DS90UB926Q-Q1 Datasheet, PDF (20/57 Pages) Texas Instruments – 5- to 85-MHz 24-Bit Color FPD-Link III Deserializer With Bidirectional Control Channel

DS90UB926Q-Q1
SNLS422B – JULY 2012 – REVISED JANUARY 2015
www.ti.com
7.3.13 Oscillator Output
The deserializer provides an optional PCLK output when the input clock (serial stream) has been lost. This is
based on an internal oscillator. The frequency of the oscillator may be selected. This feature is controlled by
register Address 0x02, bit 5 (OSC Clock Enable). See Table 11.
7.3.14 Pixel Clock Edge Select (RFB)
The RFB determines the edge that the data is strobed on. If RFB is High (‘1’), output data is strobed on the
Rising edge of the PCLK. If RFB is Low (‘0’), data is strobed on the Falling edge of the PCLK. This allows for
inter-operability with downstream devices. The deserializer output does not need to use the same edge as the
Ser input. This feature may be controlled by register. See Table 11.
7.3.15 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.
7.3.15.1 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 the serial control bus register.
7.3.15.1.1 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 DS90UB926Q-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 DS90UB926Q-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 DS90UB926Q-Q1 to enable the FRC2 function.
Examples of the three types of LUT configurations described are shown in Figure 15
7.3.15.1.2 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.
20
Submit Documentation Feedback
Copyright © 2012–2015, Texas Instruments Incorporated
Product Folder Links: DS90UB926Q-Q1