ACS411CS View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
ACS411CS Datasheet PDF : 43 Pages
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Acapella Optical Modem IC
ACS411CS
The ACS411CS comprises a chip set of two/three
(link budget dependent) highly integrated devices,
the ACS9020 and ACS4110. The ACS9020 is an
analogue device and the ACS4110 is predominately
a digital device.
The ACS9020 contains the Laser/LED driver as well
as the PIN receiver circuitry. Since the devices are
transmitting and receiving continuously, for long haul
applications two ACS9020 devices are required, one
configured as the transmitter and the other configured
as the receiver.
The ACS4110 comprises the logic necessary to time
compress and decompress the data, plus clock
recovery and all the logic associated with valid data
transmission and reception and locking status. The
ACS4110 also has a configurable parallel
microprocessor bus interface for device configuration
(control) and status analysis. The device setup is
also possible via the far end (remote control) or
directly via pins for the basic device setup.
For the purpose of this specification the chip-set will
be referred to as the ACS411CS and the individual
devices as the ACS9020 or ACS4110.
For low link budget applications (up to 10dB) two
chips, the ACS9020 analogue IC (including laser
driver and PIN receiver circuitry) and the ACS4110
are sufficient.
For applications requiring a higher link budget (up to
30dB) a three chip solution has to be used, where
the laser driver and PIN receiver circuitry are
separated.
PORB
The Power On Reset (PORB) pin resets the device
if forced low for 2ms or more. In normal operation
PORB should be held High. It is recommended that
PORB is connected to VD+ via a 100KΩ resistor
and to GND via a 100nF capacitor.
System Clock
The system clock on the ACS411CS is derived locally
using the on-chip crystal oscillator and multiplying
PLL.
The oscillator (XTO/I) requires the use of a
fundamental parallel resonance crystal with
appropriate padding capacitors. The crystal
specification should be:
Calibration tolerance: +/- 20ppm @ 25°C
Temp. tolerance:
+/-20ppm @ -40 to +85°C
Temperature range: -40 to +85°C
Load condition:
parallel load 15pF
Padding capacitor: 18-22pF (tune for desired tolerance)
The system clock defines the burst frequency at
which data is transmitted over the optical link via the
optical interface. The receive circuitry within the
ACS4110 recovers the clock from the received data
at the RXDAT inputs and produces a clock that is
synchronised to the incoming data stream. The
system clock must have a maximum tolerance of +/-
50ppm over the desired temperature range.
Inter-Modem Coding
Optical Operational Modes
The inter-IC coding between communication modems
is 8B10B. Whilst transparent to the user, 8B10B
encoding ensures that there is no DC component in
the signal, and provides frequent data transitions,
factors which ease the task of data recovery and
clock extraction.
The coding rules are continuously checked to ensure
the integrity of the link, and errors are indicated on
the ERRL and ERRC pins (see section headed
ERRC and ERRL - Error Detection ).
The ACS411CS has four optical operational modes,
all supporting twin fiber. The ACS9020 can also
utilise Lasers/LED and PIN combinations, including
a PIN with an internal Trans-Impedence Amplifier
(TIA) controlled by PINRX.
The twin fiber Laser modes in Table 1 may be
converted to single fiber operation simply by
interfacing to Wave Division Multiplexer (WDM)
device indicated by mode 5.
Transmit and Receive functions
Data presented at the near-end TPOS/TNEG is time-
compressed, encoded in the 8B10B format and
transmitted over the fiber link to the far end receiver.
Similarly, data presented at the far-end TPOS/TNEG
is time-compressed, encoded in the 8B10B format
and transmitted over the other fiber link to the near
end.
ACS411CS PRE-RELEASE Issue 6.0 July 1999.
2
Mode
1
2
3
4
5
Optical Device
Laser and PIN diode without TIA.
Laser and PIN diode with integrated TIA.
LED and PIN diode without TIA.
LED and PIN diode diode with integrated TIA.
WDM
Table 1: Optical modes
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