TDC1011_15 Datasheet, PDF (19/49 Pages) Texas Instruments – TDC1011 Single Channel Ultrasonic Sensing Analog Front End (AFE) for Level Sensing,Concentration Sensing Applications

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TDC1011
SNAS662 – JULY 2015
8.3.8.2 Temperature Measurement with a Single RTD
The temperature sensing block can be configured to measure a single RTD by setting the TEMP_MODE bit in
register CONFIG_3 to 1. When the temperature measurement runs in PT1000 mode (TEMP_RTD_SEL = 0), the
first interval corresponds to R_REF, the second interval is a redundant measurement on R_REF and should be
neglected, and the third interval corresponds to RTD1. This operation is represented in Figure 26.
TRIGGER
Reference
Discard
RTD1
START
STOP
t_REF
t_d1
t_d2
½ t_REF
t_RTD1
Figure 26. Temperature Measurement with a Single PT1000
The resistance of RTD1 can be calculated using Equation 3. The time delay between measurements can be
approximated using Equation 4 and Equation 5, with the exception that in this case, t_d1 is a function of ½ t_REF and
t_d2 is a function of t_RTD1.
If the temperature measurement runs in PT500 mode (TEMP_RTD_SEL = 1), the first interval is a redundant
measurement on R_REF and should be neglected, the second interval corresponds to R_REF, and the third interval
corresponds to RTD1. This operation is represented in Figure 27.
TRIGGER
Discard
Reference
RTD1
START
STOP
t_d1
t_d2
2 K t_REF
t_REF
t_RTD1
Figure 27. Temperature Measurement with a Single PT500
The resistance of RTD1 can be calculated using Equation 3. The time delay between measurements can be
approximated using Equation 4 and Equation 5, with the exception that in this case, t_d1 is a function of t_REF and
t_d2 is a function of t_RTD1.
8.4 Device Function Description
8.4.1 Time-of-Flight Measurement Mode
The TOF measurement mode is selected by setting the MEAS_MODE bit in the CONFIG_2 register to 0.
8.4.1.1 Liquid Level or Fluid Identification
The TDC1011 performs a single TOF measurement after receiving a trigger signal and returns to the SLEEP
mode when the measurement is complete.
8.4.2 State Machine
A state machine in the TDC1011 manages the operation of the various measurement modes (see Figure 28). At
power-on, the state machine is reset and most blocks are disabled. After the power-on sequence is complete, the
device goes into SLEEP mode if the EN pin is low or into READY mode if the EN pin is high. In the SLEEP or
READY state, the TDC1011 is able to receive SPI commands to set registers and configure the device for a
measurement mode.
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