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FEATURES
Attenuates clock and data jitter present in T1
or CEPT lines
Meets the jitter attenuation templates
outlined in TR62411, TR-TSY-000170,
G.735, and G.742
Only one external component required; either
a 6.176 MHz (T1) or 8.192 MHz (CEPT)
crystal
Selectable buffer size of 128 or 32 bits
Jitter attenuation is easily disabled
Single +5V supply; low-power CMOS
technology
Available in 16-pin DIP and 16-pin SOIC
(DS2188S)
Companion to the DS2186 Transmit Line
and DS2187 Receive Line Interface
PIN ASSIGNMENT
ORDERING INFORMATION
DS2188 16 Pin dip (0ºC-F70ºC)
DS2188S 16 Pin SOIC (0º-+70ºC)
DS2188N 16 Pin dip (-40ºC-+85ºC)
DS2188SN 16 Pin SOIC (-40ºC-+85-ºC)
DESCRIPTION
The DS2188 T1/CEPT Jitter Attenuator Chip contains a 128 X 2-bit buffer which, in conjunction with an
external 4X crystal, is used to attenuate the incoming jitter present in clock and data. The device meets all
of the latest applicable specifications including those outlined in TR 62411 (Accunet* T1.5 Service
Description and Interface Specifications, December 1990), TR-TSY-000170 (Digital Cross-Connect
System Requirements and Objectives, November 1985), and the CCITT Recommendations G.735 and
G.742. The DS2188 is compatible with the DS2180A T1/ISDN Primary Rate Transceiver and DS2181A
CEPT Transceiver and is the companion to the DS2187 T1/CEPT Receive Line Interface and DS2186
T1/CEPT Transmit Line Interface. It can also be used in conjunction with the DS2190 T1 Network
Interface Unit.
OVERVIEW
The RCLK input is fed to a 128 x 2-bit FIFO where it drives the write pointer for the positive (RPOS) and
negative (RNEG) data. The re ad pointer of the FIFO and RRCLK is generated by dividing the frequenc y
of the crystal connected to XTAL1 and XTAL2 by four. The frequency of the crystal is adjusted by a
DPLL to the long-term average frequency of RCLK. As long as the jitter present at RCLK is less than
120 unit intervals peak-to-peak (UIpp), then the FIFO buffer will be able to absorb the incoming jitter and
it will be attenuated in accordance with TR 62411 (December 1990). In this situation, the BL (Buffer
Limit) pin will remain low. Figures 1 and 2 illustrate the DS2188 Jitter Attenuator performance.
If the incoming jitter has excursions greater than 120 U Ipp, then the crystal is adjusted to track the short-
term frequency variations of the incoming signal so that there is no loss of data. This adjustment is
accomplished by dividing the 4X crystal by either 3 ½ or 4 ½ instead of 4. When the incoming jitter is
DS2188
T1/CEPT Jitter Attenuato
r
www.dalsemi.com
DJA 1 16 VDD
RPOS 2 15 RRPOS
RNEG 3 14 RRNEG
RCLK 4 13 RRCLK
BDS 5 12 RST
TEST 6 11 BL
XTAL OUT 7 10 XTAL2
VSS 8 9 XTAL1
DS2188
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greater than 120 UIpp, the BL pin will transition high. When the incoming jitter returns to less than
120 UIpp, the BL pin will return low.
The jitter attenuator in the DS2188 can be disabled by tying the DJA pin high. When the jitter attenuator
is disabled, the FIFO is bypassed and jitter received at RCLK, RPOS and RNEG is passed through the
DS2188 to RRCLK, RRPOS, and RRNEG. In this situation, the BL pin has no significance and XTAL
OUT will not be coherent with RRCLK.
How to use the DS2188 with Dallas Semiconductor’s other T1 and CEPT line interface parts is illustrated
in Figures 3 through 5. Figure 3 illustrates how to use the DS2188 in the receive path along with a
DS2187 Receive Line Interface. Figure 4 illustrates how to use the DS2188 in the transmit path with the
DS2186 Transmit Line Interface.
