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zeus074 / dramtester

Dram tester for 4116 and 4164/256
GNU General Public License v3.0
55 stars 16 forks source link

Roughly -4V instead of -5V #5

Closed seanch80 closed 2 years ago

seanch80 commented 2 years ago

Hello. Taking the 5V (more realistically 4.7V if powered via USB) from the Arduino +5V pin and routing it through the diode only gives about ~4V into the 7660S, giving a resulting negative voltage of about -4V. According to the datasheet of a randomly chosen 4116 DRAM chip, the min/max acceptable values for the -5V line is -4.5V to -5.5V.

How does that work? Are typical 4116 DRAM chips not so picky when it comes to the -5V line?

Also, I wonder why the 1N4148 diode was chosen, and not a schottky diode or other with less voltage drop?

zeus074 commented 2 years ago

Yes, you are right, the voltage could be a bit at the limit. I have seen from the tests that it works ,but to improve it without modifying the scheme, just replace the 1n4148 diode with a Schottky one such as BAT43 or similar. It is also possible to remove the diode and put a jumper, this was left over from the old version where I supplied the 12V externally.

seanch80 commented 2 years ago

Thanks for the explanation. I think I will use a jumper instead of the diode then.

seanch80 commented 2 years ago

20220508_012113

..with the diode replaced by a jumper. 😄

seanch80 commented 2 years ago

DRAMTesterBase_01.zip

STL file of 3D printed base.

DRAMTesterBase_01

zeus074 commented 2 years ago

good job! I post the file on Github with thanks. I also added the stl for print the handle to glue all the jumpers and move them more easily between the high and low position. 👍

seanch80 commented 2 years ago

Very nice. Thanks for sharing this project on github. It was fun to build and works great!