MAX192 ADC schematics?
At the moment I use Port1 for the LCD and three pins on P3 to control the LCD. Port 0 and Port 2 are not used at all, and 5 pins on port3 are not used. I guess I can use the free pins on port3 to the ADC? If I understand the datasheet of the ADC correct I need the following pins on the microcontroller:
But what about VRef ? (Can I connect this to VDD?)
To put it shortly (isn't this too late now? ) how do I have to connect it? Where do I need capacitors, and where do I need resistors?
it is generally preferred not to connect VREF to VDD.
mostly in case of sensitive ADC application u either use two separate power supplies... for Analog and digital sections or simply isolate digital ground from analog ground.
but if it is just an experiment... just add a variable resistor/pot (small value) between VDD and Vref.
u are also supposed to add a zero ohm impedance between your analog signal and the ADC analog i/p pin.(use any resistance around 50E to gain the same effect.)
Have a look at this thread .. http://www.8051projects.net/forum-t8042-last.html
Thank you for the link, but it doesn't say anything about the schematics :/ I think I have a good understand of how to interface the max192 - it's the schematics I'm not sure about. Can I just connect CS, Din and Dout to three pins on my microcontroller? (eg. P3) or do I have to use some resistors, capacitors and so on?
For Vref you can use the typical operating ckt in pg 24.It allows for a single-ended input of 0-4.096 V with a 4mV step size.
Hmm, I need to monitor values between 0 and +5.0V - so I have to make a divider to bring the voltage down? (eg. a 4/5 divider)
i think it is sufficient to connect the control pins directly to the uC.
As for the reference i would agree with shashi and shyam that u go for 4.096 internal reference ( looks fine as it has a good temperature stability too(30ppm/deg.)).So, yes , u will have to drop ur input voltage in the ratio 4/5.
using a reference close to the supply voltage of the ADC may create some non-linearity in the conversion at the full scale level ( do not know about this ADC as i have not used it as yet, but have observed this in many other ADCs i have used. )
In general you can directly connect VDD,unless the supply is very noisy,in which case use a 10ohms resistor(which forms a low pass in conjunction with the bypass caps) as specified in the datasheet.
Usually a 0.1uF bypass cap from VDD to Agnd pin(as close to the pins as possible) suffices.