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1
Single Event Effects and Total Dose Test
Results for TI TLK2711 Transceiver
R. Koga, Member, IEEE, P. Yu, and J. George
Abstract-- TLK2711 transceivers belonging to the Class V dice
manufactured by Texas Instruments were tested for their
sensitivity to radiation. We measured single event effects as well
as total ionizing dose effects.
I.
INTRODUCTION
of COTS transceivers have been
Vexaminedtypes
for their sensitivity to radiation [1]-[4]. The
ARIOUS
sensitivity may encompass bit errors as well as total ionizing
dose effects. Recently, we carried out radiation testing of the
Class V TLK2711 transceiver. Testing took place at the
Lawrence Berkeley Laboratory (LBL) 88-inch cyclotron
facility, the Radiation Effects Facility at TAMU, and the
Indiana University Cyclotron Facility (IUCF). We utilized
protons at LBL and IUCF, while heavy ions were made
available at TAMU and LBL. Samples of heavy ions used for
testing are shown in TABLE 1. Radiation tests are made up
of (1) SEU (single event upset)/SEL (single event latchup)
testing with protons, (2) SEU/SEL testing with heavy ions,
and (3) total ionizing dose (TID) testing with 50 MeV
protons.
TLK2711 is a 1.6 to 2.7 Gb/s transceiver (XCVR)
manufactured by Texas Instruments [5]. It is also called a
Serializer/Deserializer (SERDES). Our test samples were a
part of the Class V dice. One group of samples was obtained
in 2005, while another group of samples was obtained in
2007. A block diagram of TLK2711 is shown in Fig. 1. A
device may be configured for a transmitter (TX) or a receiver
(RX). It belongs to the TI CMOS (epi) 25C10 technology
with a feature size of 0.25 µm [6]. Some of the features are
listed below [5]: 2.5-V Power Supply; Low Power: <500
mW; 16-bit Parallel TTL (transistor to transistor logic)
Compatible Data/Internally Encoded Into 20 Bits Using an 8bit/10-bit (8b/10b) Encoding Format; Interfaces to
Backplane, Copper Cables, or Optical Converters; On-chip
PLL (phase lock loop) Provides Clock Synthesis From LowSpeed Reference; Receiver Differential Input Threshold 220
mV Minimum; Loss of Signal (LOS) Detection; and
Integrated 50-Ohm Termination Resistors on RX.
The 8b/10b encoding/decoding process utilizes a code,
which maps a 8-bit symbol (8-bit word) to a 10-bit symbol
Manuscript received July 10, 2007.
R. Koga, P. Yu, and J. George are with The Aerospace Corporation, El
Segundo, CA 90245 USA (telephone: 310-336-6583, e-mail:
[email protected]
All trademarks, service marks, and trade names are the property of their
respective owners.
(in TX) in order to achieve reasonable digital bit polarity
(e.g., DC-balance without a high level of bits disparity)
during the serial transmission and a reliable clock recovery
(RXCLK) at the receiver (RX) as shown in Fig. 1 [7]. The
clock recovery is accomplished with the use of PLL while the
decoding of the 8b/10b code provides the 8-bit symbol at RX.
Special symbols are utilized to designate such items as startof-frame, end-of-frame, etc. TLK2711 uses a comma symbol
(0011111) for byte alignment. TLK2711 latches 16-bit
parallel data at the transmit data terminals (TXD0 to TXD15
at TX). In order to accomplish transmission, serialized bit
stream (TXP/TXN and RXP/RXN) converted from two
parallel 8-bit words at TX (8b/10b encoding) “re-emerges” as
two parallel 8bit words at RX
(8b/10b decoding)
representing the original 16-bit parallel data.
Possible sites for SEU as well as SET (single event
transient) may take place in either the TX or RX section.
Encoding and/or decoding would be affected when an SEU
occurs at either place. It is conceivable that the PLL is a site
where an SEU may originate or the site where its capability
may be hampered by incoming low fidelity signals for proper
clock signal reconstruction. SEE sensitivity of space-born
microcircuits such as BER (bit-error-ratio) has been studied
[BER = #errors/(bit transmitted) = σ.φ/(data rate)] regarding
data links for satellite use [8]. In some cases BER has
subsequently been referred to as “bit-error-rate” [4].
