LTC1860L is true differential inputs or pseudo differential

Question

1）LTC1860L is true differential inputs in the datasheet.When search ADC through ADC>Standard A/D Converter>Precision A/D Converters<20MSPS>Single Channel A/D Converter,the LTC1860L's input type is pseudo differential.Which one is ture?
2)If a magnetic bead is connected between LTC1860L's IN- and GND,the output will be disturbed by system noise.If a 0Ω resistance is connected between LTC1860L's IN- and GND,the output will not be disturbed by system noise.Can you help me analyse the problem?

ADIApproved · Accepted Answer

1) The difference between IN+ and IN- of the LTC1860L is captured by the track and hold circuit when the CONV command is given. Therefore the LTC1860L has true differential inputs. The LTC1860L is best used in circuits where IN- is held constant and IN+ goes above and below IN-. For this reason LTC1860L is referred to as pseudo-differential. 
 2) Because IN- has a track-and-hold (T/H) circuit, there will be a glitch on IN- when the T/H goes into the track mode. This glitch must settle completely before the ADC can perform an accurate conversion. If you look at the equivalent RLC model of the magnetic bead you are using, you will begin to understand why it can cause performance problems with the ADC. The T/H circuit of the ADC can be modeled as a capacitor charged to Vref/2 that is switched onto the RLC model of the magnetic bead. It takes some time before the voltage at the junction of the T/H and the magnetic bead settles. Until the junction settles, a CONV pulse should not occur.)

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LTC1860L is true differential inputs or pseudo differential

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