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#general
Title
# general
m

Minhaz Abedin

08/07/2020, 7:43 AM
@User I will be happy to collaborate and can help you design the R2R DAC. I am currently a PhD student with Nanoelectronics masters and Electrical and Electronics Engineering bachelor's degree. Even though I am still learning on full asic design architecture. I can definitely help you design Opamps and DACs etc.
j

jrsharp

08/07/2020, 7:47 AM
Hi Minhaz! Great to meet you
I've just built installed the various tools and will start on the DAC soon
The idea is to have a script generate a netlist from R and 2R cells and use a tool to route it
I need people with more CMOS experience (I have none) to advise on the best way to lay out the cells
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yrrapt

08/07/2020, 7:52 AM
I'm curious why you're going for a R2R DAC opposed to a delta sigma DAC which is usually used in the audio bands?
j

jrsharp

08/07/2020, 7:52 AM
I need ultrasonic frequencies up to 500kHz
also I have very little faith in anything I design asic wise actually working... a simple resistor ladder seemed easier haha
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tnt

08/07/2020, 7:57 AM
you'd still probably need a buffer after the resistor ladder before going out to a pin.
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yrrapt

08/07/2020, 7:57 AM
ahh ok, thought it was lower frequency
j

jrsharp

08/07/2020, 7:57 AM
@tnt yes, potentially, it could just be a voltage follower
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yrrapt

08/07/2020, 7:59 AM
the design of a delta sigma is in a lot of ways easier than an R2R which is why I brought it up. The delta sigma has all the complexity in digital and much reduced analogue matching and hard work to get good performance. But I don't think it's viable with the frequencies you've mentioned
j

jrsharp

08/07/2020, 8:00 AM
@yrrapt yes it's annoying, there are a million I2S class D chips out there that are small for audio frequencies. I do most of my work at 330kHz
t

tnt

08/07/2020, 8:01 AM
What kind of bit depth are you looking for ?
j

jrsharp

08/07/2020, 8:01 AM
@tnt the idea is to have a script generate it from parameters. But to answer your question, 8 - 12 bits.
I don't actually need perfect monotonicity, so laser trimming is not necessary
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Minhaz Abedin

08/07/2020, 8:16 PM
@jrsharp Hi, Nice meeting you too! Let's chat private, so that we don't spam this room. @tnt you can join too.