參數(shù)資料
型號(hào)： XE8805AMI028LF
廠商： Semtech
文件頁數(shù)： 37/156頁
文件大?。?/td> 0K
描述： IC DAS 16BIT FLASH 8K MTP 64LQFP
標(biāo)準(zhǔn)包裝： 160
系列： XE880x
應(yīng)用： 感測機(jī)
核心處理器： Coolrisc816?
程序存儲(chǔ)器類型： 閃存（22 kB）
控制器系列： XE8000
RAM 容量： 512 x 8
接口： UART，USRT
輸入/輸出數(shù)： 24
電源電壓： 2.4 V ~ 5.5 V
工作溫度： -40°C ~ 85°C
安裝類型： 表面貼裝
封裝/外殼： 64-LQFP
包裝： 托盤
供應(yīng)商設(shè)備封裝： 64-LQFP（10x10）
產(chǎn)品目錄頁面： 585 (CN2011-ZH PDF)
配用： XE8000MP-ND - PROG BOARD AND PROSTART2 CARD
Semtech 2006
www.semtech.com
18-10
XE8805/05A
XE88xx
DAS_OUT
DAS_AI_M
DAS_AO
DAS_AI_P
amp
analog ground
R
C
nR
mC
kR
D
A
c
o
n
t
r
o
l
Figure 18-3. Second order low pass filter.
18.7
4-20mA loop
18.7.1
2-wire loop with first order filtering
The amplifier can be used to build a 4-20mA loop externally. Figure 18-4 shows the principle of such a 2-wire loop
using a first order low pass filter.
In a 2-wire loop, the current consumption of the sensor and read-out electronics is drawn on the same wires as the
signal current. The current consumption of the sensor and read-out electronics should therefore remain below
4mA. The signal current is then added by the bipolar transistor. The resistors Rlim1 and Rlim2 are added to protect
the bipolar transistor against high transient currents during power-up. Rlim1 is generally set to a few k. The value
of Rlim2 is chosen as a function of the external loop voltage VEXT and the transistor saturation voltage VCEsat.
mA
R
V
R
sense
CEsat
EXT
20
)
20
(
2
lim
=
If VEXT is larger than 5.5V, a voltage regulator has to be inserted. Since the quiescent current of the regulator adds
up to the 4mA budget, a component with sufficiently low quiescent current has to be selected.
The resistor Rsense measures the total current in the loop (if Rsense<<Rf2). The resistors Rf1 and Rf2 are used to set
the gain and Rf2 and Cf to set the bandwidth of the filter. The resistor Roffset adds an offset to the filter voltage so
that the code 0 of the D/A corresponds to 4mA. The amplifier will force a current through the bipolar transistor so
that the voltage on the filter Vf and VSS on Rsense is equal. This transforms the filter voltage into a loop current
Iloop=(VSS-VEXT-)/Rsense.
Not
Recommended
for
New
Designs
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參數(shù)描述
XE8805AMI028TLF 制造商:Semtech Corporation 功能描述:
XE8805MI028 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Data Acquisition MCU
XE8806A 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Ultra Low-Power Low-Voltage
XE8806AMI000 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Ultra Low-Power Low-Voltage
XE8806AMI026LF 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Ultra Low-Power Low-Voltage
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