ACS102A Semtech Corporation, ACS102A Datasheet - Page 2
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ACS102A
Manufacturer Part Number
ACS102A
Description
Acs102a Fiber Modem
Manufacturer
Semtech Corporation
Datasheet
1.ACS102A.pdf
(13 pages)
This device offers one high speed and three low speed full duplex
channels to the user in a completely transparent way, appearing as
4 full duplex channels even though the medium connecting the
devices may only be a single fiber link.
Data from the TxD and low frequency channels is time
compressed in an internal FIFO and sent over the fiber link in a
burst within a predefined window. The device at each end of the
link automatically synchronise with each other such that the
transmit and receive windows are interleaved. The TxD input data
of the transmitting modem is also data compressed. The 3B4B
encoding method is used for communication between ACS102As,
thus ensuring that there is no DC component in the signal. The
encoding and decoding is transparent to the user.
In the receiving modem, 3B4B encoding ensures easy extraction of
the bit-clock.
stored in the output memory. The memory provides time expansion,
de-jittering and frequency compensation functions. The data is then
decompressed and directed to the RxD output pin, appearing after a
minimal delay, in the same format as that presented at the TxD pin
at the far end.
The ACS102A is compatible with the ACS102 but offers over twice
the max data rate and incorporates the laser interface modes
previously associate with the ACS402. The ACS102A is a pin and
functional compatible replacement for both the ACS102 and
ACS402. The following sections detail the operating modes for all
configurations of LED, LASER and LED/PIN or LASER/PIN
combinations. Additional modes are also described for new ways of
interfacing the device with external PIN / amplifier modules.
LED Interface Modes
Mode 1 - Single Fiber LED mode
Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=0
This is the operational mode for single fiber transmission with a
PPLED. The LED is used for both transmission and reception of
data over the fiber.
necessary connections is shown in figure 4. This also shows an
example circuit for interfacing to the RS232 voltage levels of a PC
serial port.
Mode 2 - Dual Fiber LED/PIN mode
Setup : DP5=0, DP4=0, DP3=0, DP2=1, DP1=1
This is a twin-fiber mode where the LED is used for transmission
and a separate PIN Diode is used for reception. This allows the use
of less expensive standard LEDs and PINs rather than bi-directional
PPLEDs or Duplex devices. An example circuit diagram showing
the necessary connections is shown in figure 5.
LASER Interface Modes
Mode 3 - Dual Fiber LASER/PIN mode
Setup : DP5=0, DP4=1, DP3=0, DP2=1, DP1=0
This is a twin-fiber mode where the LASER is used for transmission
and a separate PIN Diode is used for reception. An example circuit
diagram showing the necessary connections is shown in figure 6.
Differential reception from the PIN diode is used to maximise
sensitivity. Since PINP is also used for LASER current control via
monitoring of the monitor diode current, the LAP and LAN pins are
automatically floated during data reception.
Either 3 or 4 pin LASERs may be used in this mode. For 4 pin
LASERS the extra pin of the monitor diode cathode is connected
to the LASER anode, the same as it is shown in figure 6 with the
internal connection of a typical 3-pin LASER.
Transmitter and Receiver Functions
Operational Modes
Advanced Communications
The received data is filtered, decoded, and then
Single/Dual Fiber Modem for Asynchronous Data Rates from DC to 160kbps
An example circuit diagram showing the
2
Mode 4 - Single Fiber 3-pin LASER/PIN mode
Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=1
This is a single-fiber mode where the LASER is used for transmis-
sion and the monitor PIN diode within the LASER is used for
reception. Differential reception from the PIN diode is used to
maximise sensitivity. Connections are shown below :
Mode 5 - Single Fiber 4-pin LASER/PIN mode
Setup : DP5=0, DP4=0, DP3=1, DP2=0, DP1=0
This is a single-fiber mode where the LASER is used for transmis-
sion and the monitor PIN diode within the LASER is used for
reception. Differential reception from the PIN diode is used to
maximise sensitivity. Connections are shown below :
LASER Duplex Device Use
The Laser duplex device is composed of a 3 or 4 pin Laser for
transmission and a PIN diode for reception in a single housing.
Mode 3, as detailed previously is used for interfacing to these
devices. The Duplex devices are driven by the ACS102A in a half-
duplex manner, even though to the user it appears as a full duplex
link. As a consequence potential cross-talk between the transmit-
ter and receiver is ignored, allowing excellent performance from
low cost components.
The previous modes detail the most common setups for most
typical LED, LED/PIN or LASER/PIN combinations. Many other
possible operating modes are possible via the DP1-5 pins setups.
Some of the other less common connection combinations are
shown below. These include modes for using a LASER as a
receiver as well as a transmitter in a single fiber link, where the
LASER device supports this, receiving from both the LASER and
monitor PIN, and modes for digital interfacing to external PIN/
transimpedance amplifier (TIA) modules.
on DP1-5 indicated in this specification, other pin combinations
may activate unpublicised functional or test modes which may lead
to damage of the LASER, where this is used.
Mode 6 - Single Fiber 4-pin LASER/PIN mode (Las & mon recv)
Setup : DP5=0, DP4=0, DP3=0, DP2=0, DP1=0
This is a single-fiber mode where the LASER is used for transmis-
sion and the LASER and the monitor PIN diode within the LASER is
used for reception. Connections are as in mode 5.
Additional Alternative Modes
3-pin LASER single fiber mode
4-pin LASER single fiber mode
LAP
PINP
LAN
PINN
PINP
LAN
LAP
LASER
LASER
ACS102A Data Sheet
Only use those setups
Fiber
Fiber