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參數(shù)資料
| 型號(hào)： | PGA309 |
| 英文描述： | Voltage Output PROGRAMMABLE SENSOR CONDITIONER |
| 中文描述： | 電壓輸出可編程傳感器空調(diào) |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 298K |
| 代理商： | PGA309 |
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SBOS292A DECEMBER 2003 REVISED AUGUST 2004
www.ti.com
15
ADC FOR TEMPERATURE SENSING
The
temperature
compensation for the sensor span and offset drift.
Either internal or external temperature sensing is
possible. The temperature can be sensed in one of the
following ways:
Bridge impedance change (excitation current
sense, in the positive or negative part of the bridge),
for sensors with large temperature coefficient of
resistance (TCR > 0.1%/
°
C).
On-chip PGA309 temperature, when the chip is
located sufficiently close to the sensor.
External diode, thermistor, or RTD placed on the
sensor membrane. An internal 7
μ
A current source
may be enabled to excite these types of
temperature sensors.
The temperature signal is digitized by the onboard
Temp ADC. The output of the Temp ADC is used by the
control digital circuit to read the data from the Lookup
Table in an external EEPROM, and set the output of the
Gain DAC and the Zero DAC to the calibrated values as
temperature changes.
An additional function provided through the Temp ADC
is the ability to read the V
OUT
pin back through the Temp
ADC input mux. This provides flexibility for a digital
output through either One-Wire or Two-Wire interface,
as well as the possibility for an external microcontroller
to perform real-time custom calibration of the PGA309.
sense
circuitry
drives
the
EXTERNAL EEPROM AND TEMPERATURE
COEFFICIENTS
The PGA309 uses an industry-standard Two-Wire
external EEPROM (typically, a SOT23-5 package). A
1k-bit (minimum) EEPROM is needed when using all 17
temperature coefficients. Larger EEPROMs may be
used to provide space for a serial number, lot code, or
other data.
The first part of the external EEPROM contains the
configuration data for the PGA309, with settings for:
Register 3—Reference Control and Linearization
Register 4—PGA Coarse Offset and Gain/Output
Amplifier Gain
Register 5—PGA Configuration and Over/Under-
Scale Limit
Register 6—Temp ADC Control
This section of the EEPROM contains its own individual
checksum (Checksum1).
The second part of the external EEPROM contains up
to 17 temperature index values and corresponding
temperature coefficients for the Zero DAC and Gain
DAC adjustments with measured temperature, and
also contains its own checksum (Checksum2).
The PGA309 lookup logic contains a linear interpolation
algorithm for accurate DAC adjustments between
stored temperature indexes. This approach allows for
a piecewise linear temperature compensation of up to
17 temperature indexes and associated temperature
coefficients.
If either Checksum1, Checksum2, or both are incorrect,
the output of the PGA309 is set to high-impedance.
FAULT MONITOR
To detect sensor burnout or a short, a set of four
comparators are connected to the inputs of the
Front-End PGA. If any of the inputs are taken to within
100mV of ground or V
EXC,
or violate the input CMR of
the
Front-End
PGA,
then
comparator sets a sensor fault flag that causes the
PGA309 V
OUT
to be driven within 100mV of either V
SA
or ground, depending upon the alarm configuration
setting
(Register
5—PGA
Over/Under-Scale Limit). This will be well above the set
Over-Scale Limit level or well below the set
Under-Scale Limit level. The state of the fault condition
can be read in digital form in Register 8—Alarm Status
Register. If the Over/Under-Scale Limit is disabled, the
PGA309 output voltage will still be driven within 100mV
of either V
SA
or ground, depending upon the alarm
configuration setting.
There are five other fault detect comparators that help
detect subtle PGA309 front-end violations that could
otherwise result in linear voltages at V
OUT
that would be
interpreted as valid states. These are especially useful
during factory calibration and setup, and are configured
through
Register
5—PGA
Over/Under-Scale Limit. Their status can also be read
back through Register 8—Alarm Status Register.
the
corresponding
Configuration
and
Configuration
and
OVER-SCALE AND UNDER-SCALE LIMITS
The over-scale and under-scale limit circuitry combined
with the fault monitor circuitry provides a means for
system diagnostics. A typical sensor-conditioned
output may be scaled for 10% to 90% of the system
ADC range for the sensor normal operating range. If the
conditioned pressure sensor is below 4%, it is
considered under-pressure; if over 96%, it is
considered over-pressure.
The PGA309 over/under-scale limit circuit can be
programmed
individually
over-scale values that clip or limit the PGA309 output.
From a system diagnostic view, 10% to 90% of ADC
range is normal operation, < 4% is under-pressure, and
> 96% is over-pressure. If the fault detect circuitry is
used, a detected fault will cause the PGA309 output to
be driven to positive or negative saturation. If this fault
for
under-scale
and
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PGA309_05 | 制造商:BB 制造商全稱:BB 功能描述:Voltage Output PROFRAMMABLE SENSOR CONDITIONER |
| PGA309_11 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Voltage Output Programmable Sensor Conditioner |
| PGA309AIPWR | 功能描述:電流靈敏放大器 PGA309 Voltage Out Prog Sensor Cndtner RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補(bǔ)償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
| PGA309AIPWRG4 | 功能描述:電流靈敏放大器 PGA309 Voltage Out Prog Sensor Cndtner RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補(bǔ)償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
| PGA309AIPWT | 功能描述:電流靈敏放大器 PGA309 Voltage Out Prog Sensor Cndtner RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補(bǔ)償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
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