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THS788
SLOS616D – MARCH 2010 – REVISED MARCH 2015
THS788 Quad-Channel Time Measurement Unit (TMU)
1 Features
3 Description
•
•
•
•
•
•
The THS788 device is a four-channel timing
measurement unit (TMU) that incorporates a time-todigital converter (TDC) architecture for fast and
accurate measurements. The TMU can provide 8 ps
of single-shot accuracy. The TDC has a 13-ps
resolution (LSB), which is derived from an external
master clock of 200 MHz. The TDC uses fast LVDScompatible interfaces for all of its event inputs and
serial result outputs, which allows for fast and reliable
data transfer. Each channel can process timestamps
at a maximum speed of 200 MSPS.
1
•
•
•
•
•
•
Four Event Channels + Sync Channel
Single-Shot Accuracy: 8 ps, One Sigma
Precision: 13 ps
Result Interface Range: 0 s to 7 s
Event Input Rate: 200 MHz
Programmable Serial-Result Interface Speed:
75 MHz to 300 MHz
High-Speed Serial Host-Processor Bus Interface:
50 MHz
High-Speed LVDS-Compatible Serial-Result Bus
per Channel
Programmable Serial-Result Bus Length
Temperature Sensor
Single 3.3-V Supply
Power: 675 mW per Channel, 18 Bits, 300 MHz,
Four Channels
The THS788 device has a wide range of
programmability that makes it flexible in different
applications.
The
serial-result
interface
has
programmable data length, frequency, and data-rate
mode (DDR and normal). The event channels can be
programmed to take timestamps on rising edges or
falling edges. The TMU has a mode for event
management, in which the user can program wait
times before measurements. This programming is
achieved through a 50-MHz LVCMOS interface.
2 Applications
•
•
•
•
•
•
•
•
The THS788 device is available in an HTQFP-100
package with a heat slug on top for easy heat-sink
access. The device is built using TI's RF SiGe
process technology, which allows for maximum timing
accuracy with low power.
Automatic Test Equipment
Benchtop Time-Measurement Equipment
Radar and Sonar
Medical Imaging
Mass Spectroscopy
Nuclear and Particle Physics
Laser Distance Measurement
Ultrasonic Flow Measurement
Device Information(1)
PART NUMBER
THS788
PACKAGE
HTQFP (100)
BODY SIZE (NOM)
14.00 mm × 14.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
4 Simplified Schematic
SYNC
EVENT
T1
T2
T3
T1 - 0000 1100
T2 - 0011 1010
T3 - 1110 0010
T0429-01
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
THS788
SLOS616D – MARCH 2010 – REVISED MARCH 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Simplified Schematic.............................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
1
2
3
5
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
5
5
5
5
6
7
7
7
8
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Host Serial Interface DC Characteristics ..................
Host Serial Interface AC Characteristics...................
Power Consumption..................................................
Typical Characteristics .............................................
Detailed Description .............................................. 9
8.1 Overview ................................................................... 9
8.2
8.3
8.4
8.5
8.6
9
Functional Block Diagram ......................................... 9
Feature Description................................................. 10
Device Functional Modes ....................................... 11
Programming .......................................................... 17
Register Maps ........................................................ 22
Application and Implementation ........................ 29
9.1 Application Information............................................ 29
9.2 Typical Application ................................................. 30
10 Power Supply Recommendations ..................... 37
11 Layout................................................................... 38
11.1 Layout Guidelines ................................................. 38
11.2 Layout Example .................................................... 38
11.3 Thermal Considerations ........................................ 39
12 Device and Documentation Support ................. 40
12.1 Trademarks ........................................................... 40
12.2 Electrostatic Discharge Caution ............................ 40
12.3 Glossary ................................................................ 40
13 Mechanical, Packaging, and Orderable
Information ........................................................... 40
5 Revision History
Changes from Revision C (January 2015) to Revision D
Page
•
Updated Features to remove "800 ps" from single-shot accuracy ......................................................................................... 1
•
Updated measurement accuracy after calibration, mean values to –8 and 8 ps and updated single-event accuracy,
one sigma parameter to 8 ps in Electrical Characteristics .................................................................................................... 6
Changes from Revision B (June 2011) to Revision C
•
2
Page
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section ................................................................................................. 1
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6 Pin Configuration and Functions
GND
RstrobeA
RstrobeA
RdataA
RdataA
VCC
NC
82
81
80
79
78
77
76
GND
VCC
85
84
GND
86
83
GND
VCC
87
GND
VCC
90
89
Reserved
91
88
GND
Reserved
92
GND
RstrobeC
95
VCC
RstrobeC
96
93
RdataC
97
94
VCC
RdataC
98
NC
99
100
PFD Package
100-Pin HTQFP
(Top View)
GND
1
75
GND
GND
2
74
GND
NC
3
73
NC
NC
4
72
NC
NC
5
71
NC
NC
6
70
NC
VCC
7
69
VCC
EventC
8
68
EventA
NC
9
67
NC
EventC
10
66
EventA
GND
11
65
GND
GND
12
64
GND
63
EventB
THS788
EventD
13
NC
14
62
NC
EventD
15
61
EventB
VCC
16
60
VCC
NC
17
59
NC
NC
18
58
VCC
47
49
50
RdataB
NC
46
RstrobeB
48
45
RCLK
RdataB
44
RCLK
RstrobeB
42
43
Hstrobe
VCC
41
VCC
GND
39
40
GND
37
38
VCC
36
VCC
GND
34
35
GND
Reset
HCLK
TEMP
51
33
52
25
Hdata
24
GND
32
Reserved
GND
OT ALARM
31
53
VCC
23
29
NC
Reserved
30
GND
54
RstrobeD
55
22
RstrobeD
21
VCC
28
GND
RdataD
SYNC
27
SYNC
56
RdataD
57
20
26
19
NC
MCLK
MCLK
P0011-03
NOTE: Pin 1 indicator is symbolized with a white dot, and is located near pin 1 corner.
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Pin Functions
PIN
NAME
TYPE
NO.
DESCRIPTION
EventA
68
LVDS-compatible input
Positive event input for channel A
EventA
66
LVDS-compatible input
Negative event input for channel A
EventB
61
LVDS-compatible input
Positive event input for channel B
EventB
63
LVDS-compatible input
Negative event input for channel B
EventC
8
LVDS-compatible input
Positive event input for channel C
EventC
10
LVDS-compatible input
Negative event input for channel C
EventD
15
LVDS-compatible input
Positive event input for channel D
EventD
13
LVDS-compatible input
Negative event input for channel D
1, 2, 11, 12, 21, 25, 32, 35, 37, 39,
42, 55, 64, 65, 74, 75, 82, 84, 85, Ground
87, 89, 92, 94
GND
Chip ground
HCLK
34
LVCMOS input
Host serial-interface clock
Hdata
33
LVCMOS I/O
Host serial-interface data I/O
Hstrobe
41
LVCMOS input
Host serial-interface chip select
MCLK
19
LVDS-compatible input
Positive master-clock input
MCLK
20
LVDS-compatible input
Negative master-clock input
No connect
Physically not connected to silicon
3–6, 9, 14, 17, 18, 26, 50, 54, 59,
62, 67, 70–73, 76, 100
NC
OT_ALARM
53
Open-drain output
Overtemperature alarm
RCLK
45
LVDS-compatible output
Positive result-interface clock
RCLK
44
LVDS-compatible output
Negative result-interface clock
RdataA
78
LVDS-compatible output
Positive result-data output for channel A
RdataA
79
LVDS-compatible output
Negative result-data output for channel A
RdataB
49
LVDS-compatible output
Positive result-data output for channel B
RdataB
48
LVDS-compatible output
Negative result-data output for channel B
RdataC
98
LVDS-compatible output
Positive result-data output for channel C
RdataC
97
LVDS-compatible output
Negative result-data output for channel C
RdataD
27
LVDS-compatible output
Positive result-data output for channel D
RdataD
28
LVDS-compatible output
Negative result-data output for channel D
23, 24, 90, 91
Engineering or test pins
Connect to VCC
Reserved
Reset
51
LVCMOS input
Chip reset, active-low
RstrobeA
80
LVDS-compatible output
Positive strobe signal for channel A
RstrobeA
81
LVDS-compatible output
Negative strobe signal for channel A
RstrobeB
47
LVDS-compatible output
Positive strobe signal for channel B
RstrobeB
46
LVDS-compatible output
Negative strobe signal for channel B
RstrobeC
96
LVDS-compatible output
Positive strobe signal for channel C
RstrobeC
95
LVDS-compatible output
Negative strobe signal for channel C
RstrobeD
29
LVDS-compatible output
Positive strobe signal for channel D
RstrobeD
30
LVDS-compatible output
Negative strobe signal for channel D
SYNC
57
LVDS-compatible input
Positive input for sync channel
SYNC
56
LVDS-compatible input
Negative input for sync channel
TEMP
52
Analog output
Die temperature
7, 16, 22, 31, 36, 38, 40, 43, 58,
60, 69, 77, 83, 86, 88, 93, 99
Power supply
Positive supply, nominal 3.3 V
VCC
4
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7 Specifications
7.1 Absolute Maximum Ratings
over operating junction temperature range (unless otherwise noted)
MIN
MAX
UNIT
4
V
–0.3
VCC + 0.3
V
–0.3
VCC + 0.3
V
VCC
Analog I/O to GND
(1)
Digital I/O to GND
TJ
Maximum junction temperature (2)
150
°C
Tstg
Storage temperature
150
°C
(1)
(2)
LVDS outputs are not short-circuit-proof to GND.
