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參數(shù)資料
| 型號： | AD7805BR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | DAC |
| 英文描述： | %2B3.3V to %2B5V Quad/Octal 10-Bit DACs |
| 中文描述： | PARALLEL, WORD INPUT LOADING, 1.5 us SETTLING TIME, 10-BIT DAC, PDSO28 |
| 封裝： | SOIC-28 |
| 文件頁數(shù)： | 11/28頁 |
| 文件大?。?/td> | 300K |
| 代理商： | AD7805BR |
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AD7804/AD7805/AD7808/AD7809
–11–
REV. A
V
BIAS
can be the internal bandgap reference, the internal V
DD
/2
reference or the external REFIN as determined by MX1 and
MX0 in the channel control register. A second external refer-
ence can be used if required by overdriving the V
DD
/2 reference
which appears at the COMP pin.
System Standby (SSTBY)
This bit allows all the DACs in the package to be put into low
power mode simultaneously but the reference is not affected.
Writing a one to the SSTBY bit in the system control register
puts all DACs into standby mode. On writing a one to this bit
all linear circuitry is switched off and the DAC outputs are
connected through a high impedance to ground. The DACs come
out of standby mode when a 0 is written to the SSTBY bit.
System Clear Function (SCLR)
This function allows the user to clear the contents of all data
and DAC registers in software. Writing a one to the SCLR bit
in the control register clears the DAC’s outputs. A zero in this
bit position puts the DAC in normal operating mode. The out-
put of the Main DACs are cleared to one of two voltages de-
pending on the input coding used. If twos complement coding
is selected, then issuing a software clear will reset the output of
the Main DAC to midscale (V
BIAS
). If offset binary coding is
selected, the Main DAC output will be reset to V
BIAS
/16 follow-
ing the execution of a software clear. This system clear function
does not affect the Sub DAC; the Sub DAC data register retains
its value during a system software clear (SCLR).
AD7804/AD7808 CHANNEL CONTROL REGISTER (MD1 = 0,
MD0 = 1)
This register allows the user to have control over individual
DACs in the package. The control bits in this register include
the address bits for the selected DAC, standby (
STBY
), indi-
vidual DAC clear (CLR) and multiplexer output selection
(MX1 and MX0). The function of these bits follows.
DAC Selection (A2, A1, A0)
Bits A2, A1 and A0 in the input registers are used to address a
specific DAC. Table IIa shows the selection table for the DACs
of the AD7804. Table IIb shows the selection table for the
DACs of the AD7808.
Table IIa. DAC Selection Table for the AD7804
A2
A1
A0
Function
X
X
X
X
0
0
1
1
0
1
0
1
DAC A Selected
DAC B Selected
DAC C Selected
DAC D Selected
Table IIb. DAC Selection Table for the AD7808
A2
A1
A0
Function
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
DAC A Selected
DAC B Selected
DAC C Selected
DAC D Selected
DAC E Selected
DAC F Selected
DAC G Selected
DAC H Selected
Standby (
STBY
)
This bit allows the selected DAC in the package to be put into
low power mode. Writing a zero to the
STBY
bit in the channel
control register puts the selected DAC into standby mode. On
writing a zero to this bit all linear circuitry is switched off and
the DAC output is connected through a high impedance to
ground. The DAC is returned to normal operation by writing a
one to the
STBY
bit.
Software Clear Function (CLR)
This function allows the user to clear the contents of the se-
lected DAC’s data in software. Writing a one to the CLR bit in
the control register clears the DAC’s output. A zero in the CLR
bit position puts the DAC in normal operating mode. This
software CLR operation clears only the Main DAC, the con-
tents of the Sub DAC is unaffected by a CLR operation. The
output of the Main DAC can be cleared to one of two places
depending on the input coding used. An
LDAC
pulse is re-
quired to activate the channel clear function and must be ap-
plied after the bit in the channel control register is set or reset. If
twos complement coding is selected, then issuing a software
clear will reset the output of the Main DAC to midscale (V
BIAS
).
If offset binary coding is selected, the Main DAC output will be
reset to V
BIAS
/16 following the execution of a software clear.
Multiplexer Selection (MX1, MX0)
These two bits are used to select the reference input for the
selected DAC. Table III shows the options available.
Table III. Multiplexer Output Selection
MX1
MX0
V
BIAS
V
DD
/2
INTERNAL V
REF
REFIN
Undetermined
0
0
1
1
0
1
0
1
AD7804/AD7808 SUB DAC DATA REGISTER
Figure 7 shows the loading sequence for writing to the data
registers of the DACs. DB15 determines whether writing is to
the Main or Sub DAC’s data register. A one in this position
selects the addressed Sub DAC’s data register. The Sub DAC is
8 bits wide and thus DB1 and DB0 of the 16-bit input word are
don’t cares when writing to the Sub DAC. This Sub DAC al-
lows the complete transfer function of each individual DAC to
be offset around the V
BIAS
point. This is achieved by either
adding or subtracting to the output of the Main DAC. This Sub
DAC has a span of
±
V
BIAS
/32 with 1/8-bit resolution. The
coding scheme for the Sub DAC is the same as that for the
Main DAC. With offset binary coding the transfer function for
the Sub DAC is
V
BIAS
16
×
(
NB
–128)
256
where
NB
is the digital code written to the Sub DAC and varies
from 0 to 255.
With twos complement coding the transfer function for the Sub
DAC is
V
BIAS
16
where
NB
is the digital code written to the Sub DAC and varies
from –128 to 127. V
BIAS
can be either the internal bandgap
reference, the internal V
DD
/2 reference or the external REFIN as
×
NB
256
(
)
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| AD7805BRS | +3.3 V to +5 V Quad/Octal 10-Bit DACs |
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| AD7808BST | High Efficiency Step-Down and Inverting DC/DC Converter; Package: SO; No of Pins: 8; Temperature Range: 0°C to +70°C |
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| AD7805BR-REEL | 制造商:Analog Devices 功能描述:DAC 4-CH 10-bit 28-Pin SOIC W T/R 制造商:Analog Devices 功能描述:DAC 4-CH 10-BIT 28SOIC W - Tape and Reel 制造商:Rochester Electronics LLC 功能描述:QUAD 10-BIT PARALLEL DAC - Tape and Reel |
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| AD7805BRS-REEL7 | 制造商:Analog Devices 功能描述:DAC 4-CH 10-bit 28-Pin SSOP T/R |
| AD7805BRSZ | 功能描述:IC DAC 10BIT QUAD PARALL 28-SSOP RoHS:是 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 設(shè)置時(shí)間:4.5µs 位數(shù):12 數(shù)據(jù)接口:串行，SPI? 轉(zhuǎn)換器數(shù)目:1 電壓電源:單電源 功率耗散（最大）:- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SOICN 包裝:剪切帶 (CT) 輸出數(shù)目和類型:1 電壓，單極；1 電壓，雙極 采樣率（每秒）:* 其它名稱:MCP4921T-E/SNCTMCP4921T-E/SNRCTMCP4921T-E/SNRCT-ND |
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