参数资料
型号: ADM2687EBRIZ-RL7
厂商: Analog Devices Inc
文件页数: 17/24页
文件大小: 0K
描述: IC TXRX ISOLATED RS485 16SOIC
标准包装: 400
系列: isoPower®
类型: 收发器
电压 - 隔离: 5000Vrms
输入类型: DC
电源电压: 3.3V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 16-SOIC(0.295",7.50mm 宽)
供应商设备封装: 16-SOIC-IC
包装: 带卷 (TR)
Data Sheet
is assumed to be unpowered or nonfunctional, in which case,
the isolator output is forced to a default state by the watchdog
timer circuit.
This situation should occur in the ADM2682E / ADM2687E devices
only during power-up and power-down operations. The limitation
on the ADM2682E / ADM2687E magnetic field immunity is set
by the condition in which induced voltage in the transformer
receiving coil is sufficiently large to either falsely set or reset the
decoder. The following analysis defines the conditions under
which this can occur.
The 3.3 V operating condition of the ADM2682E / ADM2687E
is examined because it represents the most susceptible mode of
operation. The pulses at the transformer output have an amplitude
of >1.0 V. The decoder has a sensing threshold of about 0.5 V,
thus establishing a 0.5 V margin in which induced voltages can
be tolerated. The voltage induced across the receiving coil is
given by
V = (? d β/ dt )Σπ r n 2 ; n = 1, 2, … , N
ADM2682E/ADM2687E
For example, at a magnetic field frequency of 1 MHz, the
maximum allowable magnetic field of 0.2 kgauss induces a
voltage of 0.25 V at the receiving coil. This is about 50% of the
sensing threshold and does not cause a faulty output transition.
Similarly, if such an event occurs during a transmitted pulse
(and is of the worst-case polarity), it reduces the received pulse
from >1.0 V to 0.75 V, which is still well above the 0.5 V sensing
threshold of the decoder.
The preceding magnetic flux density values correspond to specific
current magnitudes at given distances from the ADM2682E /
ADM2687E transformers. Figure 40 expresses these allowable
current magnitudes as a function of frequency for selected
distances. As shown in Figure 40, the ADM2682E / ADM2687E
are extremely immune and can be affected only by extremely
large currents operated at high frequency very close to the
component. For the 1 MHz example, a 0.5 kA current must be
placed 5 mm away from the ADM2682E / ADM2687E to affect
component operation.
1k
where:
β is magnetic flux density (gauss).
N is the number of turns in the receiving coil.
r n is the radius of the n th turn in the receiving coil (cm).
Given the geometry of the receiving coil in the ADM2682E /
ADM2687E and an imposed requirement that the induced
voltage be, at most, 50% of the 0.5 V margin at the decoder, a
maximum allowable magnetic field is calculated as shown in
100
10
1
0.1
DISTANCE = 100mm
DISTANCE = 5mm
DISTANCE = 1m
100
0.01
1k
10k
100k
1M
10M
100M
10
MAGNETIC FIELD FREQUENCY (Hz)
Figure 40. Maximum Allowable Current for Various Current-to-
1
0.1
0.01
0.001
ADM2682E / ADM2687E Spacings
Note that in combinations of strong magnetic field and high
frequency, any loops formed by PCB traces can induce error
voltages sufficiently large to trigger the thresholds of succeeding
circuitry. Take care in the layout of such traces to avoid this
possibility.
1k
10k
100k
1M
10M
100M
MAGNETIC FIELD FREQUENCY (Hz)
Figure 39. Maximum Allowable External Magnetic Flux Density
Rev. B | Page 17 of 24
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ADM2795EBRWZ 功能描述:1/1 Transceiver Half RS422, RS485 制造商:analog devices inc. 系列:- 包装:管件 零件状态:在售 类型:收发器 协议:RS422,RS485 驱动器/接收器数:1/1 双工:半 接收器滞后:30mV 数据速率:2.5Mbps 电压 - 电源:1.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C(TA) 安装类型:* 封装/外壳:* 供应商器件封装:* 标准包装:47
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