TDC1011_15 Datasheet, PDF (22/49 Pages) Texas Instruments – TDC1011 Single Channel Ultrasonic Sensing Analog Front End (AFE) for Level Sensing,Concentration Sensing Applications

TDC1011
SNAS662 – JULY 2015
Device Function Description (continued)
Damping extends the duration of
the last pulse to dissipate ringing
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Figure 31. Transmitter Damping (5 Tx Pulses With a Damping Pulse)
8.0
Damping disabled
6.0
Damping enabled
4.0
2.0
0.0
-2.0
-4.0
-6.0
-8.0
0.0
2.0
4.0
6.0
8.0 10.0 12.0 14.0 16.0 18.0 20.0
7LPHV
Figure 32. Transmitter Damped Echo
There are two invalid use combinations of the damping feature that may result in unexpected behavior. First,
damping should not be combined with the 180° pulse shift described in the previous section. Second, damping
should not be enabled if the number of TX pulses is set to 31.
8.4.4 RECEIVE Operation
8.4.4.1 Single Echo Receive Mode
Single Echo mode can be used for fluid identification measurements or level applications where transducer
carrier frequency information is required. The device can be configured for Single Echo mode by setting the
RECEIVE_MODE bit to 0 in the CONFIG_4 register. In Single Echo mode, the device will generate STOP pulses
for every zero-cross qualified by the threshold comparator, up to the number of expected STOP events
configured in the NUM_RX field in the CONFIG_1 register.
The threshold comparator qualifies the next zero-cross after an RX amplitude smaller than the programmed
threshold voltage is detected. The zero-cross detector will provide output pulses corresponding to the rising edge
of the received signal crossing the V_COM level, as shown in Figure 33. The threshold voltage can be set in the
ECHO_QUAL_THDL field in the CONFIG_3 register.
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