
Analog Integrated Circuit Device Data
Freescale Semiconductor
37
PC34708
Functional Block Requirements and Behaviors
Battery Management Block Description and Application Information
The charging LED drivers CHRGLEDR, and CHRLEDG are independent current sink channels. Each driver channel features
programmable current levels via CHRGLEDx[1:0], as well as programmable PWM duty cycle settings with CHRGLEDxDC[5:0].
By a combination of level and PWM settings, each channel provides flexible LED intensity control. By driving LEDs of different
colors, color mixing can be achieved.
The charging LED drivers include ramp up and ramp down patterns implemented in hardware. Ramping is enabled for each of
the drivers using the corresponding CHRGLEDxRAMP bits, only when the repetition rate is 256 Hz.
The ramp itself is generated by increasing or decreasing the PWM duty cycle with a 1/32 step every 1/64 seconds. The ramp
time is therefore a function of the initial set PWM cycle and the final PWM cycle. As an example, starting from 0/32 and going to
32/32 will take 500 ms, while going to from 8/32 to 16/32 takes 125 ms.
Note that the ramp function is executed upon every change in PWM cycle setting. If a PWM change is programmed via the SPI
when CHRGLEDxRAMP=0, the change is immediate rather than spread out over a PWM sweep.
For color mixing and to guarantee a constant color, the color mixing should be obtained by the current level setting, so the
intensity is set through the PWM duty cycle.
In addition, programmable blink rates are provided. Blinking is obtained by lowering the PWM repetition rate of each of the drivers
through CHRGLEDxPER[1:0], while the on period is determined by the duty cycle setting. To avoid high frequency spur coupling
in the application, the switching edges of the output drivers are softened.
Table 28. Charge LED Driver Control
CHRGLEDxEN
CHRGLEDx
CHRGLEDOVRD
0 (default)
Auto
0
1
On
1
0
Off
1
“x” represents for R, and G
Table 29. Charge LED Drivers Current Programming
CHRGLEDx[1:0]
CHRGLEDx Current Level (mA)
00
3.4
01
6.6 (default)
10
9.8
11
12.5
“x” represents for R, and G
Table 30. Charge LED Drivers Duty Cycle Programming
CHRGLEDxDC[5:0]
Duty Cycle
000000
0/32, Off
000001
1/32
…
010000
16/32
…
011111
31/32
1xxxxx
32/32, Continuously On
“x” represents R, and G