The THS788 device has an automatic power shutdown at 140°C, typical.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins (1)
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101, all
pins (2)
±250
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
over operating junction temperature range (unless otherwise noted)
MIN
VCC
Supply voltage
TJ
Junction temperature
NOM
3.135
0
MAX
UNIT
3.465
V
105
MCLOCK frequency
°C
200
MHz
7.4 Thermal Information
THS788
THERMAL METRIC (1)
PFD (HTQFP)
UNIT
100 PINS
27.2
(60.2 without heat sink)
RθJA
Junction-to-ambient thermal resistance
RθJC(top)
Junction-to-case (top) thermal resistance
0.6
RθJB
Junction-to-board thermal resistance
6.8
ψJT
Junction-to-top characterization parameter
0.6
ψJB
Junction-to-board characterization parameter
6.8
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
(1)
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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7.5 Electrical Characteristics
Typical conditions are at TJ = 55°C and VCC = 3.3 V.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
TDC CHARACTERISTICS
Time-measurement precision (LSB)
13.02
Measurement accuracy after calibration, mean
–8
Single-event accuracy, one sigma
ps
8
8
Time-measurement temperature coefficient
0.1
Time-measurement voltage coefficient
±30
Event input rate
ps
ps/°C
ps/V
200
Minimum event pulse duration
ps
MHz
With preconditioning
2.5
ns
Without preconditioning
250
ps
250
ps
Minimum event pulse duration
Turnon time (ready to take timestamp)
250
μs
MASTER CLOCK CHARACTERISTICS
Frequency
200
Duty cycle
0.4
MHz
0.6
Jitter
3
ps rms
HIGH-SPEED LVDS INPUTS: MCLK, EVENT, SYNC
Differential input voltage
100-Ω termination, line-to-line
200
Common-mode voltage
350
500
1.25
Peak voltage, either input
0.6
Input capacitance
mV
V
1.7
1
V
pF
HIGH-SPEED LVDS OUTPUTS: Rdata, Rstrobe, RCLK
Differential output voltage
100-Ω termination, line-to-line
Common-mode voltage
Rise time/fall time
250
325
400
1.125
1.28
1.375
20%/80%
Output resistance
mV
V
250
ps
40
Ω
1.69
V
TEMPERATURE SENSOR DC CHARACTERISTICS
Output voltage
TJ = 65°C
Output voltage temperature slope
5
Max capacitive load
mV/°C
30
pF
Max resistive load
10
kΩ
OVERTEMPERATURE ALARM DC CHARACTERISTICS
Trip point
Active-low pulldown
Leakage current
Temperature < trip point
Output voltage, low
Isink = 1 ma
141
°C
1
μA
0.2
V
OUTPUT INTERFACE TIMING
RCLK duty cycle
Rdata/Rstrobe to RCLK setup time
Rdata/Rstrobe to RCLK hold time
45%
300 MHz
1.4
150 MHz
3.1
75 MHz
6.4
300 MHz
1.5
150 MHz
3.2
75 MHz
6.5
50%
55%
ns
ns
OPERATING PARAMETERS
Coarse counter range
18
Coarse counter max time range
14.31
Result-interface clock
6
34
75
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300
bit
s
MHz
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Electrical Characteristics (continued)
Typical conditions are at TJ = 55°C and VCC = 3.3 V.
PARAMETER
TEST CONDITIONS
MIN
Result-interface transfer format
Result-interface time range
TYP
MAX
UNIT
16
40
bit
–7.158
7.158
s
7.6 Host Serial Interface DC Characteristics
over operating junction temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VIH
High-level input voltage
0.7 × VCC
VCC + 0.5
V
VIL
Low-level input voltage
GND – 0.3
0.3 × VCC
V
VOH
High-level output voltage
VCC – 0.5
VCC + 0.3
V
VOL
Low-level output voltage
0
0.4
V
Ilkg
Leakage current
1
µA
7.7 Host Serial Interface AC Characteristics
over operating junction temperature range (unless otherwise noted)
MAX
UNIT
HCLK frequency
PARAMETER
TEST CONDITIONS
50
MHz
Rise and fall times
3.5
ns
HCLK duty cycle
MIN
40%
Hstrobe high period between two consecutive transactions
TYP
50%
60%
40
ns
Hstrobe low to HCLK high setup
5
ns
HCLK high to Hstrobe high hold time
5
ns
Hdata in to HCLK high setup
5
ns
Hdata in to HCLK high hold time
5
ns
HCLK falling edge to Hdata out (L or H)
CL = 20 pF
3.25
ns
HCLK falling edge to Hdata out (H or L)
CL = 20 pF
3.25
ns
7.8 Power Consumption
Typical conditions are at 55°C junction temperature, VCC = 3.3 V
CONDITION
One channel plus sync, counter length = 18 bits, output interface speed = 75 MHz
As above with an additional channel
Output interface speed
Counter length
TYP
mA
mA
300 MHz
add 25
27 bits
add 60
34 bits
add 105
34 bits
UNIT
420
add 10
27 bits
MAX
add 125
150 MHz
18 bits
Four-channel current
CURRENT
mA
mA
75 MHz
795
1075
150 MHz
805
1090
300 MHz
820
1101
75 MHz
855
1150
150 MHz
865
1165
300 MHz
880
1176
75 MHz
900
1210
150 MHz
910
1225
300 MHz
925
1236
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7.9 Typical Characteristics
9
920
Supply Current (mA)
Sigma (ps)
900
7
6
5
4
3
880
27-bit Counter
860
840
820
18-bit Counter
800
780
0
1
2
3
4
Sync to Event Delay (ns)
5
6
760
8
Figure 1. Typical Per Channel Sigmas vs 5-ns (200-MHz)
Window
8
34-bit Counter
75 MHz
150 MHz
300 MHz
8
16 24 32 40
8
16 24 32 40
Rdata Size
8
16 24 32 40
D001
Figure 2. Four-Channel Supply Current vs Rdata, Counter,
and Rclock Functional Modes
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8 Detailed Description
8.1 Overview
The THS788 TMU includes four measurement channels plus a synchronization channel optimized to make highaccuracy time-interval measurements. The following is a brief description of the various circuit blocks and how
they interact to make and process the time measurements.
8.2 Functional Block Diagram
PLL
RdataA
RdataB
DLL
MCLK
(Fixed)
RdataC
Sync Input
RdataD
RCLK
Serial
Result Data
RstrobeA
EventA
Time
Stamp
Logic
Event
Logic
EventB
RstrobeB
EventC
RstrobeC
EventD
RstrobeD
Reset
Control
Registers
Hdata
Host
Interface
Output (Voltage)
TEMP
OT_ALARM
HCLK
Serial Host
Processor
Interface
Hstrobe
Temp
Sensor
B0347-01
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8.3 Feature Description
8.3.1 Counter, Latches, Clock Multiplier
The center of the TMU is a master synchronous counter which counts continuously at a rate of 1.2 GHz. This is
the master timing generator for the whole TMU and defines the basic timing interval of 833 ps, which is further
subdivided with Interpolator circuitry. The output bits of the counter are connected to five sets of latches, which
can latch and hold the counter state on command from each of the channels. In this way, when an event occurs,
the counter time is recorded in the particular channel’s latches. The latch output is converted to CMOS levels
and passed to the respective channel’s FIFO buffer, which is 15 samples deep. The counter 1.2-GHz clock is
derived from the MCLK input to the TMU at 200 MHz. This MCLK input is critical to the accuracy of the TMU, and
any error in frequency is reflected as errors in time measurement. Likewise, jitter propagates to the counter and
other circuits and adds noise to the measurement accuracy. The 200-MHz clock is the input to a clock multiplier.
The clock multiplier uses delay-lock loop (DLL) techniques and combinatorial logic to construct a six-times clock
from the reference input. This 1.2-GHz clock is passed to a high-power clock buffer, which drives all the circuitry
in the master counter and many other circuits in the TMU.
