IS31LT3948

IS31LT3948 PFM MODE BOOST LED DRIVER WITH THE EXTERNAL NMOS OCTOBER 2011 GENERAL DESCRIPTION The IS31LT3948 is a PFM step-up DC-DC converter designed for driving the white LED arrays for large size LCD panel backlighting applications. It can deliver stable constant output current from a few milliamps up to 2A, programmed via an external resistor. The IS31LT3948 utilizes a control scheme in which the output is automatically adjusted to the optimum output voltage for the system, maximizing the efficiency. Furthermore, the control scheme is inherently stable removing the need to provide additional loop compensation. The device features external PWM dimming, which allows the flexible control of the back-lighting luminance. The IS31LT3948 has a wide input voltage range from 5V to 100V (Note). An integrated OVP circuit protects the chip and the system even under no-load conditions. Note: The IS31LT3948 has an internal 5V shunt regulator connected to the VCC pin. A dropping resistor must be connected between the VCC pin and VIN to limit current flow. VIN voltages above 100V are allowed but care must be taken to ensure that the output voltage remains greater than VIN, and that the NMOS voltage rating is sufficiently large. FEATURES Wide input voltage range: 5V-100V Constant Current Output limited only by external component selection (Note) No loop compensation required Internal over-voltage protection Internal over-temperature protection Operating temperature range -40...