XRT5897 [EXAR]
Seven-Channel E1 Line Interface; 七路E1线路接口
| 型号： | XRT5897 |
| 厂家： | 
EXAR CORPORATION |
| 描述： | Seven-Channel E1 Line Interface |
| 文件： | 总21页 (文件大小：609K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
XRT5897
Seven-Channel E1
Line Interface
December 2001-3
FEATURES
D Compliant with ITU G.703 Pulse Mask Template for
D Compliant with ITU--T G.823 Jitter Tolerance Re-
2.048Mbps (E1) Rates
quirements
D Logical Inputs Accept either 3.3V or 5.0V Levels
D Ultra-Low Power Dissipation
D Seven Independent CEPT Transceivers
D Supports Differential Transformer Coupled
Receivers and Transmitters
D +3.3V Supply Operation
D Individual Transmit Channel Over Temperature
D On Chip Pulse Shaping for Both 75Ω and 120Ω Line
Protection
Drivers
D Compliant with ITU G.775 LOS Declaration/Clearing
APPLICATIONS
Recommendation
D SDH Multiplexer
D Optional User Selectable LOS Declaration/Clearing
Delay
D Digital Cross Connects
GENERAL DESCRIPTION
The XRT5897 is an optimized seven channel 3.3V line
interface unit fabricated using low power CMOS
technology. The device contains seven independent E1
channels. It is primarily targeted toward SDH multiplexers
that accommodate TU12 Tributary Unit Frames. Line
cards in these units multiplex 21 E1 interfaces into higher
SDH rates. Devices with seven E1 interfaces such as the
XRT5897 provide the most efficient method of
implementing 21 channel line cards. Each channel
performs the driver and receiver functions necessary to
convert bipolar signals to logical levels and vice versa.
The device requires transformers on both receiver and
transmitter sides, and supports both balanced and
unbalanced interfaces.
The device offers two distinct modes of LOS detection.
The first method, which does not require an external
clock, provides an LOS output indication signal with
thresholds and delay that comply with the ITU G.775
requirements. In the second mode, the user provides an
external clock that increases the delay for LOS
declaration and clearing. This feature provides the user
with the flexibility to implement LOS specifications that
require a delay greater than the G.775 requirements.
ORDERING INFORMATION
Operating
Part No.
Package
100 Lead TQFP (14 x 14 x 1.4mm)
Temperature Range
XRT5897IV
-40°C to +75°C
Rev. 1.11
E2001
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 z (510) 668-7000 z FAX (510) 668-7017
XRT5897
BLOCK DIAGRAM
Tranceiver 1
Tranceiver 2
Tranceiver 3
Tranceiver 4
Tranceiver 5
Tranceiver 6
Tranceiver 7
RTIP7 (69)
RXPOS7 (5)
1:2
R1
R2
Singnal
Receive
Comparators
RXNEG7 (6)
TIP
RX INPUT
RING
Peak
Detector
RRING7 (68)
V
CC
1
LOS7 (4)
MUX
O
LOS
Detect
Loss
Delay
LOSCNT (73)
LOSSEL (38)
Counter
Transmit
Line
Drivers
Duty
Cycle
Adjust
TXCLK7 (87)
TXPOS7 (85)
TXNEG7 (86)
R3
9.1
R4
NRZ
To
TTIP7 (89)
0
0
2:1
TIP
TX OUTPUT
RING
RZ
Pulse
MUX
Shaping
TRING7 (91)
1
1
9.1
Figure 1. XRT5897 Block Diagram
Receiver Notes
D The same type 1:2CT ratio transformer may be
D LOSCNT (pin 73) is unconnected when LOSSEL is
logic 1, or connected to an external clock when
LOSSEL is logic 0.
used at the receiver input and transmitter output.
D R1 and R2 are both 150Ω for 75Ω operation, or
240Ω for 120Ω operation.
Transmitter Notes
D Return loss exceeds ITU G.703 specification with
D Return loss exceeds ETSI 300 166 specification
these resistors and a 1:2CT ratio input transformer.
with a 1:2 ratio transformer.
D R3 and R4 are always 9.1Ω for both 75Ω and 120Ω
applications.
LOS (Loss of Signal) Notes
D An approach exists that permits the user to operate
the XRT5897 with a 5V power supply. For more
information, please see application note TAN-12.
