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부품번호 | FAN5617 기능 |
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기능 | High-Efficiency Constant-Current LED Driver | ||
제조업체 | Fairchild Semiconductor | ||
로고 | |||
전체 10 페이지수
April 2007
FAN5617
High-Efficiency, Constant-Current LED Driver with
TinyWire™ Brightness Control
Features
Description
Three-Channel Parallel LED Driver for a Large Range
of Forward Voltages
TinyWire™ Single-Wire Digital Brightness Control
32 Static Brightness Levels with 5-Bit Internal DAC
The FAN5617 is a low-ripple, low-EMI, high-efficiency,
constant-current LED driver that drives three LEDs in
parallel. The LED brightness control is programmable
through Fairchild’s proprietary single-wire digital
interface, TinyWire™. The charge pump DC/DC
Adaptive VOUT Adjustment to the Highest Diode
Forward Voltage
Matched LED Currents; Matched or Unmatched LEDs
converter operates in three modes: 1X, 1.5X, and 2X
over the entire input voltage range of 2.7V to 5.5V. The
adaptive nature of the built-in charge pump eliminates
the need for LED pre-selection (matching) and delivers
Built-in Charge Pump with Three Modes of Operation:
1x (linear), 1.5x, and 2x
Up to 90% Efficiency
high output efficiency. FAN5617 is capable of driving up
to 90mA total output current, 30mA per channel. The
driver’s built-in, proprietary auto-sense circuit ensures
the same efficiency regardless of the number of LEDs
Low EMI, Low Ripple
Up to 90mA Total Output Current
Drives up to Three LEDs at 30mA Each
connected. When the input voltage is insufficient to
sustain the LEDs programmable current level, the
FAN5617 reconfigures itself to operate as a linear
www.DataSheetr4eU.gcoumlator and the charge pump circuit turns off.
External Resistor Sets Maximum (100%) LED Current The FAN5617 features Fairchild’s TinyWire™ single-
2.7V to 5.5V Input Voltage Range
1MHz Operating Frequency
wire digital interface for LED brightness control. The
built-in 5-bit DAC provides selection of 32 dimming
levels, where each level is a percentage of the
Shutdown Isolates Output from Input, Typically <1µA
Protections: Short-Circuit; Soft-Start Limits Inrush
Current
maximum LED current set by the external resistor, RSET.
The FAN5617 includes shutdown, short-circuit, and
thermal protection circuitry.
Minimal External Components Required
3x3mm 16-Lead MLP Package
Minimal external components are required: two bucket
capacitors (2µF and 1µF), a 4.7µF input capacitor, and a
1µF output capacitor are needed for proper operation.
Applications
Portable Handheld Backlight
PDAs, DVD players, Pagers, Camcorder Backlights
Portable Medical Diagnostic Equipments Display
MP3 Player Displays
Digital Still Camera Backlight
The FAN5617 is available in a 3x3mm, 16-lead, molded
leadless package (MLP).
Ordering Information
Part Number Pb-Free Operating Temperature Range
FAN5617MPX
Yes
0°C to 85°C
TinyWire™ is a trademark of Fairchild Semiconductor Corporation.
Package
MLP-16 3x3mm
Packing Method
Tape and Reel
© 2006 Fairchild Semiconductor Corporation
FAN5617 Rev. 1.0.1
www.fairchildsemi.com
Electrical Specifications
Unless otherwise noted, VIN = 2.7V to 5.5V, ILED = 2mA to 20mA, EN = HIGH, NBR = 31, TA = -40°C to +85°C. Typical
values are at 25°C.
Parameter
Conditions
Min. Typ. Max. Units
Power Supplies
Input Under-Voltage Lockout
Current Matching with Unmatched LEDs(3)
ILED/ISET Ratio
Reference Voltage for Current Set
Start-up Time(4)
Minimum Cathode Voltage
Quiescent Current
Shutdown Supply Current
Output Short-Circuit Current
VOUT Over-Voltage Protection
VIN at Mode Transition from 1x to 1.5x
VIN at Mode Transition from 1.5x to 2x
Peak Efficiency(6)
Oscillator Frequency
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
VIN Falling
VIN Rising
2mA ≤ ILED ≤ 15mA,
2.8V ≤ LED VF <4V
VIN = 3.6V, IOUT = 15mA
ILED = 2 to 20mA
COUT = 1µF, VIN = 3.6V, ILED = 15mA
ILED = 15mA
VIN = 5.5V, IOUT = 5mA
EN=0V, DATAIN = VIN(5)
VIN = 5.5V, VOUT = 0V
LED Vf = 3.5V, ILED = 3 x 20mA
LED Vf = 3.5V, ILED = 3 x 20mA
VIN = 3.75V, LED Vf = 3.4V,
ILED = 18mA
1.6 V
2.3 V
0.6 +3
%
240 255 270
230 260 280
588 600 612
200 270 500
170 250
250
0.1 1
65 80
6
3.9
2.9
mV
µS
mV
µA
µA
mA
V
V
V
90 %
0.8 1 1.2 MHz
150 ºC
15 ºC
Logic Input Thresholds (EN and DATA)
Input Low Voltage
0.4
Input High Voltage
1.25
DATA Input Low Current
VIN = 3.6V
110
Notes:
3. Current Matching refers to the absolute value of the difference in the current between the two LED branches:
( ( ) )Current
Matching (%) ≡
ILEDi − ILEDj x 100
ILEDi + ILEDj
where i, j = 1, 2, or 3.
