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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)： | 17/20頁 |
| 文件大小： | 853K |
| 代理商： | AD5260 |
REV. 0
–17–
AD5260/AD5262
V
O
, I
D
, and V
D
are interdependent variables. With proper selection
of R2B, an equilibrium will be reached such that V
O
converges. R2B
can be in series with a discrete resistor to increase the amplitude,
but the total resistance cannot be too large to saturate the output.
In both circuits in Figures 21 and 22, the frequency tuning requires
that both RDACs be adjusted to the same settings. Since the two
channels will be adjusted one at a time, an intermediate state will
occur that may not be acceptable for certain applications. As a
result, different devices can also be used in daisy-chained mode so
that parts can be programmed to the same setting simultaneously.
+5V
OP1177
V
O
–5V
R2A
2.1k
D1
D2
R2B
10k
VN
R1
1k
A
B
W
R1 = R1 = R2B = AD5262
D1 = D2 = 1N4148
AD5262
C
2.2nF
R
10k
A
B
W
VP
C
2.2nF
FREQUENCY
ADJUSTMENT
R
10k
A
B
W
U1
AMPLITUDE
ADJUSTMENT
Figure 22. Programmable Oscillator with
Amplitude Control
Resistance Scaling
The AD5260/AD5262 offer 20 k
W
, 50 k
W
, and 200 k
W
nominal
resistance. For users who need lower resistance and still maintain the
numbers of step adjustment, they can parallel multiple devices. For
example, Figure 23 shows a simple scheme of paralleling both
channels of the AD5262. To adjust half of the resistance linearly
per step, users need to program both channels coherently with
the same settings.
W1
A1
B1
W2
A2
B2
LD
V
DD
Figure 23. Reduce Resistance by Half with Linear
Adjustment Characteristics
In voltage divider mode, a much lower resistance can be achieved
by paralleling a discrete resistor as shown in Figure 24. The equiva-
lent resistance becomes:
R
D
R
R
R
WB eq
W
_
=
§§
(
)
+
256
1
2
(16)
R
D
R
R
R
WA eq
W
_
=
-
ê
ˉ
§§
(
)
+
1
256
1
2
(17)
W
A
B
R2
R1
R2 << R1
Figure 24. Lowering the Nominal Resistance
Figures 23 and 24 show that the digital potentiometers change steps
linearly. On the other hand, log taper adjustment is usually pre-
ferred in applications like audio control. Figure 25 shows another
way of resistance scaling. In this circuit, the smaller the R2 with
respect to R
AB
, the more the pseudo-log taper characteristic behaves.
V
O
A
B
R1
R2
V
i
W
Figure 25. Resistor Scaling with Log Adjustment
Characteristics
RDAC CIRCUIT SIMULATION MODEL
The internal parasitic capacitances and the external capacitive
loads dominate the ac characteristics of the RDACs. Configured
as a potentiometer divider, the –3 dB bandwidth of the AD5260
(20 k
W
resistor) measures 310 kHz at half scale. TPC 20 provides
the large signal BODE plot characteristics of the three available
resistor versions 20 k
W
, 50 k
W
, and 200 k
W
. A parasitic simulation
model is shown in Figure 26. Listing I provides a macro model
net list for the 20 k
W
RDAC.
A
B
55pF
C
A
25pF
C
25pF
C
W
RDAC
20k
W
Figure 26. RDAC Circuit Simulation Model for RDAC = 20 k
W
Listing I. Macro Model Net List for RDAC
PARAM D=256, RDAC=20E3
*
SUBCKT DPOT (A,W,B)
*
CA
A
0
RWA
A
W
CW
W
0
RWB
W
B
CB
B
0
*
.ENDS DPOT
25E-12
{(1-D/256)
*
RDAC+60}
55E-12
{D/256
*
RDAC+60}
25E-12
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| AD5260_10 | 制造商:AD 制造商全稱:Analog Devices 功能描述:1-/2-Channel 15 V Digital Potentiometer |
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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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