D LOSSEL (pin 38) is connected to logic “1” for ITU
G.775 compliant LOS delay, or to logic 0 for user
programmable additional delay.
Rev. 1.11
2
XRT5897
PIN CONFIGURATION
51
75
LOS6
50
TXNEG4
TXPOS4
LOS4
76
TXPOS6
TXNEG6
TXCLK6
RXPOS4
RXNEG4
TXPOS5
TXNEG5
TXCLK5
RXNEG5
RXPOS5
LOS5
GND
TTIP6
V
CC
TRING6
GND
TXPOS7
TXNEG7
TXCLK7
GND
GND
LOSSEL
TTIP7
V
CC
V
CC
LOS2
TRING7
RXPOS2
RXNEG2
TXCLK2
TXNEG2
TXPOS2
RXNEG3
RXPOS3
LOS3
GND
TRING1
V
CC
TTIP1
GND
TXCLK1
TXNEG1
TXPOS1
LOS1
TXPOS3
TXNEG3
100
26
1
25
100 LEAD THIN QUAD FLAT PACK
(14 x 14 x 1.4 mm, TQFP)
Rev. 1.11
3
XRT5897
PIN DESCRIPTION
Pin #
1
Symbol
RXPOS1
RXNEG1
VCC
Type Description
O
O
Receiver 1 Positive Data Out. Positive RZ data output for channel 1.
2
Receiver 1 Negative Data Out. Negative RZ data output for channel 1.
Positive Supply (+3.3V + 5%). Digital circuitry.
3
4
LOS7
O
O
O
I
Receiver 7 Loss of Signal. Asserted during LOS condition.
Receiver 7 positive Data Out. Positive RZ data output for channel 7.
Receiver 7 Negative Data Out. Negative RZ data output for channel 7.
Receiver 1 Positive Bipolar Input.
5
RXPOS7
RXNEG7
RTIP1
6
7
8
RRING1
VCC
I
Receiver 1 Negative Bipolar Input.
9
Positive Supply (+3.3V + 5%). Analog circuitry.
Analog Ground.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
GND
VCC
Positive Supply (+3.3V + 5%). Receivers 1, 2, 3, and 7.
Receiver 2 Negative Bipolar Input.
RRING2
RTIP2
I
I
Receiver 2 Positive Bipolar Input.
GND
Analog Ground. Receivers 1, 2, 3, and 7.
TTIP2
O
O
O
O
Transmitter 2 Positive Bipolar Output.
VCC
Positive Supply (+3.3V + 5%). Transmitter channel 2.
Transmitter 2 Negative Bipolar Output.
TRING2
GND
Digital Ground. Transmitter channel 2.
TRING3
VCC
Transmitter 3 Negative Bipolar Output.
Positive Supply (+3.3V + 5%). Transmitter channel 3.
Transmitter 3 Positive Bipolar Output.
TTIP3
GND
Digital Ground. Transmitter channel 3.
RTIP3
I
I
Receiver 3 Positive Bipolar Input.
RRING3
TXCLK3
TXNEG3
TXPOS3
LOS3
Receiver 3 Negative Bipolar Input.
I
Transmitter 3 Clock Input. Use for clocked mode with NRZ data.1
Transmitter 3 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 3 Positive Data Input. Positive NRZ or RZ data input.1
Receiver 3 Loss of Signal. Asserted during LOS condition.
Receiver 3 Positive Data Out. Positive RZ data output for channel 3.
Receiver 3 Negative Data Out. Negative RZ data output for channel 3.
Transmitter 2 Positive Data Input. Positive NRZ or RZ data input.1
Transmitter 2 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 2 Clock Input. Use for clocked mode with NRZ data.1
Receiver 2 Negative Data Out. Negative RZ data output for channel 2.
Receiver 2 Positive Data Out. Positive RZ data output for channel 2.
I
I
O
O
O
I
RXPOS3
RXNEG3
TXPOS2
TXNEG2
TXCLK2
RXNEG2
RXPOS2
I
I
O
O
Note:
1
Has internal pull-up 50KΩ resistor.
Rev. 1.11
4
XRT5897
PIN DESCRIPTION (CONT’D)
Pin #
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
Symbol
LOS2
Type Description
O
Receiver 2 Loss of Signal. Asserted during LOS condition.
Digital Supply (+3.3V + 5%). Digital circuitry.