8.3.2 Channels, Interpolator
There are four event channels and one sync channel. The event channels are identical, and the sync channel
contains most of the event channel circuitry, but without a FIFO. An input pulse to the sync channel serves as
the reference time zero for the TMU. An event input to a channel is compared to the sync time reference, and the
time delay is calculated as the time difference modified by a calibration value. An event input follows the
following signal path: the event input edge sets a fast latch (hit latch). The output of the latch is current-buffered
and applied to the interpolator. The interpolator uses DLL techniques to subdivide the counter interval of 833 ps
into 64 time intervals of 13 ps each. A large array of fast latches triggered by the hit latch captures the state of
the 64 time intervals and logically determines 6 bits of timing data based on where the event occurred in the 833ps clock interval. These 6 bits are latched and eventually passed to the FIFO, where they become the LSBs of
the time-to-data conversion. A synchronizer circuit is also connected to the 64-latch array and removes the
possible timing ambiguity between the 64 latches and the master counter. This takes a few 1.2-GHz clock
pulses. When this process is complete, a pulse occurs which captures the master counter bits into the channel
latches. A subsequent pulse loads all the bits from the interpolator and the counter into the channel FIFO. While
this is happening, the hit latch is being reset, and the channel is prepared to accept another event edge. This
process is fast enough to accept and measure event edges as close together as 5 ns.
8.3.3 FIFO
Each event channel contains a 15-deep, 40-bit-wide FIFO, which allows for rapid accepting and measurement of
event inputs and a user-defined data-output rate of those measurements.
8.3.4 Calibration, ALU, Tag, Shifter
The output of the FIFO is controlled by the shifter, which is a free-running parallel-to-serial register. The shifter
generates a load pulse, which transfers the data in the FIFO output into an arithmetic logic unit, which does the
sync time and calibration time subtractions and then parallel-loads the result into the output serial register. An
LVDS output buffer outputs the clock, data, and strobe signals to transfer the time-measurement data to the user.
A TAG bit is appended to the leading edge of the data word. Currently the TAG feature is not implemented. The
bit will always be 0 representing data.
8.3.5 Serial Interface, Temperature, Overhead
The TMU functions and options are controlled and read out by a serial interface built in CMOS logic that can
operate up to 50 MB/s. There is one central controller which then drives registers, counters, etc., in each
channel. A temperature sensor is located central to the chip and outputs a voltage proportional to the chip
temperature. If the chip temperature rises above 141°C, the TMU powers down and outputs an overtemperature
alarm signal. The TMU does not restart without a command through the serial interface. A bias circuit provides a
regulated current bias and voltage reference for the TMU. The serial controller sequences some of the bias
circuits to account for some acquisition times, and thereby, turns on the TMU.
10
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8.4 Device Functional Modes
8.4.1 Serial-Results Interface
The TMU captures time-stamp results and sends them to external logic using an LVDS serial-results port. The
serial-results port consists of a clock signal (RCLK), four strobe signals (Rstrobex) and four data signals
(Rdatax). The Rstrobex signal indicates that a time-stamp data transfer is about to begin for the corresponding
channel.
The serial-result interface can be programmed to have a variable data-length format. Three register bits
(Rlength0, Rlength1, and Rlength2), are used to program the required data transfer formats.
The default length of the data field is 40 bits, and it is in 2s-complement format. Table 1 defines the various data
formats.
Table 1. Result Transfer Format and Time Range
RESULT TRANSFER FORMAT
TIME RANGE
Rlength2
Rlength1
Rlength0
8 bits
–1.653 ns to 1.667 ns
0
0
0
16 bits
–426.626 ns to 426.639 ns
0
0
1
24 bits
–109.22 µs to 109.22 μs
0
1
0
32 bits
–27.96 ms to 27.96 ms
0
1
1
40 bits
–7.158 s to 7.158 s
1
0
0
Table 1 refers to the 2s-complement format. Therefore, the 8-bit result represents a number between –127 and
128.
8.4.2 Result-Interface Clock
The result-interface clock (RCLK) is generated internally and runs at a maximum frequency of 300 MHz. RCLK is
programmable and may be programmed using two register bits (RCLK_sel0 and RCLK_sel1) according to the
following table.
8.4.3 DDR Mode
The result interface may be operated using one-half the clock frequency while keeping the data bit rate
unchanged. In this mode, data is clocked out of the device using both edges of RCLK. A register bit (DDR_EN) is
used to enable DDR mode.
Table 2. Result-Interface Clock
RCLK FREQUENCY (MHz)
NORMAL MODE
RCLK FREQUENCY (MHz)
DDR MODE
RCLK_sel1
RCLK_sel0
75 (default)
37.5
0
0
150
75
0
1
300
150
1
0
8.4.4 Output Interface Throughput
Multiple data-word lengths and bit speeds, combined with a 15-sample-deep FIFO, give exceptional flexibility to
output data throughput. The actual throughput is easily calculated, keeping in mind the following: The selected
word length includes N – 1 data bits and 1 sign bit, which are sent out last as the MSB. Two bit times do not
have meaningful data during the Rstrobe high time. The TAG bit is appended to the data bits and is sent first.
Example: for a bit rate of 300 MB/s and 16-bit length, the bit time is 3.33 ns, and the total word length is 16 + 1 +
2 = 19 bit times. Therefore, the throughput is 15.8 M samples/s. This is a constant output sample rate. The TMU
can take time measurements at up to 200 MS/s. The 15-deep FIFO buffers these two rates until it is filled, in
which case samples are lost.
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8.4.5 Counter Range
The coarse counter has three supported ranges: 18, 27, and 34 bits. The coarse counter applies to the 1.2-GHz
clock.
Table 3. Counter Range
COUNTER RANGE
MAX TIME RANGE
CNT_RNG1
CNT_RNG0
Reserved
X
0
0
18 bit
218.45 µs
0
1
27 bit
111.84 ms
1
0
34 bit
14.31 s
1
1
8.4.5.1 Preconditioning Holdoff Delay Time
The preconditioning circuitry controls the ON/OFF state of the event latches. Following a Sync input signal, the
TMU checks for a number of conditions before it proceeds with the time-measurement operation. Event input
signals are ignored until all arming conditions are met. These conditions are as follows:
The hold-off delay is a programmable delay used to inhibit the creation of the next timestamp until the hold-off
delay has expired. A 16-bit register is used for the hold-off delay count register. One holdoff delay register exists
for each of the four event input channels.
The generation of a timestamp reloads the value from the holdoff delay register into a down counting counter.
Timestamp generation pauses until hold-off delay counter reaches zero. There are seven ranges for the holdoff
delay maximum duration. Three register bits are used to specify the required range.
Table 4 defines these ranges.
Table 4. Preconditioning Holdoff Delay Time
RANGE
HOffRng2_x
HOffRng1_x
HOffRng0_x
FULL RANGE (ms)
LSB (ns)
1
0
0
0
0.655
10
2
0
0
1
2.621
40
3
0
1
0
10.486
160
4
0
1
1
41.943
640
5
1
0
0
167.772
2560
6
1
0
1
671.089
10,240
7
1
1
X
2,684
40,960
In range 1 each count in the holdoff register delays the next possible timestamps by 10 ns (100-MHz clock
period). The maximum delay range for this feature is 2.684 s for each channel. To disable this feature, a register
bit (HOffTm_EN_x) is set to 0.
12
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8.4.5.2 Arming Conditions
An additional arming condition for each event channel is based on other channels meeting some preprogrammed
conditions before it can become fully armed. These conditions are in addition to the individual channel arming
conditions.
• A given channel does not become fully armed until one, two, or all three of the other channels are armed. A
logical AND of one or more channels.
• A given channel does not become fully armed until the holdoff delay expires, the arming counter reaches
zero, and the logical OR of one or more channels has been active.
The following tables define this conditional operation.
Table 5. Channel-A Conditional Arming Definition
Arm_sel3A
Arm_sel2A
Arm_sel1A
Arm_sel0A
OUTCOME
0
0
0
0
ChA is armed if ChB is fully armed.
0
0
0
1
ChA is armed if ChC is fully armed.
0
0
1
0
ChA is armed if ChD is fully armed.
0
0
1
1
ChA is armed if ChB AND ChC are fully armed.
0
1
0
0
ChA is armed if ChB AND ChD are fully armed.
0
1
0
1
ChA is armed if ChC AND ChD are fully armed.
0
1
1
0
ChA is armed if ChB AND ChC AND ChD are fully armed.
0
1
1
1
ChA will be armed if ChB OR ChC is fully armed.
1
0
0
0
ChA will be armed if ChB OR ChD is fully armed.
1
0
0
1
ChA will be armed if ChC OR ChD is fully armed.
1
0
1
0
ChA will be armed if ChB OR ChC OR ChD is fully armed.
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
Table 6. Channel-B Conditional Arming Definition
Arm_sel3A
Arm_sel2A
Arm_sel1A
Arm_sel0A
0
0
0
0
ChB is armed if ChA is fully armed.
OUTCOME
0
0
0
1
ChB is armed if ChC is fully armed.
