CAV4201

http://onsemi.com

10

Figure 25. LED Current vs. Duty Cycle

0

50

100

150

200

250

300

0

20

40

60

80

100

DUTY CYCLE [%]

Figure 26. Circuit for PWM on CTRL

RSET

SW

GND

CAV4201

VBAT

VBAT

PWM

control

4.7 mF

C1

10 mF

C2

NPN

L

D

12 V

0 V

5 V

CTRL

22 mH

1 kW

R5

47 kW

R1

10 kW

R2

Q1

1 kW

R4

PWM on RSET Pin

Another dimming method is to place in parallel to R1

another resistor with a FET in series, as shown on Figure 27.

R1 sets the minimum LED current corresponding to 0% duty

cycle. The combined resistor of R1 and Rmax sets the

maximum LED current corresponding to 100% duty cycle.

Figure 27. Circuit for PWM on RSET

RSET

SW

GND

CAV4201

VBAT

VBAT

PWM

control

Rmax

4.7 mF

C1

10 mF

C2

NPN

R1

L

D

13 V

CTRL

22 mH

1 kW

R2

Q1

OFF ON

A resistor value for R1 of less than 90 k

W is recommended

to provide better accuracy.

Operation from High Supply Voltage Above 14 V

For operation from a supply voltage above 14 V, it is

recommended to have a slew rate of 1

ms or more for every

5 V increase in VBAT supply. When using a high supply

voltage of 24 V, a 1

W or 2 W resistor in series with the supply,

as shown on Figure 28, is recommended to limit the slew rate

of the supply voltage. A 4.7

mF minimum ceramic capacitor

is placed between the VBAT pin and ground. The

combination of the series resistor R3 and input capacitor C1

acts as a low pass filter limiting the excessive in−rush

currents and overvoltage transients which would otherwise

occur during “hot−plug” conditions, thereby protecting the

CAV4201 driver.

CTRL SW

GND

CAV4201

VBAT

VBAT

4.7 mF

C1

4.7 mF

C2

R1

R1

10 kW

1 kW

R3

1 W

L

D1

24 V

RSET

33 mH

300 mA

Figure 28. 24 V Application with 5 LEDs

Operation from High Supply Voltage of 36 V

When powering from a high supply voltage of 36 V, a 2

W

resistor in series with the supply is recommended, as shown

on Figure 29, to limit the slew rate of the supply voltage.

Inductor value should be 33

mH or higher.

CTRL SW

GND

CAV4201

VBAT

VBAT

4.7 mF

C1

2.2 mF

C2

R1

R2

10 kW

1 kW

R3

2 W

L

D1

36 V

RSET

47 mH

300 mA

Figure 29. 36 V Application with 6 LEDs

Parallel Configuration for Driving LEDs Beyond

350 mA

Several CAV4201 devices can be connected in parallel for

driving LEDs with current in excess of 350 mA. The

CAV4201 driver circuits are connected to the same LED

cathode. Figure 30 shows the application schematic for

driving 1 A into one LED with three CAV4201 connected in

parallel. Each CAV4201 is driving the LED with a current

set by its RSET resistor. The resulting LED current is equal

to the sum of each driver current.