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MSP430USB Launchpad ADC12 analog input short circuit


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Hello,

 

I started playing with MSP430USB launchpad a few weeks ago. After couple of rather simple exercises like LCD display and 1-wire bus which worked really nice, I decided to play with ADC12. I was surprised to see that when I was connecting +5V or +3.3V to ANALOG1 input (P6.0) my launchpad was disconnecting from my PC and LCD light was going off. The same was happening when I used other analog inputs. When I connected 4,5V battery between Analog1 and GND it was draining really huge current from the battery. Battery ran out flat after a few minutes. Even thought apparently all Aanlog inputs were on short to GND ADC12 was converting. I could see indication LED going off/on when I was connecting/disconnecting voltage from AnalogInput.

 

It looks my MSP430F5529 is damaged, or I am doing something totally wrong. I used example CCS ADC12 projects.

 

Has anyone experienced something similar on any other MSP430?

 

I know there is ADC12 input ESD protection that can short voltages exceeding some certain value... I must check with lower voltages than 2.5V...

 

Thanks,

Jacek

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Hello,

 

ADC12 Lesson learnt.

After doing some checks I realized that I damaged analog input while attaching +5V.

Max voltage that ADC12 accepts is 3,3V. There is some threshold above which ESD protection diodes start conducting. Of course current which ESD protection can handle is less than +5V pin on the launchpad can provide...I guess close to 500mA. Thus these diodes got broken...Fortunately I have couple more Ax's to use ;-)

 

Thanks,

Jacek

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