SC658 datasheet(12/22 Pages) SEMTECH

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Applications Information (continued)

SC658

must be followed regardless of which backlight grouping

configuration is being used. Note that it is only necessary

to set the BLEN bits for the main display.

Table 1 — Fade-In from Off State

Command

Sequence

Action

Data

Disable fade

Write to register 04h

00h

Set Main back-

lights to 0.5mA

Write to register 0h

04h

Enable fade

Write to register 04h

0h, 02h, or 03h

Set BLEN bits

Write to register 00h

Any value from 0h

through 3Fh

Set new value of

backlight current

Write to register 0h

Any value from 05h

through Fh

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 Fade register (04h). 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 04h

0h, 02h, or 03h

(but not 00h)

Set Main back-

lights to 0mA

Write to register 0h

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 Fade register (04h). This procedure 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 04h

0h, 02h, or 03h

Set new value of

backlight current

Write to register 0h

Any value from 05h

through Fh

Additional Information

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

refer to the SC658 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).

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.

Sleep Mode

When all LEDs are disabled, sleep mode is activated. This

is a reduced current mode that helps minimize overall

current consumption by disabling the clock and the

charge pump while continuing to monitor the serial inter-

face for commands. An additional current savings can be

obtained by putting the serial interface in standby mode

(see SemPulse Interface, Standby Mode).

Protection Features

The SC658 provides several protection features to safe-

guard the device from catastrophic failures. These features

include:

Output Open Circuit Protection

Over-Temperature Protection

Charge Pump Output Current Limit

LED Float Detection

Output Open Circuit Protection

Over-Voltage Protection (OVP) at the OUT pin prevents the

charge pump from producing an excessively high output

voltage. In the event of an open circuit between the OUT

pin and all current sinks (no loads connected), the charge

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