AMIS-49200 Datasheet, PDF (14/19 Pages) AMI SEMICONDUCTOR – Fieldbus MAU Chip

AMIS−49200
AMIS−49200 AS REPLACEMENT FOR YOKOGAWA mSAA22Q
The AMIS−49200 is a near pin-for-pin compatible
replacement for the Yokogawa mSAA22Q Fieldbus MAU.
There are some differences between the two chips both in the
internal operation, the required external connections and the
value (or existence) of some of the external components.
These differences are small and those who used the
mSAA22Q would most likely be able to use the
AMIS−49200 in designs with only some component value
changes.
Functional Differences between the mSAA22Q
and the AMIS−49200
Jabber Inhibit
The AMIS−49200 does not implement the Jabber Inhibit
function in the mSAA22Q. Typically the AMIS−49200 will
be connected with a link controller chip such as the
UFC100−F1 from Aniotek/Softing. This link controller has
a Jabber Inhibit function so the absence of this function in
the AMIS−49200 should not be a problem.
As can be seen in Table 12, MDS_CTRL is only
connected to ground if POL is connected to VDD. See
Table 1 for a detailed description of the interaction between
MDS_CTRL and POL.
In Table 12, the mSAA22Q recommends that the JAB/
signal (Pin 39) be connected to ground if the signal is not
used. On AMIS−49200, Pin 39 must be connected to
ground.
Low Power Mode
The low power mode on the mSAA22Q allows the user to
have a quiescent current draw of less than 10 mA yet still
communicate at the proper IEC 61158−2 signal levels. Very
few, if any, Fieldbus devices are capable of operating at such
a low current level so this capability was not included in the
AMIS−49200.
The pins affected by this are 41, 42 and 43. If the low
power mode is not being used on the mSAA22Q, these three
pins are grounded. On the AMIS−49200 it is required that
these pins be grounded.
Pin Differences between the mSAA22Q
and the AMIS−49200
Pin differences are shown in Table 12.
Table 12. PIN CONNECTION DIFFERENCES BETWEEN THE mSAA22Q AND THE AMIS−49200
mSAA22Q
AMIS−49200
Pin No.
Signal Name
Recommended
Connection
Signal Name
Required Connection
1
NC
Ground
VSS
Ground
11
NC
Ground
VSS
Ground
22
NC
Ground
VSS
Ground
26
NC
Ground
MDS_CTRL
Ground*
33
NC
Ground
VSS
Ground
39
JAB/
Ground if Not Used
VSS
Ground
41
CJB
1 mF Cap
VSS
Ground
42
VTX
Ground
VSS
Ground
43
VSL
Ground
VSS
Ground
* MDS_CTRL is only connected to ground if POL is connected to VDD. See Table 1 for a detailed description of the interaction between
MDS_CTRL and POL.
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
FOUNDATION Fieldbus Physical Layer Conformance test
as specified in FOUNDATION Fieldbus specification
FF830, Rev 1.5. This circuit is similar but not identical to the
circuit recommended by Yokogawa for the mSAA22Q.
Table 13 lists the four external component values that
need to be changed with using the AMIS−49200 in a circuit
that previously used the mSAA22Q.
Table 13. PASSIVE EXTERNAL COMPONENT VALUE
DIFFERENCES BETWEEN THE mSAA22Q AND THE
AMIS−49200
Component
mSAA22Q Value AMIS−49200 Value
C1
100 pF
150 pF
C3
100 pF
47 pF
C4
470 pF
220 pF
C8
10 nF
1 mF
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