
Over-Voltage Regulation
Channel Individual Open-LED Protection
Channel Individual Short-LED Protection
Channel Individual Over-Current Protection
Error Flag Output
28-Pin SOIC
The FAN7346 is an LED current-balance controller that
controls 4-LED arrays to maintain equal LED current.
The FAN7346 has a high withstanding voltage, so is
suitable for edge-type LED BLU and LED Lighting. To
minimize components between primary to secondary, the
FAN7346 generates a new integrated feedback signal.
The FAN7346 provides various protections, such as
over-voltage regulation, open-LED protection, thermal
protection, and drain-source voltage protection of
regulating switch (the FAN7346 monitors all LED arrays
drain-source voltage for protection). To increase system
reliability, FAN7346 applies individual string protection.
Because FAN7346 integrates so many functions it
reduces overall BOM costs.
LED brightness can be linearly varied up to LED current
by applying an external Pulse Width Modulated (PWM)
signal to the PWM pin.
The FAN7346 is available in a 28-SOIC package.
Applications
LED BLU for LCD TV
LED BLU for LCD Monitor
LED Lighting
Ordering Information
Part Number
FAN7346M
FAN7346MX
Operating
Temperature
Package
-40 to +125°C
28-Lead, Small-Outline Integrated Circuit (SOIC)
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
Packing Method
Rail
Tape & Reel
www.fairchildsemi.com
FAN7346 — 4-Channel LED Current Balance Controller
May 2011
FAN7346 — 4-Channel LED Current Balance Controller
Block Diagram
Figure 1. Internal Block Diagram
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
2
Figure 2. Package Diagram
Pin Definitions
Pin #
Name
Description
1
OVR
2
FB
3
CMP
This pin is for compensation of the minimum channel voltage feedback.
4
VMIN
Synchronous signal of channel drain-voltage. If multiple controllers are operated, this pin
must be tied together. In single operation, this pin must be open.
5
FO
6
PWM4
PWM dimming signal input pin of channel 4.
7
PWM3
PWM dimming signal input pin of channel 3.
8
PWM2
PWM dimming signal input pin of channel 2.
9
PWM1
PWM dimming signal input pin of channel 1.
This pin is input for over-voltage regulation.
This pin is for feedback of minimum drain voltage of external current regulation switch. This
pin is externally connected to the cathode of the feedback photo-coupler.
This pin is fault output. In case of OLP, SLP, and OCP; this pin is connected to ground.
10
ENA
Enable input.
11
ADIM
This pin is for the reference voltage of the LED current feedback voltage.
12
SLPR
This pin is for setting the reference of channel over-voltage protection (short-LED protection).
13
REF
This pin is the reference output. Voltage is 5V; current capability is 3mA.
14
VCC
This pin is the supply voltage of the controller.
15
FB4
This pin is for current sensing feedback of channel 4.
16
VDD
Internal gate driver power supply voltage. A large capacitor (1µF~2µF) must be connected
from this pin to ground.
17
OUT4
This pin is for gate signal to the external balance FET of channel 4.
18
CH4
This pin is for drain voltage of the external balance FET of channel 4.
19
FB3
This pin is for current sensing feedback of channel 3.
20
OUT3
21
CH3
This pin is for drain voltage of the external balance FET of channel 3.
22
FB2
This pin is for current sensing feedback of channel 2.
23
OUT2
24
CH2
This pin is for drain voltage of the external balance FET of channel 2.
25
FB1
This pin is for current sensing feedback of channel 1.
26
OUT1
27
CH1
This pin is for drain voltage of the external balance FET of channel 1.
28
GND
This pin is the ground.
This pin is for gate signal to the external balance FET of channel 3.
This pin is for gate signal to the external balance FET of channel 2.
This pin is for gate signal to the external balance FET of channel 1.
