[SI-LIST] AW: Re: (no subject)
- From: mathias.borcke@xxxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 25 Aug 2003 17:25:37 +0200
The DDR2 spec eg. see:
http://www.samsung.com/Products/Semiconductor/DRAM/DDR2SDRAM/DDR2SDRAMco=
mpon
ent/512Mbit/K4T51083QM/512M_M_DDR2_Samsung_Spec_rev0.92.pdf
On Page 78 the reference load (25R || 0pF) and timing reference point =
(at
DUT) is defined.
Whatever capacitive/resistive load you use in your system you will need =
to
estimate the RC-delay from the DDR2 Off-Chip-Driver Ron (nominal 18R @ =
0.3V
resp. 1.5V) and your complex load.
Regards
Mathias
-----Urspr=FCngliche Nachricht-----
Von: stephanie.goedecke@xxxxxxxxxxx =
[mailto:stephanie.goedecke@xxxxxxxxxxx]=20
Gesendet: Montag, 25. August 2003 12:28
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: (no subject)
Hi CKW,
I don't know that you want the capacitance to be specified, as this =
would
greatly limit design options. I don't think the resistance is =
specified
either.
The scope section of JEDEC Standard 8-9 (SSTL 2.5V) says:
"Actual selection of the resistor values is a system design decision =
and
beyond the scope of this standard."
This might be similar with the 1.8V version?
I recommend you select these values based on what gives the best =
signaling
and timing margins in the design.
best regards,
Stephanie
=20
=20
To:
si-list@xxxxxxxxxxxxx =20
cc: (bcc: =
Stephanie
Goedecke/STN/SC/PHILIPS) =20
Subject: (no =
subject)
=20
"ckw1972" Classification:
<ckw1972@xxxxxxxxxxx>
=20
Sent by:
si-list-bounce@freelists
.org
=20
2003-08-22 02:48 AM
Please respond to
ckw1972
=20
=20
Hi,
I've a question on the DDR-II SDRAM (SSTL-18 class-II) spec as below, =
can
someone help me to understand this correctly? Thanks in advance.
1. Why they is no clear capacitance load spec specify on the memory =
spec?
For example, samsung 512M 200Mhz DDR-II SSTL-18 class-II device
datasheet
only specify their AC load reference is just connect DQ pin to Vtt =
thru
one 25ohm
resistor. My understanding on this is with Cload=3D5pF & =
Cload=3D0pF will
impact on
the 200Mhz performance quite significantly.
Thanks
Regards,
CKW
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