AQ7 Design


  2015/8/26 上午 11:36:45        Administrator        General   0 Comments
AQ7-LN is Q7 platform with a CPU Module and a client-designed carrier board. The client commented that when the OS is loaded, noises can be heard coming out of the speakers. The Q7 module itself provides only a HD Audio interface, leaving the client responsible for the audio codecs. As tests done on AAEON-designed carrier boards showed nothing abnormal, initial investigation conducted after obtaining the routing and board files of the client-designed board revealed inconsistency between audio codecs on both boards. The audio verb table in the BIOS, while originally written for Realtek ALC 888, is applied for ALC 269 instead in the client’s board. While this may still serve its purpose, this mismatch in may result in unexpected results; since the BIOS verb table performs LINE-IN, LINE-OUT, and mic settings based on the codec, optimal performance can only be achieved when audio codecs are paired with their own matching verb tables. 

Regardless, the main culprit of the noise is later found to originate elsewhere; in the design guide of the audio codec, it is stated that the digital power and signals must be isolated from the analog signals, an instruction not duly carried out by client-designed board, resulting in the failure differentiate between the digital ground and analog ground, causing both digital and analog signals to be mixed and ultimately generating the noise. Our findings are thus presented to the client, who revised the board with accordance to our recommendations and “silence” the noise thereafter. 

Recommended audio codec PCB layout:

Compared to the relatively simplistic design of normal mainboards, the complexity of designing a carrier board often leads to occurrences of compatibility issues. Therefore, we suggest our clients to first consult our Q-service team before going ahead with the design of their own board. With our recommended design input, we believed both the development and troubleshooting duration will be significantly reduced.
 
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