V
V
µA
4. Start-up time is defined as the period from when the driver is turned on to the time when ILED is within 10% of its
programmed value.
5. When DATA remains low, the TinyWire interface is biased on and consumes up to 30μA of current.
6. Efficiency is expressed as a ratio between the electrical power into the LEDs and the total power consumed from the
input power supply, expressed as:
3
∑ VLEDi x ILEDi
Efficiency ≡
i=1
VIN x IIN
Some vendors calculate the efficiency as a function of VOUT instead of LED VF. That method does not account
for the power lost due to the cathode voltage not being equal to zero, which overstates efficiency by up to 5%.
© 2006 Fairchild Semiconductor Corporation
FAN5617 Rev. 1.0.1
www.fairchildsemi.com
4페이지 Circuit Description
The FAN5617 switch capacitor DC/DC converter
automatically configures its internal switches to achieve
high efficiency, providing tightly-regulated output
currents for the LEDs (see Figure 10 and Figure 11).
An internal voltage detector determines which LED
requires the highest voltage to sustain the pre-set
current levels and adjusts the charge pump regulator
accordingly. Each LED has its own linear current
regulator. In addition, a voltage regulator controls the
output voltage when the battery voltage is within a range
where linear regulation can provide maximum efficiency.
If the battery voltage is too low to sustain the LED
current in linear mode, a fractional 3:2 charge pump is
enabled. When the battery voltage drops and the mode
can no longer sustain proper operation, the pump is
automatically reconfigured to operate in 2:1 mode. As
the battery discharges and the voltage decays, the
FAN5617 switches between modes to maintain a
constant current through the LEDs throughout the
battery life. These transitions have hysteresis to prevent
toggling.
The internal supply voltage of the device is automatically
selected from the VIN or VOUT pins, whichever has a
higher voltage.
The FAN5617 enters shutdown mode to reduce overall
current consumption when the chip is disabled by the
EN pin and control register.
Start-up
When the FAN5617 is enabled, either by EN going high
or on command from the TinyWire™ interface, the soft-
start circuit linearly ramps VOUT to limit the switcher’s
inrush current (see Figure 12). When power is first
applied, the default IC brightness control register (NBR)
is set to maximum brightness (31). If EN is low at initial
power-up, the IC remains in a low-power state until
either EN goes HIGH or a non-0 brightness command is
received. If EN goes from HIGH to LOW, the IC is reset
to the low-power state until either a new brightness
command is received or EN is driven HIGH.
VIN 250∝s
VOUT
PWRUP
Figure 12. Soft-Start
An internal PWRUP signal turns on all of the IC’s logic
control circuitry and starts the charge pump. PWRUP is
high under any of the following conditions:
1. EN goes from low to high
2. A non-zero brightness command is received
© 2006 Fairchild Semiconductor Corporation
FAN5617 Rev. 1.0.1
PWRUP goes low under any of the following conditions:
1. EN is low when power is first applied and no
subsequent non- zero brightness commands are
received
2. EN goes from HIGH to LOW
3. A zero brightness command is received
TinyWire™ Single-Wire Brightness Control
This IC features a digitally controlled static brightness
adjustment to minimize both EMI and applications
processor overhead. The brightness command consists
of a 5-bit binary word (NBR). LED current is a multiple of
the current through RSET:
ILED
=
156 • (NBR + 1)
32 • RSET
for NBR > 0
(1)
NBR BIT4 BIT3 BIT2 BIT1 BIT0
00 0 0 0 0
ILED/ISET
0
1 0 0 0 0 1 260 × 2/32
2 0 0 0 1 0 260 × 3/32
3 0 0 0 1 1 260 × 4/32
4 0 0 1 0 0 260 × 5/32
5 0 0 1 0 1 260 × 6/32
6 0 0 1 1 0 260 × 7/32
7 0 0 1 1 1 260 × 8/32
8 0 1 0 0 0 260 × 9/32
9 0 1 0 0 1 260 × 10/32
10 0 1 0 1 0 260 × 11/32
11 0 1 0 1 1 260 × 12/32
12 0 1 1 0 0 260 × 13/32
13 0 1 1 0 1 260 × 14/32
14 0 1 1 1 0 260 × 15/32
15 0 1 1 1 1 260 × 16/32
16 1 0 0 0 0 260 × 17/32
17 1 0 0 0 1 260 × 18/32
18 1 0 0 1 0 260 × 19/32
19 1 0 0 1 1 260 × 20/32
20 1 0 1 0 0 260 × 21/32
21 1 0 1 0 1 260 × 22/32
22 1 0 1 1 0 260 × 23/32
23 1 0 1 1 1 260 × 24/32
24 1 1 0 0 0 260 × 25/32
25 1 1 0 0 1 260 × 26/32
26 1 1 0 1 0 260 × 27/32
27 1 1 0 1 1 260 × 28/32
28 1 1 1 0 0 260 × 29/32
29 1 1 1 0 1 260 × 30/32
30 1 1 1 1 0 260 × 31/32
31 1 1 1 1 1 260 × 32/32
Table 1. NBR Data Dimming Values
www.fairchildsemi.com
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구매 문의 | 일반 IC 문의 : 샘플 및 소량 구매 ----------------------------------------------------------------------- IGBT, TR 모듈, SCR 및 다이오드 모듈을 포함한 광범위한 전력 반도체를 판매합니다. 전력 반도체 전문업체 상호 : 아이지 인터내셔날 사이트 방문 : [ 홈페이지 ] [ 블로그 1 ] [ 블로그 2 ] |
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