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Maxim > Design Support > Technical Documents > Application Notes > 1-Wire® Devices > APP 4930
Maxim > Design Support > Technical Documents > Application Notes > Analog Switches and Multiplexers > APP 4930
Keywords: DS2409, MicroLAN, Coupler, applications, smart probe, multi-layer, network, dual-master, emulation
APPLICATION NOTE 4930
Easy Modifications to Sustain a Design with the
DS2409 MicroLAN™ Coupler
By: Bernhard Linke, Principal Member Technical Staff
Mar 04, 2011
Abstract:
The DS2409
is designed for use in access-control probe points (i.e., readers) and to lower the bus load
in large 1-Wire® networks. The part has also been used to implement a dual-master network. At this time Maxim
is phasing out the DS2409 and is encouraging all customers to plan for alternatives. This application note shows
alternative approaches to support and operate 1-Wire networks that currently use the DS2409. The design
emulations presented here do not require a complete network redesign.
Introduction
With its unique feature set, the DS2409 MicroLAN coupler can be used in a several specialized applications. This
application note first lists the features and applications of the DS2409 and then identifies alternative circuits that
can be used to achieve comparable functionality. Subsequently, the alternative circuits are discussed in more
detail.
DS2409 Description
The DS2409 is a special type of a 2-port addressable switch. Instead of switching a programmable input/output
(PIO) to high or low, the part connects its output ports to the incoming 1-Wire line using transmission gates. No
more than a single 1-Wire output can be active at any given time. Besides the 1-Wire outputs, the DS2409 has
a control output which can be associated with the main output (default), the auxiliary output, or be operated
independently. This configuration is controlled through the Status Control Byte (see data sheet). The Status Info
Byte (see data sheet) allows the master to verify the device configuration, and to check the status (active or
inactive), the logic state (high or low), and the event flag (set/cleared) of each 1-Wire output. Table 1
summarizes these and additional features and explains their benefits.
Table 1. DS2409 Features and Benefits
Feature
Name
Description Benefits
No more
than one
output
active at
any time
Only one output can be connected to the incoming
1-Wire line.
Keeps the bus load low.
The DS2409 has an open-drain control output. On
Automatically indicates the
active channel. Can also be
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