Help me connect a zener diode on the power supply pin of adc mcp3202

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vicky29

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hi
i want to connect a zener diode on the power supply pin of adc mcp3202. can anybody plz help me out for how to connet it. i am supplying 5 volts to adc.
do i need some resistance in series with diode or wht...plz help me out.
 

Re: zener on adc

Hi vicky29

I presume that you wish to connect the zener to provide a supply/reference voltage to pin 8 Vdd/Vref. Do not bother!

In my experience zeners have poor stability, high noise, a significant output slope and the first component to suspect when things go wrong.

As the MCP3202 only requires 550µA @ 5v, I would suggest you use a 3pin voltage reference IC to supply the device eg. MCP1542 or similar.

You will get better results with less effort.

hope this helps ...Polymath
 


Re: zener on adc

instead of using a zener try LM336-2.5 for 2.5 volt reference and LM336-5 for 5 volts reference. it is more stable than an ordinary zener.
 

Re: zener on adc

Hey guys,


can I ask a question, I am using the new Ti instrument CC2430, based on the 8051 MCU.
I want to do the same, i mean put an external voltage reference on pin 7, the thing is that it has an internal resistance of zero!
every time I connect the voltage source, it shorts out!!
what should I do ?
 

Re: zener on adc

Hey guys,


can I ask a question, I am using the new Ti instrument CC2430, based on the 8051 MCU.
I want to do the same, i mean put an external voltage reference on pin 7, the thing is that it has an internal resistance of zero!
every time I connect the voltage source, it shorts out!!
what should I do ?

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Dear Azaz ,

I went through the datasheet of the IC . Pin Number 7 is the DVdd it specifies ,
And It would never be internal resistance of zero .
Please verify the correct pin number you fed the input and get back.

Regards,

S.Vigneshwaran.,
Spectrum Electra Technologies,
Chennai - 92.
 

zener on adc

zeners wouldn't be a good choice for voltage reference here. they can swing materially to render a 8-bit or 10-bit adc useless.

I would use a bandgap or a high precision voltage reference chip if you are working on a 10-bit or higher adc.
 

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