参数资料
| 型号： | ISL81486IU-T |
| 厂商： | Intersil |
| 文件页数： | 9/11页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS485/422 5V HS 8-MSOP |
| 标准包装： | 2,500 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 1/1 |
| 规程： | RS422，RS485 |
| 电源电压： | 4.5 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 8-MSOP |
| 包装： | 带卷 (TR) |
7
Application Information
RS-485 and RS-422 are differential (balanced) data
transmission standards for use in long haul or noisy
environments. RS-422 is a subset of RS-485, so RS-485
transceivers are also RS-422 compliant. RS-422 is a point-
to-multipoint (multidrop) standard, which allows only one
driver and up to 10 (assuming one unit load devices)
receivers on each bus. RS-485 is a true multipoint standard,
which allows up to 32 one unit load devices (any mix of
drivers and receivers) on each bus. To allow for multipoint
operation, the RS-485 spec requires that drivers must
handle bus contention without sustaining any damage.
Another important advantage of RS-485 is the extended
common mode range (CMR), which specifies that the driver
outputs and receiver inputs withstand signals that range from
+12V to -7V. RS-422 and RS-485 are intended for runs as
long as 4000’ (~1200m), so the wide CMR is necessary to
handle ground potential differences, as well as voltages
induced in the cable by external fields.
Receiver Features
These devices utilize a differential input receiver for maximum
noise immunity and common mode rejection. Input sensitivity
is
±200mV, as required by the RS422 and RS-485
specifications. Receiver inputs function with common mode
voltages as great as 7V outside the power supplies (i.e.,
+12V and -7V), making them ideal for long networks, or
industrial environments, where induced voltages are a
realistic concern.
Receiver input resistance surpasses the RS-422 spec of
4k
, and exceeds the RS-485 “Unit Load” requirement of
12k
minimum. The 20k input resistance allows at least 50
devices on the RS-485 bus. All the receivers include a “fail-
safe if open” function that guarantees a high level receiver
output if the receiver inputs are unconnected (floating).
Receivers easily meet the data rate supported by the driver,
and receiver outputs are three-statable via the active low RE
input.
Driver Features
The RS-485/RS-422 driver is a differential output device that
delivers at least 2.3V across a 54
load (RS-485/
PROFIBUS), and at least 2.5V across a 100
load (RS-422)
even with VCC = 4.5V. The drivers feature low propagation
delay skew to maximize bit width, and to minimize EMI.
Outputs of the drivers are not slew rate limited, so faster
output transition times allow data rates of at least 40Mbps
with the ISL4486, and 30Mbps with the ISL81486. Driver
outputs are three-statable via the active high DE input.
For parallel applications, bit-to-bit skews between any two
ISL4486 transmitter and receiver pairs are guaranteed to be
no worse than 15ns (6ns max for any two Tx, 9ns max for
any two Rx).
Data Rate, Cables, and Terminations
Twisted pair is the cable of choice for RS-485, RS-422, and
PROFIBUS networks. Twisted pair cables tend to pick up
noise and other electromagnetically induced voltages as
common mode signals, which are effectively rejected by the
differential receivers in these ICs.
RS-485/RS-422 are intended for network lengths up to 4000’
(~1200m), but the maximum system data rate decreases as
the transmission length increases. According to guidelines in
the RS-422 and PROFIBUS specifications, networks
operating at data rates in excess of 3Mbps should be limited
to cable lengths of 100m (328 feet) or less, and the
PROFIBUS specification recommends that the more
expensive “Type A” (22AWG) cable be used. Nevertheless,
the ISL4486’s large differential output swing, fast transition
times, and high drive-current output stages allow operation
at 40Mbps over standard “CAT5” cables in excess of 400
feet (121m). Figure 8 details the ISL4486 performance at
this condition, with a 120
termination resistor at both the
driver and the receiver ends. Note that the differential signal
delivered to the receiver at the end of the cable (A-B) still
exceeds 1V, so even longer cables could be driven if lower
noise margins are acceptable. If more noise margin is
desired, shorter cables produce a larger receiver input signal
as illustrated in Figure 7. Performance should be even better
if the “Type A” cable is utilized. The lower data rate of the
ISL81486 allows for driving longer cables.
To minimize reflections, proper termination is imperative when
using these high data rate transceivers. In point-to-point, or
point-to-multipoint (single driver on bus) networks, the main
cable should be terminated in its characteristic impedance
(typically 120
for “CAT5”, and 220 for “Type A”) at the end
farthest from the driver. In multi-receiver applications, stubs
connecting receivers to the main cable should be kept as
short as possible. Multipoint (multi-driver) systems require that
the main cable be terminated in its characteristic impedance
at both ends. Stubs connecting a transceiver to the main cable
should be kept as short as possible.
Built-In Driver Overload Protection
As stated previously, the RS-485 spec requires that drivers
survive worst case bus contentions undamaged. These
transmitters meet this requirement via driver output short
circuit current limits, and on-chip thermal shutdown circuitry.
The driver output stages incorporate short circuit current
limiting circuitry which ensures that the output current never
exceeds the RS-485 spec, even at the common mode
voltage range extremes. In the event of a major short circuit
condition, the devices also include a thermal shutdown
feature that disables the drivers whenever the die
temperature becomes excessive. This eliminates the power
dissipation, allowing the die to cool. The drivers
automatically reenable after the die temperature drops about
15 degrees. If the contention persists, the thermal
shutdown/reenable cycle repeats until the fault is cleared.
Receivers stay operational during thermal shutdown.
ISL4486, ISL81486
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL81486IUZ | 功能描述:IC TXRX RS485/422 5V HS 8-MSOP RoHS:是 类别:集成电路 (IC) >> 接口 - 驱动器，接收器，收发器 系列:- 标准包装:250 系列:- 类型:收发器 驱动器/接收器数:2/2 规程:RS232 电源电压:3 V ~ 5.5 V 安装类型:表面贴装 封装/外壳:16-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:16-TSSOP 包装:带卷 (TR) |
| ISL81486IUZ-T | 功能描述:IC TXRX RS485/422 5V HS 8-MSOP RoHS:是 类别:集成电路 (IC) >> 接口 - 驱动器，接收器，收发器 系列:- 标准包装:250 系列:- 类型:收发器 驱动器/接收器数:2/2 规程:RS232 电源电压:3 V ~ 5.5 V 安装类型:表面贴装 封装/外壳:16-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:16-TSSOP 包装:带卷 (TR) |
| ISL81487 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:1/8 Unit Load, 5V, Low Power, High Speed or Slew Rate Limited, RS-485/RS-422 Transceivers |
| ISL81487E | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:【15kV ESD Protected, 1/8 Unit Load, 5V, Low Power, High Speed or Slew Rate Limited, RS-485/RS-422 Transceivers |
| ISL81487EIB | 功能描述:IC TXRX RS-485/422 ESD 8-SOIC RoHS:否 类别:集成电路 (IC) >> 接口 - 驱动器，接收器，收发器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 类型:发射器 驱动器/接收器数:4/0 规程:RS422，RS485 电源电压:4.75 V ~ 5.25 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.154"，3.90mm 宽） 供应商设备封装:16-SOIC 包装:带卷 (TR) |
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