Figure 3-34. Lighting Controller Overview - Motorola APX 5000 Service Manual

Theory of Operation
: Controller
3.2.6.3.2 Secondary Lighting Controller
As previously mentioned the secondary lighting controller provides illumination to the top display
backlight and Tx/Rx indicator lamp. The lighting controller and LEDs are powered by switcher 5
(V_SW_5). This lighting controller device uses a PWM output to control the dimming modes of
operation for each LED. The device is controlled through the I2C interface, however, the I2C
interface require an input high voltage between 3 V – 5.5 V, thus the level translator (U2202) is used
to boost these signals to 5V logic.
Figure 3-34 shows the major connection scheme to this secondary lighting controller. The white,
green, and red top display LEDs are connected to the lighting controller PWM outputs through ESD
filter inductors L2204, L2203, L2202, respectively. The TX/RX status indicator LED uses a tri-color
red, green, amber (RGA) LED.
OMAP
(I2C) SCL
(I2C) SDA
RST_OUT
V_SW_3.6
V-REG
VOUT
1.85V
V_SW_5
V-REG
VOUT
LEVEL
SHIFT

Figure 3-34. Lighting Controller Overview

LED DRIVER
(LM27965)
D1A
VIN
D2A
SCL D3A
SDIO D4A
D1B
RESET
D2B
FRONT DISPLAY
D3B
LED DRIVER
(LP3943)
PWR LED0
LED1
LED2
SCL
SDA
RESET
A0
LED4
A1 LED5
A2 LED6
KEYPAD WHITE
KEYPAD
ILLUMINATION
12
15
16
17
18
FRONT DISPLAY
WHITE BACKLIGHT
10
20
21
11
TOP DISPLAY
TOP DISPLAY
BACKLIGHT
W
25
G
R
26
24
23
TX/RX
STATUS
A
1
G
R
15
17
8
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