參數(shù)資料
型號(hào)： MAX1617AMEE
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 溫度/濕度傳感器
英文描述： Remote/Local Temperature Sensor with SMBus Serial Interface
中文描述： DIGITAL TEMP SENSOR-SERIAL, 8BIT(s), 3Cel, RECTANGULAR, SURFACE MOUNT
封裝： PLASTIC, QSOP-16
文件頁(yè)數(shù)： 8/18頁(yè)
文件大?。?/td> 234K
代理商： MAX1617AMEE
Excess resistance in series with the remote diode caus-
es about +1/2°C error per ohm. Likewise, 200μV of off-
set voltage forced on DXP–DXN causes about 1°C error.
A/D Conversion S equenc e
If a Start command is written (or generated automatical-
ly in the free-running auto-convert mode), both channels
are converted, and the results of both measurements
are available after the end of conversion. A BUSY status
bit in the status byte shows that the device is actually
performing a new conversion; however, even if the ADC
is busy, the results of the previous conversion are
always available.
Remote-Diode S elec tion
Temperature accuracy depends on having a good-qual-
ity, diode-connected small-signal transistor. Accuracy
has been experimentally verified for all of the devices
listed in Table 1. The MAX1617A can also directly mea-
sure the die temperature of CPUs and other integrated
circuits having on-board temperature-sensing diodes.
The transistor must be a small-signal type with a rela-
tively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage
must be greater than 0.25V at 10μA; check to ensure
this is true at the highest expected temperature. The
forward voltage must be less than 0.95V at 100μA;
check to ensure this is true at the lowest expected tem-
perature. Large power transistors don’t work at all. Also
ensure that the base resistance is less than 100
. Tight
specifications for forward-current gain (+50 to +150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
VBE characteristics.
For heatsink mounting, the 500-32BT02-000 thermal
sensor from Fenwal Electronics is a good choice. This
device consists of a diode-connected transistor, an
aluminum plate with screw hole, and twisted-pair cable
(Fenwal Inc., Milford, MA, 508-478-6000).
T hermal Mass and S elf-Heating
Thermal mass can seriously degrade the MAX1617A’s
effective accuracy. The thermal time constant of the
QSOP-16 package is about 140sec in still air. For the
MAX1617A junction temperature to settle to within +1°C
after a sudden +100°C change requires about five time
constants or 12 minutes. The use of smaller packages
for remote sensors, such as SOT23s, improves the situ-
ation. Take care to account for thermal gradients
between the heat source and the sensor, and ensure
that stray air currents across the sensor package do
not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
worst-case error occurs when auto-converting at the
fastest rate and simultaneously sinking maximum cur-
rent at the
ALERT
output. For example, at an 8Hz rate
and with
ALERT
sinking 1mA, the typical power dissi-
pation is V
CC
·
450μA plus 0.4V
·
1mA. Package theta
J -A is about 150°C/W, so with V
CC
= 5V and no copper
PC board heatsinking, the resulting temperature rise is:
dT = 2.7mW
·
150°C/W = 0.4°C
Even with these contrived circumstances, it is difficult
to introduce significant self-heating errors.
ADC Noise Filtering
The ADC is an integrating type with inherently good
noise rejection, especially of low-frequency signals
such as 60Hz/120Hz power-supply hum. Micropower
operation places constraints on high-frequency noise
rejection; therefore, careful PC board layout and proper
external noise filtering are required for high-accuracy
remote measurements in electrically noisy environ-
ments.
High-frequency EMI is best filtered at DXP and DXN
with an external 2200pF capacitor. This value can be
increased to about 3300pF (max), including cable
capacitance. Higher capacitance than 3300pF intro-
duces errors due to the rise time of the switched cur-
rent source.
Nearly all noise sources tested cause the ADC measure-
ments to be higher than the actual temperature, typically
by +1°C to +10°C, depending on the frequency and
amplitude (see Typical Operating Characteristics).
M
Remote/Loc al Temperature S ensor
with S MBus S erial Interfac e
8
_______________________________________________________________________________________
CMPT3904
Central Semiconductor (USA)
MMBT3904
Motorola (USA)
MMBT3904
SST3904
Rohm Semiconductor (J apan)
KST3904-TF
Samsung (Korea)
FMMT3904CT-ND
Zetex (England)
MANUFACTURER
MODEL NUMBER
SMBT3904
Siemens (Germany)
Table 1. Remote-Sensor Transistor
Manufacturers
Note
: Transistors must be diode-connected (base shorted to
collector).
National Semiconductor (USA)
·
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1617AMEE+ 功能描述:板上安裝溫度傳感器 Remote/Local w/SMBus Serial Interface RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
MAX1617AMEE+ 制造商:Maxim Integrated Products 功能描述:IC TEMP SENSOR 8BIT ?2.5
MAX1617AMEE+T 功能描述:板上安裝溫度傳感器 Remote/Local w/SMBus Serial Interface RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
MAX1617AMEE+TW 功能描述:板上安裝溫度傳感器 Remote/Local Temperature Sensor with SMBus Serial Interface RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
MAX1617AMEE+W 功能描述:板上安裝溫度傳感器 Remote/Local Temperature Sensor with SMBus Serial Interface RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
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