That 723

Rowena Larkins rowenal at nimrod.itg.telstra.com.au
Fri Sep 25 00:38:32 CEST 1998


Dear marjan

> > I can install the DIP on a separate board, but what about heatsinking such
> > a device? the old metal can had a heatsink.
> 
> if it's on separate board maybe you can put it against some heatsink
> 
> > The 4600 documentation says that the 5 volt should supply 60mA, which to my
> > calculation indicates about 300mW.
> > Will a plastic DIP 723 dissipate that without a heatsink?
> 
> Data says Iref is max 15mA (pin6)?

Thank you, but pin6 is not the output voltage, it is a referance voltage.
The chip is a variable power supply. It does this by comparing a voltage against
a reference voltage, available on pin 6. The current available for this 
comparison is 15mA. So designers need to keep this current in mind when, say, 
calculating the values for a resistor divider.
eg two 10 ohm resistors in series will give a volage at their juntion of 0.5Vref
but will draw way too much current (about 375 mA).
 
> > 
> > As to an alternative for a power supply, the 4600 requires +/-7 and +/-14
> > Volt supplies, so a simple 7812 or 7815 won't do.
> 
> Maplin 5600/3800 synths use the same PSU but with 7805 instead 723 for
> the same voltages. Worth looking.They are at A.Sponton's site.

Yes, and if I wanted to redesign the power supply and rebuild it on a different
board, that is an option. However I would prefer to explore the choices and 
hopefully find a quicker cheaper and easier solution. <I'm basicall lazy :-) >

Thanks for you suggestion though.

Regards, 

Rowena



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