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Interesting comment on the video: "The negative voltage requirement of RS-232 is why some ATX power supplies still provide a negative voltage reference on one

by tyingq 4y ago

Interesting comment on the video: "The negative voltage requirement of RS-232 is why some ATX power supplies still provide a negative voltage reference on one of the pins. The power supply manufacturers want to provide it in case the end user has a motherboard that uses on board RS-232 (some industrial motherboards still use it). usually the available current for the negative voltage reference is pretty small though (around 1 amp or less)"

bogantech 4y ago
I'd be surprised if any modern board didn't use something like a MAX232 or something similar though
- tyingq 4y ago
  The context being that a MAX232 only needs +5vcc, right? Edit: Apparently called 'Integrated charge pumps'
  - bloggie 4y ago
    Yes, there are low current requirements, so typical uart to rs232 transceiver ICs include the electronics necessary to provide the higher voltage +- supplies.
djmips 4y ago
I have a pile of 5 ATX power supplies of various vintages up to recent. They all had a -12 V supply. Three were 0.8 Amp. One was 0.3 Amp and one was 0.5 Amp.
toast0 4y ago
-12V was also pretty commonly used for sound cards. Not a lot of amps, as noted.