You may be right.... but 2 layers are for me OK at the moment...
What do you think about the big Vref capacitors? Are they really necessary if the regulators are placed close to the DAC on the pcb?
The attachment is for AK4490. Also take a look at the notes on page 78 of AK4458 datasheets.
Attachments
"Power lines of AVDD and VREFH1-4 should be distributed separately from LDO and etc. while keeping low impedance. If it is not possible, it is recommended to connect a LPF composed by a 10Ω resistor and a 220uF capacitor between VREFL1-4 and VREFH1-4."
I know this magic curve, but datasheet says that these are needed if the regulator is far away from the IC....
(and don't forget, the AK4490 evaluation board uses an add-in panel for the DAC chip...)
I know this magic curve, but datasheet says that these are needed if the regulator is far away from the IC....
(and don't forget, the AK4490 evaluation board uses an add-in panel for the DAC chip...)
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The AK4495 evaluation board manual shows not much benefit from bigger Vref capacitance so I think it is somewhat chip dependant, the THD for that chip goes down almost 10dB if it is used at less then -3dB below fullscale output though.
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The idea is to never leave a pin "floating", i.e. not connected to anything. So a pin should be connected to either gnd or Vcc.
However, if the pin is (or could be set by software to be) an output pin a resistor is a good idea to protect the pin from overloading in case of a fault or programmer error.
Of course, there are always exceptions to these rules. For example, if you look at your datasheet you will probably see that certain pins can be left floating / unconnected.
However, if the pin is (or could be set by software to be) an output pin a resistor is a good idea to protect the pin from overloading in case of a fault or programmer error.
Of course, there are always exceptions to these rules. For example, if you look at your datasheet you will probably see that certain pins can be left floating / unconnected.
It depends on your source and the saple rates you are going to use.
24.576MHz and 22.5796MHz are often used.
In my board is 24.576MHz.
24.576MHz seems to be good by the datasheet, if 192kHz should be considered too...
By designing the PSU, what is the current requirement (mA) for the Vref inputs? I can not find any information about that... Does it make sense to feed the 4 Vref inputs with more (e.g. 2) different regulators (shunts in my case)? I'am designing my DAC for an active system, so the L-R separation is an important point...
By designing the PSU, what is the current requirement (mA) for the Vref inputs? I can not find any information about that... Does it make sense to feed the 4 Vref inputs with more (e.g. 2) different regulators (shunts in my case)? I'am designing my DAC for an active system, so the L-R separation is an important point...