CMOS/TTL chip questions (was: Cmos Latch Octal)

[Arthur Harrison]

-----Original Message-----
From: Buck Buchanan <buchanan at qualcomm.com>
To: Arthur Harrison <theremin1 at worldnet.att.net>; Synth DIY
<synth-diy at mailhost.bpa.nl>
Cc: hugo.haesaert at skynet.be <hugo.haesaert at skynet.be>
Date: Thursday, November 19, 1998 6:57 AM
Subject: Re: CMOS/TTL chip questions (was: Cmos Latch Octal)


>At 03:31 AM 11/19/98 -0800, Arthur Harrison wrote:

>>Regarding unequal intervals in clocked metal-gate CMOS devices
>>such as the CD4017BE, CD4024BE, etc:
>>Do not clock these devices form oscillators comprised of gates
>>made of other CMOS "B" type devices, e.g., CD4001BE, CD4011BE,
>>etc.
>>Also, do not clock them from (generic number) 555 timers.
>>Both these methods will result in erratic counts.
>>A better clocking method is to use an oscillator made of "A" series parts,
>>such as the CD4069UBE, CD4001AE, CD4011AE, etc, or, for high fixed

>Hello,  Is there any chance you could explain why this is the case?  I'm
>aware of some of the differences between A and B series CMOS and have heard
>of conditons where A series is better... but it would seem like there must
>be another way to go rather than use old parts.

Hi,

To be honest, I am at a loss to explain _exactly_ why this occurs,
although it possibly has to do with anomalies in the "B" oscillators'
output transitions.  (Certainly, one "B" gate, configured as Boolean
element, driving a "B" FF or counter never seems to cause problems,
which makes this whole thing even more mysterious.)  I tested this
problem with several manufacturers' parts (Motorola, RCA, Harris,
SGS/Thompson) and found the symptoms repeatable.

(I did a previous post explaining the particular oscillator configuration,
etc.,
in response to JH's comment, but knowing this list server...)

The "UBE" devices, available from Harris in the 4001 quad NOR, 4011
quad NAND, and 4069 hex-inverter, are the modern counterparts to the
respective "A" devices. (There used to be "A" devices up to type 4066,
but they've indeed disappeared, and that can be a problem for replacements,
in some rare instances. The ideal part for an oscillator, in any case, is
the
easily-obtained CD4069UBE.  It seems to me that these UBE items have
been retained just for linear applications like these oscillators.

>From RCA's SSD-250C data book (long out of print):

Buffered [B] CMOS devices are types in which the output "on" impedance
is independent of any and all valid input logic conditions, both preceding
and present.  All such CMOS product are designated by the suffix  "B"
following the basic type number."

The reference goes on to explain the distinction between "B"  and "UB,"
devices, among other interesting facts.  Looking at earlier references
by RCA, it seems that certain specifications were changed as the technology
and standards evolved.  For example, the maximum Vdd for the "B" parts
went from 18 to 20v.

In speaking with the earliest users of these 4000 parts, I learned that they
took a while for RCA iron things out and get the parts working
right.

BTW, has anyone ever seen a CD4004 (quite rare!) or a CD4003
(even more so!).

-Art