DS90UH926Q-Q1 Datasheet, PDF (21/58 Pages) Texas Instruments – 720p 24-Bit Color FPD-Link III Deserializer With HDCP

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DS90UH926Q-Q1
SNLS337K – OCTOBER 2010 – REVISED JANUARY 2015
7.3.16 Image Enhancement Features
Several image enhancement features are provided. White balance LUTs allow the user to define and target the
color temperature of the display. Adaptive Hi-FRC dithering enables the presentation of “true-color” images on an
18–bit color display.
7.3.16.1 White Balance
The White Balance feature enables similar display appearance when using LCDs from different vendors. It
compensates for native color temperature of the display, and adjusts relative intensities of R, G, B to maintain
specified color temperature. Programmable control registers are used to define the contents of three LUTs (8-bit
color value for Red, Green and Blue) for the white balance feature. The LUTs map input RGB values to new
output RGB values. There are three LUTs, one LUT for each color. Each LUT contains 256 entries, 8-bits per
entry with a total size of 6144 bits (3 x 256 x 8). All entries are readable and writable. Calibrated values are
loaded into registers through the I2C interface (deserializer is a slave device). This feature may also be applied
to lower color depth applications such as 18–bit (666) and 16–bit (565). White balance is enabled and configured
through that serial control bus register.
7.3.16.1.1 LUT Contents
The user must define and load the contents of the LUT for each color (R,G,B). Regardless of the color depth
being driven (888, 666, 656), the user must always provide contents for 3 complete LUTs - 256 colors x 8 bits x 3
tables. Unused bits - LSBs -shall be set to 0 by the user.
When 24-bit (888) input data is being driven to a 24-bit display, each LUT (R, G and B) must contain 256 unique
8-bit entries. The 8-bit white balanced data is then available at the output of the DS90UH926Q-Q1 deserializer,
and driven to the display.
When 18-bit (666) input data is being driven to an 18-bit display, the white balance feature may be used in one of
two ways. First, simply load each LUT with 256, 8-bit entries. Each 8-bit entry is a 6-bit value (6 MSBs) with the 2
LSBs set to 00. Thus as total of 64 unique 6-bit white balance output values are available for each color (R, G
and B). The 6-bit white balanced data is available at the output of the DS90UH926Q-Q1 deserializer, and driven
directly to the display.
Alternatively, with 6-bit input data the user may choose to load complete 8-bit values into each LUT. This mode
of operation provides the user with finer resolution at the LUT output to more closely achieve the desired white
point of the calibrated display. Although 8-bit data is loaded, only 64 unique 8-bit white balance output values are
available for each color (R, G and B). The result is 8-bit white balanced data. Before driving to the output of the
deserializer, the 8-bit data must be reduced to 6-bit with an FRC dithering function. To operate in this mode, the
user must configure the DS90UH926Q-Q1 to enable the FRC2 function.
Examples of the three types of LUT configurations described are shown in Figure 17
7.3.16.1.2 Enabling White Balance
The user must load all 3 LUTs prior to enabling the white balance feature. The following sequence must be
followed by the user.
To initialize white balance after power-on (Table 3):
1. Load contents of all 3 LUTs . This requires a sequential loading of LUTs - first RED, second GREEN, third
BLUE. 256, 8-bit entries must be loaded to each LUT. Page registers must be set to select each LUT.
2. Enable white balance.
By default, the LUT data may not be reloaded after initialization at power-on.
An option does exist to allow LUT reloading after power-on and initial LUT loading (as described above). This
option may only be used after enabling the white balance reload feature through the associated serial control bus
register. In this mode the LUTs may be reloaded by the master controller through the I2C. This provides the user
with the flexibility to refresh LUTs periodically , or upon system requirements to change to a new set of LUT
values. The host controller loads the updated LUT values through the serial bus interface. There is no need to
disable the white balance feature while reloading the LUT data. Refreshing the white balance to the new set of
LUT data will be seamless - no interruption of displayed data.
It is important to note that initial loading of LUT values requires that all three LUTs be loaded sequentially. When
reloading, partial LUT updates may be made.
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