CAT3604V datasheet(10/15 Pages) CATALYST

10 / 15 page

CAT3604V

Doc. No. MD-5029, Rev. B

Characteristics subject to change without notice

Unused LED Channels

For applications not requiring all the channels, it is

recommended to connect the unused LED pins

directly to VOUT (see Figure 3).

Figure 3. Application with 3 LEDs

Protection Mode

If an LED is disconnected, the device senses that,

run the diagnostics, then ignores that channel and

goes back to the most effective mode. When all LEDs

are disconnected, the device runs diagnostics and

goes to 1x mode where the output is basically equal to

the input voltage.

As soon as the output exceeds about 6V, the driver

resets itself and reevaluate the mode.

If the die temperature reaches +150°C, the device

enters a thermal protection shutdown mode. When the

device temperature drops to about +130°C, the device

resumes normal operation.

LED Selection

LEDs with forward voltages (VF) ranging from 1.3V to

4.3V may be used. Selecting LEDs with lower VF is

recommended in order to extend battery life and keep

the driver in 1x mode longer as the battery voltage

decreases.

For example, if a 3.3V VF LED is selected instead of a

3.5V VF LED, the driver will stay in 1x mode for a

lower supply voltage of 0.2V.

External Components

The driver requires four external 1μF ceramic capa-

citors for decoupling input, output, and for the charge

pump. Both capacitors type X5R and X7R are

recommended for the LED driver application. In all

charge pump modes, the input current ripple is kept

very low by design and an input bypass capacitor of

1μF is sufficient.

In 1x mode, the device operates in linear mode and

does not introduce switching noise back onto the

supply.

Recommended Layout

In charge pump mode, the driver switches internally at

a high frequency. 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 TQFN

exposed pad (TAB) must be connected to the ground

plane underneath. The use of multiple via improves

the package heat dissipation.

Figure 4. PCB Layout

GND

VIN

LED2

LED3

LED1

LED4

RSET

CAT3604V

VIN

VOUT

1µF

CIN

C1-

C1+

C2-

C2+

1µF

COUT

RSET

ON OFF

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