LM3554 datasheet(11/43 Pages) TI1

11 / 43 page

LM3554

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SNVS549A – JUNE 2009 – REVISED APRIL 2011

Typical Performance Characteristics (continued)

VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10µF, CIN = 4.7µF, L = FDSE0312-2R2 (2.2µH, RL = 0.15Ω), TA = +25°C unless

otherwise specified.

Closed Loop Current Limit

VIN

(Flash Duration Register bits [6:5] = 10, (2))

(Flash Duration Register bits [6:5] = 11, (2))

VIN Monitor Thresholds

OVP Thresholds

Temperature

VIN

(3)

Indicator Current

Short Circuit Current Limit

VIN, VLEDI = 2V

VIN

(Torch Brightness Register bits[7:6] = 00)

(3)

The typical curve for Current Limit is measured in closed loop using the typical application circuit by increasing IOUT until the peak

inductor current stops increasing. The value given in the Electrical Table is measured open loop and is found by forcing current into SW

until the current limit comparator threshold is reached. Closed loop data appears higher due to the delay between the comparator trip

point and the NFET turning off. This delay allows the closed loop inductor current to ramp higher after the trip point by approximately

20ns × VIN/L

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LM3554 Datasheet(PDF) 11 Page - Texas Instruments