TDC1011_15 Datasheet, PDF (21/49 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
Device Function Description (continued)
8.4.3 TRANSMIT Operation
8.4.3.1 Transmission Pulse Count
The number of TX pulses generated by the TDC1011 to drive an ultrasonic transducer is programmable using
the NUM_TX field located in the CONFIG_0 register.
8.4.3.2 TX 180° Pulse Shift
As shown in Figure 29, the transmitter block can add a 180° shift at a position in the TX signal. The position of
the pulse shift is set by the TX_PH_SHIFT_POS field in the CONFIG_4 register and allows generating a specific
signal pattern.
Generation of 180° burst
for Tx Signature
Figure 29. Transmitter Pulse Signature, 180° Burst
As shown in Figure 30, enabling the TX 180° pulse shift has the effect of decreasing the number of transmitted
pulses by 1.
Normal Operation:
NUM_TX = 0x07
TX_PH_SHIFT_POS = 0x1F
180| Shift:
NUM_TX = 0x07
TX_PH_SHIFT_POS = 0x03
Pos. 0 Pos. 1 Pos. 2 Pos. 3 Pos. 4
Figure 30. Transmitter Pulse Signature
Pos. 5
Pos. 6
In some cases, the 180° pulse shift may help improving the turn-off time of a transducer, and thus suppress the
transmit ringing.
The 180° pulse shift is disabled by setting TX_PH_SHIFT_POS to position 31. Setting the 180° pulse shift to
positions 0 or 1 is not recommended.
8.4.3.3 Transmitter Damping
The transmitter damping feature allows for improved control over the transducer signal generation. Damping
extends the duration of the last TX pulse to help dissipate ringing and improve the transducer's turn-off time (see
Figure 31 and Figure 32). The accuracy of measurements can be improved by having a faster transducer turn-off
time. Damping is controlled with the DAMPING bit in the CONFIG_2 register.
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