HFCT-5964ATG NEL [Nel Frequency Controls,inc], HFCT-5964ATG Datasheet - Page 8

• Manufacturer Part Number: HFCT-5964ATG
• Description: ATG Single Mode Laser Small Form Factor Transceivers for ATM, SONET OC-3 /SDH STM-1 Part of the Agilent METRAK family
• Manufacturer: NEL [Nel Frequency Controls,inc]

Figure 6b. Recommended ac coupled interface circuit
The HFCT-5964TL/TG/NL/NG/
ATL/ATG have a transmit
disable function which is a
single-ended +3.3 V TTL input
which is dc-coupled to pin 13. In
addition these devices offer the
designer the option of
monitoring the laser diode bias
current and the laser diode
optical power. The voltage
measured between pins 17 and
18 is proportional to the bias
current through an internal 10 Ω
resistor. Similarly the optical
power rear facet monitor circuit
provides a photo current which
is proportional to the voltage
measured between pins 19 and
20, this voltage is measured
across an internal 200 Ω
resistor.
As for the receiver section, it is
internally ac-coupled between
the preamplifier and the
8
T
B
P
P
V
B
Note: C1 = C2 = C3 = 10 nF or 100 nF
Note A: CIRCUIT ASSUMES OPEN EMITTER OUTPUT
Note B: WHEN INTERNAL BIAS IS PROVIDED REPLACE SPLIT RESISTORS WITH 100 Ω TERMINATION
Note C: THE BIAS RESISTOR FOR VpdR SHOULD NOT EXCEED 200 Ω
* C4 AND C5 ARE OPTIONAL BYPASS CAPACITORS FOR ADDITIONAL LOW FREQUENCY NOISE FILTERING.
T
R
DIS
MON
MON
MON
CC
MON
X
X
RX (+3.3 V)
(LVTTL)
NOTE C
+
-
+
-
200 Ω
20 19 18 17 16 15 14 13 12 11
1
2
3
10 nF
4
5
6
7
8
postamplifier stages. The actual
Data and Data-bar outputs of the
postamplifier are dc-coupled to
their respective output pins
(pins 9, 10). The two data
outputs of the receiver should be
terminated with identical load
circuits.
+3.3 V TTL output signal that is
dc-coupled to pin 8 of the
module. Signal Detect should not
be ac-coupled externally to the
follow-on circuits because of its
infrequent state changes.
The designer also has the option
of monitoring the PIN photo
detector bias current. Figure 6b
shows a resistor network, which
could be used to do this. Note
that the photo detector bias
current pin must be connected
to V
9 10
Signal Detect is a single-ended,
V
130 Ω
82 Ω
CC
130 Ω
CC
(+3.3 V)
. Agilent also recommends
82 Ω
130 Ω
130 Ω
C2
C1
100 nF
1 µH
1 µH
100 nF
100 nF
100 nF
100 nF
C5 *
10 µF
C4 *
10 µF
Z = 50 Ω
Z = 50 Ω
Z = 50 Ω
Z = 50 Ω
Z = 50 Ω
V
CC
C3
(+3.3 V)
100 nF
10 µF
130 Ω
82 Ω
that a decoupling capacitor is
used on this pin.
Power Supply Filtering and Ground
Planes
It is important to exercise care
in circuit board layout to
achieve optimum performance
from these transceivers. Figures
6a and 6b show the power
supply circuit which complies
with the small form factor
multisource agreement. It is
further recommended that a
continuous ground plane be
provided in the circuit board
directly under the transceiver to
provide a low inductance
ground for signal return current.
This recommendation is in
keeping with good high
frequency board layout
practices.
130 Ω
V
CC
130 Ω
82 Ω
(+3.3 V)
RD+
TD-
RD-
SD
TD+
130
Ω
LVTTL
V
CC
V
(+3.3 V)
CC
(+3.3 V)
NOTE A
NOTE B