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SDRAM 100Mhz interfacing with PowerPC Processor

Question asked by ahmed047 on Feb 28, 2018
Latest reply on Feb 28, 2018 by alexander.yakovlev

I am interfacing SDRAM IS45S32160F-7BLA2 with MPC8270 PowerPC Processor.

Input capacitance of SDRAM is 6pF per data line and i am using 4 SDRAM's which add upto 24pF of capacitance load.

Processor suggest to have a minimum loading of 20pF. 

Now the problem is current . Processor datasheet says Ioh = -2mA and Iol = 6mA. at Voh = 2.4 and Vol = 0.4

Keeping this current in mind, i=C dV/dT fails, as 20pF of load capacitance needs around 60mA and Iol and Ioh is 2 to 6mA , which i cannot understand?

 

Secondly when i simulated both using IBIS models, the waveform is very wierd on 4 SDRAM, So will this waveform okay for SDRAM to work on 100Mhz or i need to do something else?

Orange is input clock to SDRAM, and Red is the signal of DATA bus with 4 SDRAM's are loaded.

 

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