Composite sync generation on AD724

Question

Hello. 
 I have a couple of queries regarding AD724. 
 1) Is it possible to drive only hsync and vsync to AD724 while grounding the RGB inputs to generate a composite sync signal? 
 2) Can a composite sync signal without color burst be generated from AD724? The datasheet provides details on providing FIN for color burst but I do not require color burst for the composite sync. 
 3) Will the chip support non-standard horizontal timing? The vertical timing (and the number of lines) will be as per NTSC/PAL standard. 
 
 Regards, 
 Akhil A

PoornimaSubramani · Accepted Answer

Hi, 
 As stated earlier, Since some monitors does not require these pulses and the decision whether to include these signals is a system tradeoff between cost and complexity and adhering strictly to the video standards. 
 As per Page 9 in AD724 datsheet, HSYNC and VSYNC are two logic level inputs that are combined internally to produce a composite sync signal. If a composite sync signal is to be used, it can be input to HSYNC while VSYNC is pulled to logic HI (> +2 V). 
 Please note two sync inputs HSYNC and VSYNC drive an XNOR gate to create a CSYNC signal for the AD724. If the user produces a true composite sync signal, it can be input to the HSYNC pin while the VSYNC pin is held high. 
 
 Thanks, 
 Poornima)

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Composite sync generation on AD724

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