#garfield Logs

Feb 09 2023

08:56 AM polprog_: On the other hand, there are the practitioners, working in the field of
09:06 AM polprog_: electronic design automation. They strive to obtain the best circuits that they can,
09:06 AM polprog_: given the computational resources at their disposal. However, they rarely speak of
09:06 AM polprog_: optimal designs. The true optimum according to any criteria – be it area, delay, power is generally unknowable to them.
09:06 AM polprog_: shots fired >_<
09:51 AM ruenahcmohr: so, take that 7 segment decoder goal
09:51 AM ruenahcmohr: optimize it for ttl chips
09:51 AM ruenahcmohr: the target moves
09:52 AM ruenahcmohr: you can optimize for gates, but a low gate count doesn't mean a low ttl chip count
09:52 AM ruenahcmohr: you can have one solution with two nand chips thats just one nor chip
09:53 AM ruenahcmohr: it can be better to use more of the wrong gate for things becasue of whats left over in other chips
09:53 AM ruenahcmohr: so I see the point
11:24 AM rue_shop3: IS61C512
11:24 AM rue_shop3: 5M51008
11:24 AM rue_shop3: --
11:25 AM rue_shop3: CY7C199
11:25 AM rue_shop3: IS61C256
11:25 AM rue_shop3: W24257
11:25 AM rue_shop3: KM62256
11:26 AM rue_shop3: SRM20256LC
11:38 AM Tom_L: numbers
11:40 AM ruenahcmohr: ram
11:56 AM ruenahcmohr: IS61C512is not rated for battery backup
11:58 AM ruenahcmohr: 5M51008 is rated for battery backup
11:59 AM ruenahcmohr: CY7C199L is rated for battery backup
12:02 PM ruenahcmohr: W24257 is not rated for battery backup
12:02 PM ruenahcmohr: KM62256 is rated for battery backup
02:02 PM ruenahcmohr: so
02:02 PM ruenahcmohr: 2F supercap, starting at 2.5V and discharging at 100uA
02:02 PM ruenahcmohr: how long to get to 2V?
02:04 PM ruenahcmohr: 2.5 hours
02:31 PM ruenahcmohr: li-ion batteries come with a whole heap of trouble
02:31 PM ruenahcmohr: 2.5 hours is probably ok
02:32 PM ruenahcmohr: its fine for development stuff
02:42 PM Tom_L: but are you sure?? ... have you tested it??
02:44 PM ruenahcmohr: I'll find out
02:44 PM ruenahcmohr: it could be longer, I think I used pesimistic numbers
02:44 PM ruenahcmohr: the supercaps were cheaper than batteries, and their eaiser
02:44 PM ruenahcmohr: so I got 2 3.3F 2.7V ones
02:45 PM ruenahcmohr: I'll charge them to 2.5V or so
02:45 PM ruenahcmohr: see if I can make up a little battery backed up memory, 512k or so
02:45 PM ruenahcmohr: well, the surface mount memories I have are 1M and 2M
02:46 PM ruenahcmohr: but for what I'm playing with, 512k is as much as I can use
05:24 PM aandrew: well q=CV, so Q is 6.25 Coloumbs at 2.5V and 5 Coloumbs at 2V. Discharging 1.25 Coloumbs at 100uA should take I=Q/t 1.25/100u or 3.5h if my math is right?
05:25 PM aandrew: the current won't exactly be constant but it'll likely be close enough during the 0.5V change