FAN5346 [FAIRCHILD]
Series Boost LED Driver with PWM Dimming Interface; 系列升压LED驱动器的PWM调光接口
| 型号： | FAN5346 |
| 厂家： | 
FAIRCHILD SEMICONDUCTOR |
| 描述： | Series Boost LED Driver with PWM Dimming Interface |
| 文件： | 总14页 (文件大小：1788K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
June 2012
FAN5346
Series Boost LED Driver with PWM Dimming Interface
Description
Features
The FAN5346 is an asynchronous constant-current LED
.
.
Asynchronous Boost Converter
Drives LEDs in Series:
driver that drives LEDs in series to ensure equal brightness
for all the LEDs. FAN5346S20X has an output voltage of
20V and can drive up to 5 LEDs in series. FAN5346S30X
has an output voltage of 30V and up to 8 LEDs in series.
Optimized for small form-factor applications, the 1.2MHz
fixed switching frequency allows the use of small inductors
and capacitors.
−
−
FAN5346S20X: 20V Output
FAN5346S30X: 30V Output
.
.
.
.
.
.
.
.
.
.
2.5V to 5.5V Input Voltage Range
PWM Dimming for LED Brightness Control
5kHz to 100kHz PWM Dimming Frequency Range
1.2MHz Fixed Switching Frequency
Soft-Start Capability
The FAN5346 uses a PWM dimming control interface to set
the brightness levels of the LEDs. A PWM signal of 5kHz to
100kHz is applied to the EN pin.
For safety, the device features integrated over-voltage, over-
current, short-circuit detection, and thermal-shutdown
protections. In addition, input under-voltage lockout
protection is triggered if the battery voltage is too low.
Input Under-Voltage Lockout (UVLO)
Output Over-Voltage Protection (OVP)
Short-Circuit Detection
The FAN5346 is available in a 6-lead SSOT23 package. It is
“green”
and
RoHS
compliant.
(Please
see
Thermal Shutdown (TSD) Protection
Small Form-Factor 6-Lead SSOT23 Package
http://www.fairchildsemi.com/company/green/index.html for
Fairchild’s definition of green).
Applications
.
.
.
.
Cellular Mobile Handsets
Mobile Internet Devices
Portable Media Players
PDA, DSC, MP3 Players
Ordering Information
Part Number
FAN5346S20X
FAN5346S30X
Output Voltage Option
Temperature Range
Package
20V
30V
6-Lead, SuperSOT™-6, JEDEC MO-193,
1.6mm Wide (MA06A)
-40 to 85°C
.
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev.1.0.1
www.fairchildsemi.com
Typical Application Diagram
Figure 1. Typical Application
Block Diagram
Figure 2. Functional Block Diagram
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
2
Pin Configuration
Figure 3. Pin Assignments, Top View
Pin Definitions
Pin #
Name
Description
Boost Output Voltage. Output of the boost regulator. Connect the LEDs to this pin. Connect COUT
(output capacitor) to GND.
5
VOUT
1
4
VIN
EN
Input Voltage. Connect to the power source and decouple with CIN to GND.
Enable Brightness Control. Program dimming levels by driving pin with the PWM signal.
Voltage Feedback. The boost regulator regulates this pin to 0.250V to control the LED string current.
Tie this pin to a current setting resistor (RSET) between GND and the cathode of the LED string.
3
FB
6
2
SW
Switching node. Tie inductor L1 from VIN to SW pin.
Ground. Tie directly to a GND plane.
GND
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
3
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.
-0.3
-0.3
-0.3
-0.3
-0.3
-0.3
Max.
6.0
Unit
V
VIN
VIN Pin
VFB, VEN FB, EN Pins
VIN + 0.3
22.0
V
FAN5346S20X
V
VSW
VOUT
ESD
SW Pin
FAN5346S30X
33.0
V
FAN5346S20X
22.0
V
VOUT Pin
FAN5346S30X
33.0
V
Human Body Model per JESD22-A114
Charged Device Model per JESD22-C101
1.5
1.5
Electrostatic Discharge Protection
kV
TJ
TSTG
TL
Junction Temperature
Storage Temperature
-40
-65
+150
+150
+260
°C
°C
°C
Lead Soldering Temperature, 10 Seconds
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
Min.
2.5
6.2
6.2
5
Max.
