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參數(shù)資料
| 型號(hào)： | MX566AJN+ |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | DAC |
| 英文描述： | PARALLEL, WORD INPUT LOADING, 0.25 us SETTLING TIME, 12-BIT DAC, PDIP24 |
| 封裝： | PLASTIC, DIP-24 |
| 文件頁(yè)數(shù)： | 9/13頁(yè) |
| 文件大?。?/td> | 877K |
| 代理商： | MX566AJN+ |
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MAX31855
Cold-Junction Compensated
Thermocouple-to-Digital Converter
9
Maxim Integrated
the same temperature as the board on which the device
is mounted) can range from -55
N
C to +125
N
C. While the
temperature at the cold end fluctuates, the device con-
tinues to accurately sense the temperature difference at
the opposite end.
The device senses and corrects for the changes in
the reference junction temperature with cold-junction
compensation. It does this by first measuring its internal
die temperature, which should be held at the same tem-
perature as the reference junction. It then measures the
voltage from the thermocouple’s output at the reference
junction and converts this to the noncompensated ther-
mocouple temperature value. This value is then added
to the device’s die temperature to calculate the thermo-
couple’s “hot junction” temperature. Note that the “hot
junction” temperature can be lower than the cold junction
(or reference junction) temperature.
Optimal performance from the device is achieved when
the thermocouple cold junction and the device are at
the same temperature. Avoid placing heat-generating
devices or components near the MAX31855 because this
could produce cold-junction-related errors.
Conversion Functions
During the conversion time, t
CONV
, three functions are
performed: the temperature conversion of the internal
cold-junction temperature, the temperature conversion of
the external thermocouple, and the detection of thermo-
couple faults.
When executing the temperature conversion for the inter-
nal cold-junction compensation circuit, the connection to
signal from the external thermocouple is opened (switch
S4) and the connection to the cold-junction compensa-
tion circuit is closed (switch S5). The internal T- reference
to ground is still maintained (switch S3 is closed) and
the connections to the fault-detection circuit are open
(switches S1 and S2).
When executing the temperature conversion of the
external thermocouple, the connections to the internal
fault-detection circuit are opened (switches S1 and S2 in
the
Block Diagram
) and the switch connecting the cold-
junction compensation circuit is opened (switch S5). The
internal ground reference connection (switch S3) and
the connection to the ADC (switch S4) are closed. This
allows the ADC to process the voltage detected across
the T+ and T- terminals.
During fault detection, the connections from the exter-
nal thermocouple and cold-junction compensation cir-
cuit to the ADC are opened (switches S4 and S5). The
internal ground reference on T- is also opened (switch
S3). The connections to the internal fault-detection cir-
cuit are closed (switch S1 and S2). The fault-detection
circuit tests for shorted connections to V
CC
or GND on
the T+ and T- inputs, as well as looking for an open
thermocouple condition. Bits D0, D1, and D2 of the
output data are normally low. Bit D2 goes high to indi-
cate a thermocouple short to V
CC
, bit D1 goes high to
indicate a thermocouple short to GND, and bit D0 goes
high to indicate a thermocouple open circuit. If any of
these conditions exists, bit D16 of the SO output data,
which is normally low, also goes high to indicate that a
fault has occurred.
Serial Interface
The
Typical Application Circuit
shows the device inter-
faced with a microcontroller. In this example, the device
processes the reading from the thermocouple and
transmits the data through a serial interface. Drive
CS
low and apply a clock signal at SCK to read the results
at SO. Conversions are always being performed in the
background. The fault and temperature data are only be
updated when
CS
is high.
Drive
CS
low to output the first bit on the SO pin. A
complete serial-interface read of the cold-junction com-
pensated thermocouple temperature requires 14 clock
cycles. Thirty-two clock cycles are required to read both
the thermocouple and reference junction temperatures
(
Table 2
and
Table 3
.) The first bit, D31, is the thermo-
couple temperature sign bit, and is presented to the SO
pin within t
DV
of the falling edge of
CS
. Bits D[30:18]
contain the converted temperature in the order of MSB
to LSB, and are presented to the SO pin within t
D0
of the
falling edge of SCK. Bit D16 is normally low and goes
high when the thermocouple input is open or shorted to
GND or V
CC
. The reference junction temperature data
begins with D15.
CS
can be taken high at any point while
clocking out conversion data. If T+ and T- are uncon-
nected, the thermocouple temperature sign bit (D31) is
0, and the remainder of the thermocouple temperature
value (D[30:18]) is 1.
Figure 1
and
Figure 2
show the serial-interface timing
and order.
Table 2
and
Table 3
show the SO output bit
weights and functions.
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| MX7542JC/D | PARALLEL, 4 BITS INPUT LOADING, 12-BIT DAC, UUC16 |
| 12508HR-04A00 | 1.25mm PITCH CONNECTOR |
| 12508HR-05A00 | 1.25mm PITCH CONNECTOR |
| 12508HR-06A00 | 1.25mm PITCH CONNECTOR |
| 12508HR-07A00 | 1.25mm PITCH CONNECTOR |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MX566AJN+ | 功能描述:數(shù)模轉(zhuǎn)換器- DAC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| MX566AJQ | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:High Speed 12-Bit Monolithic D/A Converters |
| MX566AKCWG | 功能描述:數(shù)模轉(zhuǎn)換器- DAC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| MX566AKCWG+ | 功能描述:數(shù)模轉(zhuǎn)換器- DAC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
| MX566AKCWG+T | 功能描述:數(shù)模轉(zhuǎn)換器- DAC RoHS:否 制造商:Texas Instruments 轉(zhuǎn)換器數(shù)量:1 DAC 輸出端數(shù)量:1 轉(zhuǎn)換速率:2 MSPs 分辨率:16 bit 接口類型:QSPI, SPI, Serial (3-Wire, Microwire) 穩(wěn)定時(shí)間:1 us 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-14 封裝:Tube |
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