FP7151 datasheet(10/13 Pages) FEELING

10 / 13 page

FP7151

This datasheet contains new product information. Feeling Technology reserves the rights to modify the product specification without notice.

No liability is assumed as a result of the use of this product. No rights under any patent accompany the sales of the product.

Website: http://www.feeling-tech.com.tw

Rev. 0.63

10/13

Inductor selection

Recommended inductor values for the FP7151 are in the range 47uH to 100uH. Higher values

of inductance are recommended at higher supply voltages in order to minimize errors due to switching

delays, which result in increased ripple and lower efficiency. Higher values of inductance also result in

a smaller change in output current over the supply voltage range. The inductor should be mounted as

close to the device as possible with low resistance connections to the LX and VIN pins. The chosen coil

should have a saturation current higher than the peak output current and a continuous current rating

above the required mean output current.

DC Dimming

IOUTDC= 0.08*VADJ/RS [for 0.3< VADJ <2.5V]. The ADJ pin can be driven by an external DC

voltage (VADJ), to adjust the output current to a value below the nominal average value defined by RS.

The LED current decreases linearly with the VADJ when 0.3V ≤ VADJ ≤ 2.5V, RS must be increased in

proportion to prevent IOUTDC exceeding 700mA maximum. When the VADJ falls below the threshold, 0.2V,

the output switch is turned off which allows PWM dimming.

PWM Dimming

A Pulse Width Modulated (PWM) signal with duty cycle DPWM can be applied to the ADJ pin,

The PWM signal is recommended above 50kHz.As shown below, to adjust the output current to a value

above or below the nominal average value set by resistor RS:

FP7151 Datasheet(PDF) 10 Page - Feeling Technology Corp.