VCC
LOSSEL
GND
I
Loss of Signal Delay Select. “Hi” selects G.775, “Lo” selects user programmable.1
Digital Ground.
LOS5
O
O
O
I
Receiver 5 Loss of Signal. Asserted during LOS condition.
Receiver 5 Positive Data Out. Positive RZ data output for channel 5.
Receiver 5 Negative Data Out. Negative RZ data output for channel 5.
Transmitter 5 Clock Input. Use for clocked mode with NRZ data.1
Transmitter 5 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 5 Positive Data Input. Positive NRZ or RZ data input.1
Receiver 4 Negative Data Out. Negative RZ data output for channel 4.
Receiver 4 Positive Data Out. Positive RZ data output for channel 4.
Receiver 4 Loss of Signal. Asserted during LOS condition.
Transmitter 4 Positive Data Input. Positive NRZ or RZ data input.1
Transmitter 4 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 4 Clock Input. Use for clocked mode with NRZ data.1
Receiver 4 Negative Bipolar Input.
RXPOS5
RXNEG5
TXCLK5
TXNEG5
TXPOS5
RXNEG4
RXPOS4
LOS4
I
I
O
O
O
I
TXPOS4
TXNEG4
TXCLK4
RRING4
RTIP4
GND
I
I
I
I
Receiver 4 Positive Bipolar Input.
Analog Ground.
TTIP4
O
O
O
O
Transmitter 4 Positive Bipolar Output.
VCC
Positive Supply (+3.3V + 5%). Transmitter channel 4.
Transmitter 4 Negative Bipolar Output.
TRING4
GND
Digital Ground. Transmitter channel 4.
TRING5
VCC
Transmitter 5 Negative Bipolar Output.
Positive Supply (+3.3V + 5%). Transmitter channel 5.
Transmitter 5 Positive Bipolar Output.
TTIP5
GND
Digital Ground. Transmitter channel 5.
RTIP5
RRING5
VCC
I
I
Receiver 5 Positive Bipolar Input.
Receiver 5 Negative Bipolar Input.
Positive Supply (+3.3V + 5%). Low level transmitter analog circuitry.
Analog Ground. Low level transmitter analog circuitry.
Positive Supply (+3.3V + 5%). Receiver channels 4, 5, and 6.
Receiver 7 Negative Bipolar Input.
GND
VCC
RRING7
RTIP7
RRING6
I
I
I
Receiver 7 Positive Bipolar Input.
Receiver 6 Negative Bipolar Input.
Note:
1
Has internal pull-up 50KΩ resistor.
Rev. 1.11
5
XRT5897
PIN DESCRIPTION (CONT’D)
Pin #
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Symbol
RTIP6
Type Description
I
Receiver 6 Positive Bipolar Input.
GND
Analog Ground. Receiver channels 4, 5, and 6.
LOSCNT
RXNEG6
RXPOS6
LOS6
I
O
O
O
I
Loss of Signal Timing Clock Input. For user-programmable LOS delay.1
Receiver 6 Negative Data Out. Negative RZ data output for channel 6.
Receiver 6 Positive Data Out. Positive RZ data output for channel 6.
Receiver 6 Loss of Signal. Asserted during LOS condition.
Transmitter 6 Positive Data Input. Positive NRZ or RZ data input.1
Transmitter 6 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 6 Clock Input. Use for clocked mode with NRZ data.1
Digital Ground. Transmitter channel 6.
TXPOS6
TXNEG6
TXCLK6
GND
I
I
TTIP6
O
O
Transmitter 6 Positive Bipolar Output.
VCC
Positive Supply (+3.3V + 5%). Transmitter channel 6.
Transmitter 6 Negative Bipolar Output.
TRING6
GND
Digital Ground.
TXPOS7
TXNEG7
TXCLK7
GND
I
I
I
Transmitter 7 Positive Data Input. Positive NRZ or RZ data input.1
Transmitter 7 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 7 Clock Input. Use for clocked mode with NRZ data.1
Analog Ground.
TTIP7
O
O
O
O
Transmitter 7 Positive Bipolar Output.
VCC
Positive Supply (+3.3V + 5%). Transmitter channel 7.
Transmitter 7 Negative Bipolar Output.
TRING7
GND
Digital Ground. Transmitter channel 7.
TRING1
VCC
Transmitter 1 Negative Bipolar Output.
