x

x

1

L

x D x T

Time

LM3414, LM3414HV

www.ti.com

SNVS678E – JUNE 2010 – REVISED MAY 2013

Figure 16. Waveforms of a Floating Buck LED Driver with PLM

INDUCTOR SELECTION

To ensure proper output current regulation, the LM3414/14HV must operate in Continuous Conduction Mode

(CCM). With the incorporation of PLM, the peak-to-peak inductor current ripple can be set as high as ±60% of

the defined average output current. The minimum inductance of the inductor is decided by the defined average

LED current and allowable inductor current ripple. The minimum inductance can be found by the equations

shown below:

Since:

(4)

Thus:

(5)

The LM3414/14HV can maintain LED current regulation without output filter capacitor. This is because the

inductor of the floating buck structure provides continuous current to the LED throughout the entire switching

cycle. When LEDs are driven without filter capacitor, the LED peak current must not set exceeding the rated

current of the LED. The peak LED current is governed by the following equation:

(6)

INTERNAL N_MOS POWER SWITCH

The LM3414/14HV features an integrated N-channel power MOSFET that connects between the LX and GND

pins for power switching. With the switch turned ON, the resistance across the LX and GND pins is 1.8

Ω

maximum.

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