AMIS-492X0 Datasheet, PDF (18/22 Pages) ON Semiconductor – Fieldbus MAU

AMIS-492x0
5.0 AMIS-49200 as Replacement for Yokogawa μSAA22Q
The AMIS-49200 is a near pin-for-pin compatible replacement for the Yokogawa μSAA22Q 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 μSAA22Q would most likely be able to use the AMIS-49200
in designs with only some component value changes.
5.1 Functional Differences Between the μSAA22Q and the AMIS-492x0
5.1.1. Jabber Inhibit
The AMIS-492x0 does not implement the Jabber Inhibit function in the μSAA22Q. Typically the AMIS-492x0 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-492x0 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 μSAA22Q recommends that the JAB/ signal (Pin 39) be connected to ground if the signal is not used. On AMIS-492x0,
Pin 39 must be connected to ground.
5.1.2. Low Power Mode
The low power mode on the μSAA22Q allows the user to have a quiescent current draw of less than 10mA 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-492x0.
The pins affected by this are 41, 42 and 43. If the low power mode is not being used on the μSAA22Q, these three pins are grounded.
On the AMIS-492x0 it is required that these pins be grounded.
5.2 Pin Differences Between the μSAA22Q and the AMIS-492x0
Table 12: Pin Connection Differences Between the µSAA22Q and the AMIS-492x0
μSAA22Q
AMIS-492x0
Pin No.
Signal Name
Recommended Connection Signal Name Required Connection
1
NC
11
NC
22
NC
26
NC
33
NC
39
JAB/
41
CJB
42
VTX
43
VSL
Ground
Ground
Ground
Ground
Ground
Ground if not used
1 μf cap
Ground
Ground
VSS
VSS
VSS
MDS_CTRL
VSS
VSS
VSS
VSS
VSS
Ground
Ground
Ground
Ground*
Ground
Ground
Ground
Ground
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.
Rev. 6 | Page 18 of 22 | www.onsemi.com