Positive Supply (+3.3V + 5%). Transmitter channel 1.
Transmitter 1 Positive Bipolar Output.
TTIP1
GND
Digital Ground. Transmitter channel 1.
TXCLK1
TXNEG1
TXPOS1
LOS1
I
I
Transmitter 1 Clock Input. Use for clocked mode with NRZ data.1
Transmitter 1 Negative Data Input. Negative NRZ or RZ data input.1
Transmitter 1 Positive Data Input. Positive NRZ or RZ data input.1
Receiver 1 Loss of Signal. Asserted during LOS condition.
I
O
Note:
1
Has internal pull-up 50KΩ resistor.
Rev. 1.11
6
XRT5897
ELECTRICAL CHARACTERISTICS
Test Conditions: V = 3.3V + 5%, T = -40 to 25 to 75°C, Unless Otherwise Specified
CC
A
Symbol
Parameter
Min.
Typ.
Max.
Unit
Conditions
DC Electrical Characteristics
Parameters
VCC
Inputs
Voltage Supply
3.135
2.0
3.3
3.465
V
3.3V operation
VIH
VIL
Input High Level
Input Low Level
5.0
0.8
V
V
Outputs
VOH
Output High Level
Output Low Level
2.4
0
V
V
IOH = -4mA
IOL = 4mA
VOL
0.4
12
Receiver Specifications
RXCL
Allowable Cable Loss
dB
Cable loss at 1.024MHz (Relative
to 0dB = 2.37Vp measured from
RTIP or RRING to ground).
RXIM
RXXI
Interference Margin
-15
-12
50
dB
%
With 6dB cable loss
Receiver Slicing Threshold
45
55
% of peak input voltage at -3dB
cable loss
RXLOSSET LOS Must Be Set If RX Sig.
Atten. ² 32dB (For Any Valid
Data Pattern)
15
13
2
dB
dB
Relative to 0dB = 2.37Vp
Measured from RTIP or RRING to
ground.
RXLOSCLR LOS Must Be Cleared If RX Sig.
Atten. < 9dB
Relative to 0dB = 2.37Vp
measured from RTIP or RRING to
ground.
RXLOSHYST Hysteresis on Input Data
dB
For LOS output state change
RXIN
Input Impedance
5
kΩ
Up to 3.072MHz (Measured from
RTIP or RRING to ground).
Jitter Tolerance:
20Hz
10
5
UIpp
UIpp
UIpp
700Hz
10kHz -- 100kHz
Return Loss:
0.3
51khz -- 102kHz
102kHz -- 2048kHz
2048kHz -- 3072kHz
14
20
16
dB
dB
dB
Per ITU--T G.703
Power Specifications VCC = 3.3V
PD
Power Dissipation
715
920
mW
All 1’s Transmit and Receive 75Ω
PD
PC
PC
Power Dissipation
117
1260
880
155
1465
1065
mW
mW
mW
All Drivers Power Down
Power Consumption 75Ω
Power Consumption 75Ω
All 1’s Transmit and Receive
50% data density, Transmit and Re-
ceive
Rev. 1.11
7
XRT5897
PC
PC
Power Consumption 120Ω
Power Consumption 120Ω
1025
745
1255
945
mW
mW
All 1’s Transmit and Receive
50% data density, Transmit and Re-
ceive
Note:
Bold face parameters are covered by production test and guaranteed over operating temperature range.
Rev. 1.11
8
XRT5897
ELECTRICAL CHARACTERISTICS (CONT’D)
Test Conditions: V = 3.3V + 5%, T = -40 to 25 to 75°C, Unless Otherwise Specified
CC
A
Symbol
Parameter
Min.
Typ.
Max.
