[SI-LIST] Re: SSTL termination resistor power

Folks:

Only DDR-II/GDR-III memory support the ODT function. The value chosen is 
programmable and a function of the configuration of the memory system and 
the operation taking place.  ODT dissipation can be power managed by 
programming open circuit values except when you need the specific 
termination configuration called out by the manufacturers. This raises the 
complexity for the programming of the controller and can slow down the net 
thru-put.

Memory and controller designers have to come to grips with the fact that a 
matched termination is also the condition for maximum power transfer and 
1/2 the power is always dissipated in the source driver and 1/2 in the 
termination/load.

Cheers -

ed sayre
================
At 08:16 AM 8/25/2005 -0700, Bi Han wrote:
>SSTL termination might use ODT termination for receiver side.
>
>The implementation is about 120ohm between PAD and VDDQ, another 120ohm 
>between PAD and VSSQ. Overall AC impedance is about 60ohm.
>Since signal is DC coupled, there is DC current burning in terminaion 
>resistors. If the PCB trace impedance is 60ohm, then the DC current in the 
>termination resistor is about 20mA. It is so huge that I can not believe 
>that DDR memory can afford it.
>
>Is there any way to reduce the power?
>
>thanks,
>Han
>
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