5.5
Unit
VIN
VIN Supply Voltage
VOUT Voltage(1)
V
FAN5346S20X
FAN5346S30X
18.5
28.5
25
VOUT
V
IOUT
TA
VOUT Load Current
mA
°C
Ambient Temperature
Junction Temperature
-40
-40
+85
+125
TJ
°C
Note:
1. Application should guarantee that minimum and maximum duty cycle 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
Unit
Junction-to-Ambient Thermal Resistance, SSOT23-6 Package
151
°C/W
θJA
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
4
Electrical Specifications
VIN = 2.5V 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. Unit
Power Supplies
ISD
Shutdown Supply Current
EN = GND
0.30
300
2.35
2.05
250
0.90
μA
μA
IQ(ACTIVE) Quiescent Current at ILOAD = 0mA Device Not Switching, No Load
VIN Rising
2.10
1.80
2.60
2.30
VUVLO
Under-Voltage Lockout Threshold
V
VIN Falling
VUVHYST Under-Voltage Lockout Hysteresis
mV
EN: Enable Pin
VIH
VIL
HIGH-Level Input Voltage
LOW-Level Input Voltage
EN Pull-Down Resistance
PWM Dimming Frequency(3)
EN LOW, Shutdown Pulse Width
1.2
V
V
0.4
400
100
1
REN
fPWM
tSD
200
5
300
kΩ
kHz
ms
VIN = 3.6V; from Falling Edge of EN
Feedback and Reference
ILED = 20mA from -40°C to +85°C,
2.5V ≤ VIN ≤ 5.5V
VFB
Feedback Voltage
230
250
0.1
270
1.0
mV
IFB
Feedback Input Current
VFB = 250mV
μA
Power Outputs
VIN = 3.6V, ISW = 100mA
600
650
RDS(ON)_Q1 Boost Switch On Resistance
mΩ
μA
VIN = 2.5V, ISW = 100mA
EN = 0, VIN = VSW = VOUT = 5.5V,
ISW(OFF)
SW Node Leakage(2)
0.1
2.0
VLED = 0V
FAN5346S20X: VIN = 3.2V to 4.3V,
TA =-20°C to +60°C, VF = 3.4V, 4 LEDs
200
500
300
750
400
ILIM-PK
Boost Switch Peak Current Limit
mA
FAN5346S30X
1000
Oscillator
Boost Regulator Switching
Frequency
fSW
0.95
1.15
1.35
MHz
Output and Protection
FAN5346S20X
FAN5346S30X
FAN5346S20X
FAN5346S30X
18.0
27.5
20.0
30.0
0.8
21.5
32.5
Boost Output Over-Voltage
Protection
VOVP
V
OVP Hysteresis
1.0
V
OUT Short-Circuit Detection
VTLSC
VTHSC
VOUT Falling
VOUT Rising
VIN – 1.4
VIN – 1.2
V
V
Threshold
VOUT Short-Circuit Detection
Threshold
DMAX
DMIN
Maximum Boost Duty Cycle(3,4)
Minimum Boost Duty Cycle(3,4)
Thermal Shutdown
85
%
20
TTSD
150
35
°C
°C
THYS
Thermal Shutdown Hysteresis
Notes:
2. SW leakage current includes the leakage current of two internal switches; SW to GND and SW to VOUT
3. Not tested in production; guaranteed by design.
.
