AMIS-49200 Datasheet, PDF (20/22 Pages) AMI SEMICONDUCTOR – Fieldbus MAU Chip

AMIS-49200 Fieldbus MAU
Data Sheet
5.3 External Circuitry
Figure 12 shows the external circuitry required to connect the AMIS-49200 to an IEC 61158-2 conformant network. This schematic is
the circuit that was used to pass the Fieldbus Foundation Physical Layer Conformance test as specified in Fieldbus Foundation
specification FF830, Rev 1.5. This circuit is similar but not identical to the circuit recommended by Yokogawa for the µSAA22Q.
Figure 12: AMIS-49200 Reference Circuit Implementation
Table 13 below lists the four external component values that need to be changed with using the AMIS-49200 in a circuit that previously
used the µSAA22Q.
Table 13: Passive External Component Value Differences Between the µSAA22Q and the AMIS-49200
Component
µSAA22Q Value
AMIS-49200 Value
C1
100pf
150pf
C3
100pf
47pf
C4
470pf
220pf
C8
10nf
1µf
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
AMI Semiconductor – Jan. 07, M-20532-003
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