CAT32 Datasheet, PDF (10/14 Pages) Catalyst Semiconductor – CMOS White LED Driver

CAT32
PCB LAYOUT GUIDELINES
The CAT32 is a high-frequency switching regulator and
therefore proper PCB board layout and component
placement can minimize noise and radiation and increase
efficiency. To maximize efficiency, the CAT32 design
has fast switch rise and fall times. To prevent radiation
and high frequency resonance problems minimize the
length and area of all traces connected to the SW pin and
use a ground plane under the switching regulator.
The switch, schottky output diode and output capacitor
signal path should be kept as short as possible. The
ground connection for the R resistor should be tied
SET
directly to the GND pin and not be shared with other
components.
TYPICAL APPLICATION CIRCUITS
The application diagrams below are shown for the SOT23 packages.
Two LEDs with DC Level Dimming Control:
D1
VIN
6
1
VIN
SW
2.5V DC
DIMMING
CONTROL
CAT32
5 _SHDN
3
LED
RSET
4
GND
2
15mA
Three LEDs with DC Level Dimming Control:
D1
VIN
6
1
VIN
SW
2.5V DC
DIMMING
CONTROL
CAT32
5 _SHDN
3
LED
RSET
4
GND
2
15mA
Efficiency - Three LEDs
85
80
75
70
65
60
0
Vin = 4.2V
Vin = 3.0V
5
10
15
20
LED CURRENT [mA]
Doc. No. 5001, Rev. AC
10