The KF9908 Series is a fixed frequency, constant current step-up DC/DC converter ideal for driving LEDs used in backlighting applications on cellular phones, PDAS and digital cameras etc. Output voltage of up to 23V can be derived, and from a 3.2V input six white LED's can be driven in series or alternatively, using a 2.5V input, a network of two parallel legs with three in each may be driven.
Luminance of the LED's is controlled by changing the duty cycle of a PWM signal applied to the CE pin.
In addition, an internal MOSFET with an Rds(on) of 0.80 is used. Allow profile and small board area solution can be achieved using a chip coil and an ultra small ceramic output capacitor (CL) of 0.22uF.
Features
Input voltage range : 2.5V-6V.
Output voltage range : up to 23V externally set-up reference voltage 0.25V
Oscillation frequency : 1.0MHz.
On resistance : 0.80
Control : PWM control.
Efficiency : 88%(When driving 3 white LEDs in series Vin=3.6V ILED=20mA).
Stand-by Current : ISTB=1.0Ua.
Load capacitor : 0.22uF,ceramic.
Lx limit Current :1.0A
Application
PDAs，GPSs.
For White LED Drivers.
Mobil phones, PHS.
Digital still cameras.