ADAU1701 Eval board development related.

Hello Mayuresh,

Regarding the master clock frequency. In the datasheet it describes how to set the PLL pins for different clock frequencies. 

Any incoming sample rate clocks must be exactly divided down from the master clock as shown in the table. 

The incoming rate must also not exceed the timing specifications.

Here is the specification of the built in regulator using and external pass transistor.

When you mention not getting 3.3V and getting 2.5V I hope you are talking about the IOVDD, PVDD and AVDD and not the DVDD. 

The DVDD is for the core and should not be greater than 1.8V nominal. 

If the external 3.3V regulators are not putting out the correct voltage then there is something wrong with the external regulator circuits. The ADAU1701 does not have a 3.3V regulator built in. 

Mayuresh said:

So I would like to know What exactly I need to check if the device's PINs 13 & 24 are not returning 1.8V? If there any boot sequence which fails and hence device does not return 1.8V? Or device has not booted at all? 

I just looked at this datasheet and found the application schematic is terrible in that it lists IOVDD as DVDD. You can see that pin 13 and 24 are their own net and not part of the net named "DVDD" which is really confusing!!! 

Here is a screenshot where I circled the net labels that should be IOVDD or 3V3 or something like that. 

You should have 3.3V on the emitter of Q1 that is coming from some external regulator. The base will be 0.7V less since it is a PNP. The collector should be 1.8V. The internal regulator is sensing the voltage on pins 13 & 24 and adjusting the drive to keep the collector at 1.8V. R5 is only there to ensure a correct startup and to limit the value during startup. 

The regulator is not tied to any other signals in the part like the MCLK input or the core etc. The regulator is analog and will just power up when power is applied to the part. The part does not need to be programmed or any registers need to be written to make it work. 

Mayuresh said:

Also, how to determine if the device (ADAU1701) is functional and not dead or not to booting up? 

There are many ways to do this. Some people will program a heartbeat using a GPIO pin and possibly an LED so you can see it flashing. You can do like I do in almost all my programs. I put in a DC cell and a readback. If the core is running the program I can read the readback and see if it contains the correct value. Some people use the DC cell to store either a product ID or revision number that they can read to know the rev of hardware attached to the controller. 

This is what you will see in all my programs. When using SigmaStudio you can use it to see if you are actually communicating properly with the DSP and if the program is running. 

Some people will use an oscillator to see if the value is changing. 

Mayuresh said:

And lastly, how do I output 2 different channels via SADTA_OUT to an additional DAC as I would now like to add amplifiers (2 apms with analog inputs) to the board to output 6 channels.

Here is a program I wrote that loops back digital audio if you connect the pins correctly. It shows how to send out and receive digital signals and you can see the register settings. 

1731.ADAU1701 Digital Out with Digital In Loopback test.dspproj

I think this about sums up your questions. 

Dave T

Hi Dave,

Thank you for the quick response and being helpful as always!

About the clock. What I meant was, if I have to change the existing "ABM3B-12.288MHZ-10-1-U-T" from 12.888 to something else (24.000 maybe) do I have to make any changes to hardware circuitry? Or we must keep the existing clock as is and only play around with the PLL setting?

Also, thank you for the IOVDD/DVDD/D3V3 correction. I had asked about this in this forum earlier also, (see: ez.analog.com/.../adau1701-eval-board). If as per the datasheet (EVAL-ADAU1701MINIZ), if DVDD = 1.8 and is connected to IOVDD (pin 18) then isn't IOVDD = 1.8?

In my current board,

DVDD is 5V.

D3V3 is 3.3, which is going to Q2 Base.

Q1 emitter has D3V3 and collector sends out 1.8. Pin 18 is connected to D3V3. PVDD/AVDD are too connected to D3V3.

This confusion caused me multiple failed PCBs & devices, as I followed everything there as is and nothing worked at all. I am somehow struggling currently as how come my current board is working! 

About booting up.

When there is a failure at 1.8 & 3.3, nothing works. I could connect the device to SigmaStudio, but it would always return "comms failed", it would only write the program to EPROM and then it become difficult to check anything in realtime. However with the new working board I will certainly try to your solution along with the oscilloscope I have.

Lastly thank you for the program. Will check and get back if there is anything more required.

Thanks you!
-Mayuresh

Hello Mayuresh,

If you have the EVAL-ADAU1701MINIZ then you may have received one that had a stuffing error. We had a new contractor make a build of boards several years ago and they stuffed a wrong component. Instead of a 78K7 they stuffed a 78.7ohm resistor!! Slightly different! Where it was is a really bad spot. It is the voltage feedback divider for the 3.3V regulator. So it thinks the voltage is too low and it goes up as high as it can. That is 5V because that is the input to the regulator. 

If you measure R6 located near the voltage regulator, and see if it is 78 ohms. If it is then change it to the correct value. 

Mayuresh said:

About the clock. What I meant was, if I have to change the existing "ABM3B-12.288MHZ-10-1-U-T" from 12.888 to something else (24.000 maybe) do I have to make any changes to hardware circuitry? Or we must keep the existing clock as is and only play around with the PLL setting?

Yes, you will have to change the PLL most likely. You have to know if it is 256x or 512 x fs and then do not violate the timing specifications I mentioned in my last post. If you have to change the PLL MCS then it will be difficult because on this part it is not a register setting but a setting on the pins. 

Dave T

Hello Mayuresh,

If you have the EVAL-ADAU1701MINIZ then you may have received one that had a stuffing error. We had a new contractor make a build of boards several years ago and they stuffed a wrong component. Instead of a 78K7 they stuffed a 78.7ohm resistor!! Slightly different! Where it was is a really bad spot. It is the voltage feedback divider for the 3.3V regulator. So it thinks the voltage is too low and it goes up as high as it can. That is 5V because that is the input to the regulator. 

If you measure R6 located near the voltage regulator, and see if it is 78 ohms. If it is then change it to the correct value. 

Mayuresh said:

About the clock. What I meant was, if I have to change the existing "ABM3B-12.288MHZ-10-1-U-T" from 12.888 to something else (24.000 maybe) do I have to make any changes to hardware circuitry? Or we must keep the existing clock as is and only play around with the PLL setting?

Yes, you will have to change the PLL most likely. You have to know if it is 256x or 512 x fs and then do not violate the timing specifications I mentioned in my last post. If you have to change the PLL MCS then it will be difficult because on this part it is not a register setting but a setting on the pins. 

Dave T