General Description
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 up to 17.5V is possible so that four of white LEDs can be driven in series. Since an LED current is set by one external resistor, all white LEDs placed in series can be turned on in equable. If each three serial connection LEDs are placed in two parallel lines, total six LED can be driven.
LED dimming is controlled by adjusting the duty cycle of a PWM signal (10kHz Max.) applied to the CE pin.
Efficiency is high with the low feedback reference voltage 0.2 V ensuring the RLED losses are minimal. In addition, an internal MOSFET with a low RDSON 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.
Features
- Input Voltage Range : 2.5V~6.0V
- Output Voltage Range : Up to 17.5V externally set-up, Reference voltage 0.2V +5%
- Oscillation Frequency : 1.0MHz±20%
- ON Resistance : 2.4Ω
- High Efficiency : 85%, 3 white LEDs in series, VIN=3.6V, ILED=20mA
- Control : PWM control
- Stand-by Current :ISTB=1.0μA (MAX.)
- Output Capacitor : 0.22μF, ceramic
- Lx Limit Current : 360mA(TYP.)
- Lx Overvoltage Limit : 19V (TYP.)
- Packages : SOT-25, USP-6C (under development)
Applications
- For White LED drivers
- Mobile phones
- PDAs
- Digital cameras
Typical Application Circuit
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