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
3
FAN7346 — 4-Channel LED Current Balance Controller
Pin Configuration
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
VIN
IC Supply Voltage
10.5
35.0
V
TA
Operating Temperature Range
-40
+125
C
TJ
Operating Junction Temperature
+150
C
+150
C
70
C/W
1.4
W
TSTG
Storage Temperature Range
-65
θJA
Thermal Resistance Junction-Air
PD
Power Dissipation
(1,2)
Notes:
1. Thermal resistance test board. Size: 76.2mm x 114.3mm x 1.6mm (1S0P); JEDEC standard: JESD51-2, JESD51-3.
2. Assume no ambient airflow.
Pin Breakdown Voltage
Pin #
Name
Value
1
OVR
6
15
FB4
6
2
FB
6
16
VDD
17
3
CMP
6
17
OUT4
17
4
VMIN
6
18
CH4
100
5
FO
6
19
FB3
6
6
PWM4
6
20
OUT3
17
7
PWM3
6
21
CH3
100
8
PWM2
6
22
FB2
6
9
PWM1
6
23
OUT2
17
10
ENA
6
24
CH2
100
11
ADIM
6
25
FB1
6
12
SLPR
6
26
OUT1
17
13
REF
6
27
CH1
100
14
VCC
35
28
GND
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
Unit
Pin #
V
Name
Value
Unit
V
www.fairchildsemi.com
4
FAN7346 — 4-Channel LED Current Balance Controller
Absolute Maximum Ratings
For typical values; TA = 25°C, VIN = 12V, and -25°C TA 85°C, unless otherwise specified. Specifications to -40°C ~
125°C are guaranteed by design based on final characterization results.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
Start Threshold Voltage
8.5
9.5
10.5
V
Start Threshold Voltage Hysteresis
0.5
1.0
1.5
V
100
300
µA
1
3
mA
5.0
V
0.7
V
Under-Voltage Lockout Section (UVLO)
Vth
Vthhys
Ist
Startup Current
VIN=8V
Iop
Operating Supply Current
VIN=12V, Not Switching
ON/OFF Section
Von
On-State Input Voltage
Voff
Off-Stage Input Voltage
RENA
1.4
Pull-Down Resistor
130
200
270
kΩ
4.9
5.0
5.1
V
Reference Section (Recommend 1µF X7R Capacitor)
VREF
5V Regulation Voltage
IREF=0mA
VR-LINE
5V Line Regulation
10 VIN 35V
50
mV
VR-LOAD
5V Load Regulation
0 IREF 3mA
50
mV
8.5V Regulation Voltage
VIN=12V
8.0
8.5
9.0
V
194
200
206
mV
VDD
LED Current Section
VFBX
CH LED Current Reference Voltage
VADIM=2V
VLREF
LED Current Reference Voltage
0.5V VADIM 4V
VADIM
/10
V
VADIM-CLAMPH ADIM Voltage HIGH Clamping Voltage
VIN=12V
3.84
4.00
4.16
VADIM-CLAMPL ADIM Voltage LOW Clamping Voltage
VIN=12V
0.45
0.50
0.55
VADIM=2V
-1.5
BCH
Current Balance Between Channels
V
1.5
%
1.05
V
Headroom Voltage Feedback Section
VFBR
Feedback Reference Voltage
Ileak
Channel Leakage Current
(3)
0.95
1.00
PWM ON, VCH=1V
0
100
µA
PWM OFF, VCH=30V
0
2
µA
AV
Open-Loop Gain
VVMIN=1V
65
dB
Gm
Error Amplifier Transconductance
VVMIN=1.5V
140
180
220
µmho
lsin
Output Sink Current
VVMIN=0V
70
120
170
µA
lsur
Output Source Current
VVMIN=2V
70
120
170
µA
Continued on the following page…
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
5
FAN7346 — 4-Channel LED Current Balance Controller
Electrical Characteristics
For typical values; TA = 25°C, VIN = 12V, and -25°C TA 85°C, unless otherwise specified. Specifications to -40°C ~
125°C are guaranteed by design based on final characterization results.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
PWM Dimming Section
Vbdim(ON)
PWM Dimming On Voltage
2
5
V
Vbdim(Off)
PWM Dimming Off Voltage
0
0.8
V
100
500
Hz
fbdim
PWM Dim Input Frequency Range(3)
On Duty Ratio=1%
tbdimR
(3)
PWM Dim On Rising Time
Ext. Switch Qg=4.3nC
400
ns
tbdimF
PWM Dim Off Falling Time(3)
Ext. Switch Qg=4.3nC
150
ns
VOVR=1V, ILED: 0 to
Maximum
10
ms
Soft-Start Section
tSS
Soft-Start Time(3)
Protection Section
VTH,OVR
OVR Threshold Voltage
1.35
1.42
1.49
VTH,OCP
OCP Threshold Voltage
0.95
1.00
1.05
TOCP
OCP Shutdown Time(3)
VTH,SLP
SLP Threshold Voltage
TD,SLP
(3)
20
µs
(3)
20
µs
10
VSLPR=1V
9.5
SLP Delay
TD,OLP
OLP Delay
VTH,OLP
OLP Threshold Voltage
0.27
10.0
0.30
V
V
µs
10.5
0.33
V
V
TTRIP
Internal Thermal Protection
(3)
Threshold
150
°C
TTYH
Internal Thermal Protection
(3)
Hysteresis
25
°C
Output Section
VGH
NMOS Gate High Voltage
VIN=12V
VGL
NMOS Gate Low Voltage
VIN=12V
NMOS Gate Voltage with UVLO
Activated
VIN=7V
NMOS Gate Drive Source Current
VIN=12V
50
NMOS Gate Drive Sink Current
VIN=12V
300
VG,UVLO
IG,SOURCE
IG,SINK
8.0
8.5
9.0
0
V
V
0.3
V
150
250
mA
500
700
mA
Note:
