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Doug Grant

The Elusive 12-Bit D/A Converter

Doug Grant
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fasmicro
fasmicro
9/16/2013 7:06:46 AM
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Re: Re : The Elusive 12-Bit D/A Converter
>> If 50% of the ADC resolution is lost in the averaging then what about 10 and 12 bits ADCs built inside the Microcontrollers? 

The commenter might have pointed that when you average, you lose some effective bits of course.  Good designers average at the LSBs which do not have much impact in the system performance as the MSBs.

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fasmicro
fasmicro
9/16/2013 7:04:27 AM
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Re: A-to-D Is Even Worse
>> So, there must be some averaging or some linearizing circuit present which end up giving just 24 bit result from 52 bits

That must be truly excessive averaging. Getting 24 bits from 52 seems to be over the top. A good idea would have been to have the MSBs/the first ten and then use about another 32 to get the remaining. That way you save power and real estate on silicon.

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Vishal Prajapati
Vishal Prajapati
8/30/2013 3:03:42 AM
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Re: Re : The Elusive 12-Bit D/A Converter
If 50% of the ADC resolution is lost in the averaging then what about 10 and 12 bits ADCs built inside the Microcontrollers? Do they give only 6 bit resolution? That is not the case.

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fasmicro
fasmicro
8/30/2013 2:55:03 AM
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Re: Re : The Elusive 12-Bit D/A Converter
>> My favorite pastime is to look at how PCB tracks are routed in evaluation boards. Many chip companies provide clear guidelines on this.

There are some some nice applications notes from the likes of Analog Devices, Maxim and TI that can also help.

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fasmicro
fasmicro
8/30/2013 2:50:54 AM
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Re: Re : The Elusive 12-Bit D/A Converter
@Brad, yes, I agree that analog designers have more job security than digital ones. Generally, the disruption in digital is not always possible in analog as you cannot automate much in analog design

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fasmicro
fasmicro
8/30/2013 2:46:33 AM
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Re: Re : The Elusive 12-Bit D/A Converter
@Sunita, PCB design is one of the most overlooked areas inexperienced project managers can fail. We spend all the time in college teaching ASIC, FPGA and system developments with limited time on PCB. Unfortunately, it is unlikely you can get any chip in operation without a board. So board design matters in the business.

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fasmicro
fasmicro
8/30/2013 2:39:55 AM
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Re: Re : The Elusive 12-Bit D/A Converter
>> it could easily be established that one successful lay out that provides twelve noise free bits from an analog signal may easily fail in another setting

12 bit ADC may not need a lot of heroic design to realize. I have done that easily with pipelined ADC. Even SAR can give you a 12 bit system. The challenge comes when you move into the domain of 16 bits where the resolution becomes challenging limited by the opamp performance.

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fasmicro
fasmicro
8/30/2013 2:36:10 AM
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Re: A-to-D Is Even Worse
>> So, there must be some averaging or some linearizing circuit present which end up giving just 24 bit result from 52 bits.

But that is how must commercial ADCs are being designed. You average the lower bits by have excess bits than required. But even the 25 bits you noted may actually be marketing bits. You get about 18-20 bits in ENOB and INR.

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JAYARAMAN KIRUTHI VASAN
JAYARAMAN KIRUTHI VASAN
8/27/2013 10:53:18 AM
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Re: Re : The Elusive 12-Bit D/A Converter
@BA,

It may be true for analog ic evaluation boards. However my experience with mixed signal mcu evaluation boards shows the PCB design was not the best of what is expected. The eval board designs were just that - allow evaluation of each of the features. However, if one would like to do some signal processing with an eval board, the experience could be far from pleasant.

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B_Albing
B_Albing
8/27/2013 9:19:03 AM
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Re: Re : The Elusive 12-Bit D/A Converter
@JK - I agree - I used to advise customers (previous job) that if they studied the Eval boards, they would get a clear idea on how the do their own PC board layout.

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