ADP5350ACBZ-1-R7 datasheet(31/63 Pages) AD

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Data Sheet

ADP5350

Rev. B | Page 31 of 63

The time programmed in the BL_FI timer and BL_FO timer

represents the time it takes the backlight current to go from

0 mA to 20 mA. Therefore, the fading time between

intermediate settings is shorter. Smaller changes in current

reduces the fade time. For square law fades, the fade time is

given by

Fade Time = Fade Rate × (Code/63)

where the Fade Rate is as shown in Table 17.

Table 17. Available Fade In and Fade Out Times

Code

Fade Rate (sec)

0000

Fade in or fade out disabled

0001

0.3

0010

0.6

0101

0.9

0110

1.2

0111

2.1

1000

2.4

1001

2.7

1010

3.0

1011

3.3

1100

3.6

1101

3.9

1110

4.2

1111

4.5

Backlight Fade Override

A fade override feature allows the BL_FI and BL_FO timers to

be overridden when the EN_BL bit is reasserted during a fade

in or fade out period and to set the backlight to its targeted

current setting value immediately (see Figure 50). Setting the

FOVR bit to 1 in the BST_CFG register enables the backlight

fade override feature.

Figure 50. LED Backlight Fade Override

Independent Sink Controls

The LED current sink in Channel 2 to Channel 5 can be

configured to operate as either part of a grouped backlight, or to

operate as an independent LED channel.

Setting BL_LEDx = 1 configures the selected LED channel

(Channel 2 to Channel 5) as the part of a grouped backlight. In

this setting, the backlight current setting and on/off control in

Channel 1 apply to the configured channel.

Setting BL_LEDx = 0 configures the selected LED channel

(Channel 2 to Channel 5) as an independent current sink

channel. Each channel current and on/off control are

determined by independent register settings.

Individual LED Blinking Timer

The independent current sinks in Channel 3, Channel 4, and

Channel 5 have additional timers to facilitate the blinking

functions. The on timer and the off timer in the LEDx_BLINK

various blinking modes. Blink mode can be activated by setting

the off timers to any setting other than disabled. The blink

mode setting has no effect if the channel is configured as part of

a grouped backlight.

The fade in and fade out function is effective in blink mode but

the fade override feature is not effective in blink mode. See

Figure 51 for a timing diagram of LED blinking with fading.

Some applications (for example, red/green/blue (RGB) LEDs in

blink mode) need the blinking timer to be in synchronization. If

the blinking LEDs are enabled in the same I2C command, the

rising time of the on timer for each blinking LED is synchronized.

Figure 51. LED Blinking with Fading

BACKLIGHT

CURRENT

EN_BL = 1

(REASSERTED BY USER)

EN_BL = 1

(REASSERTED BY USER)

EN_BL = 0

FADE IN

OVERRIDDEN

FADE OUT

OVERRIDDEN

MAX

TIME

OFF

TIME

EN_LEDx

TIME

FADE

OUT

TIME

FADE

OUT

ILEDx_SET

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