ADP5501 Analog Devices, ADP5501 Datasheet - Page 15

• 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

Table 5. Comparator Output Truth Table
BL_AUTO_ADJ
0
1
1
1
1
1
The L3_OUT status bit has greater priority; therefore, the back-
light operates at L3 (dark) even if L2_OUT is set.
LED CURRENT SINKS
The ADP5501 has three additional current sinks that can be
used as RGBs or auxiliary LED current sinks. Each current sink
is programmable up to 14 mA (typical) and can be independ-
ently turned on and off.
The LED0 pin is the current sink for LED0. Its sink current can
be set using LED0_CURRENT in Register 0x14. LED0 sink can
be enabled with LED0_EN in Register 0x11.
The LED1 pin is the current sink for LED1. Its sink current can
be set using LED1_CURRENT in Register 0x15. LED1 sink can
be enabled with LED1_EN in Register 0x11.
The LED2 pin is the current sink for LED2. Its sink current can
be set using LED2_CURRENT in Register 0x16. LED2 sink can
be enabled with LED2_EN in Register 0x11.
These LEDx_CURRENT registers are six bits wide, allowing the
user to set the LED sink current to one of 64 different levels
between 0 mA and 14 mA. The ADP5501 can implement two
distinct algorithms to achieve a linear and a nonlinear relation-
ship between input code and sink current.
X = don’t care.
L3_OUT
X
0
0
1
1
1
LED0_CURRENT
LED0_OFFT
LED_LAW
LED_ONT
LED0_EN
LED_FO
LED_FI
L2_OUT
X
0
1
0
1
1
COUNTERS
CONTROL
Backlight Operation
BL_LVL can be manually
set by the user.
BL_LVL = 00; backlight
operates at L1 (daylight).
BL_LVL = 01; backlight
operates at L2 (office).
BL_LVL = 10; backlight
operates at L3 (dark).
BL_LVL = 10; backlight
operates at L3 (dark).
DIGITAL
LED 1
AND
LED0
VBAT
LED1_CURRENT
LED1_OFFT
Figure 34. Status LED Current Sink
LED1_EN
Rev. 0 | Page 15 of 28
COUNTERS
CONTROL
DIGITAL
LED 2
AND
By default, the ADP5501 uses a linear algorithm (LED_LAW = 0
in Register 0x11), where the LED sink current increases linearly
for a corresponding increase of input code. The LED sink current,
in milliamperes (mA), is determined by the following equation:
where:
Code is the input code programmed by the user.
Fullscale_Current is the maximum sink current allowed
(typically, 14 mA).
The ADP5501 can also implement a nonlinear (square approx-
imation) relationship between input code and LED sink current
level. In this case (LED_LAW = 1 in Register 0x11), the LED
sink current, in milliamperes (mA), is determined by the
following equation:
LED Sink Current =
Figure 33 shows the backlight current level vs. the input code
for both the linear and square law algorithms.
LED1
VBAT
LED Sink Current = Code × (Fullscale_Current/63)
14
12
10
8
6
4
2
0
0
LED2_CURRENT
LED2_OFFT
LED2_EN
Figure 33. LED Sink Current vs. Code
16
⎛
⎜
⎜
⎝
Code
LINEAR
COUNTERS
CONTROL
×
DIGITAL
LED 3
AND
CODE
Fullscale
LED2
32
VBAT
SQUARE
63
_
Current
48
ADP5501
⎞
⎟
⎟
⎠
2
64
(3)
(4)