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PDF FAN5616 Data sheet ( Hoja de datos )
| Número de pieza | FAN5616 | |
| Descripción | Constant-Current LED Driver | |
| Fabricantes | Fairchild Semiconductor | |
| Logotipo |  |
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www.DataSheet4U.com
November 2005
FAN5616
High-Efficiency, Constant-Current LED Driver with
Adaptive Charge Pump
Features
■ 3-Channel Parallel LED Driver for a Large Range of
Forward Voltages
■ Adaptive VOUT Adjustment to the Highest Diode
Forward Voltage
■ Internally Matched LED Current Sources
■ Matched LED Currents with Matched or Unmatched
LEDs
■ Built-in Charge Pump with Three Modes of Operation:
1x, 1.5x, and 2x
■ Up to 90% Efficiency
■ Up to 50kHz PWM Dimming Frequency
■ Low EMI, Low Ripple
■ Up to 120mA Output Current
■ Drives up to 3 LEDs at 40mA each
■ External Resistor to Set Maximum (100%) LED
Current
■ Built-in 2-bit DAC to Control LED Current in Digital
Mode
■ 2.5V to 5.5V Input Voltage Range
■ ICC < 1µA in Shutdown Mode
■ 1MHz Operating Frequency
■ Shutdown Isolates Output from Input
■ Smart Soft-Start Limits In-Rush Current
■ Short Circuit Protection
■ Minimal External Components Needed
■ Available in a 3x3mm 16-lead MLP Package
Applications
■ Cell Phones
■ PDAs, DSCs, and MP3 Players
Description
The FAN5616 generates a regulated output current from
a battery with an input voltage between 2.7V to 5.5V.
Switch reconfiguration and fractional switching tech-
niques are utilized to achieve high efficiency over the
entire input voltage range. The adaptive nature of the
built-in charge pump eliminates the need for LED pre-
selection (matching) and ensures operation with high
efficiency. The driver's built-in, proprietary, auto-sense
circuitry ensures the same high efficiency regardless of
the number of LEDs. When the input voltage is suffi-
ciently high to sustain the LED’s programmed current
level, the FAN5616 reconfigures itself to operate as a lin-
ear regulator, and the charge pump is turned off.
The FAN5616 supports both digital and PWM LED
brightness control methods. The built-in 2-bit DAC offers
a selection of four LED current levels, each level is a per-
centage of the maximum LED current set by the external
RSET resistor.
The FAN5616 includes built-in shutdown, short circuit
and thermal protection circuitry. A built-in smart soft-start
circuitry prevents excessive current draw during power
on while allowing for an increased PWM frequency for
dimming.
Minimal external components are required. Only two
0.1µF to 1µF bucket capacitors, a 4.7µF input capacitor
and a 1µF output capacitor are needed for proper opera-
tion.
The FAN5616 is available in a 3x3mm 16-lead MLP
package.
Ordering Information
Product Number
FAN5616
Package Type
3x3mm 16-Lead MLP
Order Code
FAN5616MPX
©2005 Fairchild Semiconductor Corporation
FAN5616 Rev. 1.0.0
1
www.fairchildsemi.com
1 page  
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Electrical Characteristics
Unless otherwise noted, VIN = 2.7V to 5.5V, ILED = 2mA to 20mA, EN1 = EN2 = HIGH, TA = -40°C to +85°C. Typical
values are at 25°C.
Parameter
Input Under-Voltage Lockout
ILED/ISET Ratio
ILED/ISET Ratio
ILED/ISET Ratio
Current Matching with Unmatched
LEDs (Note 1)
Reference Voltage for Current Set
Start Up time
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 (Note 2)
Oscillator Frequency
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
“EN1” Logic Input Low Voltage
“EN1” Logic Input High Voltage
“EN2” Logic Input Low Voltage
“EN2” Logic Input High Voltage
Conditions
VIN falling
VIN rising
VIN = 3.6V, IOUT = 15mA
ILED = 2 to 20mA
EN1 = HIGH, EN2 = LOW
EN1 = LOW, EN2 = HIGH
2mA ≤ ILED ≤ 15mA
2.8V ≤ LED VF <4V
COUT = 1µF, VIN = 3.6V,
ILED = 15mA
ILED = 15mA
VIN = 5.5V, IOUT = 5mA
EN1 = EN2 = Logic “L”
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
Min Typ Max Unit
1.6 V
2.3
240 255 270
230 260 280
86
173
0.6 +3
%
588 600 612 mV
200 270 500
µS
170 250 mV
250 µA
0.1 1 µA
65 80 mA
6V
3.9 V
2.9 V
90 %
0.8 1 1.2 MHz
150 °C
15 °C
0.4 V
1.6 V
0.4 V
1.6 V
Notes:
