CAT3604V

© Catalyst Semiconductor, Inc.

9

Doc. No. MD-5029 Rev. B

Characteristics subject to change without notice

SET

R

V

6

.

0

132

×

BLOCK DIAGRAM

Figure 2. CAT3604V Functional Block Diagram

BASIC OPERATION

At power-up, the CAT3604V starts operating in 1x

mode where the output will be approximately equal to

the input supply voltage (less any internal voltage

losses). If the output voltage is sufficient to regulate all

LED currents, the device remains in 1x operating mode.

If the input voltage is insufficient or falls to a level

where the regulated currents cannot be maintained,

the device automatically switches into 1.33x mode

(after a fixed delay time of about 400μs). In 1.33x

mode, the output voltage is approximately equal to

1.33 times the input supply voltage (less any internal

voltage losses).

This sequence repeats in the 1.33x and 1.5x mode

until the driver enters the 2x mode. In 1.5x mode, the

output voltage is approximately equal to 1.5 times

the input supply voltage. While in 2x mode, the

output is approximately equal to 2 times the input

supply voltage.

If the device detects a sufficient input voltage is

present to drive all LED currents in 1x mode, it will

change automatically back to 1x mode. This only

applies for changing back to the 1x mode. The

difference between the input voltage when exiting 1x

mode and returning to 1x mode is called the 1x mode

LED Current Selection

The LED current is set to by the external resistor RSET

as follows:

LED current =

The EN pin enables and disables the device. The LED

driver enters a “zero current” shutdown mode if EN is

held low for 1.5ms or more.

As soon as the EN input goes low, all LED channels

are instantly disabled, where the LED current is set to

zero. As long as the CAT3604V is not in shutdown

mode, the LEDs turn on as soon as the EN goes high.

Mode Control

1, 1.3MHz

Oscillator

Current

Setting

Reference

Voltage

1x mode (LDO)

1.33x, 1.5x, 2x Charge Pump

VIN

VOUT

EN

RSET

GND

LED1

LED2

LED3

LED4

LED Channel

Current Regulators