3. These Parameters, although guaranteed, are not 100% tested in production.
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
6
FAN7346 — 4-Channel LED Current Balance Controller
Electrical Characteristics (Continued)
1.6
11
10
1.2
Vthhys [V]
1.4
Vth [V]
10.5
9.5
9
1
0.8
8.5
0.6
8
0.4
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature [Ԩ]
50
75
100
125
Temperature [Ԩ]
Figure 3. Start Threshold Voltage vs. Temperature
Figure 4. Start Threshold Voltage Hysteresis
vs. Temperature
350
3.5
300
3
250
2.5
Iop [mA]
Ist [µA]
25
200
150
100
2
1.5
1
50
0.5
0
0
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature [Ԩ]
25
50
75
100
125
Temperature [Ԩ]
Figure 5. Startup Current vs. Temperature
Figure 6. Operating Current vs. Temperature
1.5
300
1.4
Rena [KΩ]
Vonth [V]
1.3
1.2
1.1
1
250
200
0.9
150
0.8
0.7
0.6
100
-50
-25
0
25
50
75
100
125
-50
Temperature [Ԩ]
0
25
50
75
100
125
Temperature [Ԩ]
Figure 7. Enable Threshold Voltage vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
-25
Figure 8. Pull-Down Resistor vs. Temperature
www.fairchildsemi.com
7
FAN7346 — 4-Channel LED Current Balance Controller
Typical Performance Characteristics
5.15
9.2
5.1
9
8.8
VDD [V]
VREF [V]
5.05
5
8.6
8.4
4.95
8.2
4.9
8
4.85
7.8
-50
-25
0
25
50
75
100
125
-50
-25
0
25
Temperature [Ԩ]
100
125
Figure 10. 8.5V Regulation Voltage vs. Temperature
8
4.18
6
4.14
VADIM-CLAMPH [V]
4
Vofs [mV]
75
Temperature [Ԩ]
Figure 9. 5V Regulation Voltage vs. Temperature
2
0
-2
-4
-6
4.1
4.06
4.02
3.98
3.94
3.9
3.86
-8
-50
-25
0
25
50
75
100
3.82
125
-50
-25
0
Temperature [Ԩ]
25
50
75
100
125
Temperature [Ԩ]
Figure 11. Offset of CH LED Current Reference Voltage
vs. Temperature
Figure 12. ADIM HIGH Clamping Voltage
vs. Temperature
0.57
2
0.55
1.5
1
0.53
BCH [%]
VADIM-CLAMPL [V]
50
0.51
0.49
0.47
0.5
0
-0.5
-1
0.45
-1.5
0.43
-2
-50
-25
0
25
50
75
100
125
-50
Temperature [Ԩ]
0
25
50
75
100
125
Temperature [Ԩ]
Figure 13. ADIM LOW Clamping Voltage
vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
-25
Figure 14. Current Balance Between Channels
vs. Temperature
www.fairchildsemi.com
8
FAN7346 — 4-Channel LED Current Balance Controller
Typical Performance Characteristics (Continued)
1.04
220
1.02
200
Gm [µMho]
240
VFBR [V]
1.06
1
0.98
0.96
180
160
140
0.94
120
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature [Ԩ]
160
160
140
140
ISUR [µA]
ISIN [µA]
180
120
100
80
80
60
60
25
50
75
100
-50
125
-25
0
125
25
50
75
100
125
Temperature [Ԩ]
Temperature [Ԩ]
Figure 17. Error Amplifier Output Sink Current vs.
Temperature
Figure 18. Error Amplifier Output Source current vs.