1. Current Matching refers to the absolute value of the difference in the current between the two LED branches.
( ( ) )Current Matching (%) ––
ILEDi – ILEDj
x 100
, where i, j = 1, 2 or 3
ILEDi + ILEDj
2. Efficiency is expressed as a ratio between the electrical power into the LEDs and the total power consumed from
the input power supply.
Σ3
VLEDi x ILEDi
Efficiency ––
i=1
VIN x IIN
Some competitors calculate the efficiency as a function of VOUT instead of LED VF. Their method does not account
for the power lost due to the cathode voltage not being equal to zero. This method allows them to provide an
“improved” efficiency up to 5%.
FAN5616 Rev. 1.0.0
5
www.fairchildsemi.com
5 Page 
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2. Digital Control
A built-in 2-bit DAC is used to digitally control the LED’s
brightness through the EN1 and EN2 inputs. Once the
desired maximum LED current is set by the external
RSET resistor, the percentage of the maximum LED cur-
rent is selected, as described in Table 2, to perform the
dimming operation.
Table 2. LED Dimming with Internal 2-bit DAC
EN2
0
0
1
1
EN1
0
1
0
1
LED Current % of Maximum
0%
33.3% (1/3)
66.7% (2/3)
100% (3/3)
100
50
0
0 50 100
PWM Signal Duty Cycle (%)
3. PWM Control
In addition to the digital LED brightness control, the
FAN5616 features a PWM control. The LED current var-
ies according to the width of the PWM signal applied to
the EN1/EN2 input pins. Once the desired maximum
LED current (ILED-MAX) is set by the external RSET resis-
tor, the percentage of ILED-MAX to perform the dimming
operation depends on the configuration of the PWM sig-
nal with respect to the 2-bit DAC inputs (EN1 and EN2)
as described in Table 2.
For example, if RSET = 7.8kΩ then ILED-MAX = 20mA. If
EN1 and EN2 are tied together and a PWM signal is
applied, the LED current will vary between 0% and 100%
(0mA and 20mA) of the maximum LED current according
to the duty cycle of the PWM signal.
The PWM signal can be applied to either enable input
pins (EN1/EN2) or to both tied together. Depending upon
the configuration, the average LED current can be
adjusted within any range limited by 0, 1/3, 2/3, 3/3 of the
maximum LED current as described in Table 3. The
PWM duty cycle is assumed to be between 10% and
90%.
Table 3. Average LED Dimming Range
Enable Input Pins
EN2 EN1
LOW
TOGGLE
HIGH
TOGGLE
TOGGLE LOW
TOGGLE HIGH
TOGGLE TOGGLE
Average ILED
Adjustment Range
3% to 30% of ILED-MAX
70% to 97% of ILED-MAX
6% to 60% of ILED-MAX
39% to 93% of ILED-MAX
10% to 90% of ILED-MAX
Figure 7. Ideal PWM Dimming Response
4. Dimming with DC Voltage
The brightness control using a variable DC voltage is
shown in Figure 8. If R1 = 78kΩ, R2 = 7.8kΩ, adjusting
VEXT in the 0V to 0.6V range results in dimming the LED
current from 22mA to 2mA.
R2
VEXT
R1
ISET
FAN5616
Figure 8. DC Voltage Control
The FAN5616’s internal circuit maintains a constant
VSET = 0.6V. Adjusting VEXT changes the ISET and ILED
accordingly.
By selecting different values for R1, R2 and VEXT, the
ILED variation range can be changed according to the fol-
lowing equation:
ILED =
156 + (156 – 260 x )VEXT mA
R1 R2
Where, 0V < VEXT < 0.6V (1+R2/R1) and R1 and R2 are
in kΩ.
The recommended PWM frequency range is 200Hz to
50kHz for an acceptable linear response. At higher
frequencies, the current waveform can no longer follow
the PWM signal waveform, resulting in a significant
difference between the value of the average ILED and the
theoretical calculation.
FAN5616 Rev. 1.0.0
11
www.fairchildsemi.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet FAN5616.PDF ] | |
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