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AB1432 PDF даташит

Спецификация AB1432 изготовлена ​​​​«Philips» и имеет функцию, называемую «50Mb/s fiber optic receivers».

Детали детали

Номер произв AB1432
Описание 50Mb/s fiber optic receivers
Производители Philips
логотип Philips логотип 

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AB1432 Даташит, Описание, Даташиты
INTEGRATED CIRCUITS
AB1432
50Mb/s fiber optic receivers
Author: G. Lane
1988 Dec
Philips
Semiconductors









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AB1432 Даташит, Описание, Даташиты
Philips Semiconductors
50Mb/s fiber optic receivers
Application brief
AB1432
Author: G. Lane
INTRODUCTION
This application brief describes the use of four Philips
Semiconductors devices specifically designed for use as fiber optic
receiver components.
In order to simplify the design process for a prospective user, two
typical fiber optic receivers were designed, built and tested. The
design criteria for these receivers is a maximum of 50Mb/s data rate
non-return-to-zero (NRZ) format, optical wavelength of 850nm, and
readily available components.
The two receivers are topologically similar; the difference between
them is in performance, which will be pointed out in the specific
discussion of each receiver. For ease of explanation, two sets of
schematic diagrams are used. The first is a signal-only diagram
used in the description of the circuit operation. The second, and
complete set, shows the peripheral components and the power
supply decoupling networks.
The choice of which preamplifier to use with which postamplifier is
determined by the task to be accomplished. Selections were made
for the two test receivers: One receiver combination
(NE5211/NE5214) was chosen for long haul, i.e., greatest gain, and
a short (27-1)-Pseudo Random Bit Sequence (PRBS). The other
combination (NE5210/NE5217) was chosen for short haul, longer
(223-1) PRBS operation. That is to say other combinations cannot
exist; the choice is made dependent upon the application. The
optical source used in the evaluation of the receivers is the
transmitter, described in AB1121. SMA connectors were used
throughout, with the exception of the step attenuator (see Figure 1
for complete test set-up description). The test set-up shown in
Figure 1 provides measurement capability of optical power,
Bit-Error-Rate (BER), and eye pattern (duty cycle distortion).
ANRITSU
ME522A
X’MTR
X’MTR
UNDER
TEST
RECEIVER
UNDER
TEST
ANRITSU
ME522A
RECEIVER
external resistor, RHYS, is used to set the amount of hysteresis
desired. The output stage provides a single-ended TTL data signal
with matched rise and fall times to minimize duty cycle distortion.
The decoupling networks are shown in the complete schematic,
Figure 3. Because this receiver has gain >100dB and very wide
bandwidth, great care must be taken in both the physical layout and
decoupling of the stages.
The printed circuit layout shown in Figure 4 may not be optimum; it
serves only to demonstrate capability. For higher performance, a
different layout and shielding between the detector leads and the
preamplifier, and between the preamplifier and the postamplifier,
may be in order. The decoupling networks cannot be disposed of;
the value of the passive components may change to fit a particular
need, but overall they are necessary. Another feature of all of the
devices is the grounding pins which are available to separate input
grounds and output grounds, high level grounds and low level
grounds. These grounds need to be given careful consideration
when laying out a circuit.
Results
Receiver 1 was built using the layout shown in Figure 4. Input
power (PIN) (minimum) was measured for PRBS lengths of 27-1 and
223-1 with the following conditions: BER = 10-9, RTH = 39k, RHYS
= 5k;
The results obtained were:
PIN dBm optical = -32dBm for PRBS of 27-1,
PIN dBm optical = -20dBm for PRBS of 223-1,
Actual eye patterns are shown in Figure 5a and b, for PRBS of 27-1,
PIN dBm optical = -32dBm for PRBS of 223-1,
PIN dBm optical = -20dBm, respectively.
To demonstrate threshold and hysteresis, a pair of curves were
generated by measuring input power required for the signal to fall
just below the threshold (signal loss), then measuring PIN to just
exceed the threshold (regain signal) for different valves of RTH. The
value of RHYS is kept at a constant value of 5k. These curves are
shown in Figure 6.
HP8158B
OPTICAL
ATTENUATOR
TEKTRONIX 11402
OSCILLOSCOPE
TEST
HEAD
Figure 1. Test Set-Up
HP8152A
OPTICAL
POWER METER
SD00500
RECEIVER 1
The first receiver (Receiver 1) is shown in Figure 2. The optical
signal is coupled to the PIN diode. Current flowing in the diode also
flows into the input of the NE5211 preamplifier. The preamplifier is a
fixed gain block that has a 28kdifferential transimpedance and
does a single-ended to differential conversion. With the signal in
differential form, greater noise immunity is assured. The second
stage, or postamplifier (NE5214), includes a gain block, auto-zero
circuit, detection and limiting. The auto-zero circuit allows DC
coupling of the preamplifier and cancels the signal dependent offset
due to the optical-to-electrical conversion. The auto-zero capacitor
must be 1000pF or greater for proper operation. The peak detector
has an external threshold adjustment, RTH, allowing the system
designer to tailor the threshold to the individual’s need. Hysteresis
is included to minimize jitter introduced by the peak detector, and an
Receiver 2
Receiver 2, Figure 7, is similar to Receiver 1, topologically. Optical
power is coupled to the PIN photodetector diode, which is directly
coupled to the NE5210. The NE5210 is a fixed 7kdifferential
transimpedance gain block with a differential output for noise
immunity. The postamplifier, NE5217, is DC coupled to the
preamplifier. The NE5217 also has an auto-zero circuit allowing
direct coupling and cancellation of signal decoupling and
cancellation of signal dependent offsets. The peak detector has its
threshold externally adjustable by means of RTH, and hysteresis for
detector jitter reduction is adjustable using RHYS. Curves are
available in the data sheets for both RTH and RHYS. The NE5217
has a built-in Schmitt trigger, which requires coupling, capacitors,
CS1 and CS2 as shown in Figure 7. The Schmitt trigger allows this
device to function with longer PRBS NRZ signals by holding the last
state until a change is made. The penalty is that an internal
threshold is moved from 20mV to 400mV. The complete schematic
is shown in Figure 8. The discussion of grounding and layout for
Receiver 1 holds true for Receiver 2. A well through out layout will
produce superior results.
Results
Receiver 2 was built using the layout shown in Figure 9. The same
measurements were made as with Receiver 1. Input power
minimum was measured for PRBS lengths of 27-1 and 223-1 with
BER = 10-9, RTH = 39kand RHYS = 5k.
1988 Dec
2









