FUNCTIONAL DEVICE OPERATION
LIGHTING SYSTEM
External
Boost
External
Boost
External
Boost
LEDMD
LEDKP
LEDMD
LEDAD
LEDMD
LEDAD
LEDKP
6 LED Main Display
3 LED Aux Display
12 LED Keypad Arrangement
2 LED Reduced Keypad Option
6 LED Main Display
9 LED Keypad
6 LED Main Display
Figure 34. Serial LED Configurations
In the left most example in Figure 34: LEDMD is set at 15 mA (low range), LEDKP is set at 30 mA (high range). When both
are operated, then the LEDMD current will pulse at 30 mA and the LEDKP current at 60 mA. This provides an average of 15 mA
through the main display backlight LEDs and 30 mA through the keypad backlights LEDs.
SIGNALING LED DRIVERS
The signaling LED drivers LEDR, LEDG, LEDB are independent current sink channels. Each driver channel features
programmable current levels via LEDx[2:0] as well as programmable PWM duty cycle settings with LEDxDC[5:0]. By a
combination of both, the LED intensity can be adjusted. By driving LEDs of different colors, color mixing can be achieved.
Table 107. Signaling LED Drivers Current Programming
LEDx[2:0](81)
LEDx Current Level (mA)
000
001
010
011
100
101
110
111
0
3
6
9
12
15
18
21
Notes
81. “x” represents for R, G and B
Table 108. Signaling LED Drivers Duty Cycle Programming
LEDxDC[5:0](82)
Duty Cycle
000000
000001
…
0/32, Off
1/32
…
010000
…
16/32
…
011111
1xxxxx
31/32
32/32, Continuously On
Notes
82. “x” represents R, G and B
Blue LEDs or bright green LEDs require more headroom than red and normal green signal LEDs. In the application, a 5.0 V
or equivalent supply rail is therefore required. This is provided by the integrated boost converter SWBST. To make software
programming easier, an LEDSWBSTEN SPI bit has been provided in the Blue LED register to enable the boost converter. Note
13892
Analog Integrated Circuit Device Data
116
Freescale Semiconductor
FREESCALE [ Freescale ]
