dana@locus.com (Dana H. Myers) (01/11/91)
In a previous posting I speculated: [context is the DC current drain of the 80376 CPU ] > One question; where is that 68.333 of static current going? I'd >suggest two places. One may be in on-chip bias voltage generators, >though I suspect this is small. The other place is likely to be >leakage current. Assuming there are 120,000 gates in the 376 (just >guessing, but certainly within less than an order of magnitude), >this would amount to a leakage current of about 500 nA per gate, >which sounds a little high but not too far off. I received another stimulating letter about this. Gosh, I was grasping at straws with regards to where this current is going. This fellow has dropped some pretty big hints that it isn't leakage but he's left me to figure it out. I suspect this current is going into non-saturated circuitry in the CPU. One example of non-saturated circuitry found in some CPUs is the on-chip XTAL oscillator. Another example would be the sense amplifiers for on-chip RAM. Some kinds of logic may be non-saturated. CMOS op-amps are non-saturated. Of course, non-saturated means something a little different for MOS than bipolar transistors. Saturation is something that actually happens to a bipolar transistor. MOSFETs don't saturate; they just take longer to switch when driven harder. I guess this is why no one will pay me to design CMOS chips. -- /* * Dana H. Myers KK6JQ | Views expressed here are * * (213) 337-5136 | mine and do not necessarily * * dana@locus.com | reflect those of my employer *