[10 point for real help] Voltage pb

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mouzid

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Hi all,
Using a cadence platform I designed a module that generate a square wave of 1 Volt amplitude. When I connect this one to another module the voltage scale to 0.7 V.
I used 2 inverter between the 2 modules but the problem persists.
How can I resolve this problem ?
 

some schematic will help
 

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    mouzid

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Nop, i meant schematic of what is inside the module
 

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    mouzid

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I suppose its a PLL that is generating the square wave. you need to insert a buffer with an appropriate number of stages & proper sizing. You can read Digital Integrated circuits by Rabaey for details on Buffers(chap 5). Various factors like the load Cap & Cap of the generator([PLL) affect this. You can also try increasing the W/L's of the inverters that u have inserted as it is possible that the inverter is not able to drive the load. Sometimes when shifting between analog to digital or vice versa u require level shifters too.you can try using a level shifter followed by a buffer too. Hope this helps.

Added after 4 minutes:

This should help, slides from rabaey.
 

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    mouzid

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I suspect something wrong with the module-2, Can you give the input stage schema of module-2
 

The second module could be loading your first stage.

Instead of the second try it out with a capacitve load, which should give u an estimate of the capacitance to keel the voltage at 0.7 volts then resixe the output with some buffers.

Or add level restores with a psuedo pmos at thee input of the second stage.
 

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    mouzid

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