SC662 datasheet(14/30 Pages) SEMTECH

14 / 30 page

SC662

Figure 7. The overall fade range is a piece-wise linear, log-

rithmic type of function which provides for a very smooth

visual fading effect.

The fade rate may be changed dynamically when a fade

operation is active by writing new values to the fade reg-

ister. When a new backlight level is written during an

ongoing fade operation, the fade will be redirected to the

new value from the present state. An ongoing fade opera-

tion may be cancelled by disabling fade, which will result

in the backlight current changing immediately to the final

value. If fade is disabled, the current level will change

immediately without the fade delay.

The terms BLEN and FADE are used for bits which are

defined in a later section of the datasheet. The reader may

choose to skip ahead to the Register Map and Register

and Bit Definitions sections for a better understanding of

these terms before continuing with this section’s explana-

tion of the fade function and fade state diagram.

Fade State Diagram

If the main BLEN bits are disabled during an ongoing fade,

the main bank will turn off immediately. When the main

BLEN bits are re-enabled and FADE = 1, the main backlight

currents will begin at 0mA and fade to the target value. If

the main BLEN bits are re-enabled and FADE = 0, the main

backlights will proceed immediately to the target value.

The state diagram in Figure 1 describes the fade operation.

More details can be found in the Register Map section.

Write either

MFADE

bit = 0

Write new

bright level

No change

Write new

bright

level

Write new

brightness level

Fade is

redirected toward

the new value

from current

state

Fade

begins

Fade

ends

Immediate

change to

new bright

level

New rate

is used for all

remaining steps

No change

Immediate

change to new

bright level

Fade

continues

unchanged

Write all main bank

enable bits = 0

Bank

turns off

immediately

Fade begins

at 0mA

Fade

processing

Main bank

disabled

Write either or

both MFADE

bit(s) = 1

Write

MFADE1

and

MFADE0

= 0

Write a different

non-zero value

to MFADE bits

Fade is enabled:

MFADE1

and/or

MFADE0

= 1

Write

either

MFADE

bit = 1

Fade is disabled:

MFADE1

and

MFADE0

= 0

Write

either

MFADE

bit = 0

Re-write

the same

value to

MFADE

bits

Write any

main bank

enable bit(s) = 1

Figure 1 — Fade Function State Diagram

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.

Applications Information (continued)

SC662 Datasheet(PDF) 14 Page - Semtech Corporation

SC662 Datasheet(HTML) 14 Page - Semtech Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Datasheet Download

Link URL