1

1 x 10

1

-11

GND

BOOT

SW

VOUT

RON

LM3406

VIN

D2

L1

VCC

CS

COMP

VINS

D1

LED1

DIM

LM3406, LM3406HV, LM3406HV-Q1

www.ti.com

SNVS512E – SEPTEMBER 2008 – REVISED MARCH 2014

Design Example 2 (continued)

Schematic for Design Example 2

A switching frequency of 450 kHz helps balance the requirements of inductor size and overall power efficiency,

but more importantly keeps the switching frequency below 530 kHz, where the AM radio band begins. This

design will concentrate on meeting the switching frequency and LED current requirements over the nominal input

range of 9V to 16V, and will then check to ensure that the transient conditions do not cause the LM3406 to

the high accuracy equation listed in the Appendix.

(57)

(58)

The closest 1% tolerance resistor is 124 k

Ω. The switching frequency and on-time of the circuit should be

calculated with the high accuracy equations in the APPENDIX.

(59)

(60)

(61)

(62)

(63)

(64)

8.4.2 OUTPUT INDUCTOR

Since an output capacitor will be used to filter some of the LED ripple current, the inductor ripple current can be

(65)

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