Hello Dongbeom,
Let me help answer your questions. See below.
Who can verify my schematic ?
>> Schematic looks good. 2 3 wire RTD's each with there own IB current source and reference (VREFP - VREFN).
Q1. If I use two RTDs in a LMP90100, Can I use one VREF for two RTDs ?
>> I would recomend using one VREF for each RTD as you have drawn in your schematic.
Q2. Is there any difference between crystal model (XOUT, XIN/CLK of fig 70. in datasheet) and oscillator model (XIN/CLK of fig 71. in datasheet) ?
>> The LMP90100 can be connected to an external crystal oscillator or external clock input per figures 70 and 71. The LMP90100 can support either differences would be external to the LMP90100 in terms of component count, size, space of each model.
Can I use crystal model to one current source model(fig 71) ?
Yes you can use a crystal while using only one of the LMP90100 current sources. But for your praticular application it be best to use two current sources, one for each RTD.
Q3. Can I use two current source model ( fig 70. in datasheet) for two RTDs in a LMP90100,?
>> Yes. Your drawn schematic is appropriate.
How can I provide excitation current to second RTD ?
>> Use the second current source (IB2).
