[SI-LIST] Re: Fw: 5V To 3V
- From: steve weir <weirsp@xxxxxxxxxx>
- To: hariharan@xxxxxxxxxxx,"'Signal Integrity Forum'" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 15 Dec 2003 01:18:35 -0800
Hariharan, that can be used where all conditions:
1) 3V is sufficient threshold for the 5V logic.
2) The pull-ups connect to 3V.
3) The 3V side nominal output levels are insufficient or marginal for the
5V side.
4) The RC delay of the chosen pull-up resistor is sufficient to meet timing
from the 3V to 5V side.
5) The R value for the pull-ups does not excessively load the 5V side
driving in either direction, or the 3V side pulling down.
6) The R value does not cause excess power drain for low-power systems.
7) Power-sequencing is either not an issue or is handled properly.
7) Has literally burned a number of engineers, and can lead to all manner
of "benefits". Beware of all current leakage paths in multiple supply
systems, or be prepared for frequently very unwelcome surprises ranging
from: intermittent reset failures, to power supply start-up failures, to
cooked parts.
Unless cost is a severe factor, and assuming the logic thresholds are
adequate, the easiest fail-safe solution is usually a QuickSwitch type device.
Steve
At 10:01 AM 12/15/2003 +0530, hariharan wrote:
>try a pull-up on 3 to 5V path and no pull-up from 5 to 3V.. one of the
>cheapest ways...
>
>regards
>Hariharan
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Steve GullWing UK
>Sent: Saturday, December 13, 2003 4:21 PM
>To: Signal Integrity Forum
>Subject: [SI-LIST] Fw: 5V To 3V
>
>
>
>
> > Dear SI'ers,
> > I am trying to interface a 5V micro-controller to a
>3V
> > LCD Controller IC. What is the easiest and cheapest way to do this.
> >
> > Regards
> > Steve M
> > GW Ltd
> >
>
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