22 Nov
2001
22 Nov
'01
11:51 a.m.
I was concerned that if he clipped his device onto a 3-voltage device, the test
device would go poof.
if it's external to the application, it doesn't matter, since the test device
provides the supplies. I have a few of those old HP IC test clips, and the ones
I have are all malfunctioning in some way due to abuse prior to their falling
into my possession. That's actually why I have them.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, November 22, 2001 12:56 PM
Subject: Re: 1771 floppy controller questions
>
> You'll want to be careful with the early DRAMs, as they used 3 supply rails,
and
> your tester of 5-volt-only DRAMs may die from
application to a 3-supply
DRAM.
It's unlikely that an 3-rail DRAM chip will damage the tester (it's not
going to magically apply overvoltage to the tester's inputs if it's only
fed with a 5V supply). But it's not going to work, and in some cases it
might damage the DRAM (some of the older DRAMs would fail if the -ve bias
supply was missing IIRC).
64K bit chips and above are +5V only in my experience. 4K bit and below
are almost always multiple supply rail types, and some of them had logic
inputs (clock/select) that needed higher-than-TTL levels. 16K bit are
normally 3 rail (4116 and equivalents), but +5V only ones exist (4816 IIRC).
-tony