SC657 datasheet(20/22 Pages) SEMTECH

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SC657

Main Fade Control (04h)

This register sets the fade status and rate for the main

backlight group.

Bits [D5:D2]

These bits are unused and are always zeros, so the

maximum pulse count for this register is 3.

MFADE1, MFADE0[D1:D0]

These bits are used to enable and set the rise/fall rate

between two backlight currents as follows in Table 7.

Table 7 — Main Display Fade Control Bits

MFADE1

MFADE0

Fade Feature Rise�Fall Rate

(ms�step)

OFF

The number of steps used to change the backlight current

will be equal to the change in binary count of bits

MBL[4:0].

When a new backlight current is set, the backlight current

will change from its current value to a new value set by

bits MBL[4:0] at the rate determined by MFADE and

MFADE0 bits. The total fade time is determined by the

number of steps between old and new backlight values,

in Table 4, multiplied by the rate of fade in ms/step.

Backlight Grouping Configuration (05h)

This register assigns the LEDs to the back light bank

configurations.

Bits [D5:D3]

These bits are unused and are always zeros, so the

maximum pulse count for this register is 7.

MB2, MB1 and MB0 [D2:D0]

These bits are used to set the number of LED drivers dedi-

cated to each backlight group. This allows the device to

drive up to three different sets of LEDs with different

current settings. Note that any driver assigned to any LED

group can still be disabled independently if not needed.

The code set by these bits determines how the LED drivers

are assigned among the three LED groups according to

the assignments listed in Table 8. Default state for each of

these three bits is “0” (all LEDs assigned to main display).

Table 8 — Backlight Grouping Configuration

MB2 MB1 MB0

Main

Display

LED

Drivers

Sub

Display

LED

Drivers

Third

Display

LED

Drivers

BL-BL5

BL-BL3

BL4-BL5

BL-BL2

BL3-BL4

BL5

BL-BL2,

BL5

BL3

BL4

BL-BL3

BL4-BL5

BL-BL4

BL5

BL-BL5

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