MCUmall EPROM BIOS Chip Burner Forum
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 True USB Willem Programmer (GQ-2X, GQ-3X, GQ-4X)
 GQ-4X 27C256 and 27256 VPP Voltage Value Settings

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Krankshaft Posted - 06/29/2015 : 00:06:45
I have a question regarding the VPP voltage the GQ-4X applies to 27C256 CMOS EPROMS during programming.

While checking the details in the GQ-4X software I found that the programmer only applies 12 volts to VPP. While in an ST datasheet it says to apply 12.7 volts.

I then looked at the exact same size EPROM of the NMOS variety a 27256 and found the programmer applies 12.7 volts which falls into the tolerance specified on that parts datasheet (12.5V +- 0.3V).

Is there any particular reason less voltage is applied to VPP on the CMOS EPROMS compared to the NMOS or is that extra 3/4 of a volt just not that critical?

I've programmed both of these parts the code verified and they operate fine but I'm just curious.
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ZLM Posted - 07/03/2015 : 14:29:38
The standard programming voltage VPP can be 10% of standard. So, the 12V is working.

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