In attempt to design a DAC, i want to understand more about delta sigma building block inside, i have read quite some article about this and have an overview of it but there are still many things concern me:
1.For simple DAC like pcm5102, there are digital ground, charge pump ground and analog ground. This one doesn't use and external opamp as analog filter so what does the analog supply for? I think it supply current for an opamp inside the DAC to do the IV work?
2. For more complex DAC like es90x8Q2m, there are seperate Vref for Left and Right channel, as i understand, the vref is use as voltage reference for delta sigma modulator to compare to the input bitstream, but isn't that digital part and why need seperate reference for left and right channel?
Thanks!.
1.For simple DAC like pcm5102, there are digital ground, charge pump ground and analog ground. This one doesn't use and external opamp as analog filter so what does the analog supply for? I think it supply current for an opamp inside the DAC to do the IV work?
2. For more complex DAC like es90x8Q2m, there are seperate Vref for Left and Right channel, as i understand, the vref is use as voltage reference for delta sigma modulator to compare to the input bitstream, but isn't that digital part and why need seperate reference for left and right channel?
Thanks!.
1. That chip most likely has an internal opamp doing analog filtering. There may in fact not be any I/V stage as its possible the DAC works in the voltage domain (switched capacitors) rather than by current.
2. The Vref supply is for the resistor array which is analog. The delta-sigma modulator is a digital part - this derives data to feed to the resistor array.
2. The Vref supply is for the resistor array which is analog. The delta-sigma modulator is a digital part - this derives data to feed to the resistor array.
1. But isn't analog filter need some capacitor? I don't think they intergrate it it that chip.
2. Do you have any source talk about this?
Thanks!
2. Do you have any source talk about this?
Thanks!
On switched capacitor filters you could have a look at this document - http://hasler.ece.gatech.edu/Courses/ECE3400/Proj4/UCalgary_Switch_Cap_notes.pdf You can see that capacitors are integrated onto ICs.
On ESS internal architecture see attached.
On ESS internal architecture see attached.
Attachments
Is really analog filter implement that way? It use switch with high speed on/off to implement so i think it must reside in digital section or else the analog pin will carry high switching current.
The Ess internal architecture is very simple and doesn't have much information how it work inside.
I don't know if TI/BB do it that way, I just offer it as a possibility. There are S-C type filter chips you can buy and implement for yourself, for example : LTC1264 Datasheet and Product Info | Analog Devices
Yes I don't think that internal diagram is very revealing of what goes on inside the ES9018. This paper has more details but seems to be only talking about a 1bit DAC : https://www.ias.ac.in/article/fulltext/sadh/043/06/0091
Yes I don't think that internal diagram is very revealing of what goes on inside the ES9018. This paper has more details but seems to be only talking about a 1bit DAC : https://www.ias.ac.in/article/fulltext/sadh/043/06/0091
Most AKM dac chips use switched capacitor filters. AK4499 is an exception for them, the output is switched resistor, similar to ESS dac chips.
There is an excellent book that explains great deal: Understanding Delta-Sigma Data Converters, 2nd Ed.
https://www.amazon.com/Understandin...s-Microelectronic-Systems-ebook/dp/B01MT1I21F
There is an excellent book that explains great deal: Understanding Delta-Sigma Data Converters, 2nd Ed.
https://www.amazon.com/Understandin...s-Microelectronic-Systems-ebook/dp/B01MT1I21F
You can integrate capacitors on a chip, but only with small values. They quickly become expensive as their value increases, especially if they have to be linear. 5 pF is no problem, but a 100 pF linear capacitor takes quite a lot of chip area. Regarding filters, you can make continuous-time filters, switched-capacitor filters and of course digital filters on a chip (as well as mixed-signal filters consisting of a digital delay line and a series of DACs, the so-called FIRDACs).
The book at post #7 is a very excellent one. I'm sure it's the bible of DSM. If you intend to design DSM yourself, this is a perfect abstract of practical calculations for the coefficients. It would help if you had more than 5th order DSM with one or two local feedbacks(g0, g1) to have a high-end system.
PlayPcmWin / Wiki / PCMtoSDM
PlayPcmWin / Wiki / PCMtoSDM