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參數資料
| 型號： | AD7730LBR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | Bridge Transducer ADC |
| 中文描述： | 2-CH DELTA-SIGMA ADC, SERIAL ACCESS, PDSO24 |
| 封裝： | SOIC-24 |
| 文件頁數： | 30/52頁 |
| 文件大小： | 497K |
| 代理商： | AD7730LBR |
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AD7730/AD7730L
–30–
REV. A
Internally in the AD7730, the coefficients are normalized before
being used to scale the words coming out of the digital filter.
T he offset calibration register contains a value which, when
normalized, is subtracted from all conversion results. T he gain
calibration register contains a value which, when normalized, is
multiplied by all conversion results. T he offset calibration coeffi-
cient is subtracted from the result prior to the multiplication by
the gain coefficient.
T he AD7730 offers self-calibration or system calibration facili-
ties. For full calibration to occur on the selected channel, the on-
chip microcontroller must record the modulator output for two
different input conditions. T hese are “zero-scale” and “full-
scale” points. T hese points are derived by performing a conver-
sion on the different input voltages provided to the input of the
modulator during calibration. T he result of the “zero-scale”
calibration conversion is stored in the Offset Calibration Regis-
ter for the appropriate channel. T he result of the “full-scale”
calibration conversion is stored in the Gain Calibration Register
for the appropriate channel. With these readings, the microcon-
troller can calculate the offset and the gain slope for the input to
output transfer function of the converter. Internally, the part
works with 33 bits of resolution to determine its conversion
result of either 16 bits or 24 bits.
T he sequence in which the zero-scale and full-scale calibration
occurs depends upon the type of full-scale calibration being
performed. T he internal full-scale calibration is a two-step cali-
bration that alters the value of the Offset Calibration Register.
T hus, the user
must
perform a zero-scale calibration (either
internal or system) after an internal full-scale calibration to correct
the Offset Calibration Register contents. When using system
full-scale calibration, it is recommended that the zero-scale
calibration (either internal or system) is performed first.
Since the calibration coefficients are derived by performing a
conversion on the input voltage provided, the accuracy of the
calibration can only be as good as the noise level the part pro-
vides in normal mode. T o optimize the calibration accuracy, it
is recommended to calibrate the part at its lowest output rate
where the noise level is lowest. T he coefficients generated at any
output update rate will be valid for all selected output update
rates. T his scheme of calibrating at the lowest output update
rate does mean that the duration of calibration is longer.
Internal Zero-Scale Calibration
An internal zero-scale calibration is initiated on the AD7730 by
writing the appropriate values (1, 0, 0) to the MD2, MD1 and
MD0 bits of the Mode Register. In this calibration mode with a
unipolar input range, the zero-scale point used in determining
the calibration coefficients is with the inputs of the differential
pair internally shorted on the part (i.e., AIN(+) = AIN(–) =
Externally-Applied AIN(–) voltage). T he PGA is set for the
selected gain (as per the RN1, RN0 bits in the Mode Register)
for this internal zero-scale calibration conversion.
T he calibration is performed with dc excitation regardless of the
status of the ac bit. T he duration time of the calibration de-
pends upon the CHP bit of the Filter Register. With CHP = 1,
the duration is 22
×
1/Output Rate; with CHP = 0, the duration
is 24
×
1/Output Rate. At this time the MD2, MD1 and MD0
bits in the Mode Register return to 0, 0, 0 (Sync or Idle Mode
for the AD7730). T he
RDY
line goes high when calibration is
initiated and returns low when calibration is complete. Note
that the part has not performed a conversion at this time; it has
simply performed a zero-scale calibration and updated the Off-
set Calibration Register for the selected channel. T he user must
write either 0, 0, 1 or 0, 1, 0 to the MD2, MD1, MD0 bits of the
Mode Register to initiate a conversion. If
RDY
is low before (or
goes low during) the calibration command write to the Mode
Register, it may take up to one modulator cycle (MCLK IN/32)
before
RDY
goes high to indicate that calibration is in progress.
T herefore,
RDY
should be ignored for up to one modulator
cycle after the last bit of the calibration command is written to
the Mode Register.
For bipolar input ranges in the internal zero-scale calibrating
mode, the sequence is very similar to that just outlined. In this
case, the zero-scale point is exactly the same as above but since
the part is configured for bipolar operation, the output code for
zero differential input is 800000 Hex in 24-bit mode.
T he internal zero-scale calibration needs to be performed as
one part of a two part full calibration. However, once a full
calibration has been performed, additional internal zero-scale
calibrations can be performed by themselves to adjust the
part’s zero-scale point only. When performing a two step full
calibration care should be taken as to the sequence in which the
two steps are performed. If the internal zero-scale calibration is
one part of a full self-calibration, then it should take place after
an internal full-scale calibration. If it takes place in association
with a system full-scale calibration, then this internal zero-scale
calibration should be performed first.
