Voltage across pin and ground question

[jasonbe]

How many amps and volts do I have to work with between the analog pins on Cypress’ CY8C24894 at **broken link removed** and ground on a USB plug? Do I have to connect a resistor between the analog pins and ground? Can you refer me to a source where I can look this stuff up?

 

[Torben]

How many amps and volts do I have to work with between the analog pins on Cypress’ CY8C24894 at **broken link removed** and ground on a USB plug? Do I have to connect a resistor between the analog pins and ground? Can you refer me to a source where I can look this stuff up?

The document you are looking at is the ultimate resource on the chip, and is where you would go to look this stuff up. If I'm reading it right (just glancing quickly at the Absolute Maximum Ratings section) it says that you can have a maximum of +-50mA on the analog inputs at a voltage of between (Vss - 0.5)V and (Vdd + 0.5)V. So if you're running the thing on a 5VDC supply, the inputs can handle +-50mA at voltages between -0.5V and 5.5VDC.

I think I'm getting that right. If not I hope someone will correct me.


Torben

P.S. If you're looking for places to read up on electronics etc to get a grip on the terminology, is a good place to start. Also, in datasheets, look for the section labelled "Absolute Maximum Ratings" or similar and look there to see what the part can handle. Be aware that the "absolute maximum" values are also known as the "fry values"--don't run the part at those values for very long--in normal use there should be some headroom before the part hits those values. The part will last longer.

 

[jasonbe]

...it says that you can have a maximum of +-50mA on the analog inputs at a voltage of between (Vss - 0.5)V and (Vdd + 0.5)V...

Thank you for looking through the data sheet! Did you get that info from rows 4, 5, 6, and 7 of Table 3-2? I've attached the data-sheet here. The Symbols are really difficult for me to interpret. I'm also trying to figure out if I have to stick a resistor somewhere between ground and one of the pins if my signal is only going to be generated by a switch, potentiometer, or transistor. I've been looking at the first and second row of Table 3-5 and Table 3-14, trying to figure out if they contain the information that I need. Anyone who is familiar with electronic chip symbols might be able to help me. Are the symbols in the data sheet explained in the link that you provided? The link looked interesting, but I couldn't find any matching symbols.

 

[jasonbe]

If, by chance, anyone is planning on using this page for information, when researching mA ratings, it may be useful to refer to Table 10-9 of the attached document.