TABLE I
CHARACTERISTICS OF HEAVY IONS
Ions
AMU Energy (MeV) LET [MeV/(mg/cm2)
Range in Si (µ)
B
11
108
0.9
330
O
18
185
2.2
200
Ne
22
216
3.5
186
Ne
22
550
1.7
790
Ar
40
400
10
142
Cu
63
606
21
117
Kr
86
885
31
119
Kr
84
2100
29
315
Xe
136 1330
59
115
Xe
129 3225
38
250
Note: Selected ions available at TAMU and LBL are listed.
II.
EXPERIMENTAL
Test setups for all of our radiation tests were essentially
identical. Each test setup is schematically presented in Fig. 2.
Two test samples (one in the transmit mode while the other in
the receive mode) were mounted on a PCB (printed circuit
board). Both samples were exposed simultaneously during
irradiation.
2
TX
Parallel to serial
conversion
16 parallel bits
TX D0 --TX D15
TXCLK
TKLSB/TKMSB
Encoded 10b
serial, differential
-TXP --TXN --
Two sets of 8b/10b
encoding
RX
16 parallel bits
RXD0 -- RXD15
RXCLK
Serial to parallel
conversion
Encoded 10b
serial, differential
Two sets of 8b/10b
decoding
RKLSB/RKMSB
-RXP--RXN--
PLL & clock
recovery
LOS
Signal detection
Additional Lines:
RX receiving signals directly (without serializing) from TX (LOOPEN),
pseudo random bit stream (PRBS) testing (PRBSEN), &
other control lines for special k characters, etc.
Fig. 1 Block diagram of TLK2711
(Serial/Differential 10b Encoded Data)
BERT
and
Signal
Generator
(Parallel 8b Data and
RX Clock Signal)
(Serial
10b)
TLK2711
XCVR
(RX mode)
TLK2711
XCVR
(TX mode)
Test Board
(Both RX and TX are Irradiated Simultaneously)
Fig. 2. TLK2711 XCVR radiation testing setup.
3
Fig. 3. Picture of test board.
Fig. 4. Eye pattern of the TLK2711 1.6 Gb/s output at pre-rad. level. (200 mV/div and 195 ps/div).
4
A test system made up of a signal generator and a BERT (bit
error rate tester) was placed away from the PCB. A photo of
the PCB is shown in Fig. 3. A thermistor to monitor the case
temperature may be adhered with epoxy for each device on
some PCBs. Signals (single-ended RX input 210-230 mV;
ref. to VID, which is the “receiver input voltage differential”)
from the test system were led to the receiver on the PCB [5].
The parallel 8b data and the receiver clock signal were
directed from the receiver to the transmitter on the board. The
transmitter output (serial/differential 10b encoded data) was
checked for upsets at the BERT. This made it possible for a
real-time BER testing at a 2.5-Gb/s serial link rate. The serial
link transmitted a continuous flow of packets each of which
consisted of a 4-byte preamble and a 4096-byte frame
followed by a 24-idle-byte string (24-byte long). Within one
frame (4096 bytes) two bytes were used for the packet
checksum. One byte was made up of one 8-bit word in the
parallel domain. The checksum as well as any errors in each
10b word was used to identify upsets (non-burst errors). A
burst error (a large number of upsets in the stream of 10b
words) could be also detected. A burst error sometimes made
it impossible at RX to re-construct the original bit pattern in
the packet, and consequently a drop in the packet resulted.
Therefore any event that was associated with a lost packet
belonged to a sub-set of burst errors. Continuous power-on
testing of test samples made it possible to monitor device bias
current in real-time. This information could be used for
latchup detection. The eye pattern is shown in Fig. 4 for preirradiation sample obtained in 2007. V OD(pp-p) [differential,
peak–to-peak output voltage with low pre-emphasis] is about
1,360 mVp-p. Jitter, which may be a result of a random
variation in timing, etc, may be observed. The differential
output signal rise (tr) and fall (tf) times are less than about 150
picoseconds.
III.
used several sets of devices for this group of tests. We did not
expose the devices with protons with lower energies than 50
MeV. No SEL was detected. The upset cross-sections were
obtained with the serial link of 2.5-Gb/s. Taking the number
of transmitted bits in the system into consideration, we have
calculated BERs for bit-error cross-sections as shown in Fig.
6.
Fig. 5. Proton upset test results for TLK2711 XCVR. Test samples were
obtained in 2007.
