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參數(shù)資料
| 型號(hào)： | AD774B |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 串行ADC |
| 英文描述： | Complete 12-Bit A/D Converters(完備的12位A/D轉(zhuǎn)換器) |
| 中文描述： | 完整的12位A / D轉(zhuǎn)換器（完備的12位的A / D轉(zhuǎn)換器） |
| 文件頁數(shù)： | 9/12頁 |
| 文件大小： | 335K |
| 代理商： | AD774B |
AD674B/AD774B
REV. B
–9–
UNIPOLAR RANGE CONNECTIONS FOR THE AD674B
AND AD774B
The AD674B and AD774B contain all the active components
required to perform a complete 12-bit A/D conversion. Thus,
for most situations, all that is necessary is connection of the
power supplies (+5 V, +12/+15 V and –12/–15 V), the analog
input, and the conversion initiation command, as discussed on
the next page.
Figure 7. Unipolar Input Connections
All of the thin-film application resistors of the AD674B and
AD774B are factory trimmed for absolute calibration. There-
fore, in many applications, no calibration trimming will be re-
quired. The absolute accuracy for each grade is given in the
specification tables. For example, if no trims are used,
±
2 LSB
max zero offset error and
±
0.25% (10 LSB) max full-scale error
are guaranteed. If the offset trim is not required, Pin 12 can be
connected directly to Pin 9; the two resistors and trimmer for
Pin 12 are then not needed. If the full-scale trim is not required,
a 50
1% metal film resistor should be connected between Pin
8 and Pin 10.
The analog input is connected between Pins 13 and 9 for a 0 to
+10 V input range, between Pins 14 and 9 for a 0 to +20 V in-
put range. Input signals beyond the supplies are easily accom-
modated. For the 10 volt span input, the LSB has a nominal
value of 2.44 mV; for the 20 volt span, 4.88 mV. If a 10.24 V
range is desired (nominal 2.5 mV/bit), the gain trimmer (R2)
should be replaced by a 50
resistor, and a 200
trimmer in-
serted in series with the analog input to Pin 13 (for a full-scale
range of 20.48 V (5 mV/bit), use a 500
trimmer into Pin 14).
The gain trim described below is now done with these trimmers.
The nominal input impedance into Pin 13 is 5 k
, and 10 k
into Pin 14.
UNIPOLAR CALIBRATION
The connections for unipolar ranges are shown in Figure 7. The
AD674B or AD774B is trimmed to a nominal 1/2 LSB offset so
that the exact analog input for a given code will be in the middle
of that code (halfway between the transitions to the codes above
and below it). Thus, when properly calibrated, the first transi-
tion (from 0000 0000 0000 to 0000 0000 0001) will occur for
an input level of +1/2 LSB (1.22 mV for 10 V range).
If Pin 12 is connected to Pin 9, the unit will behave in this man-
ner, within specifications. If the offset trim (R1) is used, it
should be trimmed as above, although a different offset can be
set for a particular system requirement. This circuit will give ap-
proximately
±
15 mV of offset trim range.
The full-scale trim is done by applying a signal 1 1/2 LSB below
the nominal full scale (9.9963 for a 10 V range). Trim R2 to
give the last transition (1111 1111 1110 to 1111 1111 1111).
BIPOLAR OPERATION
The connections for bipolar ranges are shown in Figure 8.
Again, as for the unipolar ranges, if the offset and gain specifica-
tions are sufficient, one or both of the trimmers shown can be
replaced by a 50
±
1% fixed resistor. The analog input is
applied as for the unipolar ranges. Bipolar calibration is similar
to unipolar calibration. First, a signal 1/2 LSB above negative
full scale (–4.9988 V for the
±
5 V range) is applied and R1 is
trimmed to give the first transition (0000 0000 0000 to 0000
0000 0001). Then a signal 1 1/2 LSB below positive full scale
(+4.9963 V for the
±
5 V range) is applied and R2 trimmed to
give the last transition (1111 1111 1110 to 1111 1111 1111).
Figure 8. Bipolar Input Connections
GROUNDING CONSIDERATIONS
The analog common at Pin 9 is the ground reference point for
the internal reference and is thus the “high quality” ground for
the ADC; it should be connected directly to the analog refer-
ence point of the system. In order to achieve the high accuracy
performance available from the ADC in an environment of high
digital noise content, it is required that the analog and digital
commons be connected together at the package. In some situa-
tions, the digital common at Pin 15 can be connected to the
most convenient ground reference point; digital power return is
preferred.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD774BAD | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| AD774BAR | 功能描述:IC ADC 12BIT W/BUFF REF 28-SOIC RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 位數(shù):14 采樣率（每秒）:83k 數(shù)據(jù)接口:串行，并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應(yīng)商設(shè)備封裝:28-PDIP 包裝:管件 輸入數(shù)目和類型:1 個(gè)單端，雙極 |
| AD774BARZ | 功能描述:IC ADC 12BIT W/BUFF REF 28-SOIC RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 位數(shù):14 采樣率（每秒）:83k 數(shù)據(jù)接口:串行，并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應(yīng)商設(shè)備封裝:28-PDIP 包裝:管件 輸入數(shù)目和類型:1 個(gè)單端，雙極 |
| AD774BBD | 功能描述:IC ADC 12BIT W/BUFF REF 28-CDIP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 模數(shù)轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 位數(shù):14 采樣率（每秒）:83k 數(shù)據(jù)接口:串行，并聯(lián) 轉(zhuǎn)換器數(shù)目:1 功率耗散（最大）:95mW 電壓電源:雙 ± 工作溫度:0°C ~ 70°C 安裝類型:通孔 封裝/外殼:28-DIP（0.600"，15.24mm） 供應(yīng)商設(shè)備封裝:28-PDIP 包裝:管件 輸入數(shù)目和類型:1 個(gè)單端，雙極 |
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