SC644 datasheet(14/26 Pages) SEMTECH

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SC644

Table 1 — Fade-In from Off State

Command

Sequence

Action

Data

Disable fade for

the bank

Write to register 09h

Binary value

xx0xxx, xxxxx0,

or xx0xx0

Set Main and/or

Sub backlights to

0.5mA

Write to register 0h

and or 02h()

04h

Enable fade for

the bank

Write to register 09h

Binary value

xxxx0 , xxxx,

or xx0xx

Set BLEN bits

Write to register 00h

Any value from 0h

through 3Fh

Set new value of

backlight current

for the bank

Write to register 0h

and/or 02h

Any value from 05h

through Fh

Notes:

() Write only to the banks which will fade

Fade-Out from any On State to Off State

Fading the backlight LEDs from any active state to the off

state follows a simple procedure. The sequence of com-

mands for this action is shown in Table 2. Following these

steps explicitly will ensure that the fade-out operation will

proceed with no interruption at the rate specified in the

Main/Sub Backlight Fade register (09h). This procedure

must be followed regardless of the backlight grouping

configuration.

Table 2 — Fade-Out from any On State to Off State

Command

Sequence

Action

Data

Enable fade

Write to register 09h

Any value from 0h

through 3Fh

Set Main and/or

Sub backlights to

0mA

Write to register 0h

and/or 02h

00h

Fading Between Different On States

Fading from one backlight level to another (up or down)

also follows a simple procedure. The sequence of com-

mands for this action is shown in Table 3. Following these

steps explicitly will ensure that the fade-in/fade-out oper-

ation will proceed with no interruption at the rate specified

in the Main/Sub Backlight Fade register (09h). This proce-

Applications Information (continued)

dure must be followed regardless of the backlight

grouping configuration.

Table 3 — Fading between Different On States

Command

Sequence

Action

Data

Enable fade

Write to register 09h

Any value from 0h

through 3Fh

Set new value of

backlight current

Write to register 0h

and/or 02h

Any value from 05h

through Fh

Additional Information

For more details about the Fade-in/Fade-out function,

refer to the SC644 Backlight Driver Software User’s Guide

and SemPulse Interface Specification document and to the

associated software drivers available for this device

(contact your sales office for more details).

Programmable LDO Outputs

Four low dropout (LDO) regulators are included to supply

power to peripheral circuits. Each LDO output voltage

setting has ±3.5% accuracy over the operating tempera-

ture range. Output current greater than specification is

possible at somewhat reduced accuracy (refer to the

typical characteristic section of this datasheet for load

regulation examples). LDO, LDO3, and LDO4 have iden-

tical specifications, with a programmable output ranging

from .5V to 3.3V. LDO2 is specified to operate with pro-

grammable output ranging from .2V to .8V. LDO2 also

has lower noise specifications so that it can be used with

noise sensitive circuits.

Shutdown Mode

The device is disabled when the SPIF pin is held low for

the shutdown time specified in the electrical characteris-

tics section. All registers are reset to default condition at

shutdown. Typical current consumption is this mode is

0.µA

Sleep Mode

When all backlights are off the charge pump is disabled,

and sleep mode is activated. This is a reduced current

mode that helps minimize overall current consumption.

In sleep mode, the SemPulse interface continues to

monitor its input for commands from the host. Typical

current consumption in this mode is 90µA.

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