Entering in Stand-by without using a MAD-1

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magno
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Entering in Stand-by without using a MAD-1

Post by magno »

Hi guys,

I'm trying to make schematics from all SNES cartridges I have and I started by the "easiest": Super Mario World. The board is labeled as SHVC-1A1B-06, with SRAM but no MAD-1.
In this board, SRAM is powered by a diode during stand-by, and its /CS is driven by some weird device labeled as D2145U. I deeply searched in Google but nothing appears, altough I get to figure out that it could be PNP BJT transistor.
Does anybody know what it really is? This is the schematics:

Image

If you analyze the schematic assuming it is a PNP transistor, the circuit makes no sense at all and it can't drive /CS to high when Vcc disappears.
Is there any alternate way to put SRAM to standby mode without using MAD-1?
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lidnariq
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Re: Entering in Stand-by without using a MAD-1

Post by lidnariq »

It is a BJT, specifically the 2SD2145. And it's NPN.
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magno
Posts: 193
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Location: Spain
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Re: Entering in Stand-by without using a MAD-1

Post by magno »

lidnariq wrote:It is a BJT, specifically the 2SD2145. And it's NPN.
Really?! You made my day!! Thank you very much for the information!

I checked 2SD2145 datasheet and couldn't figure out if it is PNP or NPN, but anyway I trust you. I think the circuit I posted above makes sense now!
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