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 Post subject: Drawing power
PostPosted: Wed May 30, 2018 10:50 am 
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Joined: Sun Sep 19, 2004 11:12 pm
Posts: 20158
Location: NE Indiana, USA (NTSC)
Someone in the GBDev Discord server wants to know how much current a peripheral can safely draw over the link port. Who here has an ammeter and a worm light?


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 Post subject: Re: Drawing power
PostPosted: Wed May 30, 2018 11:18 am 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 7211
Location: Seattle
Frohwein's schematic indicates that there's a diode in series with the DMG's Vcc output.
Gekkio's pictures of the original DMG's mainboard show a silkscreened name of "1SS254" right next to the diode.
The 1SS254's datasheet says that this diode is rated for a maximum of 130mA mean, 400mA repetitive max.

I vaguely suspect, without evidence, that the DMG's flyback converter and/or battery life will impose a lower limit.

I'll note, without any idea if it's "ok", that Catskull Electronics apparently sells a simple passive adapter between the DMG's link port and a PS/2 peripheral, and apparently LSDJ can support a keyboard connected in this way.


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