0
0
1
0
ChB is armed if ChD is fully armed.
0
0
1
1
ChB is armed if ChA AND ChC are fully armed.
0
1
0
0
ChB is armed if ChA AND ChD are fully armed.
0
1
0
1
ChB is armed if ChC AND ChD are fully armed.
0
1
1
0
ChB is armed if ChA AND ChC AND ChD are fully armed.
0
1
1
1
ChB will be armed if ChA OR ChC is fully armed.
1
0
0
0
ChB will be armed if ChA OR ChD is fully armed.
1
0
0
1
ChB will be armed if ChC OR ChD is fully armed.
1
0
1
0
ChB will be armed if ChA OR ChC OR ChD is fully armed.
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
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Table 7. Channel-C Conditional Arming Definition
Arm_sel3A
Arm_sel2A
Arm_sel1A
Arm_sel0A
0
0
0
0
ChC is armed if ChA is fully armed.
OUTCOME
0
0
0
1
ChC is armed if ChB is fully armed.
0
0
1
0
ChC is armed if ChD is fully armed.
0
0
1
1
ChC is armed if ChA AND ChB are fully armed.
0
1
0
0
ChC is armed if ChB AND ChD are fully armed.
0
1
0
1
ChC is armed if ChA AND ChD are fully armed.
0
1
1
0
ChC is armed if ChA AND ChB AND ChD are fully armed.
0
1
1
1
ChC will be armed if ChA OR ChB is fully armed.
1
0
0
0
ChC will be armed if ChB OR ChD is fully armed.
1
0
0
1
ChC will be armed if ChB OR ChD is fully armed.
1
0
1
0
ChC will be armed if ChA OR ChB OR ChD is fully armed.
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
Table 8. Channel-D Conditional Arming Definition
Arm_sel3A
Arm_sel2A
Arm_sel1A
Arm_sel0A
0
0
0
0
ChD is armed if ChA is fully armed.
OUTCOME
0
0
0
1
ChD is armed if ChB is fully armed.
0
0
1
0
ChD is armed if ChC is fully armed.
0
0
1
1
ChD is armed if ChA AND ChB are fully armed.
0
1
0
0
ChD is armed if ChA AND ChC are fully armed.
0
1
0
1
ChD is armed if ChB AND ChC are fully armed.
0
1
1
0
ChD is armed if ChA AND ChB AND ChC are fully armed.
0
1
1
1
ChD will be armed if ChA OR ChB is fully armed.
1
0
0
0
ChD will be armed if ChB OR ChC is fully armed.
1
0
0
1
ChD will be armed if ChB OR ChC is fully armed.
1
0
1
0
ChD will be armed if ChA OR ChB OR ChC is fully armed.
1
0
1
1
Reserved
1
1
0
0
Reserved
1
1
0
1
Reserved
1
1
1
0
Reserved
1
1
1
1
Reserved
NOTE
When programming individual-channel arming conditions, it is important to avoid
conditions where dependency would cause a lockup situation.
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8.4.6 Resister Map Descriptions for All Channels and Central Register
Table 9. Control and Status Register Descriptions For All Channels (X)
Register
Bit
0
1
00h
20h
40h
60h
2
7
Name
Function
LogicState
Description
Enable or disable channel X by powering down the
channel. Time to enable a channel is 200 μs.
0
Channel is disabled
1
Channel is enabled
ChX_IP_EN
Enables or disables the input of channel X. Events are
prevented from entering a channel.
0
Input is disabled
1
Input is enabled
Pol_X
Defines the polarity of the event inputX for the upcoming
timestamp generation.
0
Positive edge
1
Negative edge
0
Holdoff range value
1
Holdoff range value
0
Holdoff range value
1
Holdoff range value
0
Holdoff range value
1
Hold-off range value
En_ChX
HOffRng0_X
Defines holdoff range for event input X.
8
HOffRng1_X
Defines holdoff range for event input X.
9
HOffRng2_X
Defines holdoff range for event input X.
Table 10. Control and Status Register Descriptions for All Channels (X)
Register
Bit
0
1
01h
21h
41h
61h
2
Reserved
Arm_sel0X
Arm_sel1X
Function
Reserved
Define arming conditions for channel X.
Define arming conditions for channel X.
Arm_sel2X
Define arming conditions for channel X.
4
Arm_sel3X
Define arming conditions for channel X.
Armg_Con_En_X
Logic State
Description
x
3
5
04h
24h
44h
64h
Name
Enables or disables the arming conditions for
channel X.
0
Arming value
1
Arming value
0
Arming value
1
Arming value
0
Arming value
1
Arming value
0
Arming value
1
Arming value
0
Arming cond. disabled
1
Arming cond. enabled
0
DLL locked
1
DLL not locked
0
DLL_Lock_X
Indicates the DLL lock status for channel X.
2
Reserved
Reserved
x
3
FIFO_Full_X
Indicates that the FIFO is full. Timestamps arriving
while FIFO is full are lost.
0
FIFO not full
1
FIFO full
0
FIFO not empty
1
FIFO empty
4
FIFO_Empty_X
Indicates that the FIFO is empty.
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Table 11. Central Control and Status Registers Description
Register
Bit
0
1
2
RESET
DDR_En
Reset the device. Device is fully operational after 250 μs.
It enables DDR mode allowing the result interface to
output data on both edges.
It connects channels A and B inputs together.
4
Connect_CD
It connects channels C and D inputs together.
7
Normal mode
1
DDR Mode
0
Inputs not connected
1
Inputs connected
0
Inputs not connected
1
Inputs connected
Length value
Length value
Rlength1
Length value
1
Length value
Define the result data length being used for the
timestamps.
0
Length value
1
Length value
0
Frequency value
1
Frequency value
0
Frequency value
1
Frequency value
0
Disabled
1
Enabled
Rlength2
OT_En
RST_OT_ALM
SYNC_TS_Pol
Enables or disables the overtemperature alarm circuits.
1
Reset alarm state
0
Positive edge
1
Negative edge
0
Sync disabled
1
Sync enabled
0
Powered up
1
Powered down
0
Range value
1
Range value
0
Range value
1
Range value
It disables the RCLK digital clks internal during timestamp
process. Allows for only 16 timestamps.
0
Normal mode
1
Quiet mode
Device is not ready
Defines the polarity of the Sync input for the upcoming
timestamp generation.
13
SYNC_IP_ENI
Enables or disables the sync channel
14
PWR_DN
Powers down the device
CNT_Rng0
CNT_Rng1
Quiet_Mod
0
Resets the temperature alarm.
Defines the coarse counter range
Defines the coarse counter range
0
TMU_Ready
Indicates that the internal clks, coarse counter and Sync
channel are operational.
0
1
Device is ready
1
OT_ALM
Over temperature alarm. Indicates that the junction
temperature is 140°C.
0
No alarm
1
Alarm is enabled
0
DLL is locked
1
DLL is not locked
0
DLL is locked
1
DLL is not locked
82h
2
3
16
Reset
0
0
Define RCLK frequency.
3
1
1
RCLK_sel1
2
Enabled
0
Define the result data length being used for the
timestamps.
9
1
1
Define the result data length being used for the
timestamps.
Define RCLK frequency.
12
Disabled
Rlength0
RCLK_sel0
11
Description
0
0
8
10
Logic State
Enables or disables factory test routines.
Connect_AB
6
81h
TEST_En
Function
3
5
80h
Name
DLL_Lock_Sync
DLL_Lock_1G2
Indicates the Sync channel DLL lock status.
Indicates the lock status of the 1.2-GHz internal clock.
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8.5 Programming
8.5.1 Host Processor Bus Interface
The THS788 device includes a high-speed serial interface to a host processor. The host interface is used for
writing or reading registers that reside in the TMU chip. These registers allow configuration of the device
functions. All registers are capable of both read and write operations unless otherwise stated.
8.5.1.1 Serial Interface
The TMU serial interface operates at speeds of up to 50 MHz. Register addresses are 8 bits long. Data words
are 16 bits wide, enabling more-efficient interface transactions. The serial bus implementation uses three
LVCMOS signals: HCLK, Hstrobe, and Hdata. The HCLK and Hstrobe signals are inputs only, and the Hdata
signal is bidirectional. The HCLK signal is not required to run continuously. Thus, the host processor may disable
the clock by setting it to a low state after the completion of any required register accesses.
When data is transferred into the device, Hdata is configured as an input bus, and data is latched on a rising
edge of HCLK. When data is transferred out of the part, Hdata is configured as an output bus, and data is
updated on the falling edge of HCLK. Hstrobe is the control signal that identifies the beginning of a host bus
transaction. Hstrobe must remain low for the duration of the transaction, and must go high for at least two clock
cycles before another transaction can begin.
8.5.1.2 Read vs Write Cycle
The first Hdata bit latched by HCLK in a transaction identifies the transaction type.
