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Old 17th Dec 2018, 4:46 pm   #21
M3VUV51
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Default Re: PSU using SG3532J.

Looking at the SG internal schematic ,pin 8 the shutdown pin connects to the base of a transistor that when biased on pulls the output of the error amp low, robbing current from the base of the output darlington pair and shutting them off. Looks to me like pin 8 can be left disconected unless I want to use it as say an overtemp shut down, but I'm pretty sure the IC will do that anyway.

Regards M3VUV.
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Old 17th Dec 2018, 5:42 pm   #22
Refugee
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Default Re: PSU using SG3532J.

It is shown grounded on the circuit where it is not used.
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Old 17th Dec 2018, 6:56 pm   #23
G8UWM-MildMartin
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Default Re: PSU using SG3532J.

Vref is 2.5V for the SG3523 and about 7V for the LM723.
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Old 17th Dec 2018, 9:29 pm   #24
M3VUV51
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Default Re: PSU using SG3532J.

WITH PIN 8 I was refering to the internal cct diagram, having it tied to ground makes sense that way its disabled ie pulled low. Will the lower Vref make the IC work from a lower input voltage, ie lower drop out?

I'm still learning!

Cheers M3VUV.
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Old 19th Dec 2018, 1:46 pm   #25
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Default Re: PSU using SG3532J.

well ive built it,i have r8 switched 10k low range0.5-8v or 37 ohm 8-18v,seems to work well,good to see the voltage go realy low!,just need to alter the current sense resistor as doesent limit until 3.5a min.was a direct swap for the 723 apart from pin 8!,the ic came from china was $5 ie 3.40gbp,its a ceramic package to,has a date code from 1989,thought it would be fake but if it is its a good copy! m3vuv.
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