AFE4300 impedance measurment

weyer

Other Parts Discussed in Thread: AFE4300, AFE4300EVM-PDK

Hello,

I've developed a measurement circuit with the AFE4300 Chip. Unfortunately, I have a problem with the impedance measurement. When I connect a 100 ohm resistor to the AFE4300 I get a frequency dependening behavior of an ohmic resistor (see attached). I measured in FWR mode and used a sample rate of 860SPS. I noticed that even the evaluation board shows this frequency-dependening behavior.

Is there a mistake in my circuit or is there a possibility to correct the impedance measurment? Thanks!

over 12 years ago

0 Praveen Aroul over 12 years ago

TI__Mastermind 49946 points

Hello,

There is a 2nd order low pass filter with -3dB bandwidth of 150KHz at the output of the DAC following the DDS (refer Figure 8 of the datasheet) that sets the maximum limit on the DDS frequency.

The high pass filter response at lower frequencies (1-5KHz) is due to the series external capacitor that blocks the DC current injection into the body and the internal current setting resistor.

I have attached the data from the evaluation module for 100 Ohm resistor.

0 Praveen Aroul over 12 years ago in reply to Praveen Aroul

TI__Mastermind 49946 points

FWR Data from the AFE4300EVM-PDK evaluation module for 100Ohm resistor.

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AFE4300 impedance measurment