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Número de pieza FAN5776
Descripción Synchronous Boost and Series / Parallel 10-LED Driver
Fabricantes Fairchild Semiconductor 
Logotipo Fairchild Semiconductor Logotipo



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October 2013
FAN5776
Synchronous Boost and Series / Parallel 10-LED Driver
Features
Synchronous Current-Mode Boost Converter
Drives up to 10 LEDs at 25 mA Each in a Configuration of
5 Strings of 2 LEDs in Series
5 LED Outputs: High-Side Current Sources
Two Default Groups of 3x2-LED Channels and 2x2-LED
Channels with Individual Enable and PWM Dimming
Control to Support Various Lighting Applications, such as:
o Backlighting of Dual-LCD Displays, LCD Display Plus
Keypad Illumination
Boost PFM Mode Maximizes Efficiency Under Light Loads
2.3 V to 5.5 V Input Voltage Range
1.8 MHz Switching Frequency
Input Under-Voltage Lockout (UVLO)
Output Over-Voltage Protection (OVP)
Short-Circuit and Thermal Shutdown (TSD) Protection
12-Bump, 0.4 mm Pitch, 1.42 x 1.66 x 0.50 mm WLCSP
Applications
Mid-and Large-Size LCD Modules
Cellular Mobile Handsets, Smart Phones
Smartbooks, Netbooks, MIDs
Pocket PCs
WLAN DC-DC Converter Modules
PDA, DSC, PMP, and MP3 Players
Description
The FAN5776 is a synchronous, constant-current LED driver
capable of efficiently driving up to ten LEDs in a five-string,
two-series LEDs per string configuration. Optimized for small
form-factor applications, the 1.8 MHz switching frequency
allows the use of tiny chip inductors and capacitors.
For safety, the device features integrated over-voltage, short-
circuit, and thermal shutdown protections. In addition, input
under-voltage lockout protection is triggered if the battery
voltage is too low.
The FAN5776 is comprised of low-dropout, high-side current
sources, enabling a high efficiency delivery of power from the
battery to the LEDs. The LED current control is established
with a series RSET resistor, which is connected between the
internal voltage reference on the chip and ground.
During operation, FAN5776 holds the boost regulator’s voltage
on COUT during the off cycle of the PWM dimming, which helps
minimize audible noise.
The FAN5776 is available in a very low profile, small-form-
factors 1.42 x 1.66 x 0.50 mm, 12-bump WLCSP package that
is greenand RoHS compliant.
Ordering Information
Part Number
FAN5776UCX
Temperature
Range
-40 to 85°C
Package
12-Bump, Wafer-Level Chip-Scale Package (WLCSP)
1.42 x 1.66 x 0.50 mm, 0.40 mm Pitch
Packing
Tape and Reel
© 2010 Fairchild Semiconductor Corporation
FAN5776 Rev. 1.1.0
www.fairchildsemi.com

1 page




FAN5776 pdf
Electrical Specifications
Unless otherwise specified: VIN = 2.3 V to 5.5 V, TA = -40C to +85C, and EN13 and EN45 = 1.” Typical values are VIN = 3.7 V,
TA = 25C, VOUT = 6.8 V, ILED1-5 = 20 mA. Circuit and components are according to Figure 1.
Symbol
Parameter
Condition
Power Supplies
ISD Shutdown Current
Device Disabled, (EN13 = EN45 = “0”),
VIN = 2.3 V to 4.5 V
VUVLO
Under-Voltage Lockout
Threshold
Rising VIN
Falling VIN
VUVHYST Under-Voltage Lockout Hysteresis
Oscillator
fSW Frequency
PWM Mode CCM
Boost Regulator
ILIM-PK Peak Switch Current Limit(2)
ISOFT-PK
Soft-Start Peak Switch
Current
Open Loop, VIN = 2.5 V to 5.5 V
Open Loop
ILOAD
Maximum Continuous
Output Current(3)
VIN > 2.5 V
LED Current Driver Characteristics
ILED/ILED
VLED_DO
fPWM
Line Transient Response to
VIN Variations(3)
Relative Response to 350 mV Pulses
Response to 350 mV Pulses Integrated
Over 20 ms Period
LED Driver Drop-Out Voltage(5)
LED PWM Frequency(3)
ILED_MATCH LED Current Matching
Variation between Different
ILED1 ILED5 Currents.
Matching LED Pin Voltage
Difference < 250 mV(4)
ILED = 2.5 mA
to 10 mA
ILED = 10 mA
to 25 mA
ILINEARITY LED Current Linearity(3)
1/255 PWM 24/255, 300 Hz
PWM 25/255, 300 Hz
ILED
Absolute LED Current
Accuracy
LED1 LED5
ILED = 2.5 mA
to 5 mA
ILED = 5 mA
to 25 mA
ILED_RIPPLE
Peak-to-Peak LED Current
Ripple(3)
VLED_DO 0.6 V (Typical 0.29 V),
fPWM = 300 Hz, Measurement BW = 10 MHz
ILEAKAGE LED Driver Leakage
VISET ISET Voltage
Logic Control
In OFF State
VIL
VIH
REN13
REN45
Logic LOW Threshold
Logic HIGH Threshold
EN13 Pull-Down Resistor
EN45 Pull-Down Resistor
Min. Typ. Max. Unit
0.1 4.0 A
2.1 2.2
V
1.8 1.9
V
200 mV
1.8 MHz
445 525 640 mA
250 mA
100 mA
10
%
1
290 mV
100 800 Hz
2.0 5.0
1.0 3.5
%
10
%
2
15.0
%
7.5
0.4
1.20
1.2 mAP-P
0.5 µA
V
0.5 V
1.05 V
250 k
250 k
Continued on the following page…
© 2010 Fairchild Semiconductor Corporation
FAN5776 Rev. 1.1.0
5
www.fairchildsemi.com

