[SI-LIST] Re: Power problem

Zhangkun:

It is unlikely you have an induced field problem; it is more likely you 
have not turned on the local DC-DC regulators in the right sequence and you 
are getting feed-thru effects. I would check your -48 VDC to intermediate 
power and your local DC-DC regulator designs.

Also, the DDR specifications are very clear regarding the turn-on sequence 
for DDR products.   They must be followed exactly or you run the risk of 
latch-up when you access the memory or outright damage.

Hope this helps -

ed sayre
========================
At 10:33 AM 6/28/2005 +0800, you wrote:
>Dear all
>In our product, there is one problem. When the system is turned on, some 
>SDRAM would be damaged. The -48V net shape is placed under the 2.5V net 
>shape, which is the power supply of SDRAM. I have use VNA to measure the 
>coupling between these two power. The coupling is very small. Please give 
>me some advice.
>
>Maybe my analysis method is not right.
>
>Best Regards
>
>Zhangkun
>2005.6.28
>
>
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+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
|        NORTH EAST SYSTEMS ASSOCIATES, INC.        |
|       -------------------------------------       |
|      "High Performance Engineering & Design"      |
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
| Dr. Ed Sayre               e-mail: esayre@xxxxxxxx|
| NESA, Inc.                 http://www.nesa.com/   |
| 235 Littleton Road, Ste 2  Tel +1.978.392-8787    |
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