[SI-LIST] Re: SSTL_18 Class I and SSTL_18 Class II

The spec is available from JEDEC for free:  JESD79.

Steve.
Sonu Kurian N.D wrote:
> Hi all,
>
> I am trying to understand the DDR2 terminations.
> I understand that DDR2 rely on SSTL_18 logic.
> The DDR2 device supports 'Full Drive Strength ' and 'Reduced Drive 
> Strength'.
> Does SSTL_18 Class I mean 'Reduced Drive Strength' and SSTL_18 Class II 
> mean 'Full Drive Strength '?
> A typical SSTL_18 Class I environment uses a 25 OHM series resistor(Rs) 
> and 50 OHM parallel resistor(Rt) whereas SSTL_Class II environment uses 
> a 25 OHM series resistor and 25 OHM parallel resistor.
> Is the change in the parallel resistance value due to doubled current in 
> class II environment?
>
> many thanks,
>
> Sonu
>
>
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