Unit
Conditions
AC Electrical Characteristics
VTXOUT
Output Pulse Amplitude
2.13
2.70
224
2.37
3.0
2.60
3.30
264
V
V
Trans. = 1:2 ratio, 9.1Ω in series
(RL = 75Ω)
with each end of primary
VTXOUT
Output Pulse Amplitude
(RL = 120Ω)
Trans. = 1:2 ratio, 9.1Ω in series
with each end of primary
TXPW
PNIMP
T1
Output Pulse Width
244
5
ns
%
Pos/Neg Pulse Unbalanced
TXCLK Clock Period (E1)
TXCLK Duty Cycle
488
50
ns
%
T2
30
75
70
TSU
Data Set-up Time, TDATA to
TXCLK
ns
50% TXCLK Duty Cycle
50% TXCLK Duty Cycle
THO
Data Hold Time, TDATA to
TXCLK
30
ns
TR
TF
TXCLK Rise Time (10% to 90%)
TXCLK Fall Time (10% to 90%)
40
40
35
ns
ns
ns
T3-noclk
Data Prop. Delay No-Clock
Mode
50
T3-clk
T4
Data Prop. Delay Clock Mode
Receive Data High
470
244
ns
ns
ns
ns
ns
50% TXCLK Duty Cycle
0dB Cable Loss
15pF Load
219
269
40
T5
RX Data Prop. Delay
Receive Rise Time
T6
40
15pF Load
T7
Receive Rise Time
40
15pF Load
Note:
Bold face parameters are covered by production test and guaranteed over operating temperature range.
ABSOLUTE MAXIMUM RATINGS
Storage Temperature . . . . . . . . . . . . -65°C to +150°C
Operating Temperature . . . . . . . . . . -40°C to +75°C
Supply Voltage . . . . . . . . . . . . . . . . . . +0.3V to +6.0V
Rev. 1.11
9
XRT5897
Disabling Output Drivers
Output drivers may be individually disabled (hi-z output) by either of the following methods.
1. Either connect the transmit data inputs TXPOS
and TXNEG for the channel to be disabled to a log-
2. Connect TXCLK for the channel to be disabled to
logic 0 source (Ground), and also apply data to the
TXPOS and TXNEG inputs of that channel.
ic 1 source (V ), or allow them to float (inputs
CC
have internal pull--up resistors).
TRANSFORMER REQUIREMENTS
Turns Ratio
Line Impedance
Turns Ratio
Line Impedance
1:2 CT
75Ω or 120Ω
1:2
75Ω or 120Ω
Table 1. Input Transformer Requirements
Table 2. Output Transformer Requirements
Note:
The same type 1:2 CT ratio device may be used at both receiver input and transmitter output.
The following transformers have been tested with the XRT5897:
HALO type TG26-1205(package contains two 1 CT:2 CT ratio transformers)
Pulse type PE-65535 (1:2 CT ratio)
Transpower Technologies type TTI 7154-R (1:2 CT ratio)
Magnetic Supplier Information:
HALO Electronics, Inc.
P.O. Box 5826
Redwood City, CA 94063
Tel. (415) 568-5800
Fax. (415)568-6161
Pulse
Telecom Product Group
P.O. Box 12235
San Diego, CA 92112
Tel. (619) 674-8100
Fax. (619) 674-8262
Transpower Technologies, Inc.
24 Highway 28, Suite 202
Crystal Bay, NV 89402--0187
Tel. (702) 831--0140
Fax. (702) 831--3521
Rev. 1.11
10
XRT5897
TSU THO
TXPOS (n)
TSU THO
TXNEG (n)
TXCLK (n)
TXOUT (n)
T1
T2
TR
TF
TXPW
T3
T3
VTXOUT
VTXOUT
TXPW
Figure 2. Transmit Timing Diagram
RXIN (n)
T5
T4
T6
T7
RPOS (n)
T5
T6
T7
T4
RXNEG (n)
Figure 3. Receive Timing Diagram
Rev. 1.11
11
XRT5897
RETURN LOSS SPECIFICATIONS
The following transmitter and receiver return loss specifications are based on a typical 1:2CT ratio transformer.
75Ω
120Ω
Frequency Range
51kHz to 102kHz
Min.
16
Typ.
22
Min.
10
Typ.
15
Unit
dB
102kHz to 2.048MHz
2.048MHz to 3.072MHz
16
22
10
15
dB
11
18
10
14
dB
Table 3. Transmitter Return Loss Specification
Transmit Return Loss Notes
D Output transformer ratio is 1:2 (return loss exceeds
D For both 75Ω and 120Ω applications, 9.1Ω, 1% re-
sistors are connected between each end of the
transformer primary and the XRT5897 TTIP and
TRING pins.
ETSI 300 166 with this transformer).
75Ω
120Ω
Frequency Range
51kHz to 102kHz
Min.
16
Typ.
28
Min.
15
Typ.
