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PDF FAN7346M Data sheet ( Hoja de datos )
| Número de pieza | FAN7346M | |
| Descripción | 4-Channel LED Current Balance Controller | |
| Fabricantes | Fairchild Semiconductor | |
| Logotipo |  |
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May 2011
FAN7346
4-Channel LED Current Balance Controller
Features
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
Applications
LED BLU for LCD TV
LED BLU for LCD Monitor
LED Lighting
Description
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.
Ordering Information
Part Number
Operating
Temperature
FAN7346M
FAN7346MX
-40 to +125°C
Package
Packing Method
28-Lead, Small-Outline Integrated Circuit (SOIC)
Rail
Tape & Reel
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
www.fairchildsemi.com
1 page  
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
Under-Voltage Lockout Section (UVLO)
Vth Start Threshold Voltage
Vthhys
Start Threshold Voltage Hysteresis
Ist Startup Current
Iop Operating Supply Current
ON/OFF Section
VIN=8V
VIN=12V, Not Switching
Von On-State Input Voltage
Voff Off-Stage Input Voltage
RENA
Pull-Down Resistor
Reference Section (Recommend 1µF X7R Capacitor)
VREF
5V Regulation Voltage
IREF=0mA
VR-LINE 5V Line Regulation
VR-LOAD 5V Load Regulation
VDD 8.5V Regulation Voltage
LED Current Section
10 VIN 35V
0 IREF 3mA
VIN=12V
VFBX
CH LED Current Reference Voltage VADIM=2V
VLREF LED Current Reference Voltage
0.5V VADIM 4V
VADIM-CLAMPH ADIM Voltage HIGH Clamping Voltage
VADIM-CLAMPL ADIM Voltage LOW Clamping Voltage
BCH Current Balance Between Channels
Headroom Voltage Feedback Section
VIN=12V
VIN=12V
VADIM=2V
VFBR
Ileak
AV
Gm
Feedback Reference Voltage
Channel Leakage Current
Open-Loop Gain(3)
Error Amplifier Transconductance
PWM ON, VCH=1V
PWM OFF, VCH=30V
VVMIN=1V
VVMIN=1.5V
lsin Output Sink Current
lsur Output Source Current
VVMIN=0V
VVMIN=2V
Min. Typ. Max. Unit
8.5 9.5 10.5 V
0.5 1.0 1.5
V
100 300
µA
1 3 mA
1.4 5.0 V
0.7 V
130 200 270 kΩ
4.9 5.0 5.1
V
50 mV
50 mV
8.0 8.5 9.0
V
194
3.84
0.45
-1.5
200
VADIM
/10
4.00
0.50
206
4.16
0.55
1.5
mV
V
V
%
0.95 1.00 1.05
V
0 100 µA
0 2 µA
65 dB
140 180 220 µmho
70 120 170 µA
70 120 170 µA
Continued on the following page…
© 2011 Fairchild Semiconductor Corporation
FAN7346 • 1.0.0
5
www.fairchildsemi.com
5 Page 
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 shows the work-flow of startup sequence.
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.
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, soft-
start function is not started. If OVR voltage is higher than
0.9V, the FAN7346 starts LED current balance and soft-
start. 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.
Figure 27. Startup Sequence
2. Feedback
After soft-start, the FAN7346 starts feedback drain-
voltage of external balance switch.
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.
If minimum drain voltage is higher than 1V, FB is pulled
LOW. If minimum drain voltage is lower than 1V, FB is
pulled HIGH.
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.
Internal reference voltage is decided by ADIM voltage.
The formula for LED current calculation is:
I
V
A DIM
LE D
1
0R
SENSE
(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
11
www.fairchildsemi.com
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet FAN7346M.PDF ] | |
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