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參數資料
| 型號： | AD7818AR |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 溫度/濕度傳感器 |
| 英文描述： | Single- and 4-Channel, 9 us, 10-Bit ADCs with On-Chip Temperature Sensor |
| 中文描述： | 與單核和4通道，9我們，10位ADC片上溫度傳感器 |
| 文件頁數： | 10/20頁 |
| 文件大小： | 279K |
| 代理商： | AD7818AR |
REV. C
–10–
AD7816/AD7817/AD7818
The AD7816, AD7817, and AD7818 are tested using the CCIF
standard where two input frequencies near the top end of the
input bandwidth are used. In this case, the second and third
order terms are of different significance. The second order terms
are usually distanced in frequency from the original sine waves
while the third order terms are usually at a frequency close to
the input frequencies. As a result, the second and third order
terms are specified separately. The calculation of the intermodu-
lation distortion is as per the THD specification where it is the
ratio of the rms sum of the individual distortion products to the
rms amplitude of the fundamental expressed in dBs.
Channel-to-Channel Isolation
Channel-to-channel isolation is a measure of the level of
crosstalk between channels. It is measured by applying a full-
scale 20 kHz sine wave signal to one input channel and deter-
mining how much that signal is attenuated in each of the other
channels. The figure given is the worst case across all four
channels.
Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum
deviation from a straight line passing through the endpoints of
the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal
1 LSB change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (0000 . . . 000)
to (0000 . . . 001) from the ideal, i.e., AGND + 1 LSB.
Offset Error Match
This is the difference in Offset Error between any two channels.
Gain Error
This is the deviation of the last code transition (1111. . . 110) to
(1111 . . . 111) from the ideal, i.e., VREF – 1 LSB, after the
offset error has been adjusted out.
Gain Error Match
This is the difference in Gain Error between any two channels.
Track/Hold Acquisition Time
Track/hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within
1/2 LSB, after the end of conversion (the point at which the
track/hold returns to track mode). It also applies to situations
where a change in the selected input channel takes place or
where there is a step input change on the input voltage applied
to the selected V
IN
input of the AD7817 or AD7818. It means
that the user must wait for the duration of the track/hold acqui-
sition time after the end of conversion or after a channel change/
step input change to V
IN
before starting another conversion, to
ensure that the part operates to specification.
CONTROL BYTE
The AD7816, AD7817, and AD7818 contain two on-chip regis-
ters, the Address Register and the Overtemperature Register.
These registers can be accessed by carrying out an 8-bit serial
write operation to the devices. The 8-bit word or control byte
written to the AD7816, AD7817, and AD7818 is transferred to
one of the two on-chip registers as follows.
Address Register
If the five MSBs of the control byte are logic zero, the three
LSBs of the control byte are transferred to the Address Regis-
ter—see Figure 4. The Address Register is a 3-bit-wide register
used to select the analog input channel on which to carry out a
conversion. It is also used to select the temperature sensor,
which has the address 000. Table I shows the selection. The
Internal Reference selection connects the input of the ADC to a
band gap reference. When this selection is made and a conver-
sion is initiated, the ADC output should be approximately mid-
scale. After power-up the default channel selection is DB2 = DB1
= DB0 = 0 (Temperature Sensor).
Table I. Channel Selection
DB2
DB1
DB0 Channel Selection
Device
0
0
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Temperature Sensor
Channel 1
Channel 2
Channel 3
Channel 4
Internal Ref (1.23 V)
All
AD7817/AD7818
AD7817
AD7817
AD7817
All
Overtemperature Register
If any of the five MSBs of the control byte are logic one, then
the entire eight bits of the control byte are transferred to the
Overtemperature Register—see Figure 4. At the end of a tem-
perature conversion a digital comparison is carried out between
the 8 MSBs of the temperature conversion result (10 bits) and
the contents of the Overtemperature Register (8 bits). If the result
of the temperature conversion is greater that the contents of the
Overtemperature Register (OTR), then the Overtemperature
Indicator (
OTI
) goes logic low. The resolution of the OTR is
1
°
C. The lowest temperature that can be written to the OTR is –
95
°
C and the highest is +152
°
C—see Figure 5. However, the
usable temperature range of the temperature sensor is –55
°
C to
+125
°
C. Figure 5 shows the OTR and how to set T
ALARM
(the
temperature at which the
OTI
goes low).
OTR
(
Dec
)
= T
ALARM
(
°
C
)
+
103
°
C
For example, to set T
ALARM
to 50
°
C, OTR = 50 + 103 = 153
Dec or 10011001 Bin. If the result of a temperature conversion
exceeds 50
°
C then
OTI
will go logic low. The
OTI
logic output
is reset high at the end of a serial read operation or if a new
temperature measurement is lower than T
ALARM
. The default
power on T
ALARM
is
50
°
C.
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
MSB
LSB
CONTROL BYTE
DB0
DB1
DB2
ADDRESS REGISTER
OVERTEMPERATURE
REGISTER (OTR)
IF ANY BIT DB7 TO DB3 IS SET TO
A LOGIC 1 THEN THE FULL 8 BITS
OF THE CONTROL WORD ARE WRITTEN
TO THE OVERTEMPERATURE REGISTER
IF DB7 TO DB3 ARE LOGIC 0
THEN DB2 TO DB0 ARE WRITTEN
TO THE ADDRESS REGISTER
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
Figure 4. Address and Overtemperature Register Selection
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| AD7818ARM | 功能描述:IC ADC 10BIT W/TEMP SNSR 8-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 熱管理 系列:- 標準包裝:2,500 系列:SilentSense™ 功能:溫度監控系統（傳感器） 傳感器類型:內部和外部 感應溫度:-55°C ~ 125°C，外部傳感器 精確度:±2°C 本地（最大），±3°C 遠程（最大） 拓撲:ADC（三角積分型），比較器，寄存器庫 輸出類型:I²C?/SMBus? 輸出警報:是 輸出風扇:是 電源電壓:2.7 V ~ 5.5 V 工作溫度:-55°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬） 供應商設備封裝:8-MSOP 包裝:帶卷 (TR) 其它名稱:MIC284-2BMMTRMIC284-2BMMTR-ND |
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| AD7818ARM-REEL7 | 制造商:Analog Devices 功能描述:ADC Single SAR 100ksps 10-bit Serial 8-Pin MSOP T/R 制造商:Analog Devices 功能描述:ADC SGL SAR 100KSPS 10-BIT SERL 8MSOP - Tape and Reel |
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