bcasper@eos.ncsu.edu (BRIAN CASPER) (03/11/91)
I'm building a project and using an old XT power supply for a source. On P8, I think pin 1 is labeled "Power Good". What is this for? Do I need to loop it back into ground or something to keep the PS from shutting down or something equally bizzarre? -Brian
ardai@teda.UUCP (Mike Ardai) (03/11/91)
In article <1991Mar10.173827.1690@ncsu.edu> bcasper@eos.ncsu.edu (BRIAN CASPER) writes:
-I'm building a project and using an old XT power supply for a source.
-On P8, I think pin 1 is labeled "Power Good". What is this for?
Power good is a signal generated by the supply that is supposed to tell the
rest of the system that the AC power is present. This is used to write-protect
the clock and CMOS ram (on AT's) on power failures to prevent spurious
writes.
XT supplies make good supplies for projects, but make sure you have enough
of a load on it or it may shut down.
/mike
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\|/ Michael L. Ardai Teradyne EDA East
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/|\ ...!sun!teda!ardai (preferred) or ardai@bu-pub.bu.edugrege@gold.gvg.tek.com (Greg Ebert) (03/12/91)
bcasper@eos.ncsu.edu (BRIAN CASPER) writes: >I'm building a project and using an old XT power supply for a source. > >On P8, I think pin 1 is labeled "Power Good". What is this for? Do I need >to loop it back into ground or something to keep the PS from shutting down >or something equally bizzarre? > 'Power_good' is just that... It's a TTL-level signal which goes high when the supply outputs are stabilized. It ties into the CPU reset signal. Some power supplies require a _minimum_ load before the voltages come up, so if you measure them unloaded with a meter, you get near-zero readings. I have seen load resistors which plug into systems without hard disk in order to satisfy the minimum load requirement of the power supply.