CAV4201

http://onsemi.com

11

Figure 30. Three CAV4201 in Parallel for 1 A LED

CTRL SW

GND

CAV4201

VBAT

U1

VIN

4.7 μF

C1

10 μF

C4

1 A

R4

R1

R5

8.3 kΩ

1 kΩ

1 W

L1

D1

RSET

22 μH

CTRL SW

GND

CAV4201

VBAT

U2

4.7 μF

C2

R2

8.3 kΩ

L2

D2

RSET

22 μH

CTRL SW

GND

CAV4201

VBAT

U3

4.7 μF

C3

R3

8.3 kΩ

L3

D3

RSET

22 μH

Open LED Behavior

If the LEDs are not connected, the CAV4201 stops

switching and draws very little current.

At power−up with no load connected, the capacitor C2 is

charged−up by the CAV4201. As soon as the bottom side of

the capacitor (C2−) reaches 0 volt, as shown on Figure 31,

the CAV4201 stops switching and remains in the idle mode

only drawing about 0.4 mA current from the supply.

Figure 31. Open LED Mode

Board Layout

In order to minimize EMI and switching noise, the

Schottky diode, the inductor and the output capacitor C2

should all be located close to the driver IC. The input

capacitor C1 should be located close to the VBAT pin and the

Schottky diode cathode. The CAV4201 ground pin should

be connected directly to the ground plane on the PCB. A

recommended PCB layout with component location is

shown on Figure 32. The LEDs are connected by two wires

tied to both sides of the output capacitor C2. The LEDs can

be located away from the driver if needed.

Figure 32. Recommended PCB Layout

In order to further reduce the ripple on the supply rail, an

optional Pi style filter (C−L−C) can be used. A 10

mH

inductor rated to the maximum supply current can be used.