CAT3604A

http://onsemi.com

5

Basic Operation

At power-up, the CAT3604A 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.

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