© 2006 Semtech Corp.

POWER MANAGEMENT

SC614

United States Patent No. 6,504,422

www.semtech.com

11

POWER MANAGEMENT

State Diagrams (Cont.)

Power Management

Sleep Mode

(Register

contents stored)

Shutdown

(EN low)

Sleep Mode

(Register

contents reset)

SLEEP = 1 from any Run Mode

SWRST = 1 from any Run Mode

EN low from any mode

SLEEP = 0

Return to

previous Mode

SLEEP = 0

Run Mode

There are three options for powering down the SC614 (other than writing 0x00 to each Current Control Register or

the LED On/Off Control Register):

Sleep Mode (SLEEP = 1)

Setting this bit to 1 at any time will power down the charge pump. The register contents will be stored, the bandgap

reference will remain active, and UVLO and serial interface monitoring will continue. Clearing this bit will resume

operation as before.

Sleep Mode from Reset (SWRES = 1)

Setting SWRES to 1 will reset all registers (clearing the SWRES bit), causing the part to enter Sleep Mode but with

all registers at their reset values (0x00 for registers 0x00 through 0x07, 0x20 for Control Register 0x08 (SLEEP =

1). Upon clearing the SLEEP bit, the SC614 will enter run mode and will require writing to the registers to commence

driving LEDs.

Shutdown (EN low)

All internal functions are powered down. Pulling EN high will enter Sleep Mode with all registers reset.

Device Operation With All LEDs Disabled

If the SC614 is driving LEDs and then all LEDs are disabled, the device reverts to 1x mode with a nominal output

voltage of 3V. This decreases the response time when the LEDs are enabled once more. Quiescent current in this

mode will be 700μA (nom).