CC3220S-LAUNCHXL: Opamp connection on the Launchpad

david s

Part Number: CC3220S-LAUNCHXL
Other Parts Discussed in Thread: CC3220S, CC3220MOD

Hi,

The opamp follower on the Launchpad is used to drive the ADC input of CC3220S. The input of the Opamp follower is scaled by the resistor divider in order to limit the max voltage to <1.5V.

Would it work if the resistor divider output is directly connected to the input of the ADC (with some filter capacitor on resistor divider output)? Is there a strong reason to put an opamp follower?

Thanks,

David

over 7 years ago

0 Sarah P over 7 years ago

TI__Mastermind 38980 points

Hi David,

I am looping in one of our hardware engineers. Please expect a day for further response.

Best regards,
Sarah

0 Charles Oladimeji over 7 years ago

TI__Mastermind 33805 points

Hi,

The Voltage follower is added due to the high input impedance the op amp provides. it can work without the voltage follower but the voltage follower is highly recommended

http://processors.wiki.ti.com/index.php/CC3200_ADC_Appnote#ADC_characterestics

http://www.learningaboutelectronics.com/Articles/Voltage-follower

Regards,

Charles O

0 Seong Kim over 7 years ago

TI__Mastermind 42080 points

David,

In addition to what Charles said, the ADC pins will draw a current spike from the external source while sampling and this can cause errors in measurement. The voltage follower is used as the ADC pins require external signal conditioning.

Please refer to the standard SAR ADC app note before using the ADC.

Regards,

Seong

0 david s over 7 years ago in reply to Charles Oladimeji

Genius 3005 points

Thanks.

0 david s over 7 years ago in reply to Seong Kim

Genius 3005 points

Thanks but the link goes to CC3220MOD datasheet.

David

0 Seong Kim over 7 years ago in reply to david s

TI__Mastermind 42080 points

Sorry about that. Here is the correct link: www.ti.com/.../slyp166.pdf

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CC3220S-LAUNCHXL: Opamp connection on the Launchpad