[SI-LIST] Re: Reset problem with power supply

hi

are you generating the resets based on the incoming power? thy should be 
generated based on the latest on-board-generated supply voltage in the 
voltage-sequencing chain. i hope these are sequenced to each other on your 
board, and not just staring immediatelly after they got the input voltage 
from the same common main input.

if the incoming power causes problems for you, then maybe you should 
generate all voltages on your board with controlled start times and ramp 
rates, so it will work with any input ACDC adapters. we had problems with 
some boards needing a controlled ramp rate to function correctly.

and as steve weir said, use a bigger cap at the cable input. play around 
with capacitor values in the lab, like 10uF...1000uF. use through-hole caps 
for finding the value easily, use tantalium later, but validate the 
tantalium with the chosen value. sometimes DCDC converters dont work, or 
continously or periodically limit the output current or oscillate when the 
input source is not strong and stable. a cable is never strong and stable.

Istvan Nagy
Concurrent Technologies Plc.

----- Original Message ----- 
From: "V S" <for_si2003@xxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Friday, December 05, 2008 8:39 PM
Subject: [SI-LIST] Reset problem with power supply


> When I power my board using a bench power supply it boots. When I try to 
> plug in the cable, with the one end of the cable hooked to the same power 
> supply in power on position it does not. My question is what difference 
> cable inductance makes ? The failure looks like between processor and 
> Flash core, as, the processor is always alive.
>
> The processor is freescale MX27. I am using national Semi LM2717-ADJ IC to 
> generate 1.8V for memory IO, 1.5V for core and PLL, 2.775V for processor 
> IO and 3.15 for other IO. A POR is generated using Schimtt Trigger. The 
> HRESET is generated using the same schmitt Trigger 74LCX07MX.
>
> Any one faced similar situation ?
>
>
>
>
>
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