Step-Up DC/DC Converter-LED Backlight Driver
The XC9133 series is a fixed frequency, constant current step-up DC/DC converter which is optimized for LED backlight applications in mobile phones, PDAs and digital cameras. Output voltage of up to 17.5V is possible so that four white LEDs can be driven in series.
Since the LED current is set by only one external resistor, all white LEDs placed in series can be turned on at the same time. The new DC/DC Converter is also able to drive a network of two parallel banks of three LEDs.
LED dimming is controlled by adjusting the duty cycle of a PWM signal (10kHz Max.) applied to the CE pin.
Efficiency is high with a 0.2V low feedback reference voltage ensuring the RLED losses are minimal. In addition, an internal MOSFET with a low RDSON of 2.4Ω is used. A low profile and small board area solution can be achieved using a chip inductor and a small ceramic output capacitor CL=0.22μF as a result of the high 1MHz switching frequency.
If white LEDs are opened or damaged, the detector built in the Lx pin causes the IC to stop oscillating, preventing excessive increase of the output voltage.
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||85%, 3 white LEDs in series, VIN=3.6V,ILED=20mA|
|Lx Limit Current||360mA(TYP.)|
|Lx Overvoltage Limit||19V(TYP.)|
|Package||SOT-25||Number of Pins||5|
|Pcs/Reel||3,000||Package Size(mm)||2.8 x 2.9 x 1.3|
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