ADP5501 Analog Devices, ADP5501 Datasheet - Page 12

• Manufacturer Part Number: ADP5501
• Description: Programmable Current Backlight Driver with Ambient Light Sensor Input
• Manufacturer: Analog Devices

Specifications of ADP5501

• Vin Range: 2.7 to 5.5V
• Vout (v): 24 to 27
• Synchronous: No
• Package: 24-Lead LFCSP
• Led Configuration: Serial
• Topology: Inductive
• I2c Support: Yes
• Max Iout (ma): 30mA
• Brightness Control: I2C
• Switching Frequency: 1MHz
• Over Volt Protection (v): 24V

ADP5501
The BL_FI timer in Register 0x04 can be used for smooth fade-
in transitions from low to high backlight settings such as off to
dim, off to maximum, and dim to maximum. The BL_FI timer
can be programmed to one of 15 settings ranging from 0.3 sec
to 5.5 sec. The BL_FI timer should be programmed before
asserting BL_EN.
The time programmed in BL_FI represents the time it takes the
backlight current to go from 0 mA to 30 mA. Fading between
intermediate settings is shorter.
The BL_FO timer in Register 0x04 can be used for smooth fade-
out transitions from high to low backlight settings such as
maximum to dim and dim to off. The BL_FO timer can be
programmed to one of 15 settings ranging from 0.3 sec to 5.5 sec.
The BL_FO timer should be programmed before asserting BL_EN.
The time programmed in BL_FO represents the time it takes
the backlight current to go from 30 mA to 0 mA. Fading
between intermediate settings is shorter.
30.0
27.5
25.0
22.5
20.0
17.5
15.0
12.5
10.0
30.0
27.5
25.0
22.5
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.5
7.5
5.0
2.5
0
0
0
0
0.5
0.5
1.0
1.0
Figure 23. Linear Fade-Out Times
Figure 22. Linear Fade-In Times
1.5
1.5
FADE-OUT TIME (Sec)
2.0
FADE-IN TIME (Sec)
2.0
2.5
2.5
3.0
3.0
3.5
3.5
4.0
4.0
4.5
4.5
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
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
5.0
5.0
5.5
5.5
Rev. 0 | Page 12 of 28
Figure 24 shows the fade timers in use. With BL_FI and BL_FO
programmed, if BL_EN is asserted, the backlight fades in to its
maximum setting. If DIM_EN is asserted, the backlight fades
out to its dim setting. If BL_EN is cleared, the backlight fades
out to off.
During any point in a fade-out, if BL_EN is asserted, the
backlight stops at its current fade-out position and begins
fading in.
The fade-in and fade-out timers can be used independently of
each other; that is, fade-in can be enabled while fade-out is dis-
abled. The fade timers can also be used with the off and dim timers.
Figure 25 shows the fade timers used with the dim and off timers.
MAX
BACKLIGHT
MAX
BACKLIGHT
DIM
DIM
CURRENT
CURRENT
BL_EN = 1
SET BY USER
SET BY INTERNAL STATE MACHINE
OFF-TO-MAX
BL_EN = 1
Figure 24. Backlight Turn-On/Turn-Off/Dim with Fade Timers
FADE-IN
FADE-IN
DIM_EN = 1
Figure 25. Fade/Dim/Off Timers Used Together
MAX-TO-DIM
DIM TIMER
RUNNING
FADE-OUT
DIM-TO-OFF
FADE-OUT
BL_EN = 0
DIM_EN = 1
FADE-OUT
BL_EN = 1
FADE-IN
FADE-OUT
OFF TIMER
RUNNING
BL_EN = 0
BL_EN = 1
DIM_EN = 0
BL_EN = 0
BL_EN = 0
FADE-IN
FADE-OUT
FADE-OUT