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LMH0030: BT.656 to SDI

Amy Luo
Expert 6895 points
Part Number: LMH0030
Other Parts Discussed in Thread: CLC020, CLC021, LMH0340, LMH0341, LMH0302, LMH0384

Hi team,

Background:

The customer has a thermal imaging machine with BT.656 interface output and wants to convert it into an SDI interface. BT.656 interface is D0~D7 and CK, Y-Cb-Cr 4-2-2 protocol, 640×480 25FPS (50i), the level is LVCOMS2.5V, use temperature -40℃~ 70℃. Also see if it is possible to be compatible with BT.1120 (16bit interface), what solution can I use to achieve this?

The customer's initial idea is to consider using a serializer+cable driver. Examining TI's devices, it was found that LMH0030, CLC020, CLC021 all support SDTV 27MHz interface to SDI in theory. The output of SDI does not require a separate cable driver, and the parallel input level is OK. Unfortunately none of the above 3 devices have the required temperature range. 

The customer has the following questions:

1. If I do not consider the temperature issue, how is the 8bit interface compatible with the 10bit interface of the device? What do I do with the extra 2 bits?

2.  The LMH0030 seems to be able to achieve the compatibility of the BT656 and BT1120 interfaces, so how do the two interfaces need to be handled on the circuit to achieve compatibility?

3. Is there any other solution that can do this? can meet both function and temperature requirements.

Best Regards,

Amy Luo

  • 0
    TI__Guru* 93670 points

    Hi Amy,

    1). Complete 10 bits need to be provided to the LMH0030 device. 10-bits X 27MHz is equivalent to 270MBps.

    2). 10 Bits at 27MHz clock can be used to meet these two requirements.

    3). Typically FPGA along with a serializer is used. There are two options:

    3A). Use LMH0340 plus the FPGA IP. This FPGA IP plus the LMH0340/LMH0341 devices takes care of this application.

    3B). Additionally customers can use FPGA plus devices such as intel or Xilinx FPGA plus our SDI cable driver or equalizers such LMH0302 and LMH0384 respectively.

    Regards, Nasser