Temperature
2.1
1.5
1.9
1.48
1.46
1.7
VTH,OVR [V]
Vbdim(th) [V]
100
120
100
0
75
Figure 16. Error Amplifier Transconductance
vs. Temperature
180
-25
50
Temperature [Ԩ]
Figure 15. Feedback Reference Voltage
vs. Temperature
-50
25
1.5
1.3
1.44
1.42
1.4
1.1
1.38
0.9
1.36
1.34
0.7
-50
-25
0
25
50
75
100
-50
125
0
25
50
75
100
125
Temperature, [Ԩ]
Temperature, [Ԩ]
Figure 19. PWM Dimming On Threshold Voltage
vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
-25
Figure 20. OVR Threshold Voltage vs. Temperature
www.fairchildsemi.com
9
FAN7346 — 4-Channel LED Current Balance Controller
Typical Performance Characteristics (Continued)
10.6
1.1
10.4
VTH,SLP [V]
VTH,OCP [V]
1.05
1
10.2
10
9.8
0.95
9.6
9.4
0.9
-50
-25
0
25
50
75
100
-50
125
-25
0
50
75
100
125
Temperature [Ԩ]
Temperature [Ԩ]
Figure 21. OCP Threshold Voltage vs. Temperature
Figure 22. SLP Threshold Voltage vs. Temperature
0.34
9.2
0.33
9
0.32
8.8
0.31
VGH [V]
VTH,OLP [V]
25
0.3
8.6
8.4
0.29
8.2
0.28
8
0.27
7.8
0.26
-50
-25
0
25
50
75
100
-50
125
-25
0
25
75
100
125
Temperature [Ԩ]
Temperature [Ԩ]
Figure 23. OLP Threshold Voltage vs. Temperature
Figure 24. NMOS Gate High Voltage vs. Temperature
250
700
200
600
IG,SINK [mA]
IG,SOURCE [mA]
50
150
100
50
500
400
300
0
200
-50
-25
0
25
50
75
100
125
-50
Temperature [Ԩ]
0
25
50
75
100
125
Temperature [Ԩ]
Figure 25. NMOS Gate Drive Source Current
vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
-25
Figure 26. NMOS Gate Drive Sink Current
vs. Temperature
www.fairchildsemi.com
10
FAN7346 — 4-Channel LED Current Balance Controller
Typical Performance Characteristics (Continued)
FAN7346 — 4-Channel LED Current Balance Controller
Functional Description
The FAN7346 is a high-efficiency 4-channel LED driver.
It can drive a 4-channel LED string with four external
balance switches. It provides an integrated feedback for
a DC-DC controller on the secondary side or on the
flyback / LLC controller of the primary side.
Due to the high withstanding voltage of the sensing pin
for drain voltage of external switch, the FAN7346 can be
used in high-voltage LED string operation without any
clamping circuit. Both MOSFET and transistor can be
used as external balance switch, so the FAN7346 can
drive a high-current LED string.
For four-string operation, the FAN7346 supports four
individual PWM signal input pins. The FAN7346 can be
operated by parallel connection mode.
For a primary-side direct-power control system, the
FAN7346 supports an advanced power sequence and
soft-start timing. LED driving voltage can be set before
LED ignition for a reliable LED backlight ignition.
The FAN7346 supports various and programmable
protections; Short-LED Protection (SLP), Open-LED
Protection (OLP), Over-Current Protection (OCP), and
Over-Voltage Regulation (OVR). Except OCP, all
protection are auto-recovery / auto-restart. Except OVR,
all protections are channel-individual protection. In case
of SLP, OLP and OCP; even if some strings are in
protection condition, other strings continues to operating
for higher system reliability.
Figure 27. Startup Sequence
2. Feedback
After soft-start, the FAN7346 starts feedback drainvoltage of external balance switch.
Figure 27 shows the work-flow of startup sequence.
Drain voltage of each channel is sensed on the CHx pin.
CHx means any of the CH1 / CH2 / CH3 / CH4 pins.
Minimum drain voltage is selected between four CHx
voltages. The FAN7346 feeds back drain voltage to
control minimum drain voltage at 1V.
1. Startup
When VCC voltage is higher than UVLO threshold
voltage, internal 5V regulation output is operated. At the
same time, feedback starts to control OVR voltage as 1V.
If OVR voltage is lower than 1V, feedback is pulled up. If
OVR voltage is higher than 1V, feedback is pulled down.
