SC643 datasheet(14/26 Pages) SEMTECH

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SC643

Table 1 — Fade-In from Off State

Command

Sequence

Action

Data

Disable fade for

the bank

Write to register 09h

00h

Set the bank to

0.5mA

Write to register 01h

and/or 02h(1)

04h

Enable fade

Write to register 09h

Binary value

xx1xx0, xx1xx1,

or xx0xx1

Set BLEN bits

Write to register 00h

Any value from 01h

through 1Fh

Set new value of

backlight current

for the bank

Write to register 01h

and/or 02h

Any value from 05h

through 1Fh

Notes:

(1)

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 01h

through 3Fh

(but not 00h)

Set Main and/or

Sub backlights to

0mA

Write to register 01h

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

Applications Information (continued)

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-

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 01h

through 3Fh

(but not 00h)

Set new value of

backlight current

Write to register 01h

and/or 02h

Any value from 05h

through 1Fh

Additional Information

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

refer to the SC643 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). LDO1, LDO3, and LDO4 have iden-

tical specifications, with a programmable output ranging

from 1.5V to 3.3V. LDO2 is specified to operate with pro-

grammable output ranging from 1.2V to 1.8V. LDO2 also

has lower noise specifications so that it can be used with

noise sensitive circuits.

LDO4 is controlled by both the enable pin ENL4 and the

LDO4 control register. ENL4 may be permanently con-

nected to V

for software-only control. Alternately, power

sequencing logic may be used to enable LDO4 via the

ENL4 pin after writing to the LDO4 control register.

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