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器件3D模型￥ 176.68
MAX5253BCAP+T 其他数据使用手册 - Maxim Integrated（美信）
制造商:
Maxim Integrated（美信）
分类:
DA转换器
封装:
SSOP-20
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
MAX5253BCAP+T数据手册
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若手册格式错乱，请下载阅览PDF原文件
Figure 4. Adding a high-voltage op amp to the Figure 3 circuit provides vigorous gate drive to the
MOSFET, enabling longer-distance current-loop transmissions.
An external MOSFET (Table 2) drives the loop with a current determined by the 50Ω resistor:
I
OUT
= (V
REF
/R
SENSE
)(D
IN
/2
N
)
The DAC's resolution is N and the decimal equivalent of its input code is D
IN
, which represents the
sensor's digitized output after processing by the microcomputer. Resolution for the serial, 3V/5V
MAX535/MAX5351 converters is 13 bits, yielding a full-scale range of 2
N
= 2
13
= 8192. For a 1.2V
reference, 50Ω current-sense resistor, and full-scale DAC output of D
IN
= 8192, the output current is I
OUT
= V
REF
/R
SENSE
= 1.2V/50Ω = 24mA.
With outputs of 1.200V typical, the MAX6120/MAX6520 references are well suited for these applications.
Accuracy is 100ppm/°C (30ppm typical) for the MAX6120 and 50ppm/°C (25ppm typical) for the higher-
precision MAX6520. The small packages in Figures 3 and 4 (µMAX for the MAX535/MAX5351 and
SOT23 for the MAX6120/MAX6520) support space-critical applications. Some industrial-control current
loops have 60Ω sense resistors that allow maximum loop currents of only 20mA. This is not quite enough,
because most loops must be capable of delivering a 10% over-range (i.e., 20mA + 2mA = 22mA in this
case). Setting the reference voltage slightly higher (to 1.44V) solves this problem.
Table 2. N-Channel MOSFETS for 4–20mA Current Loops
Part
Number
FET Type
I
DSS
(mA)
BV
DS
(V) Manufacturer
ND2410L/B N-channel depletion 180/460 240 Siliconix
ND2020L/E N-channel depletion 132/180 200 Siliconix
BF245B N-channel depletion 25 30 Texas Instruments
BS107
N-channel
enhancement
120 200
Siliconix (similar to
BST80)
Monitoring Peak Currents through a Motor Block
Another application common to industrial environments is the digital control of synchronous/asynchronous
motors and servomotors. The circuit in Figure 5 detects excessive current in the motor block (i.e., motor
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