FP7151 datasheet(8/13 Pages) FEELING

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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

8/13

Function Description

Operation

The FP7151 is a continuous mode inductive step-down converter that is easily to be configured in

varies applications ranging from 7V~26V input. The converter employs a high side current sensing

resistor RS to detect and regulate the LED current. The voltage across the current sensing resistor is

kept measured and regulated in 100mV±15mV range.

The internal 1.25V reference voltage is utilized to provide a 0.25V reference for enabling the part

and a 1.25V pulling-up voltage as current reference voltage. When VADJ>0.25V the output of the

comparator becomes high and the other blocks are enabled.

When input voltage VIN is first applied, the initial current in L1 and RS is zero and there is no

output from the current sense circuit. Under this condition, the output of comparator is high. This turns

on an internal switch and switches the SW pin low, causing current to flow from VIN to ground, via RS,

L1 and the LED(s). The current rises at a rate determined by VIN and L1 to produce a voltage ramp

across RS. When (VIN - VSENSE) > 115mV, the output of Comparator switches low and the switch turns

off. The current flowing on the RS decreases at another rate. When (VIN- VSENSE) < 85mV, the switch

turns on again and the mean current on the LED is 100mV/RS.

Adjusting output current

The device contains a low pass filter between the ADJ pin and the threshold comparator and an

internal current limiting resistor (250k nom) between ADJ and the internal reference voltage. This

allows the ADJ pin to be overdriven with either DC or pulse signals to change the VSENSE switching

threshold and adjust the output current.

Output Shutdown

The output of the low pass filter drives the shutdown circuit. When the input voltage to this circuit

falls below the threshold (0.2V nom), the internal regulator and the output switch are turned off. The

voltage reference remains powered during shutdown to provide the bias current for the shutdown

circuit. Quiescent supply current during shutdown is nominally 15uA and switch leakage is below 1uA.

Dimming Control

The FP7151 provides two dimming methods: PWM dimming and DC analog dimming. To use

PWM dimming, apply a square wave to the EN/DIM pin. To used analog dimming, apply a 0.3V~2.5V

DC voltage to this pin.

FP7151 Datasheet(PDF) 8 Page - Feeling Technology Corp.