CAT3603HV2 Datasheet, PDF (9/12 Pages) ON Semiconductor – 3-Channel LED Driver in 3 x 3mm Package

LED CURRENT SETTING
The LED current is set by the external resistor R_SET
connected between the RSET pin and ground. Table
1 lists various LED currents and the associated R_SET
resistor value for standard 1% precision surface
mount resistors.
Table 1. RSET Resistor Selection
LED Current (mA)
1
2
5
10
15
20
30
R_SET (kΩ)
649
287
102
49.9
32.4
23.7
15.4
The unused LED channels must be disabled by
connecting the respective LED pins to VOUT. A
disabled channel sinks only 0.2mA typical. When the
following equation is true on any channel, the driver
turns off the LED channel:
VOUT - V_LED ≤ 1V (LED channel OFF)
Note: The CAT3603 is designed to drive LEDs with forward
voltage greater than 1V and is not compatible with resistive
loads less than 5kΩ.
External Components
The driver requires a total of four external 1μF ceramic
capacitors: two for decoupling input and output, and
two for the charge pump. Both capacitor types X5R and
X7R are recommended for the LED driver application.
In the 1.5x charge pump mode, the input current ripple
CAT3603
is kept very low by design, and an input bypass
capacitor of 1μF is sufficient. In 1x mode, the device
operating in linear mode does not introduce switching
noise back onto the supply.
Recommended Layout
In 1.5x charge pump mode, the driver switches
internally at a high frequency of 1MHz. It is
recommended to minimize trace length to all four
capacitors. A ground plane should cover the area
under the driver IC as well as the bypass capacitors.
Short connection to ground on capacitors CIN and
COUT can be implemented with the use of multiple
via. A copper area matching the TDFN exposed pad
(GND) must be connected to the ground plane
underneath. The use of multiple via improves the
package heat dissipation.
Figure 3. Recommended Layout
© 2008 SCILLC. All rights reserved.
9
Characteristics subject to change without notice
Doc. No. MD-5017 Rev. F