From: Jim Thompson
Subject: Re: Interfacing 3.3V chips with 5V bus ??
X-Newsreader: Forte Agent 1.91/32.564
Date: Tue, 14 Jan 2003 20:42:02 GMT
NNTP-Posting-Date: Tue, 14 Jan 2003 15:42:02 EST
Organization: Cox Communications
On Tue, 14 Jan 2003 12:19:33 -0800,
Thierry Nouspikel ,
In Newsgroup: sci.electronics.design,
Entitled: "Interfacing 3.3V chips with 5V bus ??",
Wrote the following:
|There are lots of cool memory chips around: 32 MB flash, huge SRAMs,
|even combo Flash/SRAM chips. Unfortunately, they all seem to come only
|I'd like to use these chips with an old 8-bit computer which has a 5V
|TTL bus. What kind of interface do I need? If I connect the 3.3V chip
|directly to the 5V bus, will it damage the chip?
|I thought of using a tension divider for the address bus (e.g. 1K
|serial, with 2K pull-down?), but the data bus must be bidirectional. Can
|I 3.3V chip achieve a TTL "high" level?
|I'm sure there are well known design tricks for this purpose. Could
|somebody explain them to me, or point me to a site describing this?
|Thanks for your help,
0 to +3.3V CMOS can drive TTL *inputs* just fine.
However TTL *outputs* are capable of providing 0 to +3.6V or *higher*,
depending on the type of totem-pole output structure, which might
destroy your CMOS.
There are CMOS chips made to interface between +3.3V and +5V, you
should look for those.
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
For proper E-mail replies SWAP "-" and "_"
I love to cook with wine. Sometimes I even put it in the food.