Step up DC/DC Converter - Backlight LED Driver
The XC9116 series is a fixed frequency, constant current step-up DC/DC converter ideal for driving LEDs used in backlighting applications such as cellular phones, PDAs and digital cameras. Output voltage of up to 17.5V can be derived, therefore, four white LEDs in series can be driven. Since an LED current can be set by an external resistor when LEDs are in-series connection, all white LEDs can be turned on equably. A network of two parallel legs with three in each LED can be also driven. Luminance of the LEDs is controlled by changing the duty cycle of a PWM signal applied to the CE pin. Efficiency is high with the low feedback reference voltage ensuring the RLED losses are minimal. In addition, an internal MOSFET with an RDSON of 2.0Ω is used. A low profile and small board area solution can be achieved using a chip coil and an ultra small ceramic output capacitor (CL) of 0.22μF as a result of the high 1.0MHz switching frequency.
The 'B' type of XC9116 has an additional fault detection circuit. If the LEDs are disconnected or damaged, excess or run away output voltage is prevented by stopping the drive of the internal MOSFET.
Typical Application Circuit
|Input Voltage Range||2.5V～6.0V|
|Output Voltage Range||Up to 17.5V externally set-up,Reference voltage 0.2V±5.0%|
|High Efficiency||86%(TypeB),84%(TypeD), (VIN=3.6V,ILED20mA when driving 3 white LEDs in series)|
|Load Capacitors||0.22μF, Ceramic|
|Lx Limit Current||325mA|
|Lx Overvoltage Limit||XC9116 TypeB|
|No Lx Overvoltage Limit||XC9116D Type|
|Package||SOT-25||Number of Pins||5|
|Pcs/Reel||3,000||Package Size(mm)||2.8 x 2.9 x 1.3|
|Package||USP-6B||Number of Pins||6|
|Pcs/Reel||3,000||Package Size(mm)||1.8 x 2.0 x 0.6|
What is the standby current?
The current that flows through the IC in the standby mode. The standby mode means the state where the IC has been turned off by the CE function.
What does the FB product mean?
An IC for which any output voltage can be set by the reference voltage of the FB pins and the external dividing resistor. The output voltage is determined by the RFB1 and RFB2 values, using the following formula: VOUT = Vref × (RFB1 + RFB2)/RFB2