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AB1432 Даташит, Описание, Даташиты
Philips Semiconductors
50Mb/s fiber optic receivers
Application brief
AB1432
The results obtained were:
PIN dBm optical = -30dBm for PRBS of 27-1,
PIN dBm optical = -21dBm for PRBS of 223-1,
Actual eye patterns are shown in Figure 10a and b, for PRBS of
27-1, and 223-1, respectively.
The curves showing power input (PIN) required for the signal to fall
just below the threshold (signal loss) and PIN required to just exceed
the threshold (regain signal) for different values of RTH, are shown in
Figure 11. The value of RHYS is kept at a constant value of 5k.
NOTE: Recall that the transimpedance of the NE5210 is 1/4 the
transimpedance of the NE5211 when comparing the results.
CONCLUSION
Two 50Mb/s fiber optic receivers were presented along with full
schematic diagrams and printed circuit layouts. Individual circuit
descriptions were give, along with suggestions of how further
performance improvement could be gained. Performance
characteristics were shown for each circuit under actual operating
conditions.
NOTE: The available bandwidth of both receivers is far greater than
necessary for the applications shown. Capacitor C1, shown in all
schematic diagrams, serves to limit the overall bandwidth to 60MHz.
PHILIPS
BPF31
+5V
100
NE5211
NE5214
TTL DATA OUT
C1
RTH
RHYS
VCC
Figure 2.
VCC SD00501
+VCC
47µF
C1
C2 .01µF
GND
R2 D1
220 LED
C9
100pF
L2
10µH
C10
10µF
R3
47k
C11
.01µF
L3
10µH
C12
10µF
C13
.01µF
1 LED
2 CPKDET
3 THRESH
4 GNDA
5 FLAG
6 JAM
7 VCCD
8 VCCA
9 GNDD
10 TTLOUT
VOUT (TTL)
C7
IN1B 20
IN1A 19
CAZP 18
100pF
C8
CAZN 17
OUT1B 16
0.1µF
IN2B 15
OUT1A 14
IN2A 13
RHYST 12
RPKDET 11
R4
5.1k
NOTE:
The NE5211/NE5214 combination can operate at data rates in excess of 100Mb/s NRZ.
8 GND
9 GND
10 GND
11 GND
12 OUT
13 GND
14 OUT
1988 Dec
Figure 3. Eye Patterns for Receiver 1
3
VCC 7
VCC 6
NC 5
IIN 4
NC 3
GND 2
GND 1
L1
10µH
R1
100
C5
1.0µF
C4
.01µF
C3
10µF
.01µF
C6
BPF31
OPTICAL
INPUT
SD00353










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