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參數(shù)資料
| 型號： | XTR108EA |
| 英文描述： | 4-20mA, TWO-WIRE TRANSMITTER Smart Programmable with Signal Conditioning |
| 中文描述： | 的4 - 20mA，兩線制變送器可編程智能與信號調(diào)理 |
| 文件頁數(shù)： | 18/27頁 |
| 文件大?。?/td> | 497K |
| 代理商： | XTR108EA |
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XTR108
SBOS187B
18
www.ti.com
For a test or calibration operation, it may be necessary to
write to a few select registers. This may be accomplished
without writing to register 15. To accomplish this, write to
the necessary registers and release CS1. There is no need to
update register 15.
If the command is to disable the automatic read-back func-
tion by setting the RDB bit in register 4, it is necessary to
rewrite the entire register set data with a correct checksum
value in register 15. The automatic read-back mode will be
disabled upon successful checksum operation.
The checksum error flag is also cleared when the XTR108
is reset (i.e.: at power ON). Write operations that do not
write to the checksum register will have no effect on the
checksum error flag. By locating the checksum register after
the last configuration register and including the checksum
register in the EEPROM read operation, the data is validated
by the checksum function.
EEPROM DATA SECURITY
Since the data in the EEPROM directly affects the analog
output of the XTR108, the data in the EEPROM needs to be
secure from accidental write operations. SPI EEPROM de-
vices have a write-protect function on one of the pins. An
additional connection to the calibration controller would be
required if the write-protect pin is used to prevent accidental
write operations. SPI EEPROM devices require a special
write enable instruction to be executed to write data to the
EEPROM. It is unlikely that this would accidentally be
written to the EEPROM device and then be followed by a
valid write operation. Further security can be obtained by
using an SPI EEPROM device that has internal write-protect
control bits. These bits are nonvolatile and must be cleared
before write operations are allowed.
SURGE PROTECTION
Remote connections to current transmitters can sometimes
be subjected to voltage surges. It is prudent to limit the
maximum surge voltage applied to the XTR108 with various
zener diodes and surge-clamping diodes specially designed
for this purpose. Since the maximum voltage on the XTR108
loop is limited by the external MOSFET breakdown voltage,
usually more than 200V, the requirement to the clamping
devices are not very strict. For example, a 50V protection
diode will assure proper transmitter operation at normal loop
voltages without significant leakage yet provide an appro-
priate level of protection against voltage surges. In case of
prolonged (seconds and longer) overvoltage, lower voltage
clamps may be used to limit the power dissipation on the
transmitter.
Most surge-protection zener diodes have a diode character-
istic in the forward direction that will conduct excessive
current, possibly damaging receiving-side circuitry if the
loop connections are reversed. If a surge protection diode is
used, a series diode or diode bridge should be used for
protection against reversed connections.
REVERSE-VOLTAGE PROTECTION
The XTR108’s low compliance rating (7.5V) permits the
use of various voltage protection methods without compro-
mising operating range. Figure 8 shows a diode bridge
circuit which allows normal operation even when the volt-
age connection lines are reversed. The bridge causes a two
diode drop (approximately 1.4V) loss in loop supply volt-
age. This results in a compliance voltage of approximately
9V—satisfactory for most applications. If 1.4V drop in loop
supply is too much, a diode can be inserted in series with the
loop supply voltage and the V+ pin. This protects against
reverse output connection lines with only a 0.7V loss in loop
supply voltage.
RADIO FREQUENCY INTERFERENCE
The long wire lengths of current loops invite radio frequency
interference. RF energy can be rectified by the sensitive
input circuitry of the XTR108 causing errors. This generally
appears as an unstable output current that varies with the
position of loop supply or input wiring.
If the RTD sensor is remotely located, the interference may
enter at the input terminals. For integrated transmitter as-
semblies with short connection to the sensor, the interfer-
ence more likely comes from the current loop connections.
Bypass capacitors on the input reduce or eliminate this input
interference. Connect these bypass capacitors to the I
RET
terminal, see Figure 9. Although the DC voltage at the I
RET
terminal is not equal to 0V (at the loop supply, V
PS
) this
circuit point can be considered the transmitter’s “ground.”
The 0.01
μ
F capacitor connected between V
LOOP
and I
O
may
help minimize output interference.
FIGURE 8. Reverse Voltage and Over-Voltage Protection.
XTR108
11
V+
I
O
V
PS
10
0.01
μ
F
R
L
D
1(1)
14
13
NOTE: (1) Zener Diode 36V: 1N4753A or General
Semiconductor Transorb
TM
1N6286A. Use lower
voltage zener diodes with loop power supply
voltages less than 30V for increased protection.
See
“
Over-Voltage Surge Protection.
”
Maximum V
must be
less than minimum
voltage rating of zener
diode.
The diode bridge causes
a 1.4V loss in loop supply
voltage.
1N4148
Diodes
12
I
RET
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| XTR108EA/2K5 | 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
| XTR108EA/2K5G4 | 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
| XTR108EA-2K5 | 制造商:BB 制造商全稱:BB 功能描述:4-20mA, TWO-WIRE TRANSMITTER a??Smarta?? Programmable with Signal Conditioning |
| XTR108EA-2K5G4 | 制造商:BB 制造商全稱:BB 功能描述:4-20mA, TWO-WIRE TRANSMITTER a??Smarta?? Programmable with Signal Conditioning |
| XTR108EAG4 | 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
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