[SI-LIST] Re: Reset problem with power supply
- From: V S <for_si2003@xxxxxxxxx>
- To: olaney@xxxxxxxx
- Date: Sat, 6 Dec 2008 19:19:28 -0800 (PST)
Orin,
Thnaks for taking time to write. I finally found that the processor was booting
everytime. But it did not get the first byte from the Flash. Flash did not seem
to start.
I finally solved the problem by using a small controller to generate a POR
followed by double HReset ( Low then High, then again low and then high).
Thanks everyone for reply
Vikas
http://referencedesigner.com
--- On Fri, 12/5/08, olaney@xxxxxxxx <olaney@xxxxxxxx> wrote:
> From: olaney@xxxxxxxx <olaney@xxxxxxxx>
> Subject: Re: [SI-LIST] Reset problem with power supply
> To: for_si2003@xxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Date: Friday, December 5, 2008, 2:57 PM
> Cable inductance absolutely should not be an issue. If it
> actually is,
> be grateful that you found a design flaw before you reached
> production!
> This might be related to the power risetime. Your POR
> circuit needs to
> operate properly even if you slowly bring the voltage up
> manually. Some
> circuits depend on fast power risetime to operate properly,
> and work
> OK... most of the time. The worst ones capacitor couple
> the voltage bus
> into a transistor. Not only do these fail to reset on a
> slow rise, if an
> aluminum electrolytic cap is used, the value will drop with
> age as it
> dries out and eventually the circuit won't work even
> for normal supply
> risetime. A Schmitt trigger is a good basis for a
> bullet-proof approach,
> as are any number of supervisor ICs that also check for
> overvoltage,
> brown-out, and the like.
>
> In any instance, if you can section the power distribution,
> start by
> running everything off the bench supply, then one by one
> move each
> section to power through the cable. When the problem
> reappears you have
> found where to dig deeper. Power up and down between each
> change, rather
> than doing this with a live circuit.
>
> Orin Laney
>
> On Fri, 5 Dec 2008 12:39:22 -0800 (PST) V S
> <for_si2003@xxxxxxxxx>
> writes:
> > 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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