FAN5345 [FAIRCHILD]
Series Boost LED Driver with Single-Wire Digital Interface; 系列升压LED驱动器，具有单线数字接口
| 型号： | FAN5345 |
| 厂家： | 
FAIRCHILD SEMICONDUCTOR |
| 描述： | Series Boost LED Driver with Single-Wire Digital Interface |
| 文件： | 总14页 (文件大小：1121K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
September 2011
FAN5345
Series Boost LED Driver with Single-Wire Digital Interface
Description
Features
The FAN5345 is an asynchronous constant-current LED
driver that drives LEDs in series to ensure equal brightness
for all the LEDs. FAN5345S20X has an output voltage of
20V and can drive up to 5 LEDs in series. FAN5345S30X
has an output voltage of 30V and drive 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.
.
.
Asynchronous Boost Converter
Drives LEDs in Series:
FAN5345S20X: 20V Output
FAN5345S30X: 30V Output
.
.
2.5V to 5.5V Input Voltage Range
Single-Wire Digital Control Interface to Set LED
Brightness Levels
The FAN5345 uses a simple single-wire digital control
interface to program the brightness levels of the LEDs in 32
linear steps by applying digital pulses.
32 Linear Steps
.
.
.
.
.
.
.
1.2MHz Fixed Switching Frequency
Soft-Start Capability
For safety, the device features integrated over-voltage, over-
current, short-circuit detection, and thermal-shutdown
protection. 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 FAN5345 is available in a 6-lead SSOT23 package.
It is “green” and RoHS compliant. (Please see
http://www.fairchildsemi.com/company/green/index.html for
Fairchild’s definition of green).
Thermal Shutdown (TSD) Protection
Small Form-Factor 6-Lead SSOT23 Package
Applications
.
.
.
.
Cellular Mobile Handsets
Mobile Internet Devices
Portable Media Players
PDA, DSC, MP3 Players
Ordering Information
Part Number
FAN5345S20X
FAN5345S30X
Output Voltage Option
Temperature Range
Package
20V
30V
6-Lead, Super-SOT™-6, JEDEC MO-193,
1.6mm Wide (MA06A)
-40 to 85°C
.
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
Typical Application Diagram
Figure 1. Typical Application
Block Diagram
Figure 2. Functional Block Diagram
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
2
Pin Configuration
1
2
3
6
5
4
VIN
GND
FB
SW
VOUT
EN
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 power source and decouple with CIN to GND.
Enable Brightness Control. Program dimming levels by driving pin with digital pulses.
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
FAN5345 • Rev. 1.0.0
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
FAN5345S20X
V
VSW
VOUT
ESD
SW Pin
FAN5345X30X
33.0
V
FAN5345S20X
22.0
V
VOUT Pin
FAN5345X30X
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
Comments
Min.
2.5
6.2
6.2
5
Max.
5.5
Unit
VIN
VIN Supply Voltage
V
FAN5345S20X
FAN5345S30X
18.5
28.5
25
VOUT
VOUT Voltage(1)
V
IOUT
TA
VOUT Load Current
mA
°C
Ambient Temperature
Junction Temperature
-40
-40
+85
+125
TJ
°C
Note:
1. The application should guarantee that minimum and maximum duty cycle should 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
JA6
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
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
A
A
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
EN Low Time for Dimming(3)
Delay Between Steps(3)
1.2
V
V
0.4
400
300
REN
TLO
THI
200
0.5
0.5
300
k
µs
µs
ms
VIN = 3.6V; Figure 28
VIN = 3.6V; Figure 28
TSD
EN Low, Shutdown Pulse Width
VIN = 3.6V; from Falling Edge of EN
1
Feedback and Reference
I
LED = 20mA from -40°C to +85°C,
VFB
Feedback Voltage
230
250
0.1
270
1.0
mV
2.7V ≤ VIN ≤ 5.5V
IFB
Feedback Input Current
VFB = 250mV
A
Power Outputs
VIN = 3.6V, ISW = 100mA
VIN = 2.5V, ISW = 100mA
600
650
RDS(ON)_Q1 Boost Switch On Resistance
m
A
EN = 0, VIN = VSW = VOUT = 5.5V, VLED
0V
=
ISW(OFF)
SW Node Leakage(2)
0.1
2.0
FAN5345S20X: 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
FAN5345S30X
1000
Oscillator
Boost Regulator Switching
Frequency
fSW
0.95
1.15
1.35
MHz
Output and Protection
FAN5345S20X
FAN5345S30X
FAN5345S20X
FAN5345S30X
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
VOUT Short-Circuit Detection
Threshold
VTLSC
VTHSC
VOUT Falling
VOUT Rising
VIN – 1.4
VIN – 1.2
V
V
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
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
5
Typical Characteristics
VIN = 3.6V, TA = 25C, 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
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
6
Typical Characteristics
VIN = 3.6V, TA = 25C, 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
COUT =1.0µF
ILED = 25mA
5 LEDs
L = 10µH
COUT = 1.0µF
