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PDF FAN5606 Data sheet ( Hoja de datos )
| Número de pieza | FAN5606 | |
| Descripción | Serial LED Driver | |
| Fabricantes | Fairchild Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de FAN5606 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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www.fairchildsemi.com
FAN5606
Serial LED Driver with Current-Regulated, Step-Up
DC/DC Converter
Features
• Drives Up to Six LEDs in Series
• Pulse Skip PWM Mode of Operation of the Boost Circuit
• Up to 90% Peak Efficiency
• No External Schottky Diode Required
• Up to 25mA Output
• Built-in DAC for Digital Brightness Control
• LED’s Current Can be Duty-Cycle-Modulated
• Digital, Analog, and PWM Brightness Control
• 2.7V to 5.5V Input Voltage Range
• 0.5MHz Operating Frequency (8MHz internal clock)
• Soft Start
• Low Shutdown Current: ICC < 1µA
• LED Short Circuit Protection
• Minimal External Components Needed
• Available in an 8-lead MLP Package
Applications
• Cell Phones
• Handheld Computers
• PDAs, DSCs, MP3 Players
• Keyboard Backlights
• LED Display
Description
The FAN5606 LED driver generates regulated output cur-
rents from a battery with input voltage varying between 2.7V
to 5V. An internal NMOS switch drives an external inductor,
and a Schottky diode delivers the inductor’s stored energy to
the load. Soft start circuitry prevents excessive current drawn
from the supply during power on. Any number of LEDs can
be connected in series as long as the summed forward volt-
ages do not lead to exceeding the specified operating output
voltage range.
In the FAN5606 device, the internal two-bit D/A converters
provide programmability of the output channel current.
Analog programming of the output current is also possible
in the FAN5606. To do this, ground the “B” pin and connect
a resistor between the “A” pin and a fixed supply voltage.
The output current can then be programmed to any desired
value within its specified range. The analog version uses a
single external resistor to set the current, and to turn the
device ON and OFF. The device is available in an 8-lead
MLP package.
Typical Applications
Analog Brightness Control
2.7V to 5.5V L = 6.8µH
CIN
VExternal
R
IND VOUT GINND
VIN CAT
AB
4.7µF
Digital Brightness Control
VOUT
2.7V to 5.5V L = 6.8µH
CIN
IND
VIN
DAC Inputs
A
GINND
CAT
B
4.7µF
VOUT
REV. 1.0.3 1/7/05
1 page  
PRODUCT SPECIFICATION
FAN5606
Where VRef = 1.22V
25
R=10Kohm
20
15
10 R=100kohm
5
0
1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5
VExternal (V)
If the analog input A is driven in digital mode by an open
drain output, it is important to choose the appropriate value
of the pull-up resistor. Its resistance should be low enough to
ensure less than 0.7V dropout, hence VA > (VIN–0.7V), as
required for HIGH logic level:
Rpull-up < 7---6-0--0-0--µ-m---A--V--- = 11kΩ
Pulse-Width-Modulation (PWM) Control
A variable duty cycle (δ) can modulate any DAC input. Care
should be taken not to use a too low frequency, otherwise a
flickering effect may occur. The minimum range is 100Hz to
1KHz. For a maximum range of LED current, both A and B
inputs can be modulated at the same time.
Open Circuit Protection
A built-in over voltage protection circuit prevents the device
from being damaged when it is powered up with no load.
This circuit reduces the boost converter duty cycle, to a min-
imum thus limiting the output voltage to a safe value when
no load condition is detected. However, the FAN5606 can be
damaged when a full load (Six LEDs driven by 20mA) is
suddenly disconnected from VOUT. To protect the FAN5606
against this unlikely event, an external 24 V Zener diode can
be connected between VOUT and GND.
Shutdown Mode
The device can be disabled by applying LOW logic level
voltage to the A and B inputs. In Shutdown mode the supply
current is reduced to less than 1µA.
PWM Control
1. A is PWM Controlled, B is Low. ILED (Average) = δ x 5mA, where δ is Duty Cycle. (Note 4)
A Input (PWM)
ss
B Input (0)
30%
Duty Cycle
1KHz
ss
70%
Duty Cycle
1KHz
ss
ILED (Average) = 0.7 x 5mA = 3.5mA
ILED
0mA
ILED (Average) = 0.3 x 5mA = 1.5mA ss
OFF
2. A is High and B is PWM. ILED (Average) = 5mA + δ x 15mA, where δ is Duty Cycle.(Note 5, 6)
A Input
ss
B Input (PWM)
ILED
REV. 1.0.3 1/7/05
ss
0mA
30%
Duty Cycle
1KHz
ss ss
70%
Duty Cycle
1KHz
ILED (Average) = 0.7 x 20mA + 0.3 x 5mA = 15.5mA
ILED (Average) =
0.3 x 20mA
+ 0.7 x 5mA = 9.5mA
ss
OFF
5
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet FAN5606.PDF ] | |
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