TDC1011_15 Datasheet, PDF (16/49 Pages) Texas Instruments – TDC1011 Single Channel Ultrasonic Sensing Analog Front End (AFE) for Level Sensing,Concentration Sensing Applications

TDC1011
SNAS662 – JULY 2015
Signal into
COMPIN
VCOM
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V_HYST = 10 mV
Zero Cross
Detect Output
Figure 21. Zero-Cross Detector Output Signal
The output of the zero-cross detect comparator is passed to the event manager, where depending on the
decision of the threshold-detect comparator.
8.3.6.3 Event Manager
The event manager is a digital state machine in the STOP pulse generation circuit of the TDC1011. The event
manager controls the maximum number of STOP pulses to generate on the STOP pin and the receive mode for
the STOP pulse generation. The number of STOP pulses is configured in the NUM_RX field in the CONFIG_1
register. The receive mode is selected in the RECEIVE_MODE bit of the CONFIG_4 register. See sections
Single Echo Receive Mode and Multiple Echo Receive Mode for details about the receiver modes of the
TDC1011.
An example for NUM_RX = 2h and RECEIVE_MODE = 0 is shown in Figure 22. When the echo signal amplitude
exceeds values smaller than V_THLD, the threshold detect comparator indicates to the event manager to qualify the
next zero-cross event as valid. When the qualified zero-cross is detected by the zero-cross detect comparator,
the event manager passes the pulse to the STOP pin until the number of receive events programmed in
NUM_RX is reached.
STOP
COMPIN
V_COM
V_THLD
GND
Passes V_THLD
Passes V_THLD
Qualified for
zero-cross
Qualified for
zero-cross
Figure 22. Signal Qualification, Zero-cross Detection and STOP Pulse Generation
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