SC667 datasheet(14/47 Pages) SEMTECH

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SC667

Applications Information (continued)

blink and breathe lighting effects. Details of the fade,

breathe, and blink effects are introduced later in this

Applications Information section.

Target Backlight Settings for Lighting Effects

The target backlight setting is the current which will result

at the end of a blink or breathe lighting effect cycle. The

target backlight currents for each bank. Registers 06h,

07h, 08h, and 09h contain the target current values for:

bank #1, bank #2, bank #3, and bank #4, respectively.

Bank #1 also uses the target value of register 06h in asso-

ciation with the ALS function. Bank #1 can be set to

automatically change to the target value of register 06h

when the ADC exceeds a programmable rising threshold.

ALS is defined in more detail under Ambient Light Sense,

and in the Register Map section under ADC Function

Breathe Lighting Effect

The breathe lighting effect may be applied independently

to each group. When this feature is enabled, the bank’s

backlight current will increase and decrease periodically

at a rate that mimics calm and smooth breathing. Once

initialized via the I2C interface, this function will run con-

tinuously, independent of the host processor, saving

instruction cycles and simplifying timing requirements.

Three timing parameters must be set to define the

breathe effect timing: effect rate, start time, and target

time. Group #1 and group #2 have independent timing

parameters to support a variety of options. When a bank

is assigned to a group, it adopts the timing parameters of

the respective group.

When enabled, the breathe function causes the back-

lights to change brightness by stepping the current

incrementally, using the effect rate parameter, until the

final backlight current is reached. The current will remain

at the target value for a time set by the target time param-

eter. When the target time has ended, the brightness will

again change, this time in reverse order, stepping the

current incrementally, using the effect rate parameter,

until the current returns to the start value. The current

will remain at the start value for the time set by the start

time parameter. When the start time has ended, the

breathe cycle begins again.

The breathe effect rate is programmable for group #1 and

group #2 and can be independently set to 4, 8, 16, 24, 32,

48, or 64ms for each group. Also, the start time and target

time parameters for group #1 and group #2 can be inde-

pendently set to 32, 64, 256, 512, 1024, 2048, 3072, or

4096ms.

In addition to the group’s timing parameters, start current

and target current values and BxBEN (blink/breathe enable)

and BxFEN (fade enable) bits are set for each bank to define

that bank’s min and max current during a breathe cycle

and enable the breathe function.

The five parameters that define the breathe effect are:

Effect rate — write value to register 0Fh

Start current — write value to register 02h, 03h, 04h,

or 05h (bank dependent)

Target current — write value to registers 06, 07h, 08h,

or 09h (bank dependent)

Start time — write value to register 10h or 11h (group

dependent)

Target time — write to register 10h or 11h (group

dependent

Figure 3 illustrates the breathe effect with respect to time.

For an example of the breathe effect, with bank #1

assigned to group #1, the terms used in the illustration

are as follows:

BL_START = contents of register 02h (B1FEN must

equal 1)

BL_TARGET = contents of register 06h (B1BEN must

equal 1)

START = contents of bits ST1_[2:0] in register 10h

TARGET = contents of bits TT1_[2:0] in register 10h

BREATHE = breathe time. Equal to the breathe rate

times the number of steps between I

BL_START and

BL_TARGET. Breathe time is set with the bits ER1_

[2:0] in register 0Fh.

Blink Lighting Effect

The blink lighting effect provides an automatic LED blink-

ing function that can be applied to a single LED driver or

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