4. Application should guarantee that minimum and maximum duty cycle fall between 20-85% to meet the specified range.
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
5
Typical Characteristics
VIN = 3.6V, TA = 25°C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
Figure 4. 3 LEDs: Efficiency vs. LED Current
vs. Input Voltage
Figure 5. 4 LEDs: Efficiency vs. LED Current
vs. Input Voltage
Figure 6. 5 LEDs: Efficiency vs. LED Current
vs. Input Voltage
Figure 7. 6 LEDs: Efficiency vs. LED Current
vs. Input Voltage
Figure 8. 7 LEDs: Efficiency vs. LED Current
vs. Input Voltage
Figure 9. 8 LEDs: Efficiency vs. LED Current
vs. Input Voltage
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
6
Typical Characteristics
VIN = 3.6V, TA = 25°C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
Figure 10. Efficiency vs. Input Voltage vs. Temperature
for 5 LEDs in Series
Figure 11. Efficiency vs. Input Voltage vs. Temperature
for 7 LEDs in Series
Figure 12. Delta of VFB Over Input Voltage and
Temperature for 7 LEDs with L=10µH and COUT=1.0µF
Figure 13. Frequency vs. Input Voltage vs. Temperature
7 LEDs
L = 10µH
5 LEDs
L = 10µH
COUT = 1.0µF
C
OUT = 1.0µF
ILED = 25mA
ILED = 25mA
Figure 14. OVP vs. Input Voltage: FAN5346S20X
Figure 15. OVP vs. Input Voltage: FAN5346S30X
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
7
Typical Characteristics
VIN = 3.6V, TA = 25°C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
Figure 16. Shutdown Current vs. Input Voltage
Figure 17. Quiescent Current vs. Input Voltage
Figure 18. LED Current vs. Duty Cycle, fPWM = 20kHz
Figure 19. Line Transient Response for 5 LEDs
Figure 20. Line Transient Response for 6 LEDs
Figure 21. Line Transient Response for 7 LEDs
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
8
Typical Characteristics
VIN = 3.6V, TA = 25°C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
Figure 22. Startup Waveform for Switch Voltage, Inductor
Current, VFB, and EN for 5 LEDs
Figure 23. Steady-State Waveform for VOUT
Switch Voltage, and Inductor Current for 5 LEDs
,
Figure 24. Startup Waveform for Switch Voltage, Inductor
Current, VFB, and EN for 6 LEDs
Figure 25. Steady-State Waveform for VOUT
Switch Voltage, and Inductor Current for 6 LEDs
,
Figure 26. Startup Waveform for Switch Voltage, Inductor
Current, VFB, and EN for 7 LEDs
Figure 27. Steady-State Waveform for VOUT
Switch Voltage, and Inductor Current for 7 LEDs
,
© 2011 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN5346 • Rev. 1.0.1
9
Circuit Description
Overview
The FAN5346 is an inductive current-mode boost serial
LED driver that achieves LED current regulation by
maintaining 0.250V across the RSET resistor. The current
through the LED string (ILED) is given by:
0.250
ILED
=
(1)
RSET
The voltage VOUT is determined by the sum of the forward
voltages across each LED, plus the voltage across RSET
which is always 250mV.
,
Driving Eight LEDs in Series
Figure 28. Block Diagram of FB and EN Circuit for
PWM Dimming
FAN5346S30X can drive 8 LEDs in series, but the minimum
input voltage (VIN) must be greater than or equal to 2.9V,
while the forward voltage of the white LED should be less
than or equal to 3.2V, and the maximum LED current
cannot exceed 20mA to maintain stable operation.
Over-Current and Short-Circuit Detection
The boost regulator employs a cycle-by-cycle peak inductor
current limit of 300mA (typical) and 750mA (typical) for
FAN5346S20X and FAN5346S30X, respectively.
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.
Over-Voltage / Open-Circuit Protection
If the LED string is an open circuit, FB remains at 0V and the
output voltage continues to increase in the absence of an over-
voltage protection (OVP) circuit. The FAN5346S20X OVP
circuit disables the boost regulator when VOUT exceeds 20V
and continues to keep the regulator off until VOUT drops below
19V. For FAN5346S30X, the OVP is 30V and it turns back on
when VOUT is below 29V
PWM Dimming
The FAN5346 uses a PWM signal to directly modulate
output current in the LED string to vary the perceived LED
brightness. When the EN pin is held HIGH, the FB voltage
is 250mV. This voltage is reduced when a PWM signal is
applied to the EN pin, thereby enabling the LEDs to be
dimmed. The FB voltage is given by the equation:
Thermal Shutdown
When the die temperature exceeds 150°C, a reset occurs and
remains in effect until the die cools to 115°C; at which time, the
circuit is allowed to begin the soft-start sequence.
(2)
VFB = DutyCycle× 250mV
where DutyCycle = the duty cycle of the PWM signal
and 250mV is the internal reference voltage.
Figure 28 illustrates how the FAN5346 divides the internal
250mV reference voltage at the duty cycle of the PWM
signal. A low-pass filter filters the PWM signal, which then
is input into the error amplifier as the reference voltage for
the FB pin.
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
10
Application Information
The reference schematic diagram is shown in Figure 29.
