Beginner - Simple Question. I hope!
BenClark
Posts: 20
I know this is probably very simple for most of you out there but I am just getting started so I need a little help.
I am looking at using a MAX6816 to debounce 8 buttons for the Propeller. http://www.maxim-ic.com/datasheet/index.mvp/id/1896
According to the datasheet on the MAX6818, the output lines are;
VCC........................-0.3V to +6V
OUT_, CH ...............-0.3V to (VCC + 0.3V)
Output I SINK = 1.6mA· I SOURCE = 0.4mA
Looking at the Propeller data sheet, it says the I/O lines are;
P0-P31: General purpose I/O.· Can source/sink 40 mA each at 3.3 VDC
For the propeller, I am assuming that the 40 mA means that it can handle UP TO that amount at 3.3 VDC,
so I don't think that the mA rating is a problem because the MAX6818 has output 1.6mA.
However, the MAX6818, shows its output at VCC + 0.3V. Does this mean GREATER than .3V???
Will that be suficient voltage for the Propeller I/O pin, or do I need something inbetween the MAX and the PROP?
Thanks again for all your help.
Ben
·
I am looking at using a MAX6816 to debounce 8 buttons for the Propeller. http://www.maxim-ic.com/datasheet/index.mvp/id/1896
According to the datasheet on the MAX6818, the output lines are;
VCC........................-0.3V to +6V
OUT_, CH ...............-0.3V to (VCC + 0.3V)
Output I SINK = 1.6mA· I SOURCE = 0.4mA
Looking at the Propeller data sheet, it says the I/O lines are;
P0-P31: General purpose I/O.· Can source/sink 40 mA each at 3.3 VDC
For the propeller, I am assuming that the 40 mA means that it can handle UP TO that amount at 3.3 VDC,
so I don't think that the mA rating is a problem because the MAX6818 has output 1.6mA.
However, the MAX6818, shows its output at VCC + 0.3V. Does this mean GREATER than .3V???
Will that be suficient voltage for the Propeller I/O pin, or do I need something inbetween the MAX and the PROP?
Thanks again for all your help.
Ben
·
Comments
I always get these mixed up so if I get it wrong hopefully someone can point it out. From what I remember, the Source current is the maximum current that will flow OUT of the device while Sink current is the maximum current that can flow INTO the device.
To answer your question, it means the output is VCC + .3v so if VCC is 3.3v then output will be 3.6v. Just put a small resistor in serial with the source and the prop pin and you will be fine.
Post Edited (soshimo) : 7/27/2010 6:26:03 PM GMT
It's probably a good idea to use 1K resistors between the Propeller I/O pins and the MAX6816 outputs even if the MAX6816 is running off the same 3.3V supply as the Propeller. The reason is that the Propeller pins can be configured as outputs and you can damage the MAX6816 if its outputs are connected to Propeller output pins and the outputs are in opposite states (one 0 and the other 1). The 1K resistor would protect against damage in this case.
Post Edited (Mike Green) : 7/27/2010 6:56:51 PM GMT
Thank you!
Your question interested me because a few months ago I made a small board with 8 debouncing switches based on bistable 555
www.kpsec.freeuk.com/555timer.htm
I was reading the datasheet of the Max6816 and I saw in the electrical characteristics that the output voltage for High position is VCC - 1.0V
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Jean-Marie
I was in the middle of a lengthly reply earlier today when we had a two second power outage.· My UPS batteries must be dead because the·computer died and I lost the reply I was writting.
From my reading of the data sheet, I think you've listed the maxium values the chip can take without being damaged.· The operating voltages are between 2.7V and 5.5V.· I'm pretty sure you can use the chip with the Prop without any resistors.· Even if the Prop outputs a "high" to the output (of the MAX8616), it shouldn't damage the chip (as indicated by·the "Vdd + .3V" rating of the output pin).
I've only been reading data sheets for a couple of years, but I'm pretty sure·the chip·and Prop·will·play safe together.
Duane