Fairchild FAN5345S30X Series boost led driver with single-wire digital interface Datasheet

FAN5345
Series Boost LED Driver with Single-Wire Digital Interface
Features
Description


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
 32 Linear Steps







1.2MHz Fixed Switching Frequency
Soft-Start Capability
Input Under-Voltage Lockout (UVLO)
Output Over-Voltage Protection (OVP)
Short-Circuit Detection
Thermal Shutdown (TSD) Protection
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.
For safety, the device features integrated over-voltage, overcurrent, short-circuit detection, and thermal-shutdown
protection. In addition, input under-voltage lockout protection
is triggered if the battery voltage is too low.
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).
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
Output Voltage Option
FAN5345S20X
20V
FAN5345S30X
30V
Temperature Range
-40 to 85°C
Package
6-Lead, Super-SOT™-6, JEDEC MO-193,
1.6mm Wide (MA06A)
.
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
September 2011
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
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
VIN
1
6
SW
GND 2
5
VOUT
4
EN
FB
3
Figure 3. Pin Assignments Top View
Pin Definitions
Pin #
Name
Description
5
VOUT
Boost Output Voltage. Output of the boost regulator. Connect the LEDs to this pin. Connect COUT
(output capacitor) to GND.
1
VIN
Input Voltage. Connect to power source and decouple with CIN to GND.
4
EN
Enable Brightness Control. Program dimming levels by driving pin with digital pulses.
3
FB
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.
6
SW
Switching Node. Tie inductor L1 from VIN to SW pin.
2
GND
Ground. Tie directly to a GND plane.
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
www.fairchildsemi.com
3
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
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
VIN
Parameter
VIN Pin
VFB, VEN FB, EN Pins
VSW
SW Pin
VOUT
VOUT Pin
ESD
Electrostatic Discharge Protection
Min.
Max.
Unit
-0.3
6.0
V
-0.3
VIN + 0.3
V
FAN5345S20X
-0.3
22.0
V
FAN5345X30X
-0.3
33.0
V
FAN5345S20X
–0.3
22.0
V
FAN5345X30X
-0.3
33.0
V
Human Body Model per JESD22-A114
1.5
Charged Device Model per JESD22-C101
1.5
kV
TJ
Junction Temperature
-40
+150
°C
TSTG
Storage Temperature
-65
+150
°C
+260
°C
TL
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
VIN
VOUT
IOUT
Parameter
Comments
VIN Supply Voltage
VOUT Voltage(1)
Min.
Max.
Unit
V
2.5
5.5
FAN5345S20X
6.2
18.5
FAN5345S30X
6.2
28.5
VOUT Load Current
V
5
25
mA
TA
Ambient Temperature
-40
+85
°C
TJ
Junction Temperature
-40
+125
°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
JA6
Parameter
Junction-to-Ambient Thermal Resistance, SSOT23-6 Package
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
Typical
Unit
151
°C/W
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4
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Absolute Maximum Ratings
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
0.30
0.90
A
Power Supplies
ISD
IQ(ACTIVE)
Shutdown Supply Current
EN = GND
Quiescent Current at ILOAD = 0mA
Device Not Switching, No Load
VUVLO
Under-Voltage Lockout Threshold
VUVHYST
Under-Voltage Lockout Hysteresis
A
300
VIN Rising
2.10
2.35
2.60
VIN Falling
1.80
2.05
2.30
250
V
mV
EN: Enable Pin
VIH
HIGH-Level Input Voltage
VIL
LOW-Level Input Voltage
REN
EN Pull-Down Resistance
TLO
EN Low Time for Dimming(3)
(3)
THI
Delay Between Steps
TSD
EN Low, Shutdown Pulse Width
1.2
200
VIN = 3.6V; Figure 28
0.5
VIN = 3.6V; Figure 28
0.5
V
0.4
V
400
k
300
µs
1
ms
250
270
mV
1.0
A
300
µs
VIN = 3.6V; from Falling Edge of EN
Feedback and Reference
VFB
Feedback Voltage
ILED = 20mA from -40°C to +85°C,
2.7V ≤ VIN ≤ 5.5V
IFB
Feedback Input Current
VFB = 250mV
0.1
230
Power Outputs
RDS(ON)_Q1 Boost Switch On Resistance
ISW(OFF)
ILIM-PK
SW Node Leakage(2)
Boost Switch Peak Current Limit
VIN = 3.6V, ISW = 100mA
600
VIN = 2.5V, ISW = 100mA
650
EN = 0, VIN = VSW = VOUT = 5.5V, VLED =
0V
0.1
2.0
m
FAN5345S20X: VIN = 3.2V to 4.3V, TA
= 20°C to +60°C, VF = 3.4V, 4 LEDs
200
300
400
FAN5345S30X
500
750
1000
0.95
1.15
1.35
FAN5345S20X
18.0
20.0
21.5
FAN5345S30X
27.5
30.0
32.5
A
mA
Oscillator
fSW
Boost Regulator Switching
Frequency
MHz
Output and Protection
VOVP
Boost Output Over-Voltage
Protection
OVP Hysteresis
FAN5345S20X
0.8
FAN5345S30X
1.0
V
VTLSC
VOUT Short-Circuit Detection
Threshold
VOUT Falling
VIN – 1.4
V
VTHSC
VOUT Short-Circuit Detection
Threshold
VOUT Rising
VIN – 1.2
V
DMAX
Maximum Boost Duty Cycle(3,4)
DMIN
Minimum Boost Duty Cycle(3,4)
TTSD
Thermal Shutdown
150
°C
THYS
Thermal Shutdown Hysteresis
35
°C
85
20
%
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
