AAT2833 Datasheet, PDF (13/20 Pages) Advanced Analogic Technologies – 240mA Total Display Solution for Portable Devices

RGB Control
The Red, Green, and Blue LED PWM timing, along
with the overall period, is controlled by five registers.
The current level for the RGB LEDs is controlled by
another register (Address 12) which makes it possi-
ble to change the peak currents from 33% up to
200% of the backlight maximum current set by
R_BSET. A mode register (Address 11) sets the
method of update for the color and intensity regis-
ters. All registers are updated simultaneously or indi-
vidually, depending on how the mode register is set.
If updated simultaneously, the color registers are
updated when the period register is updated. Up to
4096 different color/brightness combinations are pro-
grammable in the AAT2833 and 64 color/brightness
combinations are programmable in the AAT2834.
Address 7, 8, 9: RGB Color Registers
The AAT2833's RGB color registers store up to 16
levels of lighting intensity for a given color channel.
The first level (DATA = 1) is reserved for the off-state.
Every setting thereafter increases the on-time of the
respective LED by 128µs. The settings can be cal-
culated as follows:
R = (DATA₇ - 1) · 128μs
G = (DATA₈ - 1) · 128μs
B = (DATA₉ - 1) · 128μs
Where R, G, and B are the on-times of the respec-
tive LEDs and DATA₇, DATA₈, and DATA₉ are the
data inputs into Registers 7, 8, and 9, respectively.
DATA_N can be set to a value from 1 to 16 with the
default DATA_N value equal to 1. Since the AAT2834
supports 64 color/brightness combinations, DATA_N
can be set from 1 to 4.
Address 10: RGB Timebase Register - T
The overall period is set by the AAT2833/34's T reg-
ister. Adjusting this register allows a user to adjust
how often the RGB LED sequence is repeated. The
longer the period, the smaller the effective duty cycle,
and thus RGB light intensity (brightness) is reduced.
AAT2833/34
240mA Total Display Solution
for Portable Devices
The RGB period can be calculated using the follow-
ing equation:
T = [(DATA₁₀ - 1) · 3 + 15] · 128μs
Where T is the period of repetition and DATA₁₀ is
the data input into Register 10. In the AAT2833,
DATA₁₀ can be set to a value from 1 to 16, with the
default DATA₁₀ value equal to 1. In the AAT2834,
DATA₁₀ can be set from 1 to 4, with the default
DATA₁₀ value equal to 1.
Please note that if the user sets the period to be
smaller than the combined on-times (R+G+B),
then the RGB sequence will automatically begin
again once time T has been reached, whether or
not all on-times have been completed.
Address 11: RGB Mode Register
The AAT2833/34's RGB mode register can have
one of two DATA₁₁ values. If DATA₁₁ is set to 1 (the
default), then each RGB LED on-time will be updat-
ed immediately after their respective register is set.
If DATA₁₁ is set to 2, then as the user sets the Red,
Green, and Blue on-time registers, none of the
LEDs will be updated until the timebase register is
set. For example, if the user wants to set a certain
Red-Green-Blue combinations, the Red on-time
can be programmed first, followed by the Green on-
time, followed by the Blue on-time, and then the
RGB period T last. If DATA₁₁ is set to 1, then after
the Red on-time is programmed the user will see
the Red LED turn on immediately. After the Green
on-time is programmed, the Red-Green color com-
binations will appear, etc. If DATA₁₁ is set to 2, then
none of those intermediate colors will appear until
the RGB period register T has been set and loaded.
Address 12: RGB Current Level Register, I_SINK
The I_SINK current level in the RGB LED can be
adjusted by writing data to Register 12. The maxi-
mum current is two times (200%) the maximum
backlight current set by R_BSET (see Table 7). By
increasing or decreasing the current, the brightness
level can easily be changed for any particular color
combination.
2833.2007.09.1.0
13