CAT3606

http://onsemi.com

5

Basic Operation

At power-up, the CAT3606 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, to boost the output voltage high

enough to achieve the nominal LED current.

The above sequence 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 Main and Sub display enable pins

(ENM or ENS) does not affect the mode of operation.

LED Current Setting

connected between the RSET pin and ground. Table 5 lists

for standard 1% precision surface mount resistors.

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

The enable lines ENM and ENS allow to turn On or Off

a group of LEDs as shown in Table 6.

Table 6. LED Selection

Control Lines

LED Outputs

EN

ENM

ENS

Main

LED1 − LED4

Sub

LED5 − LED6

0

X

X

–

–

1

1

1

–

–

1

0

1

ON

−

1

1

0

−

ON

1

0

0

ON

ON

NOTES: 1 = logic high (or VIN)

0 = logic low (or GND)

– = LED output OFF

X = don’t care

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 0.2 mA. When the

following equation is true on any channel, the driver turns

off the LED channel:

Note: The CAT3606 is designed to drive LEDs with forward

voltage greater than 1 V and is not compatible with resistive

loads.