CC1310: ADC Input Impedance value , in datasheet, it only said more than 1Mohm

Derek Lin

Part Number: CC1310

Dear anyone,

Is anyone can help to clarify the input impedance value of the ADC in TI CC1310.

In the documents SWRS181C, it only write the value will more than 1 Mohm. And also give one more information is

Capacitive input,input impedance depends on sampling frequency and sampling time. That mean the input impednace will have different value in the frequency and sampling time.

Is possible we can know how many input impednace in such 3h = 2P7_US : 16x 6 MHz clock periods = 2.7us ? If there are a table list for all of them will be very great.

Thanks,

Derek Lin

over 7 years ago

0 TA12012 over 7 years ago

TI__Mastermind 36395 points

Derek,

There is also about 1pF of capacitance on that pin, but at 200khz it is not significant.

Regards,
/TA

0 Derek Lin over 7 years ago in reply to TA12012

Prodigy 20 points

Dear Ta,

Thanks for you reply.

Do you have any information regarding the input impedance in different sampling frequency and time.? Thanks a lot.

Derek Lin

0 TER over 7 years ago in reply to Derek Lin

TI__Guru**** 317180 points

Sampling time should not impact the impedance if you have designed your system correctly.

The input to the ADC looks like the circuit described in the first section in en.wikipedia.org/.../Switched_capacitor. The sampling time should be set long enough to charge the cap to the same voltage as you want to measure (or with an error lower than 0.5 LSB)

If you do multiple samplings the equivalent input impedance scale with 1/f meaning that if you have a sampling frequency lower than the 200 k used in the datasheet the impedance will be higher than stated in the datasheet.

Sub-1 GHz

Sub-1 GHz forum

CC1310: ADC Input Impedance value , in datasheet, it only said more than 1Mohm