18
Unit
dB
102kHz to 2.048MHz
2.048MHz to 3.072MHz
22
34
22
25
dB
18
26
20
30
dB
Table 4. Receiver Return Loss Specification
Receiver Return Loss Notes
D Input transformer ratio is 1:2 CT.
D Each half of transformer secondary is terminated
with 150Ω for 75Ω operation, or 240Ω for 120Ω op-
eration (resistors are 1% tolerance).
D Transformer center tap is grounded.
Rev. 1.11
12
XRT5897
SYSTEM DESCRIPTION
This device is a seven channel E1 transceiver that
provides an electrical interface for 2.048Mbps
applications. Its unique architecture includes seven
receiver circuits that convert ITU G.703 compliant bipolar
signals to TTL compatible logic levels. Each receiver
includes a LOS (Loss of Signal) detection circuit that may
be configured for either a fixed or a user-programmable
LOS response time delay. Similarly, in the transmit
direction, seven transmitters convert TTL compatible
logic levels to G.703 compatible bipolar signals. Each
transmitter may be operated either with RZ, or NRZ data
types. In NRZ mode a transmit clock is required as well.
The following description applies to any of the seven
receivers or transmitters contained in the XRT5897.
Therefore, the suffix numbers for a particular channel are
deleted for simplicity. i.e. “RTIP” applies to RTIP1 through
RTIP7.
compliance with ITU G.775 specification. When LOSSEL
is connected to logic “0”, the user-programmable delay
mode is enabled. In this mode the user has the option of
extending the delay of LOS declaration and clearing
specified in the ITU G.775. This is done by providing a
user-supplied clock to LOSCNT (pin 73). The “user
programmable mode” is provisioned to allow systems
designers to comply with older versions of LOS
specifications in legacy systems. It needs to be stressed
that the delay for declaration and clearing of the LOS
condition will never be less than the range specified in the
G.775 specification (10-255 pulse intervals).
The LOS detection/clearing circuitry of the XRT5897 in
“automatic” mode will detect LOS when the incoming
signalhas “no transitions,” i.e. when the signal levelis less
than or equal to a signal level A dB below nominal signal
D
level, for N consecutive pulse intervals, where 10<N<255.
The value of A
can vary between 10dB to 32dB
D
Receiver Operation
depending on the ones density of the incoming signal
assuming the received data has minimum permissible
ones density. Furthermore LOS detect is cleared when
the incoming signal has “transitions,” i.e. when the signal
level is greater than or equal to a signal level of A dB
below nominal, for N consecutive pulse intervals, where
A bipolar signal is transformer-coupled to the receiver
differential inputs (RTIP and RRING). The receiver is able
to tolerate up to 12dB of line loss measured at 1.024MHz.
It contains slicing circuitry that automatically samples the
incoming data at a fixed percentage (50% nominal) of the
peak signal amplitude. A precision peak detector
maintains the slicing level accuracy. The TTL compatible
receiver output data rails appear at the RXPOS and
RXNEG pins. The pulse width of this data; which is in RZ
format, is a function of the amount of the cable loss
present.
C
10<N<255. The value of A can vary between 9dB to
C
31dB depending on the ones density of the incoming
signal assuming the received data has minimum
permissible ones density. Each pulse interval is 488ns at
E1 rates. The absolute value of A is always smaller than
A by at least 1dB.
D
C
The LOS detection/clearing criteria described above is
fully compliant with G.775 LOS specification. In the “user
programmable” mode the user has the option of
extending the declaration and clearing delay (10<N<255)
by an amount which is equal to 2048 x T. T is the time
period of the clock supplied to LOSCNT (pin 73) by the
user.
Receiver Loss Of Signal Detection (LOS)
Absence of signal at any receiver input is detected by the
loss of signal (LOS) circuit. One LOS detection circuitry is
provisioned for each receiver. The LOS signal is asserted
(LOS=1) when a LOS condition is detected and is cleared
(LOS=0) when a valid input signal is restored.
Nominal signal level is defined as 2.37V peak measured
between RTIP or RRING and ground. (This voltage will
be present in 75Ω applications using a 1:2 CT ratio input
transformer terminated in 300Ω with the center tap
grounded with 0dB of cable and a 2.37V peak amplitude
transmit pulse at the cable input.)
Two modes of LOS circuit operation are supported.