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Electrical Specifications
90%
90%
80%
80%
Efficiency
Efficiency
VIN = 3.6V, TA = 25C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
70%
VIN=2.5V
VIN=2.7V
60%
70%
VIN=2.5V
VIN=2.7V
60%
VIN=3.6V
VIN=3.6V
VIN=4.2V
VIN=4.2V
VIN=4.5V
VIN=4.5V
50%
50%
5
10
15
20
25
5
10
25
Figure 5. 4 LEDs: Efficiency vs. LED Current
vs. Input Voltage
90%
90%
80%
80%
Efficiency
Efficiency
Figure 4. 3 LEDs: Efficiency vs. LED Current
vs. Input Voltage
70%
VIN=2.5V
VIN=2.7V
70%
VIN=2.5V
VIN=2.7V
60%
VIN=3.6V
VIN=3.6V
VIN=4.2V
VIN=4.2V
VIN=4.5V
VIN=4.5V
50%
50%
5
10
15
20
5
25
10
Figure 6. 5 LEDs: Efficiency vs. LED Current
vs. Input Voltage
20
25
Figure 7. 6 LEDs: Efficiency vs. LED Current
vs. Input Voltage
90%
80%
80%
Efficiency
90%
70%
VIN=2.5V
70%
VIN=2.9V
VIN=2.7V
60%
15
LED Current (mA)
LED Current (mA)
Efficiency
20
LED Current (mA)
LED Current (mA)
60%
15
60%
VIN=3.6V
VIN=3.6V
VIN=4.2V
VIN=4.2V
VIN=4.5V
VIN=4.5V
50%
50%
5
10
15
20
5
25
LED Current (mA)
15
20
25
LED Current (mA)
Figure 8. 7 LEDs: Efficiency vs. LED Current
vs. Input Voltage
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
10
Figure 9. 8 LEDs: Efficiency vs. LED Current
vs. Input Voltage
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FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Typical Characteristics
90%
90%
80%
80%
Efficiency
Efficiency
VIN = 3.6V, TA = 25C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
70%
60%
70%
60%
-40C
-40C
+25C
+25C
+85C
+85C
50%
50%
2.5
3.0
3.5
4.0
2.5
4.5
3.0
Input Voltage (V)
0.2
1250
0.1
1200
0.0
-0.1
4.5
-0.2
-40°C
1150
1100
-40°C
1050
+25°C
+25°C
+85°C
+85°C
-0.4
1000
2.5
3.0
3.5
4.0
4.5
2.5
3.0
Input Voltage (V)
3.5
4.0
4.5
Input Voltage (V)
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
31.5
21.0
5 LEDs
L = 10µH
COUT = 1.0µF
ILED = 25mA
7 LEDs
L = 10µH
COUT = 1.0µF
ILED = 25mA
31.0
OVP (V)
20.5
OVP (V)
4.0
Figure 11. Efficiency vs. Input Voltage vs. Temperature
for 7 LEDs in Series
Frequency (kHz)
Delta Feedback (mV)
Figure 10. Efficiency vs. Input Voltage vs. Temperature
for 5 LEDs in Series
-0.3
3.5
Input Voltage (V)
20.0
19.5
19.0
30.5
30.0
29.5
18.5
29.0
2.5
3.0
3.5
4.0
4.5
2.5
Input Voltage (V)
3.5
4.0
4.5
Input Voltage (V)
Figure 14. OVP vs. Input Voltage: FAN5345S20X
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
3.0
Figure 15. OVP vs. Input Voltage: FAN5345S30X
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7
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Typical Characteristics
0.80
265
Quiescent Current (µA)
Shutdown Current (µA)
VIN = 3.6V, TA = 25C, ILED = 25mA, L = 10µH, COUT = 1.0µF, and CIN = 10.0µF.
0.60
0.40
0.20
0.00
2.50
3.00
3.50
4.00
260
255
250
245
240
235
230
225
2.50
4.50
3.00
3.50
4.00
4.50
VIN (V)
VIN (V)
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
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8
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
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
FAN5345 • Rev. 1.0.0
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9
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Typical Characteristics
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.
I LED 
0.250
RSET
(1)
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
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10
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Circuit Description
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
COUT return trace.
Component Placement and PCB
Recommendations
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
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11
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Application Information
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
2
sense resistor, is 67.2mm (7.47mm x 8.99mm).
Table 1. Recommended External Components
Part Number
Manufacturer
LQH43MN100K03
Murata
NLCV32T-100K-PFR
TDK
VLF3010AT-100MR49-1
TDK
DEM2810C 1224-AS-H-100M
TOKO
CV105X5R105K25AT
AVX/Kyocera
GRM21BR71A106KE51L
Murata
N/A
RBS520S30
Fairchild Semiconductor
N/A
RB520S-30
Rohm
Inductor (L)
10.0µH
Minimum COUT
1.0µF
Minimum CIN
10.0µF
Schottky Diode
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
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12
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
Output Capacitor and Return Trace
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
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
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13
FAN5345 — Series Boost LED Driver with Single-Wire Digital Interface
© 2011 Fairchild Semiconductor Corporation
FAN5345 • Rev. 1.0.0
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14