CAT3604

http://onsemi.com

5

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.

LED Current Setting

connected between the RSET pin and ground. Table 5 lists

for standard 1% precision surface mount resistors.

The digital control lines CTR0, CTR1 and CTR2 allow to

turn On or Off a combition of LEDs as shown in Table 6.

Short Circuit Detect/Disables

The unused LED channels can also be turned off by

connecting the respective LED pins to VOUT. In which

case, the corresponding LED driver is disabled and the

typical LED sink current is only about 20

mA. When the

following equation is true on any channel, the driver turns

off the LED channel:

Note: The CAT3604 is designed to drive LEDs with forward

voltage greater than 1 V and is not compatible with resistive

loads.

Table 5. RSET Resistor Selection

LED Current (mA)

1

649

2

287

5

102

10

49.9

15

32.4

20

23.7

30

15.4

Table 6. LED Selection

Control Lines

LED Outputs

CTR2

CTR1

CTR0

LED4

LED3

LED2

LED1

0

0

0

–

–

–

ON

0

0

1

–

–

ON

–

0

1

0

–

ON

–

–

0

1

1

ON

−

–

–

1

0

0

–

–

ON

ON

1

0

1

–

ON

ON

ON

1

1

0

ON

ON

ON

ON

1

1

1

–

–

–

–

NOTE: 1 = logic high (or VIN)

0 = logic low (or GND)

– = LED output OFF