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Old 17th July 2017, 10:08 AM   #1
power Thread Starter
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Default Flash Carts Could Be Slowly Killing Your Retro Consoles

Flash Carts Could Be Slowly Killing Your Retro Consoles

Original big technically article

well for many of us who use these carts (not me) this could be quite scary to think that poorly made carts could actually kill their host console.

Buyer beware, PSA and all that.

Quote:
When the console outputs 5V into a 3.3V input the extra voltage must go somewhere; 1st law of thermodynamics. It is converted to heat through the unintended conduction of clamping diodes, which can be harmful to integrated circuits. These diodes are there for protection against electrostatic discharge (ESD), which are very short and infrequent bursts of energy. They are not designed for continuous conduction and, therefore, continuous heat dissipation. Let’s take a look into why this occurs.
To understand what happens when a 5V signal is applied to a 3.3V input, we must first understand what a 3.3V input looks like. Typically, a digital input has 2 clamping diodes (D1 and D2 below) on its input to protect against small electrostatic discharges (ESD). When a logic high of 5V is applied to the circuit below, D1 starts conducting and essentially short circuits the additional voltage to the 3.3V supply. In certain flashcarts, including several Everdrive designs there is a small resistor (R1 – 100 ohms) to limit the short circuit current to approximately 12.5 mA between the 5V supply and 3.3V supply – this protection is inadequate since typical CMOS current ratings are 5.2mA.
On other common devices, such as multicarts, there is no R1 and a logic high of 5V driven directly into the 3.3V flash results in a short circuit between the 5V and 3.3V supplies. In either case, this causes unnecessary and potentially damaging stress on both ends:
+ On the console output since it is not designed to supply nearly 12.5mA (or more on multicarts) per pin
+ On the 3.3V Flash input since the clamping diodes D1 and D2 are not designed to dissipate large amounts of heat
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Old 17th July 2017, 11:29 AM   #2
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I think this rings true for anyone using cheaply made electronics. You get what you paid for.

I'd be inclined to think the problem is not as bad as they are stating. The current/voltages are very low and not likely to generate a lot of heat (12.5mA x 5V = 0.0625W ?).

It's a shame the devices aren't being built to spec though, since they are built to do a specific job. Logic level IC chips can be had for less than a dollar, and are relatively simple circuits to design into a device.
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Old 17th July 2017, 4:39 PM   #3
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Originally Posted by azzachaz View Post
I think this rings true for anyone using cheaply made electronics. You get what you paid for.
Well, specific to this topic, no. Some of these flash carts cost a fortune, but still exhibit the problem that Rene from db-electronics has documented.

There's even cases where one manufacturer has 50% of their stuff with the wrong voltages, and 50% with the correct ones.

At least the problem is documented now, and hopefully the people manufacturing these flash carts can attempt to fix it. Although the issue seems to stem from volume-availability of the correct voltage regulator components, which means potentially a product shortage to solve it long term.
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