CAT3603

9

Doc. No. 5017 Rev. C

Characteristics subject to change without notice

LED CURRENT SETTING

connected between the RSET pin and ground. Table

resistor value for standard 1% precision surface

mount resistors.

Table 1. RSET Resistor Selection

LED Current (mA)

1

649

5

287

10

102

15

49.9

20

32.4

25

23.7

30

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:

≤ 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 5k

Ω.

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

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