Author Topic: MCP3421 absolute maximum ratings  (Read 895 times)

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Offline mc172Topic starter

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MCP3421 absolute maximum ratings
« on: March 15, 2019, 02:24:14 pm »
I'm looking at this datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22003b.pdf

Two things are a bit confusing to me. On the second page are the absolute maximum ratings for the device.

The datasheet says that the current on the input pins must not exceed 2 mA, but the input impedance is 2.25 M \$\Omega\$ so how could it ever get anywhere close? VDD max is 7 V...

The only thing I can think it could be is when the inputs exceed VDD + 0.3 V and the ESD diodes start conducting, but 2 mA seems pretty low for that.

The datasheet also says "output short circuit current.... continuous" and then 2 lines later says "output current..... 10 mA". Which is it?
 

Online wraper

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Re: MCP3421 absolute maximum ratings
« Reply #1 on: March 15, 2019, 02:30:42 pm »
It means that ESD diodes are quite weak and are rated only for 2 mA.
 

Online wraper

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Re: MCP3421 absolute maximum ratings
« Reply #2 on: March 15, 2019, 02:33:29 pm »
Max output current is not related to ESD diodes.
 

Online magic

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Re: MCP3421 absolute maximum ratings
« Reply #3 on: March 15, 2019, 06:35:47 pm »
I would read it: don't allow output over/undervoltage or shorting to VCC while the chip drives low, if any of that causes the output current to exceed 10mA.
Not sure whether shorting to VCC while the chip drives low causes that limit to be exceeded or not. Perhaps that's what they meant? Either way, it's a pathological situation which doesn't happen in normal operation.
 

Offline mc172Topic starter

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Re: MCP3421 absolute maximum ratings
« Reply #4 on: March 19, 2019, 05:51:42 pm »
Thank you chaps.
 


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