RESULTS AND DISCUSSION
A. Proton Induced SEU/SEL Sensitivity
50 MeV protons at LBL as well as higher energy ones at
IUCF were used to measure SEU/SET (single event
upsets/single event transients) and single event latchup
(SEL). Some upsets were made up of a one-bit error (or a
few-bit errors in some cases) in the stream of 10b words as
detected by the BERT (please see Fig. 2.) We call these bit
errors. The other type consisted of events with many upset
bits (often larger than 100 bits, but normally less than about
1000 bits) in the stream of 10b words. We call these burst
errors. Proton induced upsets are shown in Fig. 5. The tests
were carried out with test samples obtained in 2007. Bit error
cross-sections are shown with black diamonds, while burst
error cross-sections are shown with white squares. The crosssections for burst errors were consistently larger than those
for bit errors. It should be noted again that the number of bits
in one burst is numerous. The cross-sections for upsets were
measured while the two test samples (RX and TX) were
irradiated simultaneously (thus, “set” in the vertical axis). We
Fig. 6. Proton induced BER. Test samples were obtained in 2007.
BER often depends on the bit rate with respect to the particle
(e.g., proton) flux. An example of this phenomenon is shown
in Fig. 7 for an ATTDA215B transmitter (silicon bipolar
PECL device for fiber channel communication) operated at 1
Gb/s rate. BERs tend to increase (often drastically) when the
5
transmission rate reaches the critical point with respect to the
particle flux. During data collections we have paid attention
to the existence of micro pulsation of the beam flux. At LBL,
for example, the pulse width is about a few nanoseconds
every several tens of nanoseconds. At flux values close to
what we utilized, the micro pulsation has minimum effect on
our measurements. Test samples obtained earlier (~2005)
showed similar responses to proton irradiations. The SEE
sensitivity is shown in Fig. 8. The number of bit errors was
comparable (within a factor of two) to that of burst errors.
The upset cross-sections were obtained with the serial link of
2.5-Gb/s. Taking the number of transmitted bits in the system
into consideration, we have calculated BERs for bit-error
cross-sections. Relevant BER for these results are shown in
Fig. 9. BER in Fig. 9 seems comparable to that in Fig. 6.
Fig. 9. Proton induced BER. Test samples were obtained in 2005.
B. Heavy Ion Induced SEU/SEL Sensitivity
Heavy ions were used to measure SEU and SEL sensitivity
of the transceiver to these ions available at TAMU and LBL.
As in the protons’ cases, some upsets were made up of a onebit error (or a few-bit errors in some cases) in the stream of
10b words as detected by the BERT (please see Fig. 2.) We
again call these bit errors. The other type consisted of events
with many upset bits (often larger than 100 bits, but normally
less than 1000 bits) in the stream of 10b words. We again call
these burst errors. The number of burst errors consistently
was larger than that of bit errors for each irradiation, as
shown in Fig. 10.
Fig. 7. Proton induced BER for ATTDA215B for various proton flux
values.
Fig. 10. Heavy ion upset test results for TLK2711 XCVR. Test samples
were obtained in 2005.
Fig. 8. Proton upset test results for TLK2711 XCVR. Test samples were
obtained in 2005.
The cross-sections were measured while the two test
samples (RX and TX) were irradiated simultaneously (thus,
“set” in the vertical axis). We used two devices (SN9 and
SN12 obtained in 2005) for this group of tests. No SEL was
6
detected. For SEL tests with these samples the case
temperature was about 60 degrees (Centigrade), while the
fluence was about 1 x 106 particles/cm2 at the LET value of
60 MeV/(mg/cm2). In order to extend SEL testing range, we
plan to test samples obtained in 2007 at higher temperatures
with increased values of fluence. No LOS was detected
during irradiation.
C. Total Ionizing Dose Sensitivity
1) BER vs. TID
TID sensitivity was measured for SN1 (obtained in 2005)
while observing the functionality of the test samples as well
as BER. BER is defined as the ratio of the number of upset
bits to the number of transmitted bits as defined before [8].
We used only non-burst errors for this analysis. (An analysis
that involves burst errors is shown below in section C-2.) The
flux of the 50 MeV proton was about 5.5 rd (Si)/sec. We
applied a 20 krd (Si) of dose, and measured degradation of
the sample before applying additional 20 krd (Si). For each
20 krd (Si) of dose (during which about 3 x 108 packets were
compared), we measured the number of upsets. No upsets
were observed except for the 100 krd (Si) window as shown
in Fig. 11. TID effects were observed when the TID was
between 120 and 140 krd (Si). This was characterized by the
functional degradation of the transceiver as well as eye
pattern measurements. No major bias current change took
place. For another sample obtained in 2007, no measurable
TID effects were detected at 140 krd (Si). At 140 krd (Si), an
eye pattern measurement was taken as shown in Fig. 12.
