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参数资料
| 型号： | LTC2856CDD-2#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 5/20页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS485/RS422 8-DFN |
| 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-WFDFN 裸露焊盘 |
| 供应商设备封装： | 8-DFN-EP（3x3） |
| 包装： | 带卷 (TR) |
LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
13
285678ff
For more information www.linear.com/LTC2856-1
applicaTions inFormaTion
High Speed Considerations
A ground plane layout is recommended. A 0.1F bypass
capacitorlessthanone-quarterinchawayfromtheVCCpin
is also recommended. The PC board traces connected to
signals A/B and Z/Y should be symmetrical and as short
as possible to maintain good differential signal integrity.
To minimize capacitive effects, the differential signals
should be separated by more than the width of a trace
and should not be routed on top of each other if they are
on different signal planes.
Care should be taken to route outputs away from any
sensitive inputs to reduce feedback effects that might
cause noise, jitter or even oscillations. For example, in the
full-duplex LTC2857-1, DI and A/B should not be routed
near the driver or receiver outputs.
Thelogicinputshave100mVofhysteresistoprovidenoise
immunity. Fast edges on the outputs can cause glitches in
the ground and power supplies which are exacerbated by
capacitive loading. If a logic input is held near its threshold
(typically 1.5V), a noise glitch from a driver transition may
exceed the hysteresis levels on the logic and data input
pins causing an unintended state change. This can be
avoided by maintaining normal logic levels on the pins
and by slewing inputs through their thresholds by faster
than 1V/s when transitioning. Good supply decoupling
and proper line termination also reduce glitches caused
by driver transitions.
Cable Length vs Data Rate
For a given data rate, the maximum transmission distance
is bounded by the cable properties. A typical curve of cable
length vs data rate compliant with the RS485 standard is
showninFigure9.Threeregionsofthiscurvereflectdiffer-
entperformancelimitingfactorsindatatransmission.Inthe
flat region of the curve, maximum distance is determined
by resistive losses in the cable. The downward sloping
region represents limits in distance and data rate due to
AC losses in the cable. The solid vertical line represents
the specified maximum data rate in the RS485 standard.
The dashed line at 250kbps shows the maximum data rate
of the low-EMI LTC2856-2, LTC2857-2, and LTC2858-2.
Thedashedlineat20Mbpsshowsthemaximumdatarates
of the LTC2856-1, LTC2857-1 and LTC2858-1.
Figure 8. Supply Current vs Data Rate
Cable Termination
Proper cable termination is very important for good signal
fidelity. If the cable is not terminated with its characteristic
impedance, reflections will result in distorted waveforms.
RS485 transceivers typically communicate over twisted-
pair cables with characteristic impedance ranging from
100
Ω to 120Ω. Each end of the network should be termi-
nated with a discrete resistor matching the characteristic
impedance or with an LTC2859/LTC2861 transceiver with
integrated termination capability.
Figure 9. Cable Length vs Data Rate
(RS485 Standard Shown in Solid Vertical Lines)
DATA RATE (kbps)
102
45
CURRENT
(mA)
65
70
75
103
104
105
285678 F08
60
55
50
RDIFF = 54
CL = 1000pF
CL = 100pF
285678 F09
DATA RATE (bps)
CABLE
LENGTH
(F
T)
10k
1M
10M
100k
100M
100
1k
10
10k
LOW-EMI MODE
MAX DATA RATE
RS485 MAX
DATA RATE
NORMAL
MODE MAX
DATA RATE
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| LTC2856CMS8-1#PBF | 功能描述:IC TXRX RS485/RS422 8-MSOP RoHS:是 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:RS-232 & USB Transceiver 标准包装:2,000 系列:- 类型:收发器 驱动器/接收器数:1/1 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-SSOP（0.209"，5.30mm 宽） 供应商设备封装:16-SSOP 包装:带卷 (TR) 其它名称:296-19849-2 |
| LTC2856CMS8-1#TRPBF | 功能描述:IC TXRX RS485/RS422 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:121 系列:- 类型:收发器 驱动器/接收器数:1/1 规程:RS422，RS485 电源电压:3 V ~ 3.6 V 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-DFN（3x3） 包装:管件 |
| LTC2856CMS8-2#PBF | 功能描述:IC TXRX RS485/RS422 8-MSOP RoHS:是 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:RS-232 & USB Transceiver 标准包装:2,000 系列:- 类型:收发器 驱动器/接收器数:1/1 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-SSOP（0.209"，5.30mm 宽） 供应商设备封装:16-SSOP 包装:带卷 (TR) 其它名称:296-19849-2 |
| LTC2856CMS8-2#TRPBF | 功能描述:IC TXRX RS485/RS422 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:121 系列:- 类型:收发器 驱动器/接收器数:1/1 规程:RS422，RS485 电源电压:3 V ~ 3.6 V 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-DFN（3x3） 包装:管件 |
| LTC2856HDD-1#PBF | 功能描述:IC TXRX RS485/RS422 8-DFN 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:121 系列:- 类型:收发器 驱动器/接收器数:1/1 规程:RS422，RS485 电源电压:3 V ~ 3.6 V 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-DFN（3x3） 包装:管件 |
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