Building the $99 ES9018 DAC Board (Part III)
It’s taken a long time to get this project finished. This would be my third ES9018-based DAC. Finally ordered some ceramic bypass caps and an oscillator. I wanted to do more before posting this, but that may take me more time than I thought…
You can read the previous postings here:
I will start with a “standard” 3.3V 100 MHz clock from Fox if for no other reason that these cost about $3 and readily available. These are the specs [link]:
Typical “standard” jitter numbers. Additionally, I am not sure if ultra-low jitter clocks would really make a difference since the DAC itself has intrinsic jitter as the signal passes through the electronic components on its way through the device. If you look at the ESS evaluation board, they have implemented a lowly quartz crystal. Not even an oscillator.
Epson SAW oscillators
I also want to try the SAW oscillators from Epson [datasheet]. Unfortunately, the 100 MHz parts are not so easy to obtain in the US. They are available from Newark but charges $20 “transportation charge” for these parts.
According to myl8test [link]:
For asynchronous operation (the normal way you use the ES9018 chip), having tried over 6 clocks now, I’d recommend the Epson SAW 75Mhz 50ppm as suggested above. It’s actually better than the much more expensive Crystek CCHD-957 IMO. I even prefer it to synch from the CM6631A.
CERAMIC BYPASS CAPS
Murata 0.1uF 50V X7R dielectric in 1206 size. Got these because they were CHEAP, under $3 for 100 pieces. (C0G dielectric, which are preferred for the signal path, would cost more than 10x-20x the price. For bypass, these are fine).
Here is some wisdom from Cypress on what to use for circuit bypass [link]
Decoupling capacitors should be ceramic type of a stable dielectric. For lower value capacitance, it is appropriate to use Class 1 dielectric capacitors, C0G (also referred to as NPO). Class 2 X7R should be used for the larger values.
It is recommended that 0.01-µF and 0.001-µF (pins 7 and 11 of CY7C68013A respectively) capacitors be used to decouple supply pins nearest the pair of USB transceiver circuits. The 0.001-µF should be C0G dielectric. This will help decouple the power supply at the frequency range of high speed USB switching.
The other power supply pins should be decoupled with 0.1-µF X7R capacitors.
Bypass capacitors on the DAC board
- 4 positions for AVCC L (3.3V Analog)
- 4 positions for AVCC R (3.3V Analog)
- 2 positions for 3.3V Digital
- 3 position for 1.2V (used 22 uF instead of 10 uF)
First time soldering SMD caps. Didn’t come out too bad. These are size 1206. Probably could have done 0603 caps too…
Here is the TPA AVCC V 1.0 supply (previously used in my BII DAC) on the other side of the board. In a previous post I had shown how to separate AVCC L from AVCC R. The AVCC module will be powered with 5V.
The large capacitors are 22 uF in value used to bypass the 1.2V supply. I am not very good with soldering, but these came out pretty good (at least in the photo :-))
Compare with BII construction, the BII uses CoG ceramic capacitors (more costly)
Decoupled the 1.2v lines by piggybacking 0.1uF ceramic caps on top of the 22 uF ceramic caps. (the 1.2V lines do not have low value cap decoupling anywhere else)
INSTALLING THE CLOCK
As described in previous posts, I’m using Ian’s clock carrier board for the clock. This way I can easily change the clock in the board.
The board’s default power connection is to use the digital 3.3v which is shared with the DAC. FB1 connects the 3.3v to the clock. I will leave this disconnected as I plan to use a separate supply for the clock.
Opted to get the 4x TPS7A47 board from diyinhk.
The plan is to use the following configuration:
- 5V: AVCC shunt regulator
- 3.3V: Digital 3.3V and Digital 1.2V regulator
- 3.3V: clock
- Still leaves one supply available for other things such as the Arduino controller
The implementation is straight out of the evaluation board. The only differences are:
- Voltage settings limited to 3.3V and 5V (although you can notice that there are three traces from the chip that are used to adjust the voltage and if you also cut the traces, you can have the following voltages: 1.4v, 3.3v, 3.7v, 4.6v, 5.0v, 6.5v, 6.9v. If you don’t cut the traces and just combine the jumpers, you can have 1.4v, 3.3v, 5.0v and 6.9v – In fact not very useful voltage values…)
- Can take AC input (bridge rectifiers and smoothing capacitors are installed in the board)