HV9903

· Color LCD Backlighting
· Cell phones, smart phones
· PDAs, pocket PCs
· Organizers
· Digital Cameras
· MP3 Players

The Supertex HV9903 is a fixed frequency DC-DC boost converter designed for driving Light Emitting Diodes (LEDs) with constant current where the light intensity is proportional to the current through them.

The input supply voltage range into the device (VDD) is 2.6 to 4.6V. Operation of the driver at lower voltages is possible as long as a 2.64.6V lowcurrent supply is available for the HV9903. The device uses a single inductor and a minimum number of passive components. The device HV9903 can be enabled/disabled via the SHDN pin.

The HV9903 has an internal oscillator. The oscillator frequency is at fixed frequency of 1.2MHz that allows use of small value inductors. The LED current can be adjusted from 5 to 40mA by an external resistor connected between the RSET and the GND pins. The amount of current though the LED can also be adjusted via DC voltage or a pulse width modulated (PWM) signal to the R_SET pin.

Soft-start is implemented on-chip HV9903, minimizing inrush current to only 30% over steady state current. An open LED circuit detects an open LED condition, disables the driver, and sets the RSET pin high. The driver is re-enabled by asserting SHDN low, then high. If the open LED condition persists, the driver will again latch off.