SRAM chips

[Jeroen Proveniers]

> -----Original Message-----
> From: danial stocks [mailto:diode at hotmail.com]
> Sent: Friday, August 18, 2000 1:25 PM
> To: synth-diy at node12b53.a2000.nl
> Subject: RE: SRAM chips
> 
> 
> 
> >IMHO every SRAM goes in sleep mode when it is not selected, 
> eg. /CS is 
> >high.
> >
> Yes but you have to look at the current consumption is when 
> in this mode.. 
> sure it will be less than what the chip draws in active mode, 
> but it can in 
> some cases still be several ma.. far too much for a lithium backup..
> Cheers,
> Dan

I took a quick look at 62c256 of ISSI. Standby mode Vcc=5V, 0.5 mA, in CMOS
mode. When you reduce the supply to 3V it's 200uA, indeed too much for a
battery to last lang.

An DALLAS DS1244 32K SRAM with backupbattery could also be considered. This
is a module slighty bigger dan DIP-28 and has an onboard lithium battery
that should last 10 years. Advantage of such module is that it contains
protection circuits to prevent inadvert writes at power up/down. These units
are reliable, but rather expensive. One thing, you know it's guaranteed to
work.

JJ