FAN5346 is able to drive up to eight LEDs with input voltage
equal to or greater than 2.9V (VIN ≥ 2.9V). However, the
number of LEDs that can be used FAN5346 depends on
forward voltage. It is recommended that the forward voltage
(VF) of the white LED be no greater than 3.2V and the
maximum LED current be 20mA. FAN5345 can be also used
as a boost convertor by connect the VOUT point to the load
directly. The return trace of the load should also return to
GND through a sense resistor (R1).
Figure 29. Reference Application Schematic Diagram
Component Placement and PCB Recommendations
Input Capacitor and Return Trace
FAN5346 switches at 1.2MHz to boost the output voltage.
Component placement and PCB layout need to be carefully
taken into consideration to ensure stable output and to
prevent generation of noise. Figure 30 is a portion of the
evaluation board layout. The critical layout elements are: the
L1, CIN, CIN return trace, COUT, and the COUT return trace.
The input capacitor is the first priority in a switching buck or
boost regulator PCB layout. A stable input source (VIN)
enables a switching regulator to deliver its best performance.
During the regulator’s operation, it is switching at a high
frequency, which makes the load of CIN change dynamically
since it is trying to make the input source vary at the same
switching frequency as the regulator. To ensure a stable
input source, CIN needs to hold enough energy to minimize
the variation at the input pin of the regulator. For CIN to have
a fast response of charge / discharge, the trace from CIN to
the input pin of the regulator and the return trace from GND
of the regulator to CIN should be as short and wide as
possible to minimize trace resistance, inductance, and
capacitance. During operation, the current flow from CIN
through the regulator to the load and back to CIN contains
high-frequency variation due to switching. Trace resistance
reduces the overall efficiency due to I2R loss. Even a small
trace inductance could effectively yield ground variation to
add noise on VOUT. The input capacitor should be placed
close to the VIN and GND pins of the regulator and traces
should be as short as possible. Avoid routing the return trace
through different layers because vias have strong inductance
effect at high frequencies. If routing to other PCB layers is
unavoidable, place vias next to the VIN and GND pins of the
regulator to minimize the trace distance.
Output Capacitor and Return Trace
The output capacitor serves the same purpose as the input
capacitor, but also maintains a stable output voltage. As
explained above, the current travels to the load and back to
the COUT GND terminal. COUT should be placed close to the
VOUT pin. The traces of COUT to L1, VOUT, and the return
Figure 30. Reference PCB Layout
© 2011 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN5346 • Rev. 1.0.1
11
trace from load to COUT should be as short and wide as
possible to minimize trace resistance and inductance. To
minimize noise coupling to load, a small-value capacitor can
be placed between VOUT and COUT to route high-frequency
noise back to GND before it gets to the load.
noise is coupled into the FB pin, it causes unstable operation
of the switching regulator, which affects application
performance. The return trace from the sense resistor to the
FB pin should be short and away from any fast-switching
signal traces. The ground plane under the return trace is not
necessary. If the ground plane under the return trace is
noisy; but not the same ground plane as the regulator; the
noise could be coupled into the FB pin through PCB parasitic
capacitance, yielding noisy output.
Inductor
Inductor (L1) should be placed as close to the regulator as
possible to minimize trace resistance and inductance for the
reasons explained above.
As shown in Figure 30; CIN, COUT, and L1 are all placed next
to the regulator. All traces are on the same layer to minimize
trace resistance and inductance. Total PCB area, not
Sense Resistor
The sense resistor provides a feedback signal for the
regulator to control output voltage. A long trace from the
sense resistor to the FB pin couples noise into the FB pin. If
including the sense resistor, is 67.2mm2 (7.47mm
8.99mm).
x
Table 1. Recommended External Components
Inductor (L)
Part Number
LQH43MN100K03
Manufacturer
Murata
TDK
NLCV32T-100K-PFR
VLF3010AT-100MR49-1
DEM2810C 1224-AS-H-100M
10.0µH
TDK
TOKO
Minimum COUT
1.0µF
CV105X5R105K25AT
AVX / Kyocera
Murata
Minimum CIN
10.0µF
GRM21BR71A106KE51L
Schottky Diode
N/A
RBS520S30
RB520S-30
Fairchild Semiconductor
Rohm
N/A
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
12
Physical Dimensions
Figure 31. 6-Lead, SuperSOT™-6, JEDEC MO-193, 1.6mm Wide
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
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
13
© 2011 Fairchild Semiconductor Corporation
FAN5346 • Rev. 1.0.1
www.fairchildsemi.com
14
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