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參數(shù)資料
| 型號： | AD5260 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 通用總線功能 |
| 英文描述： | 4-Channel Digital Potentiometers(???é??é????°?-???μ?????¨) |
| 中文描述： | 4通道數(shù)字電位器（四通道數(shù)字電位器） |
| 文件頁數(shù)： | 9/20頁 |
| 文件大?。?/td> | 853K |
| 代理商： | AD5260 |
REV. 0
–9–
AD5260/AD5262
D7
D6
D5
D4
D3
D2
D1
D0
RDAC
LATCH
AND
DECODE
Ax
Wx
Bx
R
S
= R
AB
/2
N
R
S
R
S
R
S
R
S
SHDN
DIGITAL CIRCUITRY
OMITTED FOR CLARITY
Figure 11. Simplified RDAC Architecture
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistances of the RDAC between terminals A and B
are available with values of 20 k
W
, 50 k
W
, and 200 k
W
. The final
three digits of the part number determine the nominal resistance
value, e.g., 20 k
W
= 20; 50 k
W
= 50; 200 k
W
= 200. The nominal
resistance (R
AB
) of the VR has 256 contact points accessed by the
wiper terminal, plus the B terminal contact. The 8-bit data in the
RDAC latch is decoded to select one of the 256 possible settings.
Assuming a 20 k
W
part is used, the wiper’s first connection starts
at the B terminal for data 00
H
. Since there is a 60
W
wiper contact
resistance, such connection yields a minimum of 60
W
resistance
between terminals W and B. The second connection is the first tap
point corresponds to 138
W
(R
WB
= R
AB
/256 R
W
= 78
W
60
W
)
for data 01
H
. The third connection is the next tap point represent-
ing 216
W
(78
2 60) 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 19982
W
[R
AB
1 LSB R
W
]. The wiper
does not directly connect to the B terminal. See Figure 11 for a
simplified diagram of the equivalent RDAC circuit.
The general equation determining the digitally programmed
output resistance between W and B is:
R
D
( )
=
D
R
R
WB
AB
W
￥
+
256
(1)
where D is the decimal equivalent of the binary code which is
loaded in the 8-bit RDAC register, and R
AB
is the nominal end-
to-end resistance.
For example, R
AB
= 20 k
W
, when V
B
= 0 V and A–terminal is
open circuit, the following output resistance values R
WB
will be
set for the following RDAC latch codes. The result will be the
same if terminal A is tied to W:
D
(DEC)
R
WB
(
W
)
19982
10060
138
60
Output State
256
128
1
0
Full-Scale (R
AB
– 1 LSB + R
W
)
Mid-Scale
1 LSB
Zero-Scale (wiper contact resistance)
Note that in the zero-scale condition a finite wiper resistance of
60
W
is present. Care should be taken to limit the current flow
between W and B in this state to no more than 20 mA to avoid
degradation or possible destruction of the internal switches.
Like the mechanical potentiometer the RDAC replaces, the
AD5260/AD5262 parts are totally symmetrical. The resistance
between the wiper W and terminal A also produces a digitally
controlled complementary resistance R
WA
. Figure 12 shows the
symmetrical programmability of the various terminal connections.
When R
WA
is used, the B–terminal can be let floating or 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:
R
D
( )
=
D
R
R
WA
AB
W
-
￥
+
256
256
(2)
For example, R
AB
= 20 k
W
, when V
A
= 0 V and B–terminal is open,
the following output resistance R
WA
will be set for the following
RDAC latch codes. The result will be the same if terminal B is
tied to W:
D
(DEC)
R
WA
(
W
)
60
10060
19982
20060
Output State
256
128
1
0
Full-Scale
Mid-Scale
1 LSB
Zero-Scale
R
WB
R
WA
R
AB
= 20K
D – CODE in decimal
20
0
64
128
192
256
R
W
(
W
(
16
12
8
4
0
Figure 12. AD5260/AD5262 Equivalent RDAC Circuit
The typical distribution of the nominal resistance R
AB
from
channel to channel matches within
±
1%. Device-to-device match-
ing is process lot dependent with the worst case of
±
30% variation.
On the other hand, since the resistance element is processed in
thin film technology, the change in R
AB
with temperature has a
low 35 ppm/
∞
C temperature coefficient.
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|---|---|
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| AD5260BRU200 | 制造商:Analog Devices 功能描述:Digital Potentiometer 256POS 200KOhm Single 14-Pin TSSOP 制造商:Analog Devices 功能描述:IC DIGITAL POTENTIOMETER 8-BIT |
| AD5260BRU200-REEL7 | 制造商:Analog Devices 功能描述:Digital Potentiometer 256POS 200KOhm Single 14-Pin TSSOP T/R 制造商:Rochester Electronics LLC 功能描述:8-BIT SPI DIG POT - Tape and Reel |
| AD5260BRU20-REEL7 | 制造商:Analog Devices 功能描述:Digital Potentiometer 256POS 20KOhm Single 14-Pin TSSOP T/R |
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