VOD(pp-p) [differential, peak–to-peak output voltage with
low pre-emphasis] is 1,340 mVp-p. Jitter, which may be a
result of a random variation in timing, etc, may be observed.
The differential output signal rise (tr) and fall (tf) times are
less than 150 picoseconds.
Fig. 11. BER vs. TID for TLK2711 XCVR. Test sample was obtained in
2005.
2) The Number of Dropped Packets vs. TID
TID sensitivity was measured for SN1 obtained in 2005
while observing the number of dropped packets. A burst error
sometimes made it impossible to re-construct the original bit
pattern in the packet, and consequently a drop in the packet
resulted. Therefore any event that was associated with a
dropped packet belonged to a sub-set of burst errors. We used
only burst errors for this analysis. During this run all burst
errors ended up in a dropped packet. (An analysis that
involves non-burst errors is shown above in section C-1.) The
flux of the 50 MeV proton was about 5.5 rd (Si)/sec. For each
20 krd (Si) of dose (during which about 3 x 108 packets were
compared), we measured the number of dropped packets as
shown in Fig. 13. TID effects were observed when the TID
was between 120 and 140 krd (Si). This was characterized by
the functional degradation of the transceiver as well as eye
pattern measurements. No major bias current change took
place.
IV.
CONCLUSION
The Class V TLK2711 devices were tested for single event
effects as well as proton induced total dose effects. Single
event upsets are made up of two types of errors: (1) one-bit
error (or a few-bit errors in some cases) in the stream of 10b
words and (2) a burst of errors with many upset bits in the
stream of 10b words. A burst of errors sometimes made it
impossible to re-construct the original bit pattern in the
packet and consequently a drop in the packet resulted. The
proton induced total dose limit was beyond 100 krd (Si). This
is based on results including (1) functional and (2) eye pattern
measurements. (We have not included parametric test results
with gamma ray irradiation.) These results show that this
device type is less sensitive to SEU effects for both heavy
ions and protons than some device types of the previous
generation (e.g., ATTDA215B). No single event latchup was
detected up to the LET value near 60 MeV/(mg/cm2 ).
Devices such as VSC7216 (fiber optic transceiver) and TI
SN65LVDS95/96 (LVDS SERDES transmitter) have shown
to be SEL immune at this LET range (Sept, 2000 testing with
VSC7216 and May 2007 testing with SN65LVDS95/96)
[9,10]. We plan to test for SEL with TLK2711 beyond this
LET range in the near future. No LOS was detected during
irradiation.
7
Fig. 12. Eye pattern of the TLK2711 1.6Gb/s output after 140 krd (Si) radiation. (200 mV/div and 195 ps/div).
[4]
Hamilton, B.J. and T.L. Turflinger, “Total dose testing of 10-bit low
voltage differential signal (LVDS) serializer and deserializer,” IEEE
REDW, pp177-181, 2001.
[5] TLK2711 (1.6 to 2.7 Gb/s TRANCEIVER), “SLLS501--September
2001,” Texas Instruments, Dallas, Texas.
[6] “TI
radiation
data,”
http://focus.ti.com/pdfs/hirel/space/
RadCharRdmp.pdfC.
[7] Widmer, A.X. and P.A. Franaszek, “A DC-balanced, partitionedblock, 8b/10b transmission code,” The IBM Journal of Research and
Development, 27, pp440-451, 1983.
[8] Marshall, P.W., et al., “Space radiation effects in high performance
fiber optic data links for satellite data management,” IEEE Trans. Nucl.
Sci., 43, pp645-653, 1996.
[9] VSC7216 Low Power 1.25Gb/s Transceiver, “PB-VSC7216-001,”
Vitesse, Camarillo, CA, 2002.
[10] SN65LVDS95-Q1 LVDS SERDES transmitter, “SGLS207A-October
2003,” Texas Instruments, Dallas. TX.
Fig. 13. The number of dropped packets vs. TID for TLK2711 XCVR.
Test sample was obtained in 2005.
V.
[1]
[2]
[3]
REFERENCES
Carts, M.A., et al., “Single event test methodology and test results of
commercial gigabit per second fiber channel hardware,” IEEE Trans.
Nucl., 44, pp1878-1884, 1997.
LaBel, K.A., et al., “Single event effect results for candidate spacecraft
electronics,” IEEE REDW, pp14-21, 1997.
Koga, R., et al., “Comparison of heavy ion and proton-induced single
event effects sensitivities,” IEEE Trans. Nucl. Sci., 49, pp3135-3141,
2002.
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