BUFFER DEPTH SELECT
The buffer size on the DS2188 can be confi gured to either 128 or 32 bits via the BDS pin. If BDS is tied
low, then the buffer depth will be 128 bits and hence can handle input jitter up to 120 UIpp without losing
its full attenuation capabilities as is described above in the Over-view. If BDS is tied high, then the
buffer depth is shortened to 32 bits. In this configuration, the DS2188 can handle input jitter up to
28 UIpp without losing its full jitter attenuation capabilities. The user may wish to limit the buffer size to
32 bits in applications where through-put delay is critical or into existing applications that al-ready have
32 bits of buffer space.
RESET
The buffer on the DS2188 is automatically centered on power-up. The user can recenter the 128-bit (or
32-bit) buffer on demand via the RST pin. The RST pin on the DS2188 is negative-edge tri ggered. When
this pin transitions from high-to-low, the buffer is recentered. The RST pin can be held either high or low
during operation of the DS2188; only a negative going signal will initiate a recentering. In most cases, a
reset of the DS2188 will corrupt data that is currently passing through the buffer.
DS2188 TI JITTER ATTENUATION PERFORMANCE Figure 1
DS2188
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DS2188 CEPT JITTER ATTENUATION PERFORMANCE Figure 2
DS2188 IN THE RECEIVE PATH Figure 3
DS2188 IN THE TRANSMIT PATH Figure 4
DS2188
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PIN DESCRIPTION Table 1
PIN SYMBOL TYPE DESCRIPTION
1DJA I
Disable Jitter Attenuation. When high, jittered data and clock at RPOS,
RNEG, and RCLK are passed directly to RRPOS, RRNEG, and RRCLK.
2RPOS I
Receive Positive Data Input. Jittered data input. Sampled on the falling
edge of RCLK.
3RNEG IReceive Negative Data Input. Jittered data input. Sampled on the falling
edge of RCLK.
4 RCLK I Receive Clock Input. Jittered input 1.544 MHz or 2.048 MHz clock.
5BDS I
Buffer Depth Select.
0 = 128 bits
1 = 32 bits
6 TEST I Test Input. In normal applications, this pin should be tied low.
When tied high, used to verify free running frequency of XTAL.
7XTAL
OUT OCrystal Frequency Output. Buffered output of the 4X crystal connected
to XTAL1 and XTAL2.
8V
SS -Ground. 0.0V
9
10 XTAL1
XTAL2 I
OCrystal Connections. In T1 environments, connect a 6.176 MHz crystal
to these pins. In CEPT environments, connect an 8.192 MHz crystal to
these pins.
11 BL O Buffer Limit. Transitions high when the buffer fills or empties to within
either 4 bits (BDS=0) or 2 bits (BDS=1) of its capacity. Indicates that the
jitter at RCLK is greater than 120 UIpp (BDS=0) or 28 UIpp (BDS=1).
12 RST IReset. Negative-edge triggered; a high-low transition will recenter the
buffer. Activation of this pin may corrupt data through the DS2188.
13 RRCLK O Receive Reference Clock. Dejittered 1.544 MHz or 2.048 MHz clock.
14 RRNEG O Receive Reference Negative Data Output. Dejittered data output.
Updated on the rising edge of RRCLK.
15 RRPOS O Receive Reference Positive Data Outpu t. Dejittered data output.
Updated on the rising edge of RRCLK.
16 VDD -Positive Supply. 5.0V
CRYSTAL REQUIREMENTS
The DS2188 must have a crystal connected to the XTAL1 and XTAL2 pins. For T1 environments, the
frequency of this crystal should be 6.176 MHz. For CEPT environments, the frequency of this crystal
should be 8.192 MHz. Table 2 lists some suggested crystal manufacturers that are recommended for use
with the DS2188. Also, see DS2188 Application Note, “Operation at Speeds Greater than E1” for
additional information.