If minimum drain voltage is higher than 1V, FB is pulled
LOW. If minimum drain voltage is lower than 1V, FB is
pulled HIGH.
After enable is applied, the FAN7346 begins soft-start
procedure. The FAN7346 checks if OVR voltage is
higher than 0.9V. If OVR voltage is lower than 0.9V, softstart function is not started. If OVR voltage is higher than
0.9V, the FAN7346 starts LED current balance and softstart. The LED current of each string is increased
gradually for 10ms, which is fixed soft-start timing. During
soft-start timing, SLP and OLP are disabled.
Feedback response can be controlled by adding a
resistor and capacitor to the CMP pin.
3. Analog Dimming
In the FAN7346, LED current can be modified by
changing ADIM voltage.
LED current is controlled by the FBx pin voltage. FBx
means any of the FB1 / FB2 / FB3 / FB4 pins. External
current balance switch is operating in the saturation
region to control LED current. Sensed voltage on the FBx
pin is compared with internal reference voltage and the
controller supplies a gate / base signal for the external
current balance switch.
M
I
D
D
E
IL
E
S
N
E
S
AR
V
0
1
Internal reference voltage is decided by ADIM voltage.
The formula for LED current calculation is:
(1)
ADIM voltage is clamped internally from 0.5V to 4V. If
ADIM voltage is lower than 0.5V, it is clamped as 0.5V. If
ADIM voltage is higher than 4V, it is clamped as 4V.
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
11
If PWM dimming voltage is higher than 2V, an external
balance switch is turned on and conducts constant
current operation. If PWM dimming voltage is lower than
0.8V, an external balance switch is turned off and blocks
LED current.
LED Current
Output
CHx Voltage
During PWM dimming off, open-LED protection and
short-LED protection is disabled.
CHx drain voltage is sampled during PWM dimming on
and held during PWM dimming off to maintain drain
voltage regardless of dimming on/off signal.
5. Short-LED Protection (SLP)
To sense a short-LED condition, the FAN7346 uses the
drain voltage of external balance switch. If some LEDs
are shorted, its LED forward voltage is lower than other
LED strings, so the drain voltage of the external balance
switch is higher than other drain voltage.
6. Open LED Protection (OLP)
To sensing open-LED condition, the FAN7346 use the
drain voltage of an external balance switch. If an LED
string is open, the drain voltage of external balance
switch is grounded, and the FAN7346 can detect openLED condition. OLP threshold voltage is 0.3V.
If CHx voltage is lower than 0.3V for 20µs, its drainvoltage feedback is pulled up to 5V. This means the open
LED string is eliminated from minimum drain voltage
feedback loop. Without OLP, if minimum drain voltage is
0V, drain voltage feedback forces the FB signal to
increase output power. This can cause SLP or thermal
stress in other channels.
R
P
L
S
V
*
0
1
H
T
P
L
S
V
SLP
Figure 28. Short-LED Protection Operation
SLP threshold voltage can be programmed by SLPR
(Short-LED Protection Reference) voltage. Internal SLP
threshold voltage is calculated as:
︳
SLPR
Normal
(2)
Minimum SLP threshold voltage is 0V and maximum SLP
threshold voltage is 45V.
SLP is a channel-individual protection. If any string is in
SLP condition, the SLP strings is turned off and other
string operate normally.
OLP is an auto-recovery protection. As soon as drain
voltage is higher than 0.3V, OLP is finished and the drain
voltage feedback system is restored.
If the sensed-drain voltage (CHx voltage) is higher than
the programmed threshold voltage for 20µs, CHx goes into
short-LED protection, which forces the corresponding
channel to turn off. To increase reliability, the SLP channel
is restarted in the next PWM dimming signal rising timing.
After restarting, the FAN7346 checks the drain voltage. If
the drain voltage is higher than the SLP threshold voltage
for 20µs, the switch is turned off. If drain voltage is lower,
the channel is restored to normal operation. Shorted LED
channel operation is minimum duty PWM dimming with a
20µs dimming on period. During 100% full duty PWM
dimming, auto restart is not activated.
Figure 29 shows the OLP operation. Before open CH2,
CH2 is the headroom channel. (CH2 drain voltage is
minimum voltage – 1V.) As soon as open CH2, its drain
voltage is 0V, OLP is activated, and CH2 is removed
from headroom feedback control loop. CH1 is selected
as minimum drain voltage channel, so its drain voltage is
controlled as 1V. Reconnecting CH2 string, restores
normal operation.
