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參數(shù)資料
| 型號： | AD5235 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 通用總線功能 |
| 英文描述： | Audio digital potentiometers |
| 中文描述： | 音頻數(shù)字電位器 |
| 文件頁數(shù)： | 7/10頁 |
| 文件大?。?/td> | 102K |
| 代理商： | AD5235 |
PRELIMINARY TECHNICAL DATA
Nonvolatile Memory Digital Potentiometers
Detail Potentiometer Operation
AD5235
REV PrD 6 NOV, 2000
Information contained in this Product Concept data sheet describes a product in the early definition stage. There is no guarantee that the
information contained here will become a final product in its present form. For latest information contact Walt Heinzer/Analog Devices, Santa Clara,
CA. TEL(408)562-7254; FAX (408)727-1550; walt.heinzer@analog.com
7
The actual structure of the RDAC is designed to emulate the
performance of a mechanical potentiometer. The RDAC contains a
string of connected resistor segments, with an array of analog
switches that act as the wiper connection to several points along the
resistor array. The number of points is the resolution of the device.
The AD5235 has 1024 connection points allowing it to provide
better than 0.5% set-ability resolution. Figure 3 provides an
equivalent diagram of the connections between the three terminals
that make up one channel of the RDAC. The SW
A
and 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 depends upon the resistance step decoded from
the Data Bits. Note that there are two 50
wiper resistances, R
W
.
The resistance contributed by R
W
must be accounted for when
calculating the output resistance. R
W
is the sum of the resistances of
SW
A
+ SW
X
and SW
B
+ SW
X
for A-to-Wiper and B-to-Wiper
respectively.
A
X
R
S
R
S
R
S
W
X
B
X
RDAC
WIPER
REGISTER
&
DECODER
R
S
= R
AB
/2
N
SW
A
SW
B
SW(2
N
-1)
SW(2
N
-2)
SW(0 )
SW(1 )
DIGITAL
CIRCUITRY
OMITTED FOR
CLARITY
Figure 3. Equivalent RDAC structure
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistance of the RDAC between terminals A and B
are available with values of 25K
, and 250K
. The final digits of
the part number determine the nominal resistance value, e.g., 25K
= 25; 250K
= 250. The nominal resistance (R
AB
) of the AD5235
VR has 1024 contact points accessed by the wiper terminal, plus
the B terminal contact. The 10-bit data word in the RDAC latch is
decoded to select one of the 1024 possible settings. The wiper's
first connection starts at the B terminal for data 00
H
. This B–
terminal connection has a wiper contact resistance, R
W
of 50
,
regardless of what the nominal resistance R
AB
is. The second
connection (25K
part
)
is the first tap point where R
WB
=74
[R
WB
=R
AB
/1024 + R
W
= 24
+50
)] for data 01
H
. The third connection
is the next tap point representing R
WB
=49+50=99
for data 02
H
.
Each LSB data value increase moves the wiper up the resistor
ladder until the last tap point is reached at R
WB
=25025
. See figure
3 for a simplified diagram of the equivalent RDAC circuit.
The general equation, which determines the digitally programmed
output resistance between Wx and Bx, is:
R
WB
(Dx) = (Dx/2
N
) * R
AB
+ R
W
eqn. 1
Where N is the resolution of the VR, Dx is the data contained in
the RDACx latch, and R
AB
is the nominal end-to-end resistance.
Since N=10 and R
W
=50
for AD5235, eqn. 1 becomes:
R
WB
(Dx) = (Dx/1024) * R
AB
+ 50
eqn. 2
For example, when V
B
= 0V and A–terminal is open circuit the
following output resistance values will be set for the following
RDAC latch codes (applies to R
AB
=25K
potentiometers):
Dx
(DEC)
R
WB
(
)
Output State
1023
512
1
0
25025
Full-Scale
12500
Mid-Scale
74
1 LSB
50
Zero-Scale (Wiper contact resistance)
Note that in the zero-scale condition a finite wiper resistance of
50
is present. Care should be taken to limit the current flow
between W and B in this state to no more than 20mA to avoid
degradation or possible destruction of the internal switch contact.
Figure 4. Symmetrical RDAC Operation
Like the mechanical potentiometer the RDAC replaces, the
AD5235 part is totally symmetrical. The resistance between the
wiper W and terminal A also produces a digitally controlled
resistance R
WA
. Figure 4 shows the symmetrical programmability
of the various terminal connections. When these terminals are used,
the B–terminal should be tied to the wiper. Setting the resistance
value for R
WA
starts at a maximum value of resistance and
decreases as the data loaded in the latch is increased in value. The
general equation for this operation is:
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| AD5235BRU25 | 制造商:Analog Devices 功能描述:Digital Potentiometer 1024POS 25KOhm Dual 16-Pin TSSOP 制造商:Analog Devices 功能描述:IC DIGITAL POT 25KOHM 1024 DUAL 16-TSSO |
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| AD5235BRU25-RL7 | 功能描述:IC DGTL POT DUAL 1024POS 16TSSOP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)字電位器 系列:- 標準包裝:2,500 系列:XDCP™ 接片:256 電阻（歐姆）:100k 電路數(shù):1 溫度系數(shù):標準值 ±300 ppm/°C 存儲器類型:非易失 接口:I²C（設(shè)備位址） 電源電壓:2.7 V ~ 5.5 V 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:14-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:14-TSSOP 包裝:帶卷 (TR) |
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