ADP5501 datasheet(16/28 Pages) AD

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ADP5501

Rev. 0 | Page 16 of

Similar to the backlight current sink, the ADP5501 contains

timers to facilitate the smooth fading between off and on states

of the LED current sinks. All three LED sinks share a common

fade-in (LED_FI) timer as well as a common fade-out (LED_FO)

timer. The fade-in and fade-out timers are located in Register 0x13

and can be programmed to one of 15 settings ranging from 0.3 sec

to 5.5 sec. Fade-in times represent the time it takes to fade from

0 mA to 14 mA. Fade-out times represent the time it takes to fade

from 14 mA to 0 mA. Fading between intermediate settings is

shorter. The fade timers should be programmed before asserting

LEDx_EN in Register 0x11.

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

FADE-IN TIME (Sec)

2.1 SEC

2.4 SEC

2.7 SEC

3.0 SEC

3.5 SEC

4.0 SEC

4.5 SEC

5.0 SEC

5.5 SEC

0.3 SEC

0.6 SEC

0.9 SEC

1.2 SEC

1.5 SEC

1.8 SEC

By default (LED_LAW = 0 in Register 0x11), the ADP5501

implements a fading scheme using the linear algorithm (see

Equation 3).

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

FADE-IN TIME (Sec)

0.3 SEC

0.6 SEC

0.9 SEC

1.2 SEC

1.5 SEC

1.8 SEC

2.1 SEC

2.4 SEC

2.7 SEC

3.0 SEC

3.5 SEC

4.0 SEC

4.5 SEC

5.0 SEC

5.5 SEC

Figure 35. Linear Fade-In Times

0.51.01.52.02.5

3.03.54.04.55.05.5

FADE-OUT TIME (Sec)

0.3 SEC

0.6 SEC

0.9 SEC

1.2 SEC

1.5 SEC

1.8 SEC

2.1 SEC

2.4 SEC

2.7 SEC

3.0 SEC

3.5 SEC

4.0 SEC

4.5 SEC

5.0 SEC

5.5 SEC

Figure 36. Linear Fade-Out Times

To provide a more natural fading experience for the user, the

fade timers can be used in conjunction with the square law

approximation codes (see Equation 4) by setting LED_LAW = 1.

Figure 37. Square Law Fade-In Times

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

FADE-OUT TIME (Sec)

0.3 SEC

0.6 SEC

0.9 SEC

1.2 SEC

1.5 SEC

1.8 SEC

2.1 SEC

2.4 SEC

2.7 SEC

3.0 SEC

3.5 SEC

4.0 SEC

4.5 SEC

5.0 SEC

5.5 SEC

Figure 38. Square Law Fade-Out Times

The LED current sinks have additional timers to facilitate blinking

functions. A shared on timer (LED_ONT in Register 0x12) used

in conjunction with three off timers (LED0_OFFT, LED1_OFFT,

and LED2_OFFT) allows the LED current sinks to be configured

in various blinking modes. The on timer can be set to four

different settings: 0.2 sec, 0.6 sec, 0.8 sec, and 1.2 sec. The off

timers also have four different settings: disabled, 0.6 sec, 0.8 sec,

and 1.2 sec. Blink mode is activated by setting the off timers to

any setting other than disabled.

All fade-on and fade-off timers should be programmed before

enabling any of the LED current sinks. If LEDx is on during a

blink cycle and LEDx_EN is cleared, LEDx goes off (or fades to

off if fade-out is enabled). If LEDx is off during a blink cycle and

LEDx_EN is cleared, LEDx stays off.

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