First Hdata bit = 1 for read; data flows out of the chip.
First Hdata bit = 0 for write; data flows into the chip.
8.5.1.3 Parallel (Broadcast) Write
Parallel write is a means of allowing identical data to be transferred to more than one channel in one transaction.
The second Hdata bit of a transaction indicates whether a parallel write occurs.
Second Hdata bit = 0; data goes to the selected channel.
Second Hdata bit = 1; data goes to all four channels.
8.5.1.4 Address
After the R/W bit and the parallel write bit, the following 8 bits on the Hdata line contain the source address of the
data word for a read cycle or the destination address of the data word for a write cycle. Address bits are shifted
in MSB first, LSB last.
Third HCLK – Address Bit 7 (MSB)
Tenth HCLK – Address Bit 0 (LSB)
8.5.1.5 Data
The data stream is 16 bits long, and it is loaded or read back MSB first, LSB last. The timing for read and write
cycles is different, as the drivers on Hdata alternate between going into high-impedance and driving the line.
8.5.1.6 Reset
Reset is an external hardware signal that places all internal registers and control lines into their default states.
The THS788 device resets after a power-up sequence (POR). Hardware reset is an LVCMOS active-low signal
and is required to stay low for approximately 100 ns.
Reset places the TMU in a predetermined idle state at power on, and anytime the system software initializes the
system hardware. In the idle state, the TMU ignores state changes on the Event inputs and never creates
timestamps. The TMU is capable of switching within 250 μs from the idle state to a state that creates accurate
timestamps.
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Programming (continued)
8.5.1.7 Chip ID
Address (83h) is a read-only register that identifies the product and the die revision. The 16-bit register is divided
into two 8-bit sections. The LSB represents the revision history and the MSB represents the last two digits of
THS788 device (i.e., 80). The first revision (1.0) is as follows:
1000 0000 0001.0000
8.5.1.8 Read Operations
Reading the THS788 device registers via the host interface requires the following sequence:
The host controller initiates a read cycle by setting the host strobe signal, Hstrobe, to a low state. The serial
Hdata sequence starts with a high R/W bit, followed by (either 1 or 0) for parallel-write bit and 8 bits of address,
with most-significant bit (A7) first. The host controller should put the Hdata signal in the high-impedance state
beginning at the falling edge of HCLK pulse 10. The THS788 device allows one clock cycle, (r0) for the host to
reverse the data-channel direction and begins driving the Hdata line on the falling edge of HCLK pulse 11. The
data is read beginning with the most-significant bit (D15) and ending with the least-significant bit (D0).
The host must drive Hstrobe to a high state for a minimum of two HCLK periods beginning at the falling edge of
HCLK pulse 27 to indicate the completion of the read cycle. Figure 3 shows the timing diagram of the read
operation.
Hstrobe
1
2
R/W
1
X
3
4
5
6
7
8
9
10
11
A7
A6
A5
A4
A3
A2
A1
A0
r0
12
13
14
15
D15
D14
D13
D12
16
17
D11
D10
18
27
28
29
X
X
HCLK
Hdata
Register Address (A7:A0)
D0
D9
R/W
Data Out
Hdata becomes output
Driving the line
Data transfer protocol for Read operations
T0427-01
Figure 3. Read Operation
8.5.1.9 Write Operations
Writing into the THS788 device registers via the host interface requires the following sequence:
After the Hstrobe line is pulled low (start condition), the R/W bit is set low, followed by a 0 for the parallel-write bit
(single-register write), then the memory address (A7–A0) followed by the data (D15:D0) to be programmed. The
next clock cycle (w) is required to allow data to be latched and stored at the destination address (or addresses in
the case of a parallel write), followed by at least two dummy clock cycles during which the Hstrobe is high,
indicating the completion of the write cycle. Figure 4 and Figure 4 show timing diagrams of write operations.
Hstrobe
st
1
2
3
4
A7
A6
5
6
7
8
9
10
11
12
13
14
A5
A4
A3
A2
A1
A0
D15
D14
D13
D12
24
25
26
27
28
29
1 clock for next
transaction = 30
HCLK
Hdata
R/W
1
0
Register Address (A7:A0)
D2
D1
D0
w0
X
X
R/W
Data In
Data transfer protocol for single write operation
T0425-01
Figure 4. Write Operation
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Programming (continued)
8.5.1.10 Write Operations to Multiple Destinations
This is similar to the single-write operation except the parallel-load bit is set to 1.
Hstrobe
st
1
2
3
4
A7
A6
5
6
7
8
9
10
11
12
13
14
A5
A4
A3
A2
A1
A0
D15
D14
D13
D12
24
25
26
27
28
29
1 clock for next
transaction = 30
HCLK
Hdata
R/W
1
1
Register Address (A7:A0)
D2
D1
D0
w0
X
X
R/W
Data In
Data transfer protocol for parallel write operation
T0426-01
Figure 5. Write Operations to Multiple Destinations
8.5.2 Serial-Results Interface and ALU
8.5.2.1 Event Latches
Each event channel and the sync channel include two event latches whose inputs are both connected to the
LVDS input-buffer output. One latch is the time-measurement signal path and connects to the interpolator and
synchronizer. The other latch connects to the preconditioning circuitry. A selectable rising or falling edge of an
event pulse sets the latch. the latch remains set until the interpolator has finished processing the event, at which
time the interpolator resets the latch. The latch, however, does not accept another event pulse until the event
input returns to its initial state and remains for the initial event-pulse duration. Any event transitions which occur
before the interpolator has completed processing the previous event are ignored. For example, assume that
rising edge is selected. Two rising edges can occur as quickly as 5 ns apart. The falling edge can occur
anywhere from 250 ps after the rising edge to 250 ps before the next rising edge. Any other edges or glitches are
ignored. In addition to the rising/falling-edge selection, the event latch includes the gating function whereby the
preconditioning logic controls whether the TMU accepts and processes an event input. The second event latch
operates similarly to the main signal-path latch with the following exceptions: The latch is followed by and ECLto-CMOS converter , because all the preconditioning logic is CMOS instead of the fast ECL circuitry in the
measurement chain. The preconditioning logic rather than the interpolator resets this latch, and the timing of the
reset pulse is slightly faster than the interpolator.
8.5.2.2 FIFO
Timestamps are written to a FIFO at high speed and read for further processing at a lower speed before being
sent to the result interface. This FIFO is 15 bits deep and 40 bits wide. There are four FIFOs in THS788 device,
one for each channel. There are two status registers (FIFO_Full_x and FIFO_Empty_x), which are set when a
FIFO reaches its full capacity and when it is empty, respectively.
Timestamps are taken and loaded into the FIFO as events occur. Timestamps are mathematically processed by
an arithmetic logic unit (ALU) which calculates the difference between the event and the sync timestamps and
factors in the appropriate calibration value from the calibration register. The ALU operates on the data as it is
read out of the FIFO and sent out through the serial-results interface. The serial-results interface controls the
output of the FIFO.
8.5.2.3 Result-Interface Operation
The TMU initiates a read cycle by setting the strobe signal, Rstrobe, to a low state, indicating that the data
transfer is about to begin. The serial Rdata sequence starts with a TAG bit, followed by the 40-bit data (R0 to
R39). R39 (MSB) is the sign bit. Following the last data bit (R39), the strobe signal (Rstrobe) goes high for two
clock cycles, indicating the end of the transaction.
The data is clocked out of the TMU on the rising edge of RCLK. The receiving device clocks the data in on the
rising edge of RCLK. Figure 6 and Figure 7 show a 40-bit result on the result interface.
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Programming (continued)
Rstrobe
RCLK
Rdata
0
0
0
R0
R1
R2
R3
R4
R5
R34 R35 R36 R37 R38 R39
Result Data
Sign bit when
programmed
TAG
TAG = 0, Valid Data
0
0
0
R0
R1
R2
R3
R4
R5
R6
R7
New Cycle
Cycle
End
T0428-01
Figure 6. Result-Interface Operation A
Rstrobe
RCLK
Rdata
0
0
0
R0
R1
R2
R3
R4
R5
R10
R11
R12 R13 R14 R15
Result Data
Sign bit when
programmed
TAG
0
0
0
R0
R1
R2
R3
R4
R5
R6
R7
New Cycle
Cycle
End
T0455-01
Figure 7. Result-Interface Operation B
NOTE
In the preceding diagrams, only RCLK_P is drawn to indicate the correct edge with
respect to data.
8.5.2.4 Serial Results Latency
The event stored in the FIFO will be transferred to ALU and subsequently to the free running results data shift
register when the shift register enters a load pulse. The load pulse is generated once per ALU/shift register
processing cycle. The load pulse will trigger the ALU and transfer result to the parallel to serial shift register for
output. The cycle time of the load pulse is dependent upon the depth of the result transfer register and data rate.