ILED = 25mA
Figure 14. OVP vs. Input Voltage: FAN5345S20X
Figure 15. OVP vs. Input Voltage: FAN5345S30X
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
7
Typical Characteristics
VIN = 3.6V, TA = 25C, 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. Dimming Operation
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
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
8
Typical Characteristics
VIN = 3.6V, TA = 25C, 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
FAN5345 • Rev. 1.0.0
9
Circuit Description
Overview
Digital Dimming Control
The FAN5345 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 therefore given by:
The FAN5345 starts driving the LEDs at the maximum
brightness level. After startup, the control logic is ready to
accept programming pulses to decrease the brightness level
by the number of positive edges applied to the EN pin.
Figure 28. Digital Pulse-Dimming Control Diagram shows the
digital pulse dimming control. The dimming control function
has no effect before soft-start finishes. The soft-start takes
about 2ms.
0.250
ILED
(1)
RSET
Over-Current and Short-Circuit Detection
The voltage VOUT is determined by the sum of the forward
voltages across each LED, plus the voltage across RSET
which is always 250mV.
,
The boost regulator employs a cycle-by-cycle peak inductor
current limit of 300mA (typical) and 750mA (typical) for
FAN5345S20X and FAN5345S30X respectively.
UVLO and Soft-Start
Over-Voltage / Open-Circuit Protection
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.
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 FAN5345S20X
OVP circuit disables the boost regulator when VOUT exceeds
20.0V and continues to keep the regulator off until VOUT drops
below 19.0V. For FAN5345S30X, the OVP is 30.0V and it
turns back on when VOUT is below 29.0V.
Driving Eight LEDs in Series
FAN5345S30X 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 in order to maintain stable operation.
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.
Digital Interface
The FAN5345 implements a single-wire digital interface to
program the LED brightness to one of thirty-two (32) levels
spaced in linear steps. With this single-wire solution, the
FAN5345 does not require the system processor to constantly
supply a signal to drive the LEDs.
Figure 28. Digital Pulse-Dimming Control Diagram
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
10
Application Information
The reference schematic diagram is shown in Figure 29.
FAN5345 is able to drive up to eight LEDs with input voltage
equal or greater than 2.9V (VIN ≥ 2.9V). However, the
number of LEDs that can be used depends on forward
voltage. It is recommended that the forward voltage (VF) of
the white LEDs be no greater than 3.2V and the maximum
LED current is 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
prevent generation of noise. Figure 30 is the FAN5345 a
portion of the evaluation board layout. The critical layout
elements are: the L1, CIN, CIN return trace, COUT, and the
Component Placement and PCB
Recommendations
COUT return trace.
Input Capacitor and Return Trace
The input capacitor is the first priority in a switching buck or
boost regulator 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 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.
Figure 30. Reference PCB Layout
FAN5345 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
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
11
Output Capacitor and Return Trace
Sense Resistor
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 return 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.
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
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
necessary. If the ground plan 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.
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 including the
sense resistor, is 67.2mm2 (7.47mm x 8.99mm).
Table 1. Recommended External Components
Part Number
Manufacturer
Inductor (L)
LQH43MN100K03
Murata
TDK
NLCV32T-100K-PFR
10.0µH
VLF3010AT-100MR49-1
TDK
DEM2810C 1224-AS-H-100M
CV105X5R105K25AT
TOKO
AVX/Kyocera
Murata
Minimum COUT
1.0µF
Minimum CIN
10.0µF
GRM21BR71A106KE51L
Schottky Diode
N/A
RBS520S30
RB520S-30
Fairchild Semiconductor
Rohm
N/A
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
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
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
13
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
14
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