Datasheet FAN5613 (Fairchild) - 9

F AN561 Example 3: Drive white, blue, red, amber LEDs string
– VDROP < 0.3V Assuming a boost circuit or existing voltage bus, the – VIN_MIN = N ¥ VF + VDROP – V
1/F
FAN561X series of LED drivers can be used to drive a IN _MAX = N ¥ VF + 5.5V whole string of LEDs with flexible brightness control via where V
AN5612/F
IN = existing bus, boost voltage. analog and/or PWM. VIN
Key advantage:
• No need for current matching resistors and discrete transistor for brightness control. 'N' number of
A
LEDs Per Branch
N5613/F
ISET I4 I3 I2 I1 VCONTROL CTRL R FAN5613
A
SET ENABLE
N5614
ON/OFF GND
LED Brightness Control
All of the FAN561X LED drivers feature analog and
2. FAN5612
PWM controls to give designers flexible brightness con- VIN trol. These control methods can be applied to the circuit in two different ways to provide more flexibility than other solutions. To determine the value of RSET, use the ISET vs. VCTRL graph in Figure 4. I3 I2 I1 ISET VCONTROL CTRL FAN5612
1. FAN5611
RSET ON/OFF VIN ENABLE GND
- Analog
I4 I3 I2 I1 ISET Set VCONTROL and RSET for LED current using: VCONTROL (3V) CTRL FAN5611 R
- PWM - 1
SET × ( ) GND 200 V – V I CONTROL CTRL LED = ------------------------------------- RSET VCONTROL = PWM
- Analog
Set V – Amplitude sets maximum LED current. CONTROL and RSET for LED current using: – Pulse width controls between 0 and maximum. 200 × (V – V ) CONTROL CTRL
- PWM - 2
I = ------------------------------------- LED RSET Set VCONTROL and RSET for maximum LED current using:
- PWM
I ∼ 200 × I LED SET VCONTROL = PWM – Amplitude sets maximum LED current. ON/OFF = PWM – Pulse width controls between 0 and maximum. – Amplitude has no effect on current. – Pulse width controls between 0 and maximum. © 2003 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN5611/FAN5612/FAN5613/FAN5614 Rev. 1.0.9 9