ADP5501 Analog Devices, ADP5501 Datasheet - Page 16

• 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
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.
By default (LED_LAW = 0 in Register 0x11), the ADP5501
implements a fading scheme using the linear algorithm (see
Equation 3).
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.
15
12
15
12
9
6
3
0
9
6
3
0
0
0
0.5
0.5
1.0
1.0
Figure 36. Linear Fade-Out Times
Figure 35. 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 16 of
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.
28
15
12
15
12
9
6
3
0
9
6
3
0
0
0
0.5
0.5
Figure 38. Square Law Fade-Out Times
1.0
1.0
Figure 37. Square Law 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
0.3 SEC
0.6 SEC
0.9 SEC
1.2 SEC
1.5 SEC
1.8 SEC
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
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