Datasheet

18 LMP90100 EVB User’s Guide August 2012
Figure 16 - Recommended LMP90100 Configuration for a PT-100 RTD
1. Step 1: Select a Sensor - select “RTD”  “ P R TF -10-2-100-1/4-6-E”.
2. Step 2: Configure Inputs – click on the “INPUT MUX” block to set “VINP = 000: VIN0”
and “VINN = 001: VIN1”. Click on the “Eval. Board Settings” button located next to
the block diagram. This should open up a PDF of the schematic and calculation for this 3-
wire RTD example.
3. Step 3: Source IB1/IB2? – click on the “EXC. Current” block to set “RTD_CUR_SEL =
1010: 1000 uA”.
4. Step 4: Select Reference – click on the “VREF MUX” block to choose
“VREF_SEL = 1: VREF2”. Make sure the value for VREF2 (upper left hand side of the
GU I) is 2.0V = [RREF * (IB1+IB2)] = [1k * (1mA + 1mA)].
5. Step 5: Set Gain – since VIN = 0.109 V at room temperature for IB1 = IB2 = 1000 uA, the
maximum gain can be 16x. Click on the “FGA” block, “PGA” block, or the “Gain” slider
to select the gain. (For this exercise, the gain can be set to 1x).
6. Step 6: Set Buffer – click on the “ B U F F” block to include or exclude the buffer from the
signal path. (For this exercise, the buffer can be disabled).