These distinct modes are called “automatic” and
“user-programmable”. When LOSSEL (pin 38) is set to
logic “1”, the automatic mode is selected. In this mode the
LOS condition will be declared and cleared in full
Rev. 1.11
13
XRT5897
Transmitters
This device contains four identical ITU G.703 compliant
transmitters. The output stage of each transmitter is a
differential voltage driver. External resistors need to be
connected to the primary of output transformer. This is
necessary to maintain an accurate source impedance
that ensures compliance to ETSI 300 166 return loss
requirement.
modes of operation referred to as “clocked” or “clockless”
modes. The operational mode is selected automatically
based on the signal provided to TXCLK input. If a clock is
present at this pin, the transmitter detects its presence
and operates in the clocked mode. In this mode, the
transmit input should be supplied with full-width NRZ
pulses. If a clock is not present at the TXCLK input (pin is
left open), the part operates in the clockless mode. In this
mode, RZ data should be supplied to the device. Each
transmit channel of XRT5897 has a duty cycle correction
circuitry. This enables the device to produce output
bipolar pulses fully compliant with G.703 despite having
TXCLK signal with 30% to 70% duty cycle.
TTL compatible dual rail transmit data signals are
supplied to TXPOS and TXNEG inputs. The transmitter
differential outputs TTIP and TRING are connected to the
output transformer primary through series 9.1Ω resistors.
All the four transmitters can be operated in two distinct
269 ns
(244 + 25)
Nominal pulse
20%
10%
V = 100%
194 ns
(244 -- 50)
10%
20%
50%
244 ns
219 ns
(244 -- 25)
10%
0%
10%
10%
10%
20%
488 ns
(244 + 244)
Note: V corresponds to the nominal peak value
Figure 4. CCITT G.703 Pulse Template
Rev. 1.11
14
XRT5897
Transmitter Output Pulse Measurement
Figure 1 shows a typical transmit pulse plotted on the template shown in ITU G.703 Figure 15/G.703. The following
conditions apply:
V =3.30V
CC
Transmitter output transformer secondary terminated with 120Ω.
All ones signal.
Receiver output looped backed into transmitter digital input.
Operation without transmitter clock (RZ data).
Measurement made with a Tektronix TDS640 digital scope set to full bandwidth.
1.2
1.0
0.8
0.6
0.4
0.2
0
-0.2
-244
-122
0
122
244
Time (ns)
Figure 5. XRT5897 Output Pulse
Rev. 1.11
15
XRT5897
Transmitter Output Return Loss Measurements
The following measurements were made with a Wandel
and Goltermann SNA--2 Network Analyzer equipped with
an RFZ--1 75Ω Return Loss Bridge. A 75Ω to 120Ω
impedance matching transformer was used to make the
120Ω measurement. A network analyzer calibration run
subtracted out the effects of this transformer.
This configuration was used for both 75Ω and 120Ω
measurements. The only change was the termination
resistance provided by the return loss bridge.
Test Results:
Table 5 compares measured output return loss with
requirements in ETSI FINAL DRAFT prETS 300 166,
June 1993. These results show that measured return loss
is mainly determined by the characteristics of the output
transformer. This is particularly evident for the 120Ω load
where the measured result is better than the calculated
value.
Test Conditions:
D Output transformer ratio was 1:2.
D Transmitter series resistors (R3 and R4 in Figure 1)
were 9.1Ω.
D Device was powered from a 3.3V source, transmitter
was enabled, and no output data was present.
Specified
Frequency
Frequency
(KHz)
ETSI Spec.
(Min. dB)
Meas. Value (dB)
Meas. Value (dB)
75Ω Load
120Ω Load
0.025 fb
0.05 fb
1.5 fb
51.2
102.4
3072
6
8
8
22.6
22.6
18.0
15.4
15.7
14.6
Table 5. Transmitter Output Return Loss Measurements
Notes:
fb = 2048KHz
This data shows that the XRT5897 is fully compliant with the ETSI Output Return Loss Specification for E1 operation with either
75Ω or 120Ω loads.
Rev. 1.11
16
XRT5897
The following pictures show typical results of measurements that made over a 50 KHz to 3.5MHz frequency range.
Figure 6. 75Ω Return Loss Measurement
Figure 6, shows a return loss better than 20dB at low frequencies that decreases to about 12dB at 3.5MHz. Since the
source and load resistances are well--matched, the return loss degradation is due to the transformer.
