FAN5611 Datasheet, PDF (8/12 Pages) Fairchild Semiconductor – Low-Dropout LED Drivers for White, Blue or any Color LED

FAN5611/FAN5612/FAN5613/FAN5614
PRODUCT SPECIFICATION
In some cases, there is already a voltage bus in the system,
which can be utilized. Due to the ultra-low voltage drop of
the FAN561X series of LED drivers to drive high VF white
or blue LEDs. The VIN needs to be only 300mV higher than
the highest VF in the circuit.
V_IN
V_CONTROL
I_SET
I4
I3
I2
I1
CTRL
R_SET
FAN5613
ENABLE ^ON/OFF
GND
Key advantage:
• No need for current matching resistors and discrete
transistor for brightness control
LED Brightness Control
All of the FAN561X LED Drivers feature analog and PWM
controls to give designers flexible brightness control. These
control methods can be applied to the circuit in two different
ways, to provide more flexibility than any other solution. To
determine the value of RSET, use the “ISET vs. VCTRL” graph
under the Typical Performance Characteristics section.
1. FAN5611
V_IN
– VDROP < 0.3V
– VF (at 20mA) < 3.3V to 4.0V (High VF)
– VIN (at 20mA) =VDROP + VF = 3.6V to 4.3V
– VIN (at 5mA Typical) ~ 3.3V
Where VIN = Existing bus = 3.3V to 4.3V
Key advantages:
• No boost circuit needed for LCD or keyboard backlight
• Driver utilizes the existing bus
• Ultra-low voltage drop provides the full 20mA LED
current at the lowest possible voltage level.
Example 3: Drive white, blue, red, amber LEDs
string
Assuming boost circuit, or existing voltage bus, the
FAN561X series of LED drivers can be used to drive a whole
string of LEDs and flexible brightness control - analog
and/or PWM.
V_IN
I_SET
I4
I3
I2
I1
V_CONTROL (3V)
CTRL _FAN5611
R_SET
GND
- Analog
Set VCONTROL and RSET for LED current
I_LED = ²----⁰---⁰-----^×-----⁽--^V----^C----^O---_R-^N----_ST---^RE----_TO----^L----–-----^V----^C---^T----^R---^L----⁾
- PWM
VCONTROL = PWM
– Amplitude sets maximum LED current
– Pulse width controls between 0 and maximum
2. FAN5612
V_IN
'N' number of LEDs Per Branch
I_SET
I4
I3
I2
I1
V_CONTROL
CTRL
R_SET
ENABLE
FAN5613
ON/OFF
GND
I_SET
I3
I2
I1
V_CONTROL
CTRL
FAN5612
R_SET
ENABLE ^ON/OFF
GND
– VDROP < 0.3V
– VIN_MIN = N × VF + VDROP
– VIN _MAX = N × VF + 5.5V
Where VIN = Existing bus, boost voltage
- Analog
Set VCONTROL and RSET for LED current
- PWM - 1
I_LED = ²----⁰---⁰-----^×-----⁽--^V----^C----^O---_R-^N----_ST---^RE----_TO----^L----–-----^V----^C---^T----^R---^L----⁾
VCONTROL = PWM
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REV. 1.0.4 6/4/04