Figure 28 shows the SLP operation. As soon as
SLPR*10 (blue line) is lower than CHx voltage, CHx is
forced into minimum duty dimming operation.
Output
CH2 LED Current
CH1 Drain Voltage
CH2 Drain Voltage
CH2 Open
Figure 29. Open-LED Protection Operation
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
12
FAN7346 — 4-Channel LED Current Balance Controller
4. PWM Dimming
The FAN7346 has four PWM dimming signal pins. Each
PWM dimming pin controls an LED string.
current damage. To sense over-current condition, the
FAN7346 monitors FBx (FB1~FB4) pin voltage.
If FBx voltage is higher than 1V for 20µs, CHx is
considered an over-current condition. After sensing OCP
condition, CHx dimming switch is turned off.
OCP is channel individual and latched protection. If one
channel is in OCP condition, other channels keep
operating. OCP channel is restarted after UVOL is reset.
In FAN7346, OVR voltage uses two kinds of feedback
and control: and regulating output voltage during enable
off and clamping output voltage during enable on.
9. Error Flag (FO)
To make error flag signal, the FAN7346 uses the FO pin.
FO pin is open-drain type.
When ENA pin is LOW, the FAN7346 controls FB voltage
to maintain OVR voltage as 1.0V. Through this output
voltage control during ENA off, the FAN7346 reaches
adequate LED driving voltage before turning ENA on.
During normal operation, the FO pin is open. If using an
external pull-up resistor, this signal is HIGH.
After ENA pin is HIGH, OVR pin voltage is used for overvoltage regulation. If OVR pin voltage is lower than
1.42V, the FB pin voltage follows headroom control to
maintain minimum voltage of drain voltages as 1V. If
OVR pin voltage is higher than 1.42V, the FAN7346
controls FB (FB is pulled LOW). Through feedback
regulation, OVR pin voltage cannot exceed 1.42V.
If used OLP / OCP / SLP protection, the FO pin is
connected to ground. If using an external pull-up resistor,
this signal is LOW.
If a single channel is in protection condition, error-flag
signal is detected. Only if all channels are operating
normally is the FO pin pulled HIGH.
8. Over-Current Protection (OCP)
Through over-current protection, the FAN7346 can
protect external balance switches from shorted over-
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
13
FAN7346 — 4-Channel LED Current Balance Controller
7. Over-Voltage Regulation (OVR)
To prevent LED driving voltage from exceeding the
withstanding voltage of system components, the
FAN7346 controls LED driving voltage with OVR pin
voltage. The FAN7346 senses output LED driving
voltage through the OVR pin voltage. Resistor divided
output voltage is applied to the OVR pin voltage.
FAN7346 — 4-Channel LED Current Balance Controller
Short Lamp Protection
Figure 30. Block Diagram of Short LED Protection
Figure 31. Timing Diagram of Short LED Protection
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
14
Application
Device
Input Voltage Range
LED String
32~46 Inch LED TV
FAN7346
380V
8-String / 90V / 100mA
1
2
3
4
5
6
7
8
9
10
CN3
CON10
Q4
FQT4N25
Q8
FQT4N25
R54
R58
3.9R
Q3
FQT4N25
3.9R
Q7
FQT4N25
R53
R57
3.9R
Q2
FQT4N25
3.9R
Q6
FQT4N25
R52
R56
3.9R
Q1
FQT4N25
C32
open
C31
open
C33
open
C34
open
3.9R
Q5
FQT4N25
R51
C35
open
C36
open
C37
open
C38
open
R55
3.9R
C14
OUT4
VDD
