in
the datasheet of the AD9230 (page 5) I saw that the voltage level for
logic 1 voltage is 0.8xVDD min I want to know what is the maximum
voltage level. the same a logic 0 voltage is 0.2xVDD max, what is the voltage level min
You are referring to the input voltage, not output voltage. AD9230 Vdd is 1.8V. This makes VIN(low) = 360mV and VIN(high) = 1.44V.
Compare this to the Virtex-6 datasheet specifications (Table 7, LVCMOS25): VOUT(low) = 400mV and VOUT(high) = 1.4V
Conclusion: Virtex-6 is not able to directly drive AD9230. You will need a buffer.
Here is an example buffer which should work, either for driving from V-6 to AD9230 or receiving from AD9230 to V-6. There are many similar buffers which will work, this is one which I picked for low cost, small size, and acceptable speed. It is a 3-state device which should work for the bidirectional SDIO signal.
The SPI device must support I/Os of 2.5V or lower. Is there a lower limit?
The only lower limit for IO voltage swings is what the various devices will support. The AD9230 is a 1.8V device. It cannot accept lower voltage swings, nor can it sustain higher voltages (for example 2.5V).
I hope this helps... Bonne chances.
-- Bob Elkind
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