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參數(shù)資料
| 型號： | ADN2850ACP250-RL7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 數(shù)字電位計 |
| 英文描述： | Nonvolatile Memory, Dual 1024 Position Programmable Resistors |
| 中文描述： | DUAL 250K DIGITAL POTENTIOMETER, 3-WIRE SERIAL CONTROL INTERFACE, 1024 POSITIONS, QCC16 |
| 封裝： | 5 X 5 MM, LFCSP-16 |
| 文件頁數(shù)： | 11/18頁 |
| 文件大?。?/td> | 270K |
| 代理商： | ADN2850ACP250-RL7 |
PRELIMINARY TECHNICAL DATA
Nonvolatile Memory Programmable Resistors
ADN2850
REV PrH, 13, AUG 2001
11
RDAC STRUCTURE
The RDAC contains a string of equal resistor segments, with an
array of analog switches, that act as the wiper connection. The
number of positions is the resolution of the device. The
ADN2850 has 1024 connection points allowing it to provide
better than 0.1% set-ability resolution. Figure 8 shows an
equivalent structure of the connections between the two
terminals that make up one channel of the RDAC. The SW
B
will
always be ON, while one of the switches SW(0) to SW(2
N
-1)
will be ON one at a time depending on the resistance position
decoded from the Data Bits. Since the switch is not ideal, there
is a 50
wiper resistance, R
W
. Wiper resistance is a function of
supply voltage and temperature. The lower the supply voltage,
the higher the wiper resistance. Similarly, the higher the
temperature, the higher the wiper resistance. R
W
is the sum of
the resistance of SW(D)
+ SWB from Wiper-to-B terminals
Users should be aware of the contribution of the wiper
resistance when accurate prediction of the output resistance is
needed.
R
S
R
S
R
S
W
B
RDAC
WIPER
REGISTER
&
DECODER
R
S
=R
WB_FS
/2
N
SW(2
N
-1)
SW(2
N
-2)
SW(0 )
SW(1 )
DIGITAL
CIRCUITRY
OMITTED FOR
CLARITY
SWB
Figure 9. Equivalent RDAC structure
Table 5. Nominal individual segment resistor values
Device
Resolution
25 K
Version
250 K
Version
10-Bit
24.4
244
CALCULATIING THE PROGRAMMABLE
RESISTANCE
The nominal full scale resistance of the RDAC between
terminals W-and-B, R
WB_FS
, are available with 25K
and 250K
with 1024 positions (10-bit resolution). The final digits of the
part number determine the nominal resistance value, e.g., 25K
= 25; 250K
= 250.
The 10-bit data word in the RDAC latch is decoded to select one
of the 1024 possible settings. The following discussion
describes the calculation of resistance R
WB
(D) at different codes
of a 25K
part. The wiper first connection starts at the B
terminal for data 000
H
. R
WB
is 50
because of the wiper
resistance and it is independent to the full-scale resistance. The
second connection is the first tap point where R
WB
(1) becomes
24.4
+50=74.4
for data 01
H
. The third connection is the next
tap point representing R
WB
(2)=48.8+50=98.8
for data 02
H
and
so on. Each LSB data value increase moves the wiper up the
resistor ladder until the last tap point is reached at
R
WB
(1023)=25026
. See Figure 9 for a simplified diagram of
the equivalent RDAC circuit.
0
5
10
15
20
25
0
256
512
768
D - Code in Decim al
R
1023
R
WB_FS
= 25K
Figure 10. R
WB
(D) vs Code
The general equation, which determines the programmed output
resistance between Wx and Bx, is:
W
R
FS
WB
R
N
D
D
WB
R
+
=
_
2
)
(
(1)
Where D is the decimal equivalent of the data contained in the
RDAC register, 2
N
is the number of steps, R
WB_FS
is the full
scale resistance between terminals W-and-B, and R
W
is the wiper
resistance.
For example, the following output resistance values will be set
for the following RDAC latch codes (applies to R
WB_FS
=25K
programmable resistors):
D
(DEC)
R
WB
(D)
(
)
Output State
1023
512
1
0
25026
12550
74.4
50
Full-Scale
Mid-Scale
1 LSB
Zero-Scale (Wiper contact resistance)
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ADN2850ACP25-RL7 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Nonvolatile Memory, Dual 1024 Position Programmable Resistors |
| ADN2850ARU | 制造商:Analog Devices 功能描述:DUAL 10-BIT PROGRAMMABLE NON-VOLATILE RESISTOR - Bulk |
| ADN2850ARU25 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Nonvolatile Memory, Dual 1024 Position Programmable Resistors |
| ADN2850ARU25-REEL7 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Nonvolatile Memory, Dual 1024 Position Programmable Resistors |
| ADN2850BCP25 | 制造商:Analog Devices 功能描述:Digital Potentiometer 1024POS 25KOhm Dual 16-Pin LFCSP EP 制造商:Rochester Electronics LLC 功能描述:DUAL 9-BIT SPI DIG. POT - Bulk |
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