Figure 7. 120Ω Return Loss Measurement
Figure 7, shows that for the 120Ω case, transformer characteristics improve return loss at lower frequencies. At 3.5
MHz, return loss is close to the calculated 13.8dB for a 75Ω source terminated with 120Ω.
Rev. 1.11
17
XRT5897
Output Transformer Selection
A 1:2 ratio transformer is recommended for both 75Ω and 120Ω operation because the transmitter, when equipped with
this device, meets both the ITU G.703 output pulse amplitude requirement and, the ETSI return loss specification.
Although a center--tapped output transformer is not required, choosing a part with a center-tapped secondary allows the
use of the same type of unit at the receiver input.
A theoretical justification for the 1:2 ratio transformer follows:
RS
TTIP
R3
pos
1:n
VS
VS
pos
neg
V
R
L
O
TRING
RS
R4
neg
Figure 8. Transmitter Line Driver Model
Where:
Vs
Rs
= Vs
= 1.25V typical (Differential line driver peak output voltage swing)
pos
pos
neg
= Rs
= 0.8Ω typical (Differential line driver internal source resistance)
neg
R3 = R4 = 9.1Ω (Differential line driver external source resistance from Figure 1)
R = 75Ω or 120Ω (Transmitter load resistance)
L
n = 2 (Transformer turns ratio)
Vo = Transmitter peak output voltage (Measured across R = 75Ω or R = 120Ω)
L
L
Figure 9 may be converted to a single--ended model:
RS
RS
ext
int
1:n
V
S
V
R
L
O
Figure 9. Single-ended Line Driver Model
Where:
VS = Vs + Vs
neg
pos
RS = RS
+ Rs
neg
int
pos
RS = R3 + R4
ext
Rev. 1.11
18
XRT5897
This may be further simplified:
R
I
T
V
V
eq
s
Figure 10. Equivalent Circuit
Where:
R = RS + Rs
T
int
ext
R
L
R
=
eq
n2
Therefore:
I =
Vs
+ Req
R
T
V
eq
= I R
eq
V = n V
o
eq
And:
R + R
T
eq
Return Loss = 20 log
R -- R
T
eq
Table 6. contains the results of calculations madewith theseequations. The numbers showthat outputpulse amplitude
is within millivolts of the nominal values of 2.37V and 3.00V specified by ITU G.703 for 75Ω and 120Ω operation. Also,
the 1:2 ratio transformer provides an almost-perfect match for 75Ω operation, and return loss is well within the ETSI
specification for the 120Ω load.
Load Resistance
Pulse Amplitude
Vo (Volts Peak)
Output
Return Loss (dB)
RL (Ω)
75
2.43
3.01
31.3
13.8
120
Table 6. Calculated Transmitter Pulse Amplitude and Return Loss
Rev. 1.11
19
XRT5897
100 LEAD THIN QUAD FLAT PACK
(14 x 14 x 1.4 mm, TQFP)
Rev. 2.00
D
75
51
76
50
D
100
26
1
25
A
2
B
C
A
α
Seating Plane
A
1
L
INCHES
MILLIMETERS
SYMBOL
MIN
MAX
MIN
MAX
A
0.055
0.002
0.053
0.007
0.004
0.622
0.547
0.020 BSC
0.018
0°
0.063
0.006
0.057
0.011
0.008
0.638
0.555
1.40
0.05
1.60
0.15
A
A
B
C
D
D
e
1
2
1.35
0.17
0.09
15.80
13.90
1.45
0.27
0.20
16.20
14.10
0.50 BSC
0.75
1
L
0.030
0.45
α
7°
0°
7°
Note: The control dimension is the millimeter column
Rev. 1.11
20
XRT5897
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to im-
prove design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits de-
scribed herein, conveys no license under any patent or other right, and makes no representation that the circuits are
free of patent infringement. Charts and schedules contained herein are only for illustration purposes and may vary
depending upon a user’s specific application. While the information in this publication has been carefully checked;
no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly
affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation
receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the
user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circum-
stances.
Copyright 2001 EXAR Corporation
Datasheet October 2001
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Rev. 1.11
21
相关型号：
XRT5997IV-F
PCM Transceiver, 1-Func, CEPT PCM-30/E-1, CMOS, PQFP100, 14 X 14 MM, 1.40 MM HEIGHT, GREEN, TQFP-100
EXAR
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