Wide Input Voltage Range, High Efficiency

Fault Tolerant LED Driver

A8521

33

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Step 9

across it:

0.24 (A) 0.765

0.92 μF

==

2 (MHz)

0.1 (V)

(50)

The rms current requirement of the coupling capacitor is given

by:

1 – D(max)

D(max)

0.848 (A)

0.47 A

==

1 – 0.765

0.765

(51)

The voltage rating of the coupling capacitor must be greater than

2.2 μF 25 V will suffice for this application.

Figure 34. Typical application showing SEPIC configuration, with accurate input current sense, and VSENSE

to ground protection.

GATE

SW

Q1

2.2 μF

2.2 μF

4.7 μF

0.47 μF

120 pF

10 μH

10 μH

22 nF

0.1 μF

100 kΩ

10 kΩ

150 Ω

11 kΩ

20 Ω

39.2 kΩ

249 Ω

0.033 Ω

L1

2 A / 60 V

D1

OVP

VSENSE

VIN

VDD

PWM/EN

APWM

ISET

FSET/SYNC

AGND

PGND

COMP

FAULT

LED4

LED1

LED2

LED3

PAD

A8521

9 to 16 V

L2