Because the results parallel to serial register are free running, the load pulse will be asynchronous to the actual
event. So, the latency will depend upon where in the current cycle the load pulse occurred relative to the event
being captured into the FIFO.
The worst case for data to be output from serial bus:
Tevent + 5(Rclkcycles) + (Rdatalength + 3) x Rclkcycles + (Rdatalength + 3) × Rclkcycles
(1)
The best case for data to be output from serial bus:
Tevent + 5(Rclkcycles) + (Rdatalength + 3) × Rclkcycles
where
•
•
•
•
Tevent = 5 ns (minimum repeat capture time)
5(Rclkcycles) = number cycles for FIFO to ALU to Shift register
Rclkcycles is period of RCLK data = 300 MHz, SDR = 3.33 ns
Rdatalength = number of results bits = 40 for THS788 device
(2)
In the case where RCLK = 300 MHz, with 40-bit serial result:
Min Latency = 5 ns + 17 ns + (40 + 3) × 3.33 ns = 165 ns
20
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Programming (continued)
Max Latency = 5 ns + 17 ns + (40 + 3) × 3.33 ns + (40 + 3) × 3.33 ns = 308 ns
(4)
NOTE
The THS788 device was intended for sync-event, event, event, sync-event ... processing.
However, some applications desire the use of a sync pulse that is a fixed period. During a
sync period, there could be multiple events, or no events. The TMU can be used
effectively for this scenario as well.
For applications using the THS788 device in this fashion, it is important to consider the
uncertainty that is introduced by the load pulse timing. Because the load pulse is free
running and asynchronous to any events, the latency will vary based on this timing.
Additionally, the load pulse is the mechanism that will cause the ALU to grab the current
sync value for the result calculation.
If an event is in the FIFO, waiting for the load pulse and a new sync occurs, the ALU will
use the new sync value for calculating the result. In this case, the event would precede the
sync resulting in a negative result. The system could then offset the result by one sync
cycle as the result is negative, indicating that is was captured during a prior sync cycle.
8.5.2.5 TMU Calibration
The TMU calibration process is identical to a normal TMU time-stamp measurement. The process involves
measuring a known interval and calculating the difference between the measured value and the actual value.
The result is then stored into calibration registers inside the TMU. The TMU takes the stored calibration values
and corrects the subsequent time-stamp measurements.
There are four calibration registers for each channel. These are identified as follows:
• A calibration register for positive sync edge and positive event edge
• A calibration register for positive sync edge and negative event edge
• A calibration register for negative sync edge and positive event edge
• A calibration register for negative sync edge and negative event edge
Calibration due to temperature changes following the initial system calibration may be required if temperature
variations are significant.
8.5.2.6 Temperature Sensor
A temperature sensor has been located centrally in the THS788 device for monitoring the die temperature. There
are two monitor outputs for this feature. An analog voltage proportional to the die temperature is presented at the
TEMP pin. Also, an overtemperature alarm output is available at the OT_ALARM pin. The overtemperature alarm
(OT_ALARM) is an open-drain output that is activated when the die temperature reaches 141°C.
The overtemperature alarm sets a register bit (OT_ALM) in the central register and may be accessed through the
serial interface.
The overtemperature alarm initiates an automatic power down to prevent overheating of the device. The digital
blocks remain functional when in automatic power down. Following a power down, the user is required to reset
OT_ALM using the serial interface. A register bit (RST_OT_ALM) is used for this purpose.
The temperature-monitoring function and its associated overtemperarture alarm circuit may be disabled by the
user, using a register bit (OT_EN). The default for the temperature-monitoring function is enabled.
OT_EN = 1: Temperature-monitoring function is enabled.
OT_EN = 0: Temperature-monitoring function is disabled.
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8.6 Register Maps
8.6.1 Register Address Space
Table 12. Channel-A Registers
Address (Hex)
Register
00h–01h
Control register
02h–03h
Not used
NA
04h
Status registers
RO
05h
Not used
NA
06h
Holdoff delay time register
R/W
07h
Not used
R/W
08h
Not used
R/W
09h
Not used
R/W
0Ah
Not used
R/W
0Bh
Not used
R/W
0Ch
Positive edge sync and positive edge hit calibration register, 16 bits
R/W
0Dh
Positive edge sync and negative edge hit calibration register, 16 bits
R/W
0Eh
Negative edge sync and positive edge hit calibration register, 16 bits
R/W
0Fh
Negative edge sync and negative edge hit calibration register, 16 bits
R/W
10h–12h
Timestamp register, 40 bits
13h–1Fh
Not used
R/W
R
NA
Table 13. Channel-B Registers
Address (Hex)
Register
20h–21h
Control register
22h–23h
Not used
NA
24h
Status registers
RO
25h
Not used
NA
26h
Hold_off delay time register
R/W
27h
Not used
R/W
28h
Not used
R/W
29h
Not used
R/W
2Ah
Not used
R/W
2Bh
Not used
R/W
2Ch
Positive edge sync and positive edge hit calibration register, 16 bits
R/W
2Dh
Positive edge sync and negative edge hit calibration register, 16 bits
R/W
2Eh
Negative edge sync and positive edge hit calibration register, 16 bits
R/W
2Fh
Negative edge sync and negative edge hit calibration register, 16 bits
R/W
30h–32h
Timestamp register, 40 bits
33h–3Fh
Not used
22
R/W
R
NA
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Table 14. Channel-C Registers
Address (Hex)
Register
40h–41h
Control register
42h–43h
Not used
NA
44h
Status registers
RO
45h
Not used
NA
46h
Not used
R/W
47h
Not used
R/W
48h
Not used
R/W
49h
Not used
R/W
4Ah
Not used
R/W
4Bh
Not used
R/W
4Ch
Positive edge sync and positive edge hit calibration register, 16 bits
R/W
4Dh
Positive edge sync and negative edge hit Calibration register, 16 bits
R/W
4Eh
Negative edge sync and positive edge hit Calibration register, 16 bits
R/W
4Fh
Negative edge sync and negative edge hit Calibration register, 16 bits
R/W
50h–52h
Timestamp register, 40 bits
53h–5Fh
Not used
R/W
R
NA
Table 15. Channel-D Registers
Address (hex)
Register
60h-61h
Control register
62h-63h
Not used
NA
64h
Status registers
RO
65h
Not used
NA
66h
Not used
R/W
67h
Not used
R/W
68h
Not used
R/W
69h
Not used
R/W
6Ah
Not used
R/W
6Bh
Not used
R/W
6Ch
Positive sync edge and positive hit edge, calibration register, 16 bits
R/W
6Dh
Positive sync edge and negative hit edge, calibration register, 16 bits
R/W
6Eh
Negative sync edge and positive hit edge, calibration register, 16 bits
R/W
6Fh
Negative sync edge and negative hit edge, calibration register, 16 bits
R/W
71h-73h
Timestamp register, 40 bits
74h-7Fh
Not used
R/W
R
NA