Internal Full-Scale Calibration
An internal full-scale calibration is initiated on the AD7730 by
writing the appropriate values (1, 0, 1) to the MD2, MD1 and
MD0 bits of the Mode Register. In this calibration mode, the
full-scale point used in determining the calibration coefficients is
with an internally-generated full-scale voltage. T his full-scale
voltage is derived from the reference voltage for the AD7730
and the PGA is set for the selected gain (as per the RN1, RN0
bits in the Mode Register) for this internal full-scale calibration
conversion.
In order to meet the post-calibration numbers quoted in the
specifications, it is recommended that internal full-scale calibra-
tions be performed on the 80 mV range. T his applies even if the
subsequent operating mode is on the 10 mV, 20 mV or 40 mV
input ranges.
T he internal full-scale calibration is a two-step sequence that
runs when an internal full-scale calibration command is written
to the AD7730. One part of the calibration is a zero-scale cali-
bration and as a result, the contents of the Offset Calibration
Register are altered during this Internal Full-Scale Calibration.
T he user must therefore perform a zero-scale calibration (either
internal or system) AFT ER the internal full-scale calibration.
T his zero-scale calibration should be performed at the operating input
range.
T his means that internal full-scale calibrations cannot be
performed in isolation.
T he calibration is performed with dc excitation regardless of the
status of the ac bit. T he duration time of the calibration de-
pends upon the CHP bit of the Filter Register. With CHP = 1,
the duration is 44
×
1/Output Rate; with CHP = 0, the duration
is 48
×
1/Output Rate. At this time the MD2, MD1 and MD0
bits in the Mode Register return to 0, 0, 0 (Sync or Idle Mode
for the AD7730). T he
RDY
line goes high when calibration is
initiated and returns low when calibration is complete. Note
that the part has not performed a conversion at this time. T he
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| AD7730LBRU | Bridge Transducer ADC |
| AD7730 | Bridge Transducer ADC |
| AD7730BN | Bridge Transducer ADC |
| AD7730BR | Bridge Transducer ADC |
| AD7730BRU | Bridge Transducer ADC |
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| AD7730LBR-REEL | 制造商:Analog Devices 功能描述:ADC Single Delta-Sigma 600sps 24-bit Serial 24-Pin SOIC W T/R 制造商:Analog Devices 功能描述:ADC SGL DELTA-SIGMA 0.6KSPS 24BIT SERL 24SOIC W - Tape and Reel |
| AD7730LBR-REEL7 | 功能描述:IC ADC TRANSDUCER BRIDGE 24SOIC RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模擬前端 (AFE) 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數:- 通道數:2 功率（瓦特）:- 電壓 - 電源，模擬:3 V ~ 3.6 V 電壓 - 電源，數字:3 V ~ 3.6 V 封裝/外殼:32-VFQFN 裸露焊盤 供應商設備封裝:32-QFN（5x5） 包裝:帶卷 (TR) |
| AD7730LBRU | 功能描述:IC ADC TRANSDUCER BRIDGE 24TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模擬前端 (AFE) 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數:- 通道數:2 功率（瓦特）:- 電壓 - 電源，模擬:3 V ~ 3.6 V 電壓 - 電源，數字:3 V ~ 3.6 V 封裝/外殼:32-VFQFN 裸露焊盤 供應商設備封裝:32-QFN（5x5） 包裝:帶卷 (TR) |
| AD7730LBRU-REEL | 功能描述:IC ADC TRANSDUCER BRIDGE 24TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模擬前端 (AFE) 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數:- 通道數:2 功率（瓦特）:- 電壓 - 電源，模擬:3 V ~ 3.6 V 電壓 - 電源，數字:3 V ~ 3.6 V 封裝/外殼:32-VFQFN 裸露焊盤 供應商設備封裝:32-QFN（5x5） 包裝:帶卷 (TR) |
| AD7730LBRU-REEL7 | 功能描述:IC ADC TRANSDUCER BRIDGE 24TSSOP RoHS:否 類別:集成電路 (IC) >> 數據采集 - 模擬前端 (AFE) 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 位數:- 通道數:2 功率（瓦特）:- 電壓 - 電源，模擬:3 V ~ 3.6 V 電壓 - 電源，數字:3 V ~ 3.6 V 封裝/外殼:32-VFQFN 裸露焊盤 供應商設備封裝:32-QFN（5x5） 包裝:帶卷 (TR) |
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