J
Jon Slaughter
- Jan 1, 1970
- 0
Reading over some layout issues involving data conversion it seems that most
of the stuff is well covered such as using seperate supplies, grounds,
bypass caps on power pins, etc...
Some issues I'm not sure about are when going from analog to digital and
vice versa.
In a datasheet involving a DAC(DAD1793 from TI) they show the recommended
layout but I'm a bit confused. The DAC is on the analog side but its half
digital. Its digital ground is grounded to the analog side. Would it not be
better to have its digital ground go to the digital ground plane? Of course
since the IC is over the analog ground plane it means that the there would
have to be a little routing but I'm thinking that maybe the digital ground
plane could be extendend to half between the chip and vias would go directly
to it?
Also, is there any reason for the ground plane to be on a seperate layer? Is
it for just convenience and to maximize area or is there some other concept
involved. Since I don't have any double sided pcb boards and if I did(which
I suppose I could make but sticking two single sided ones together) I'm not
sure how to make the vias(drill and solder/maybe use a wire connector). I'm
sure I can get away with using a single side for prototyping though? (As
noise issues won't be the ultimate factor unless its pretty bad)
What I was thinking about was splitting the ground plane/pcb board into two
halfs where the ic's that were partially digital and partially analog would
straddle both sides. This would allow me to sorta seperate the two sides to
some degree but not sure if it would cause other issues.
Also, in this case would using one digital supply for all digital elements
work? In the two layouts I have saw for ADC's and DAC's they use one supply
for the digital and then one supply for the the DAC and/or ADC.
i.e., one supply is completely digital but the one supplying analog power
also supplies the digital for the ADC's and DAC's. Is this necessary(in
that, is it better or worse than having only two supplies one for digital
and one for analog)?
One more question. I didn't realize that the DAC's and ADC's where
synchronous devices and need external clocks(thought they had them build in
and I could use interrupts to transfer data). Can I use the same clock for
both/all conversion ic's? I need a pretty stable and fixed clock because I'm
using it for audio so the pitch needs to be right(I don't think this will be
an issue but I'd like not to introduce more complications by having many
different clocks it isn't necessary).
Thanks,
Jon
of the stuff is well covered such as using seperate supplies, grounds,
bypass caps on power pins, etc...
Some issues I'm not sure about are when going from analog to digital and
vice versa.
In a datasheet involving a DAC(DAD1793 from TI) they show the recommended
layout but I'm a bit confused. The DAC is on the analog side but its half
digital. Its digital ground is grounded to the analog side. Would it not be
better to have its digital ground go to the digital ground plane? Of course
since the IC is over the analog ground plane it means that the there would
have to be a little routing but I'm thinking that maybe the digital ground
plane could be extendend to half between the chip and vias would go directly
to it?
Also, is there any reason for the ground plane to be on a seperate layer? Is
it for just convenience and to maximize area or is there some other concept
involved. Since I don't have any double sided pcb boards and if I did(which
I suppose I could make but sticking two single sided ones together) I'm not
sure how to make the vias(drill and solder/maybe use a wire connector). I'm
sure I can get away with using a single side for prototyping though? (As
noise issues won't be the ultimate factor unless its pretty bad)
What I was thinking about was splitting the ground plane/pcb board into two
halfs where the ic's that were partially digital and partially analog would
straddle both sides. This would allow me to sorta seperate the two sides to
some degree but not sure if it would cause other issues.
Also, in this case would using one digital supply for all digital elements
work? In the two layouts I have saw for ADC's and DAC's they use one supply
for the digital and then one supply for the the DAC and/or ADC.
i.e., one supply is completely digital but the one supplying analog power
also supplies the digital for the ADC's and DAC's. Is this necessary(in
that, is it better or worse than having only two supplies one for digital
and one for analog)?
One more question. I didn't realize that the DAC's and ADC's where
synchronous devices and need external clocks(thought they had them build in
and I could use interrupts to transfer data). Can I use the same clock for
both/all conversion ic's? I need a pretty stable and fixed clock because I'm
using it for audio so the pitch needs to be right(I don't think this will be
an issue but I'd like not to introduce more complications by having many
different clocks it isn't necessary).
Thanks,
Jon