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参数资料
| 型号： | MAX1481 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| 中文描述： | 软件可选的、半/全双工、限摆率、12Mbps、RS-485/RS-422收发器，µMAX封装 |
| 文件页数： | 10/16页 |
| 文件大小： | 184K |
| 代理商： | MAX1481 |
M
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in μMAX Package
10
______________________________________________________________________________________
_______________Detailed Desc ription
The MAX1481/MAX1484/MAX1485/MAX1486 high-
speed transceivers for RS-485/RS-422 communication
contain one driver and one receiver. The MAX1481/
MAX1485 feature reduced-slew-rate drivers that mini-
mize EMI and reduce reflections caused by improperly
terminated cables, allowing error-free data transmission
up to 250kbps. The MAX1484/MAX1486 driver slew
rates are not limited, making transmission speeds up to
12Mbps possible.
These transceivers are designed to operate on a +5V
single supply and typically draw 300μA of supply cur-
rent when unloaded or fully loaded with the drivers dis-
abled. The MAX1481 has a shutdown mode in which
supply current is typically reduced to 0.1μA.
Drivers are output short-circuit current limited and are
protected against excessive power dissipation by ther-
mal-shutdown circuitry that places the driver outputs
into a high-impedance state.
All devices have a 1/8-unit-load receiver input imped-
ance that allows up to 256 transceivers on the bus. The
MAX1481/MAX1484 are designed for full-duplex com-
munications. The H/
F
pin on the MAX1485/MAX1486
allows the user to select between half-duplex or full-
duplex operation (Figure 4).
MAX 1485/MAX 1486
Half-/Full-Duplex Mode Operation
The MAX1484/MAX1485 can operate in full- or half-
duplex mode. Drive the H/
F
pin low or connect it to
GND for full-duplex operation, or drive it high for half-
duplex operation. In full-duplex mode, the pin configu-
ration of the driver and receiver is the same as a
MAX1481 (Figure 1).
__________Applic ations Information
256 T ransc eivers on the Bus
The standard RS-485 receiver input impedance is 12k
(1-unit load), and the standard driver can drive up to
32-unit loads. The MAX1481/MAX1484/MAX1485/
MAX1486 transceivers have a 1/8-unit-load receiver
input impedance (96k
), allowing up to 256 trans-
ceivers to be connected in parallel on one communica-
tion line. Connect any combination of these devices
and/or other RS-485 transceivers totaling 32-unit loads
or less.
Reduc ed EMI and Reflec tions
The MAX1481/MAX1485 are slew-rate limited, minimiz-
ing EMI and reducing reflections caused by improperly
terminated cables. Figure 14 shows the driver output
waveform and its Fourier analysis of a 20kHz signal
transmitted by a MAX1484. High-frequency harmonic
components with large amplitudes are evident. Figure
15 shows the same signal displayed for a MAX1481
transmitting under the same conditions. Figure 15’s
high-frequency harmonic components are much lower
in amplitude compared to Figure 14’s, significantly
reducing potential EMI.
In general, a transmitter’s rise time relates directly to
the length of an unterminated stub, which can be dri-
ven with only minor waveform reflections. The following
equation expresses this relationship conservatively:
Length = t
RISE
/ (10 x 1.5ns/ft)
where t
RISE
is the transmitter’s rise time.
For example, the MAX1481’s rise time is typically
500ns, which results in excellent waveforms with a stub
length up to 33 feet. A system may work well with
longer unterminated stubs, even with severe reflec-
tions, if the waveform settles out before the UART
samples them.
MAX1485
MAX1486
B
DI
DE
RO
V
CC
GND
A
Z
Y
H/F
Figure 4. MAX1485/MAX1486 Functional Diagram
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1481-MAX1486 | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| MAX1481CUB | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| MAX1481EUB | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| MAX1484CUB | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| MAX1484EUB | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
相关代理商/技术参数 |
参数描述 |
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| MAX14811CTN+ | 制造商:Maxim Integrated Products 功能描述:DUAL, UNIPOLAR/BIPOLAR, HIGH-VOLTAGE DIGITAL PULSERS WITH FA - Rail/Tube |
| MAX14811CTN+T | 制造商:Maxim Integrated Products 功能描述:DUAL, UNIPOLAR/BIPOLAR, HIGH-VOLTAGE DIGITAL PULSERS WITH FA - Tape and Reel |
| MAX1481CPD | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1481CUB | 功能描述:RS-422/RS-485 接口 IC RoHS:否 制造商:Maxim Integrated 数据速率:1136 Kbps 工作电源电压:3 V to 5.5 V 电源电流:5.9 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-28 封装:Tube |
| MAX1481CUB+ | 功能描述:RS-422/RS-485 接口 IC RS-485/RS-422 Transceivers RoHS:否 制造商:Maxim Integrated 数据速率:1136 Kbps 工作电源电压:3 V to 5.5 V 电源电流:5.9 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-28 封装:Tube |
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