ACS411CS Semtech Corporation, ACS411CS Datasheet - Page 23

• Manufacturer Part Number: ACS411CS
• Description: Acapella Optical Modem ic
• Manufacturer: Semtech Corporation

Since LEDs or Lasers from different suppliers may
emit different wavelengths, it is recommended that
the Lasers/LEDs in a communicating pair of modems
are obtained from the same supplier. Acapella will
assist with contact names and addresses on request.
The ACS9020 contains a highly sensitive amplifier,
capable of responding to extremely low current levels.
To exploit this sensitivity it is important to reduce
external noise to a low level compared to the input
signal from the Laser/LED. The modem should have
an independent power trace to the point where power
enters the board.
The Laser/LED should be sited very close to the
PMN, PINP, PINN, LAN and LAP pins. A generous
ground plane should be provided, especially
surrounding the sensitive PINP and PINN tracks from
the ACS9020 pins to the optical component. The
modem should be protected from EMI/RFI sources
in the standard ways.
Laser/LED Considerations
Power Supply Decoupling
GND pins are
84, 108, 122, 123, 124, 128,
130, 138, 159, 160
VD+ pins are
82, 85, 94, 105, 139, 161,
162
VD+
5, 37, 51, 81,
ACS4110
6, 38, 52,
Figure 13: Power supply considerations.
VA+
100nF
23
There are two conditions that will make LOSS go to
Logic 1. These are:
i) Loss of synchronisation - synchronisation windows
incorrectly aligned i.e DCD=0.
ii) 64 received symbols break the 8B10B encoding
rules in a sequence of 256 symbols.
In order to return LOSS to the Logic 0 state the
following criteria must be met:
i)
synchronisation windows correctly aligned i.e DCD=1.
ii) There are no received symbols in a sequence of
256 symbols which break the 8B10B coding rules.
LOSS ( Loss Of Synchronisation)
The
devices
TXVDD
ACS9020
must
GND pins are
(2 off)
ACS411CS PRE-RELEASE Issue 6.0 July 1999.
be
synchronised
9, 24, 42, 58
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