CAT4201TD-GT3 Datasheet, PDF (11/15 Pages) ON Semiconductor – 350mA High Efficiency Step Down LED Driver

CAT4201
Operation from high supply voltage above 14V
For operation from a supply voltage above 14V, it is
recommended to have a slew rate of 1µs or more for
every 5V increase in VBAT supply. When using a high
supply voltage of 24V, a 1Ω or 2Ω resistor in series
with the supply, as shown on Figure 7, is
recommended to limit the slew rate of the supply
voltage. A 4.7µF minimum ceramic capacitor is placed
between the VBAT pin and ground. The combination
of the series resistor R3 and input capacitor C1 atcs
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 CAT4201 driver.
VBAT R3
24V 1Ω C1
4.7µF
R1
10kΩ
VBAT
CAT4201
RSET
CTRL
SW
GND
D1
C2
4.7µF
L
33µH
R1
300mA
1kΩ
Figure 7. 24V Application with 5 LEDs
Operation from high supply voltage of 36V
When powering from a high supply voltage of 36V, a
2Ω resistor in series with the supply is recommended,
as shown on Figure 8, to limit the slew rate of the
supply voltage.
VBAT R3
36V 2Ω C1
4.7µF
R1
10kΩ
VBAT
CAT4201
RSET
CTRL
SW
GND
D1
C2
2.2µF
L
47µH
R2
300mA
1kΩ
Figure 8. 36V Application with 6 LEDs
Parallel configuration for driving LEDs beyond
350mA
Several CAT4201 devices can be connected in
parallel for driving LEDs with current in excess of
350mA. The CAT4201 driver circuits are connected to
the same LED cathode. Figure 9 shows the
application schematic for driving 1A into one LED with
three CAT4201 connected in parallel. Each CAT4201
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.
VIN R5
1Ω
C1
4.7µF
R1
8.3kΩ
U1
VBAT
CAT4201
RSET
CTRL
SW
GND
D1
L1
22µH
C4
10µF
1A
R4
1kΩ
C2
4.7µF
R2
8.3kΩ
U2
VBAT
CAT4201
RSET
CTRL
SW
GND
D2
L2
22µH
C3
4.7µF
R3
8.3kΩ
U3
VBAT
CAT4201
RSET
CTRL
SW
GND
D3
L3
22µH
Figure 9. Three CAT4201 in Parallel for 1A LED
© 2008 SCILLC. All rights reserved.
11
Characteristics subject to change without notice
Doc. No. MD-5025 Rev. E