FAN5333BSX

The onsemi FAN5333BSX is a general-purpose LED driver featuring fixed-frequency PWM operation and an integrated FET switch. The high output power makes it suitable for driving flash LEDs in serial connections. The 1.5MHz switching frequency minimizes switching noise measured at the battery terminal of handheld communications equipment. The low on-resistance of the internal N-channel switch ensures high efficiency and low power dissipation. The 315mV feedback voltage minimizes power loss in the current-setting resistor. Cycle-by-cycle current limiting keeps the peak switch current below 1.5A, while over-voltage protection and thermal shutdown provide comprehensive fault protection.

The FAN5333BSX operates as a fixed-frequency boost converter for LED driving: 1) Boost Regulation: The internal N-channel MOSFET switches at 1.5MHz, storing energy in an external inductor during the on-time and releasing it to the output through an external Schottky diode during the off-time. The output voltage rises to whatever level is needed to drive the LED string current. 2) Current Regulation: The feedback (FB) pin monitors the voltage across an external current-setting resistor in series with the LEDs. The regulator adjusts the switch duty cycle to maintain 315mV at the FB pin, setting the LED current to ILED = 315mV/RSET. 3) Protection: Cycle-by-cycle current limiting protects the switch during overload. Over-voltage protection activates if the output exceeds the safe range. Thermal shutdown disables the device at excessive junction temperatures.

• Serial flash LED driver in cell phone camera modules
• LED backlight boost supply for handheld displays
• Display bias voltage generation in portable devices