FB4
SLPR
REF
VCC
ENA
PWM1
PWM2
PWM3
PWM4
FAN7346
FO
1u
CH4
FB3
R58
0R
ADIM
OUT3
FB2
R57
0R
CH3
OUT2
FB1
CH2
VMIN
CH1
OUT1
FB
OVR
28-SOIC
R56
0R
CMP
GND
FB4
VDD
IC2
FAN7346
VCC
OUT4
REF
ADIM
ENA
PWM1
PWM2
PWM3
FO
PWM4
FAN7346
3.9R
C20
R55
0R
1u
SLPR
FB3
R38
0R
CH4
OUT3
CH3
OUT2
FB1
CH2
VMIN
CH1
OUT1
CMP
GND
5V
FB
OVR
REF1
R37
0R
FB2
R32
0R
R31
0R
IC3
FAN7346
28-SOIC
VCC2
R19
0R
R18
open
PWM3 PWM2 PWM1
U2A
R17
1
C6
1n
2
1k
ZD102
PC817A
R9
10k
REF1
PWM4
REF1
PWM7 PWM6 PWM5
C19
1n
REF2
PWM8
R13
open
100k
R25
10k
R27
10k
SOD-123
C16
1u
ENA
1u
C10
1n
R10
R11
open
VCC2
C11
ENA
10k
R720R
R12
REF2
C22
1n
R26100k
R28 open
R710R
C3
open
C203
R3
R4
C2
C1
10n
10k
R6
R24
open
open
VCC2
PWM5
PWM6
PWM7
REF1
PWM8
PWM4
R2
12k
PWM1
10n
R1
1M
C202
100uF/200V
R23
open
PWM2
100k
R5
PWM3
100uF/200V
open
open
REF2
C13
22uF/50V
C12
C201
1u
R14
22R
D212
FEP16JT
1
2
3
4
5
6
7
8
9
10
0
ENA
12
9
10
7
11
D211
FEP16JT
8
100uF/200V
TM103
EER39HS-16
C4
10n
CN6
CON10
6
5
4
3
2
1
R8
10k
C102
R7
1k
C106
MPE630V223J
1
2
3
2A224K
FSFR2100
M101
FDD5N50F
M102
FDD5N50F
R109
10k
R107
3.3R
D101
UF4007
CN5
CON3
R110
10k
R108
3.3R
D101
LMBD914
D102
LMBD914
U1
FAN7621
R113
390k
VCC1
0
14.LO
2.CTR
9.CS
U4
ZD101
2N2222
10.SG
6.CON
U5
2N2907 R112
16.PG
FAN7621
8.RT
12.LVcc
3.HO
1.HVcc
16-SOIC
R106
10R
6.8V/1N4736
C112
C103
0.33uF/25V
680pF/50V
R107
C109
25V/47uF
1.8k
R105
R101
0.1R/1W
CN6
CON3
100pF/50V
R102
C107
3
2
1
C105
10k
R114
10k
0
1k
16V / 33uF
C108
VCC1
4.7k
R109
R110
R111
1M
1M
47k
12nF/100V
R104
4
910R
3
U2B
PC817A
C101
0
220uF/450V
F2
FUSE
PFC_OUT(380Vdc)
Figure 32. LCD Backlight Driver
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
15
FAN7346 — 4-Channel LED Current Balance Controller
Typical Application Circuit (Backlight)
Application
Device
Input Voltage Range
LED String
LED Lighting
FAN7346
380V
4-String
C123
TM2
D201
C201
VLED
C202 C203
VAUX
R129
RS8
Q104
R131 R123 R132
R128
C115
R133
D109
Q103
U102
R130
D202
LVCC
VDL
CS6
RS10
R201
D203
HVCC
Q1
U201
Q4
IC1
ADIM
SLPR
ENA
RS19
RS27
RS21
RS24
RS20
RS28
CS17
RS22
RS18
RS17
RS15
RS14
R126
RS12
FB
VMIN
REF
PG
Fault
GND
FB4
OUT4
CH4
FB3
OUT3
CH3
FB2
OUT2
CH2
CS9
PWM1
C116
SG
RS32
CS13
RS25
RS31
CS11
RS23
RS30
CS10
RS16
FLS-XS
Series
Q3
VDD
PWM2
CS
CS8
PWM3
R127
RS13
FO
C125
Q2
CMP
C114
PWM4
C127
D204
RS29
PC101
R202
VCTR
FB1
AR
OUT1
C126
CH1
R134
VCC
R135
C205
OVR
R136
C206
CS7
R203
C204
C124
RT
RS11
D107
PC101
CS14
CS15
CS12
CS16
Figure 33. LED Lighting Driver
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
16
FAN7346 — 4-Channel LED Current Balance Controller
Typical Application Circuit (Lighting) (Continued)
FAN7346 — 4-Channel LED Current Balance Controller
Typical Application Circuit (Continued)
Figure 34. Multiple Controller Driving
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
17
FAN7346 — 4-Channel LED Current Balance Controller
Physical Dimensions
Figure 35. 28-Lead, Small-Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300-Inch, Wide Body
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative 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/
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
18
FAN7346 — 4-Channel LED Current Balance Controller
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
19
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