CRYSTAL M ANUFACTURERS Table 2
MANUFACTURER PART # FREQUENCY
JAN Crystal 6323-00, JC6A14
6323-00, JC8A14 6.176 MHz
8.192 MHz
M-TRON 4575-002
4575-001 6.176 MHz
8.192 MHz
DS2188
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CRYSTAL SELECTION GUIDELINES FOR THE DS2188
PARAMETER SPECIFICATION
Parallel resonant frequency 6.176 MHz (T1) or 8.192 MHz (CEPT)
Mode Fundamental
Load capacitance 14 to 20 pF (16 pF preferred)
Tolerance ±50 ppm over 0 to 70°C
Pullability CL = 10 pF, delta_f = +175 to +250 ppm
CL = 45 pF, delta_f = -175 to -250 ppm
Effective series resistance 40 ohms maximum for 6.176 MHz
30 ohms maximum for 8.192 MHz
Crystal cut AT
DS2188
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ABSOLUTE MAXIMUM RA TINGS*
Voltage on Any Pin Relative to Ground -0.1V to +7.0V
Operating Temperature 0° to 70°C
Storage Temperature -55°C to +125°C
Soldering Temperature See J-STD-020A Specification
* This is a stress rating only and functional operation of the d evice at these or an y other conditions abov e
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS Commercial (0°C to 70°C)
Industrial (-40ºC to 85º C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Logic 1 VIH 2.0 VCC+0.3 V 1
Input Logic 0 VIL -0.3 +0.8 V 1
Supply VDD 4.50 5.50 V
NOTE:
1. Does not apply to XTAL1.
CAPACITANCE (tA=25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Capacitance CIN 5pF
Output COUT 10 pF
DC ELECTRICAL CHARACTERISTICS
Commercial (0°C to 70°C; VDD = 5.0V ± 10%)
Industrial (-40ºC to 85ºC)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Current IDD 712mA 1
Input Leakage IL-1.0 +1.0 µA 2, 3
Output Current (2.4V) IOH -1.0 mA 3
Output Current (0.4V) IOL +4.0 mA 3
NOTES:
1. RCLK = 1.544 MHz; VDD = 5.50; outputs open.
2. VSS < VIN < VDD: XTAL1 = XTAL2 = VDD.
3. Does not apply to XTAL1 or XTAL2.
DS2188
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AC E LEC TRICAL CHARACTER ISTIC S
Commercial (0°C to 70°C; VDD = 5.0V ± 0%)
Industrial (-40ºC to 85ºC)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
RCLK Period -200 +200 ppm 1
RCLK Pulse Width 100 ns
RCLK Rise and Fall Times 50 ns
RPOS, RNEG Setup to RCLK 50 ns
RPOS, RNEG Hold for
RCLK 50 ns
Propagation delay from
RRCLK to RPOS, RRNEG
Valid
50 ns
Propagation delay from
XTAL OUT to RRCLK 50 ns 2
RST Pulse Width 1µA
NOTES:
1. The average period of RCLK must be within Ù200 ppm of the fundamental frequency of the crystal
divided by four.
2. Only valid when the incoming jitter is less than 120 Ulpp (BDS=0) or 28 Ulpp (BDS=1).
DS2188
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AC TIMING DIAGRAM Figure 5
NOTE:
1. The phase relationship between XTAL OUT and RRCLK can be of either form.
DS2188
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DS1288 T1/CEPT JITTER ATTENTUATOR 16-PIN DIP
PKG 16-PIN
DIM MIN MAX
AIN
MM 0.740
18.80 0.780
19.81
B IN
MM 0.240
6.10 0.260
6.60
C IN
MM 0.120
3.05 0.140
3.56
D IN
MM 0.300
7.62 0.325
8.26
E IN
MM 0.015
0.38 0.040
1.02
F IN
MM 0.120
3.04 0.140
1.02
G IN
MM 0.090
2.29 0.110
2.79
H IN
MM 0.320
8.13 0.370
9.40
J IN
MM 0.008
0.20 0.012
0.30
K IN
MM 0.015
0.38 0.021
0.53
DS2188
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DS1288S T1/CEPT JITTER ATTENTUATOR 16-PIN SOIC
PKG 16-PIN
DIM MIN MAX
AIN
MM 0.402
10.21 0.412
10.46
B IN
MM 0.290
7.37 0.300
7.65
C IN
MM 0.089
2.26 0.095
2.41
E IN
MM 0.004
0.102 0.012
0.30
F IN
MM 0.094
2.38 0.105
2.68
G IN
MM 0.050 BSC
1.27 BSC
H IN
MM 0.398
10.11 0.416
10.57
J IN
MM 0.009
0.229 0.013
0.33
K IN
MM 0.013
0.33 0.019
0.48
L IN
MM 0.016
0.40 0.40
1.02
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