CAT3604

Doc. No. MD-5008 Rev. J

4

Characteristics subject to change without notice

BLOCK DIAGRAM

Figure 1. CAT3604 Functional Block Diagram

BASIC OPERATION

At power-up, the CAT3604 starts operation in 1x

mode. If it is able to drive the programmed LED

current, it continues in 1x mode. If the battery voltage

drops to a level where the LED current cannot be met,

the driver automatically switches into 1.5x mode. The

1.5x charge pump will boost the output voltage

accordingly to achieve the nominal LED current.

The operating mode is reinitialized each and every

time the chip is powered up or is taken out of

shutdown mode (via EN pin). The use of the control

pins (CTR0, CTR1, CTR2) does not reconfigure the

mode of operation.

VIN

Battery

3V to 4.2V

1µF

CIN

Current

Setting

1.2V Ref

1MHz

Oscillator

Mode Control

1x mode (LDO)

1.5x Charge Pump

EN

RSET

GND

CTR0

CTR1

CTR2

LED1

LED2

LED3

LED4

LED

Output

Select

4 Current

Sink Regulators

VOUT

20mA

C1-

C1+ C2-

C2+

1µF

1µF

1µF

24kΩ