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參數(shù)資料
| 型號(hào)： | MAX1490A |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Complete, Isolated RS-485/RS-422 Data Interface(2.5Mbps，全雙工，完全隔離的RS-485/422收發(fā)器) |
| 中文描述： | 完備的隔離型、RS-485/RS-422數(shù)據(jù)接口 |
| 文件頁(yè)數(shù)： | 19/20頁(yè) |
| 文件大小： | 315K |
| 代理商： | MAX1490A |
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M
Complete, Isolated,
RS -485/RS -422 Data Interfac e
______________________________________________________________________________________
19
Doubly Isolated RS -485 Repeater
The RS-422/RS-485 standard is specified for cable
lengths up to 4000 feet. When approaching or exceed-
ing the specified maximum cable length, a ground-
potential difference of several tens of volts can easily
develop. This difference can be either DC, AC, at
power-line frequency, or any imaginable noise or
impulse waveform. It is typically very low impedance so
that if a connection between the two grounds is
attempted, very large currents may flow. These cur-
rents are by their nature unstable and unpredictable. In
addition, they may cause noise to be injected into sen-
sitive instrumentation and, in severe cases, might actu-
ally cause physical damage to such equipment.
Figure 15 shows a half-duplex (two-wire), bidirectional,
party-line repeater system that prevents interference
and/or damage from ground-potential differences. Two
MAX1480A/MAX1480B isolated RS-485 transceivers
are used to isolate each of the network segments from
the electrical environment of the repeater. The
MAX1480A/MAX1480B also regenerate bus signals that
may have been degraded by line attenuation or disper-
sion.
In the idle state, both transmitters are disabled, while all
receivers in the system are enabled. If any device on
the system has information for any other device, it starts
sending its data onto the bus. Each data transmission
on the bus retriggers the one-shot, keeping the sending
transmitter enabled until there are no more transmis-
sions. All receivers receive all data; if this is undesir-
able, the protocol must allow for an address field so
receivers can ignore data not directed to them.
Each node must refrain from transmitting when data
already exists on the bus, and must resend data that is
corrupted by the collisions that inevitably occur with a
party-line system. With the repeater of Figure 15, there
might be transmitters up to 8000 feet apart. That repre-
sents more than 8μs (assuming 1ns/foot of delay) in
which two nodes could be transmitting simultaneously.
The circuit in Figure 15 can be used either directly as
shown, with the slew-rate-limited MAX1480B, for data
transfer rates up to 250kbps, or with the MAX1480A for
data rates up to 2.5Mbps (see Table 1 for pull-up and
LED resistor values when using the MAX1480A). If
dual-port isolation is not needed, one of the MAX1480
devices can be replaced by a MAX485 for 2.5Mbps
applications, or by a MAX483 for 250kbps applications.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1490ACPG | 功能描述:RS-422/RS-485 接口 IC RoHS:否 制造商:Maxim Integrated 數(shù)據(jù)速率:1136 Kbps 工作電源電壓:3 V to 5.5 V 電源電流:5.9 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-28 封裝:Tube |
| MAX1490ACPG+ | 功能描述:RS-422/RS-485 接口 IC Isolated RS-485/422 Data Interface RoHS:否 制造商:Maxim Integrated 數(shù)據(jù)速率:1136 Kbps 工作電源電壓:3 V to 5.5 V 電源電流:5.9 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-28 封裝:Tube |
| MAX1490AEPG | 功能描述:RS-422/RS-485 接口 IC RoHS:否 制造商:Maxim Integrated 數(shù)據(jù)速率:1136 Kbps 工作電源電壓:3 V to 5.5 V 電源電流:5.9 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-28 封裝:Tube |
| MAX1490AEPG+ | 功能描述:RS-422/RS-485 接口 IC Isolated RS-485/422 Data Interface RoHS:否 制造商:Maxim Integrated 數(shù)據(jù)速率:1136 Kbps 工作電源電壓:3 V to 5.5 V 電源電流:5.9 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-28 封裝:Tube |
| MAX1490BCPG | 功能描述:RS-422/RS-485 接口 IC RoHS:否 制造商:Maxim Integrated 數(shù)據(jù)速率:1136 Kbps 工作電源電壓:3 V to 5.5 V 電源電流:5.9 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-28 封裝:Tube |
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