feature

LED Drivers (2 to 4) for Parallel LEDs Supports Ultra Low Voltage Drop (<300mV) for DC Li-Ion Applications No EMI, No Switching Noise Current Matching Does Not Need External Components Analog and PWM Brightness Control FAN5611 , FAN5613 have Up to 160mA bias current (up to 40mA per LED) FAN5612 with up to 120mA bias current (up to 40mA per LED) FAN 5614 with up to 160mA bias current (up to 80mA per LED An) enable/disable control (FAN5612, FAN5613, FAN5614) Shutdown current < 1 μA Small footprint SC-70 and MLP

application

Mobile phone PDA, digital camera, MP3 player Handheld computer LCD display module Keyboard backlight LED display

illustrate

The FAN5611/12/13/14 low dropout product family is designed to drive two to four parallel LEDs, providing matched current source bias for all color LEDs. LED current is set by external resistor RSET. The FAN5611/13 supports four parallel LEDs with 160mA bias current (up to 40mA per output). The FAN5612 supports three LED currents up to 120mA biased (40mA per output). The fan 5614 drives two high current LEDs (80mA each). Pin I1 should always be connected to the LED to supply current to match any additional LEDs. Use enable to select fan 5612/13 and 14 pins. When the chip is not selected (enable pin is low), the supply current drops to less than 1 µA. FAN5611, FAN5612 and FAN5614 are packaged in SC-70. FAN5611 and FAN5613 are provided in the MLP package.

Absolute Maximum Ratings "Absolute Maximum Ratings" are values for which the safety of the device is not guaranteed. This device should not operate within these limitations. The parameter values defined in the Electrical Characteristics table are not guaranteed to be at absolute maximum ratings. The "Recommended Operating Conditions" table defines the conditions for actual equipment operation.

Application Information: Operation Description The regulated current through each LED is a multiple of the ISET current. The ISET value is determined by the RSET value. The ISET value can be calculated as: ISET=ILED/current gain reference graph, ISET vs VCTRL graph, estimate VCTRL. The value of RSET is based on the formula as follows: RSET=(VCONTROL-VCTRL)/ISET For example, when VCONTROL=3V, the current limit is 10mA through the LED display, ISET=50µA, that is, the approximate value of VCTRL is 1.2V, as shown in Figure 4 shown. The RSET value to maintain 10mA regulation is 36kΩ. The LED intensity can be adjusted by varying the duty cycle to adjust the period of the square wave applied to the enable pin. Frequency greater than 100Hz is best to avoid the "flicker" effect. The maximum operating frequency is 10MHz. Efficiency Considerations The low-dropout structure of the FAN561X driver can significantly improve efficiency compared to using simple ballast resistors. System efficiency, defined as the ratio between LED power and input power, can be calculated as: The lower the VCATHODE, the higher the system efficiency. Use a higher VIN and more LEDs, as shown in Example 3.

Application Notes

The FAN561X series of ultra-low voltage drop LED drivers allow devices to drive white, blue and other color LEDs over a wide range of input voltages. This driver can be used in many applications. Although only the FAN5613 is shown in all three examples, any of the FAN561X series LED drivers can be used in the applications presented due to their similar operation. Example 1: Directly driving a low VF white or blue LED from a single cell Li-Ion When using a white or blue low VF LED, using driver voltage reduction, VIN requires only 3.4V full 20mA LED current . At 3.1V, there is a typical voltage LED of 5mA current available. Single-cell Li-ion is used in applications such as cell phones or digital cameras. In most cases, the voltage level of the Li-Ion battery is reduced to the 3.0V voltage level, not to the fully discharged level (2.7V) before requiring a charger.

– VDROP < 0.3V – VF (20mAh) < 3.1V (low VF) – VIN (20mAh) = VDROP + VF = 3.4V – VIN (5mA typical) ~ 3.1 volts where VIN = lithium-ion voltage of a single cell. Main advantage: LCD or keyboard does not need a boost circuit backlight. The drive connects directly to the Li-Ion battery. No EMI, no switching noise, no loss of boost efficiency, no capacitance, and no inductance. Example 2: From an existing bus from 4.0V to 5.5V a high VF white or blue LED has a forward voltage drop ranging from 3.2V to 4.0V. Using a maximum current of 20mA for maximum brightness, single-cell Li-Ion typically requires a boost circuit voltage range. In some cases, there is already a bus in the voltage system that can be utilized. Due to the ultra-low voltage drop of the FAN561X series LED drivers driving high VF white or blue LEDs, the VIN needs to be only 300mV higher than the highest VF in the circuit. – VDROP < 0.3V – VF (20mA) < 3.3V to 4.0V (High VF) – VIN (20mA) = VDROP + VF = 3.6V to 4.3V – VIN (typical 5 mAh) ~3.3V where VIN = existing bus = 3.3V to 4.3V. Main advantage: LCD or keyboard does not need a boost circuit backlight. The driver utilizes the existing bus. The ultra-low voltage drop provides full 20mA LED current at the lowest voltage level.

Example 3: Driving a white, blue, red, amber LED string Assuming a boost circuit or an existing voltage bus, the FAN561X series of LED drivers can be used to drive an overall string of LEDs with flexible brightness control analog and/or pulse width modulation.

– VDROP < 0.3V

– V IN_MIN = N ¥ V F + V DROP

– V IN _MAX = N ¥ V F + 5.5V

Where, VIN=existing bus, boost voltage. Key benefits: No current matching resistors and discrete brightness co-transistors

LED Brightness Control All FAN561X LED drivers have analog and PWM control, giving designers flexible brightness control. These control methods can be applied to circuit solutions in two different ways to provide more flexibility. To determine the value of RSET, use the VCTRL diagram from the ISET diagram.