AMIS-49200 Datasheet, PDF (16/19 Pages) AMI SEMICONDUCTOR – Fieldbus MAU Chip

AMIS−49200
C1 connects to signal CCD (Pin 32) and controls the
carrier detect assert and drop-out timing. Particular
implementations may require that the value of C1 be
changed to accommodate received signal level changes
introduced by the addition of intrinsic safety components
added to the external circuitry. C3 and C4 are part of the
receive filter and determine the band pass characteristics of
the receive filter. It is unlikely that these would need to be
changed. C8 is a noise filter for VMID. It is important that
VMID have as little noise as possible as it is used as a
reference for many sub-circuits in the AMIS−49200. C8
must be a large capacitor with maximum of 100 nF. C8
recommended value is 1 mF.
There is one other minor difference in the recommended
external circuitry between the mSAA22Q and the
AMIS−49200. Figure 13 shows the start-up circuits
recommended for the mSAA22Q and the AMIS−49200. The
circuit shown for the AMIS−49200 is different from that
shown for the mSAA22Q but either one will work. Both are
current sources that turn on when power is applied to the H1
segment terminals so that the AMIS−49200 can turn on
without any turn-on transients on the network.
mSAA22Q
Start-up Circuit
AMIS−49200
Start-up Circuit
Loop +
R5
100 kW
Loop +
R6
1 kW
V Shunt
D3
5.1 V
Q1
V Shunt
Active Components
Transistors Q1–Q4 are ordinary small signal transistors.
Diodes D1 and D2 are similarly ordinary small signal
diodes. Users desiring to replace a mSAA22Q with the
AMIS−49200 in an existing design should be able to use
whatever transistors and diodes were used with the
mSAA22Q. For new designs, the specified transistors can be
used or other devices may be chosen.
Alternative Designs
Some users of the Yokogawa mSAA22Q did not use the
exact recommended external circuit for the media interface
circuit (see Figure 12). Using the AMIS−49200 without the
Yokogawa recommended external circuit may result in
some compatibility problems. There are many alternative
designs and it is beyond the scope of this document to
identify all possible configurations and their associated
design implications. Please refer to the AMIS−49200
Fieldbus MAU Reference Design Application Note for a
recommended, FOUNDATION Fieldbus certifiable board
design.
Verification
All designs using the AMIS−49200 should re-run the
entire physical layer conformance test as defined in
FOUNDATION Fieldbus document FF−830,
FOUNDATION^ Specification 31.25 kbit/s Physical Layer
Conformance Test. Board layout can alter the behavior of all
circuit implementations, even designs that follow the
recommended implementation.
Figure 13. Recommended Start-up Circuits
Table 14. ORDERING INFORMATION
Part Number
Package
Temperature Range
Shipping^†
AMIS−49200−XTD
44 LQFP 10  10 mm
(Pb−Free/RoHS Compliant)
−40C to 85C
160 / Tray
AMIS−49200−XTP
44 LQFP 10  10 mm
(Pb−Free/RoHS Compliant)
−40C to 85C
1,500 / Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specification Brochure, BRD8011/D.
http://onsemi.com
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