5 Page





FAN5776 arduino
Circuit Description
Overview
The FAN5776 is a 1.8 MHz synchronous step-up DC-DC
converter with integrated constant-current high-side LED
drivers capable of driving one to five LED strings up to 5 x
25 mA LED current.
The device starts when at least one LED string is utilized and
the appropriate EN pin is enabled. The device is disabled in
30 ms by setting both EN pins LOW.
The VOUT voltage is internally set to 290 mV above the highest
LED string voltage, and it is sampled at every falling LED PWM
cycle. For 100% duty cycle, the LED-pin voltage is sampled
and the VOUT voltage is refined every 10 ms.
The LED strings can be disabled by connecting them to VOUT
or shorting them to GND. They can also be left disconnected. If
the LED string is temporarily disabled or shorted, the device
must be re-enabled to enable the string again.
The LED drivers work independently and allow multiple LED
voltages, such that many types of LEDs can be driven at the
same time and some strings can be used to drive a single LED
while other channels are driving two LEDs in series. The VOUT
voltage is defined by the highest LED voltage and the LED
driver dropout voltage is increased to provide the LED string a
specific voltage. If the voltage difference between the LED
strings is large, the system efficiency may decrease.
LED Current
The LED string current is set by the resistor, RSET, between the
ISET and GND pins. The same current is applied to across all
strings such that total output current: IOUT = 5 x ILED = 5 x
20 mA = 100 mA if RSET = 25 kand all LED strings are used.
In general, the LED string current can be calculated as follows:
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=
500
������������������������
(1)
25
20
15
10
5
0
20 40 60 80 100 120 140 160 180 200
Resistor RSET (k)
Figure 26. LED Current vs. RSET Value
Startup
The three different startup functions depend on the system
configuration:
1. All LED strings are utilized: Setting one or both EN pins
HIGH enables the device and VOUT rises to 7.5 V.
FAN5776 starts to step up or down to the appropriate
regulated voltage.
2. At least one LED string in a group is shorted to GND. VOUT
rises to 7.5 V while the shorted LED string is disabled and
the device starts to step up or down to regulated voltage.
3. At least one LED string is floating or connected to VOUT.
VOUT rises to 9.0 V, the floating LED string is disabled, and
the device starts to step down to regulated voltage.
These functions work for each group independently. If all five
strings are utilized and EN13 is HIGH, VOUT rises to 7.5 V (case
1) and goes to the highest voltage required by LED1-3. Then
EN45 is raised and VOUT is stepped up again to 7.5 V and
regulates to highest voltage required by LED1-5.
If VOUT cannot reach 7.5 V within 1.2 ms after an enable cycle,
the device stays disabled and a new enable cycle is required.
PWM Dimming
A LED PWM signal of 100 Hz to 800 Hz can be applied to
EN13 and EN45 pins to control LED1-3 and LED4-5 light
intensity. The LED current is a linear function of the LED
PWM duty cycle from 100% down to 0.4%. The FAN5776
can be started by a PWM signal with a low duty cycle to
enable smooth startup. EN13 and EN45 pins can be
operated either synchronously or asynchronously, which
makes it possible to use the device to backlight two
separate displays at the same time.
Under-Voltage Lockout (UVLO)
The Under-Voltage Lockout circuitry turns off all MOSFETs and
the device remains in a very low quiescent current state until
VIN has risen above the UVLO threshold.
Short-Circuit Protection (SCP)
The LED driver output current is limited to 0.5 µA or less when
a LED number pin voltage is below 1.0 V. This limit shall be
applied within one LED PWM cycle, or 10 ms, whichever
elapses first.
Over-Voltage Protection (OVP)
When the regulator is active, it monitors the VOUT pin. If the
VOUT voltage reaches 9.0 V, the regulator stops switching until
the capacitor at VOUT discharges below 8.5 V.
LED-Open Detection
If VOUT is detected above >9.0 V, the LED voltages are
scanned. All LED pins with voltage greater than VOUT - 0.5 V
are disabled. If all LED pins’ voltages exceed 8.5 V and VOUT is
greater than 9.0 V, device is disabled and a new startup cycle
is required.
Over-Current Protection (OCP)
The PWM converter is protected against overload through
cycle-by cycle current limit using a fixed internal limit.
Thermal Shutdown
When the die temperature exceeds 150°C, reset occurs and
remains in effect until the die cools to 125°C; at which time,
the circuit enters the normal soft-start sequence.
© 2010 Fairchild Semiconductor Corporation
FAN5776 Rev. 1.1.0
11
www.fairchildsemi.com

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