THS789 Datasheet, PDF (22/34 Pages) Texas Instruments – THS789 Quad-Channel Time Measurement Unit (TMU)

THS789
SLOS776A – SEPTEMBER 2012 – REVISED DECEMBER 2015
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The THS789 device is a high-speed, high-resolution time-measurement unit that measures the difference in time
between a signal applied to an event channel and the signal applied to the sync channel. This difference is then
transmitted to a result interface in the form of a digital word. Figure 6 shows an example of three time
measurements (T1, T2, and T3).
SYNC
EVENT
T1
T2
T3
T1 - 0000 1100
T2 - 0011 1010
T3 - 1110 0010
T0429-01
Figure 6. Time-Measurement Example With 8-Bit Words Triggered by Rising Edges
The previous time difference is calculated by an internal ALU that subtracts the timestamps created by the Event
signal and the SYNC signal stored in a FIFO. These timestamps are performed by the TDC that is composed by
the following: an interpolator, a synchronizer, a 34-bit counter, and a 1.2-GHz clock. It is important to note that
the event and sync channels share the same TDC. When a valid edge is applied to the event channel, the TDC
uses the value in the counter and stores it in the FIFO. Then the ALU uses the value of the event and the value
of the sync, stored in the FIFO already, and subtracts them. After the operation is done, the final value is shifted
out to the result interface for retrieval.
All the programming to the THS789 device is achieved through an LVCMOS host-serial interface. With this
interface, the user has the ability to set up the THS789 device for time measurements. It also provides the user
with different modes to retrieve the results.
Results are available through an LVDS-compatible high-speed serial interface. Data-word length and speed are
programmable to cover a wide range of data rates. Each channel has it own output to maximize data throughput.
All of the data ports (RdataA, -B, -C, and -D) are synchronized to a global clock.
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