Table 16. Central Registers
Address (hex)
Register
80h
Control register
R/W
81h
Control register
R/W
82h
Status register
RO
83h
Chip ID
RO
84h
Test key register
R/W
85h
Test1
R/W
86h
Test2
R/W
87h
Reserved
R/W
88h
Reserved
R/W
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8.6.2 Register Map Detail
Table 17. Channel A
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En_ChA
D0
DLL_Lock_A
D0
D0
0000h
0000h
D0
D1
D1
D1
D1
D33 D17
0000h
0000h
D0
0000h
0000h
D32 D16
ChA_IP_En
Arm_sel0_A
X
D1
X
Pol_A
Arm_sel1_A
X
D2
D4
D4
D4
D4
D4
D36 D20
D5
D5
D5
D5
D37 D21
0
D6
0
D6
0
D6
0
D6
0
D7
0
D7
0
D7
0
X
D2
X
D2
X
D2
X
D2
X
D34 D18
X
Arm_sel2_A
X
FIFO_Full_A
X
0000h
D3
X
X
D3
X
Default Value
X
D3
X
0
0000h
D3
FIFO_Empty_A
X
1
0
D3
X
2
0000h
D35 D19
X
Arm_sel3_A
ArmgCon_En_A
X
D5
X
D6
HOffRng0_A
X
D7
X
D38 D22
12h
X
D8
Timestamp
X
D8
10h
X
D8
Calibration:Neg Sync
EdgeNeg Event Edge
X
D8
0Fh
X
D8
Calibration:Neg Sync
EdgePos Event Edge
X
D9
0Eh
X
D9
Calibration:Pos Sync
EdgeNeg Event Edge
X
D9
0Dh
X
D9
Calibration:Pos Sync
EdgePos Event Edge
X
D9
Reserved
0
D7
X
06h
0Ch
0
D39 D23
X
0
HOffRng1_A
Status
3
X
D24
04h
4
X
D25
X
D26 D10 D10 D10 D10 D10
X
5
0
D27 D11 D11 D11 D11 D11
Control
6
0
D28 D12 D12 D12 D12 D12
01h
7
0
D29 D13 D13 D13 D13 D13
X
D30 D14 D14 D14 D14 D14
X
8
D31 D15 D15 D15 D15 D15
Control
9
HOffRng2_A
15 14 13 12 11 10
00h
11h
24
Word/Bit
HOffTm_En_A
Register Name
PreCon_En_A
Register
Address
0000h
0000h
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Table 18. Channel B
Word/Bit
D0
0000h
D0
0000h
D0
0000h
D0
En_ChB
DLL_Lock_B
DLL_Lock_B
0000h
0000h
D0
ChB_IP_En
Pol_B
Arm_sel0_B
D1
0000h
0000h
D32 D16
D8
D8
D8
D8
D9
D9
D9
D9
D1
0
D1
0
D1
0
X
D1
0
X
D33 D17
0
D5
0
D8
0
D9
0
D5
Timestamp
D5
30h
D5
Calibration:Neg Sync
EdgeNeg Event Edge
D37 D21
2Fh
D6
Calibration:Neg Sync
EdgePos Event Edge
D6
2Eh
D6
Calibration:Pos Sync
EdgeNeg Event Edge
D6
2Dh
D38 D22
Calibration:Pos Sync
EdgePos Event Edge
Arm_sel1_B
X
D2
X
D2
X
D2
X
D2
X
D2
X
D34 D18
X
Arm_sel2_B
X
FIFO_Full_B
X
X
FIFO_Full_B
X
Default Value
X
D3
X
D3
X
D3
X
0
0000h
D3
X
1
0
D3
X
2
0000h
D35 D19
X
Arm_sel3_B
X
D4 FIFO_Empty_B FIFO_Empty_B
X
D4
X
D4
ArmgCon_En_B
X
D4
X
D4
X
D36 D20
X
D5
X
D6
HOffRng0_B
X
D7
2Ch
32h
X
D7
X
31h
X
D7
Reserved
0
D7
26h
0
D7
X
0
D39 D23
Status
3
HOffRng1_B
24h
4
X
D24
X
D25
X
5
0
D26 D10 D10 D10 D10 D10
Control
6
0
D27 D11 D11 D11 D11 D11
21h
7
0
D28 D12 D12 D12 D12 D12
X
D29 D13 D13 D13 D13 D13
X
D30 D14 D14 D14 D14 D14
Control
8
D31 D15 D15 D15 D15 D15
20h
9
HOffRng2_B
15 14 13 12 11 10
HOffTm_En_B
Register Name
PreCon_En_B
Register
Address
0000h
0000h
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Table 19. Channel C
Word/Bit
En_ChC
DLL_Lock_C
D0
0000h
0000h
D0
X
0000h
D0
X
0000h
D0
X
0000h
D0
ChC_IP_En
X
0000h
D32 D16
D4
D4
D4
D4
D8
D8
D8
D8
D9
D9
D9
D9
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D4
0
D36 D20
0
D5
0
D5
0
D5
0
D5
0
D8
0
D9
0
D37 D21
Timestamp
D6
50h
D6
Calibration:Neg Sync
EdgeNeg Event Edge
D6
4Fh
D6
Calibration:Neg Sync
EdgePos Event Edge
D38 D22
4Eh
Arm_sel0_C
X
D1
X
D1
X
D1
X
D1
X
D1
X
D33 D17
X
Pol_C
X
Arm_sel1_C
X
0000h
D2
X
X
D2
FIFO_Empty_C
X
X
D2
X
D2
X
D2
X
D34 D18
X
Arm_sel2_C
X
Default Value
FIFO_Full_C
X
D3
X
D3
X
D3
X
0
0000h
D3
ArmgCon_En_C
X
1
0
D3
X
2
0000h
D35 D19
X
Arm_sel3_C
X
D5
X
D6
HOffRng0_C
Calibration:Pos Sync
EdgeNeg Event Edge
26
X
D7
4Dh
52h
X
D7
X
Calibration:Pos Sync
EdgePos Event Edge
51h
X
D7
Reserved
4Ch
0
D7
46h
0
D7
X
0
D39 D23
Status
3
HOffRng1_C
44h
4
X
D24
X
D25
X
5
0
D26 D10 D10 D10 D10 D10
Control
6
0
D27 D11 D11 D11 D11 D11
41h
7
0
D28 D12 D12 D12 D12 D12
X
D29 D13 D13 D13 D13 D13
X
D30 D14 D14 D14 D14 D14
Control
8
D31 D15 D15 D15 D15 D15
40h
9
HOffRng2_C
15 14 13 12 11 10
HOffTm_En_C
Register Name
PreCon_En_C
Register
Address
0000h
0000h
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Table 20. Channel D
Word/Bit
En_ChD
DLL_Lock_D
D0
0000h
0000h
D0
X
0000h
D0
X
0000h
D0
X
0000h
D0
ChD_IP_En
X
0000h
D32 D16
D4
D4
D4
D8
D8
D8
D8
D9
D9
D9
D9
D4
0
D4
0
D36 D20
0
D5
0
D5
0
D5
0
D8
0
D9
0
D5
Timestamp
D37 D21
70h
D6
Calibration:Neg Sync
EdgeNeg Event Edge
D6
6Fh
D6
Calibration:Neg Sync
EdgePos Event Edge
D6
6Eh
D38 D22
Calibration:Pos Sync
EdgeNeg Event Edge
Arm_sel0_D
X
D1
X
D1
X
D1
X
D1
X
D1
X
D33 D17
X
Pol_D
X
Arm_sel1_D
X
0000h
D2
X
X
D2
FIFO_Empty_D
X
X
D2
X
D2
X
D2
X
D34 D18
X
Arm_sel2_D
X
Default Value
FIFO_Full_D
X
D3
X
D3
X
D3
X
0
0000h
D3
ArmgCon_En_D
X
1
0
D3
X
2
0000h
D35 D19
X
Arm_sel3_D
X
D5
X
D6
HOffRng0_D
X
D7
6Dh
72h
X
D7
X
Calibration:Pos Sync
EdgePos Event Edge
71h
X
D7
Reserved
6Ch
0
D7
66h
0
D7
X
0
D39 D23
Status
3
HOffRng1_D
64h
4
X
D24
X
D25
X
5
0
D26 D10 D10 D10 D10 D10
Control
6
0
D27 D11 D11 D11 D11 D11
61h
7
0
D28 D12 D12 D12 D12 D12
X
D29 D13 D13 D13 D13 D13
X
D30 D14 D14 D14 D14 D14
Control
8
D31 D15 D15 D15 D15 D15
60h
9
HOffRng2_D
15 14 13 12 11 10
HOffTm_En_D
Register Name
PreCon_En_D
Register
Address
0000h
0000h
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Table 21. Central Registers
Word/Bit
X
82h
Status
X
X
X
X
X
X
X
X
X
X
X
X
83h
Chip ID
ID
ID
ID
ID
ID
ID
ID
ID
28
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Test_En
X
X
0000h
TMU_Ready
X
0000h
0000h
Rev
X
Default Value
RESET
X
0
OT_ALM CNT_Rng0
X
1
8010h
Rev
X
DDR_En
X
2
Rev DLL_Lock_Sync CNT_Rng1
X
Connect_AB
X
Quiet_Mod
Connect_CD
X
3
DLL_Lock_1G2
Rlength0
X
Rev
Rlength1
Control
Rev
Rlength2
81h
Rev
Control
Rev
80h
RCLK_sel0
4
RCLK_sel1
5
OT_En
6
RST_OT_ALM
7
Sync_TS_Pol
8
Sync_IP_En
9
PWR_DN
15 14 13 12 11 10
RCLK_En
Register Name
Rev
Register
Address
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9 Application and Implementation
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.
9.1 Application Information
The THS788 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 8 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 8. 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 programmable (18-, 27-, 34-bit) counter, 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 THS788 device is achieved through an LVCMOS host-serial interface. With this
interface, the user has the ability to set up the THS788 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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9.2 Typical Application
Time Stamp
Processor
Sequencer
Formatter
Timing Logic
Error Logic
PLL
RdataA
RdataB
DLL
MCLK
(Fixed)
RdataC
Sync Input
RdataD
Serial
Result Data
RCLK
RstrobeA
EventA
Time
Stamp
Logic
Hold-Off
Logic
EventB
DCL/PPMU
RstrobeB
EventC
RstrobeC
EventD
DUT
RstrobeD
Reset
Control
Registers
Output (Voltage)
TEMP
OT_ALARM
Hdata
Host
Interface
HCLK
Hstrobe
Serial Host
Processor
Interface
Temp
Sensor
B0387-01
Figure 9. Example of Application Diagram in ATE Environment
30
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Typical Application (continued)
9.2.1 Design Requirements
For this design example, use the parameters listed in Table 22 as the input parameters.
