Single HDMI 8:1 multiplexer using two AD8197s

Question

Hello, 
 I'm looking to build a single HDMI 8:1 multiplexer using two AD8197s. I saw that a similar topic already exists on EZ, but I could not find answers to my questions there. 
 Please tell me how can I create such a scheme. Which output pins will I need to combine? Which mode should I choose: dual 8:1 switch, or a single 16:1 switch? How will the ICs know that they are working together and in what order are they assigned source inputs? Will I need to specify the same I2C address for each AD8197? 
 And one general question. What do I need to do with parallel IOs when working with a serial interface? Just leave them unconnected? 
 I'm just starting to work with such integrated circuits, so I don't understand everything that's going on very deeply. Sorry for my stupid questions :) 
 Thanks in advance for your answer. 
 Sincerely, Eugene

zpandangan · Accepted Answer

Hi Eugene, 
 Apologies for the delay, and thank you for your patience. 
 You can build an 8:1 HDMI multiplexer with two AD8197s by using the wired-OR technique as the datasheet suggests. To do this, the output pins of one IC should be connected to their corresponding pins on the other, and they should be controlled in a way that only one AD8197 output is enabled at any given time. Thus, if you plan to control the devices using I 2 C, you have to assign them with unique addresses so that the target IC can correctly be enabled/disabled. 
 
 Note that the output needs to be pulled either high or low to establish a known value in the event that both devices are in the high impedance state at the same instance. Moreover, since HDMI signals will be routed (with each link consisting of four channels), the devices should be set to quad mode. 
 Alternatively, you can achieve the same by cascading AD8197s so that you can use one of the switches to control which output to use, but this would require three ICs. An example is provided in the AD8192 datasheet (p. 21). 
 For the unused parallel interface pins, they should be tied to either 0 V or 3.3 V (depending on your preferred default values for the affected registers). These pins must be in a defined state as they dictate the device configuration upon reset (prior to the first serial control event) and thus should not be left floating. 
 
 Hope this helps. 
 Regards, Zaeefa)

Partner Forums

Partner Libraries

Products Mentioned

Single HDMI 8:1 multiplexer using two AD8197s