Table 22. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Results interface size
40 bit
Results time range
–7.158 to 7.158 s
Rclock
300 MHz
DDR mode
Off
Temperature monitor
On
Connect CD/Connect AB
Off
Counter size
34 bit
REGISTER WRITE (80h)
0xA680
REGISTER WRITE (81h)
0x0003
9.2.2 Detailed Design Procedures
9.2.2.1 Time Measurement
Time measurements in the THS788 device follow the timing of Figure 10. This diagram illustrates that time
measurements are valid as long as events do not happen at speeds higher than 200 MHz. If an event happens
at less than 5 ns from the previous one, then this event is ignored. The same applies to the SYNC signal. Even
though the minimum period is 5 ns, the pulse duration of both Event and SYNC signals can be as low as 200 ps.
SYNC
200 ps Min PW
Max Freq.
200 MHz
EVENT
T1
T2
T3
T0430-01
Figure 10. Time-Measurement Example at Maximum Retrigger Rate and Minimum Pulse Duration
The TH788 is capable of making time measurements using any combination of rising-falling edge between Event
and SYNC. The example in Figure 10 uses rising edges only to trigger the time measurement. Table 23
describes what registers bits must be programmed to achieve the desired combination. Registers to be
programmed are 00h, 20h, 40h, and 60h for event channels and 80h for the sync channel. The examples in
Figure 11 illustrate the other three combinations. All of the channels can be programmed individually with respect
to the sync channel.
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Table 23. Trigger Polarity Programmability
REGISTER BITS
TRIGGER POLARITY FROM
SYNC TO EVENT
SYNC_TS_Pol
Pol_X
0
0
Pos to Pos
0
1
Pos to Neg
1
0
Neg to Pos
1
1
Neg to Neg
SYNC
SYNC
SYNC_TS_Pol = 1
Pol_X = 0
SYNC_TS_Pol = 0
Pol_X = 1
EVENT
EVENT
T1
T3
T2
T1
SYNC
SYNC_TS_Pol = 1
Pol_X = 1
EVENT
T1
T2
T0431-01
Figure 11. Time-Measurement Examples With Different Edge Polarities
9.2.2.2 Output Clock to Data/Strobe Phasing
The output of each channel is an Rdata and Rstrobe signal. The RCLK for all the channels is a common output.
Operating at 300 MHz, these signals must be handled carefully. Particularly important are the termination and
phase alignment of the signals at the receiving circuitry. Termination has been discussed previously. Phase
alignment is now discussed: The two outputs from each channel are clocked out through identical flip-flops with
the same internal clock. Data and strobe output edges from a particular channel match well (< 50 pS). The match
channel-to-channel is not as good due to the greater wiring distances internal to the TMU. However, the total
time difference is below 125 pS. Because the RClock is a common output, the wiring lengths from the four
channels must be matched and controlled to achieve good setup and hold times at the input to the receiving
circuit. The RClock rising edge is adjusted internal to the TMU to be close to the center of the eye diagram of the
data/strobe signals. (The internal clock has a good 50/50 duty cycle. The rising edge clocks out the data/strobe.
The falling edge is inverted and used as the RClock after appropriate adjustments for the internal propagation
delay times.) The receiving circuitry requirements for setup and hold timing must be carefully examined for the
proper timing. Delays may be added to the PCB microstrips to adjust timing. A good rule is 125 ps of delay per
inch of microstrip length.
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9.2.2.3 Master Clock Input and Clock Multiplier
All of the internal timing of the TMU is derived from the 200-MHz master clock. Therefore, its quality is critical to
the accurate operation of the TMU. Absolute accuracy of the master clock linearly affects the accuracy of the
measurements. This imposes little burden upon the master clock, as accurate oscillators are easy to procure or
distribute. However, the jitter of the master clock is also highly critical to the single-event precision of the TMU
and should be absolutely minimized (.6 ns).
Discussion of the clock multiplier follows: The TMU operates from a master-clock frequency of 1200 MHz, which
implies a measurement period of 0.833 ns. The master counter runs from this frequency, and all the other clocks
are divided down from this main clock. An interpolator allows finer precision in time measurement, as discussed
elsewhere. The clock multiplier is the circuit that takes the 200-MHz master-clock reference and generates from
that the high quality 1200-MHz clock. The clock multiplier consists of five major sections: First is the delay-lock
loop (DLL), which is a series connection of 12 identical and closely matched variable time-delay circuits. A single
control voltage connects to each of the delay elements. The master 200-MHz clock connects to the input of the
DLL. Because the period of 200 MHz is 5 ns, if the control voltage is adjusted to make the time delay of the DLL
equal to 5 ns, the input and the output of the delay line is exactly phase matched. A phase detector connected to
the input and the output of the delay line can sense this condition accurately, and a feedback loop with a lowoffset-error amplifier is included in the clock multiplier to achieve this result. These are the second and third
circuit blocks. With 12 equally spaced 200-MHz clock phases, select out six equally spaced 833-ps-wide pulses
with AND gates and combine these pulses into a single 1200-MHz clock waveform with a six-input OR gate. The
last circuit element is a powerful differential signal buffer to distribute the 1200-MHz clock to the various circuit
elements in the TMU. The DLL feedback loop is fairly narrowband, so some time is required to allow the DLL to
initialize at start-up (about 100 μs, typical). The DLL is insensitive to the duty cycle of the input 200-MHz clock.
Duty cycles of 40/60 to 60/40 are acceptable. What matters most is as little jitter as possible.
9.2.2.4 Temperature Measurement and Alarm Circuit
Chip temperature of the TMU is monitored by a temperature sensor located near the center of the chip. A small
buffer outputs a voltage proportional to the absolute temperature of the TMU. The buffer drives a load of up to
100 pF typical (50 pF minimum) and open circuit to 10 kΩ to ground resistive. The output voltage slope is 5 mV,
typical. Therefore, the output voltage equation is as follows:
Output Voltage = (Temperature in °C × 5 mV) + 1.365 V
(5)
Also included in the TMU is an overtemperature comparator. At approximately 140°C, the alarm goes active, and
at approximately 7°C below this temperature, the alarm becomes inactive (hysteresis of 7°C prevents tripping on
noise and comparator oscillations). If the alarm goes active, the chip powers down and sets a bit in the serial
register.
An alarm output pin is provided that is an open-drain output. Connect this output through a pullup resistor to the
3.3-V power supply. The resistor must be at least 3.3 kΩ. This creates a slow-speed, low-voltage CMOS digital
output with a logical 1 being the normal operating state and a logical 0 being the overtemperature state.
9.2.2.5 LVDS-Compatible I/Os
The Event, SYNC, and master-clock inputs are LVDS-compatible input receivers optimized for high-speed and
low-time-distortion operation. The Rdata, Rstrobe, and RCLK outputs are similarly LVDS-compatible output
drivers optimized for high-speed/low-distortion operation, driving 50-Ω transmission lines. Typically, LVDS data
transmission is thought of in terms of 100-Ω twisted-wire-pair (TWP) transmission lines. TWP is not applicable to
printed wiring boards and high-speed operation. Therefore, the THS788 device interfaces were designed to
operate most effectively with 50-Ω, single-ended transmission lines. Instead of a current-mode output with its
correspondingly high output impedance, a more-nearly impedance-matched voltage-mode output driver is used.
This minimizes reflections from mismatched transmission line terminations and the resulting waveform distortion.
The input receivers do not include the 100-Ω terminating resistor, which must be connected externally to the
THS788 device. This was done to accommodate daisy-chaining the THS788 inputs. Input offset voltage was
minimized, and the fail-safe feature in the LVDS standard was eliminated in order to minimize distortion.
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9.2.2.6 LVDS-Compatible Inputs
The four event inputs, the sync input and the master-clock input all use the same input interface circuitry.
Figure 12 is a simplified schematic diagram of the LVDS-compatible receiver input stage. The input signal is
impedance-transformed and level-shifted with a PNP emitter-follower and translated into ECL-like differential
signals with a common-emitter amplifier. There is no internal termination resistor and no internal pullup/pulldown
resistors. Unused inputs may be tied off by connecting both input terminals to ground. If the input terminals are
left floating, they are protected by ESD clamps from damage; however, noise may be injected into the THS788
device and may degrade accuracy. The peak input voltage limits are 0.6 V to 1.7 V. Outside of these limiting
voltages, parts of the input circuit may saturate and distort the timing.
VCC
R
R
2.5 nH
Bond Wire
IN
0.5 pf
Package
0.1 pf
Bond Pad
0.4 pf
VCC
2.5 nH
Bond Wire
IN
0.5 pf
Package
0.1 pf
Bond Pad
0.4 pf
S0389-01
Figure 12. Simplified Schematic of the LVDS Input
Figure 13 shows the typical input connections. The transmission line lengths must be matched from the driver to
the THS788 input [