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参数资料
| 型号： | AD5255BRU250 |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 数字电位计 |
| 英文描述： | 3-Channel Digital Potentiometer with Nonvolatile Memory |
| 中文描述： | TRIPLE 250K DIGITAL POTENTIOMETER, INCREMENT/DECREMENT CONTROL INTERFACE, 512 POSITIONS, PDSO24 |
| 封装： | MO-153AD, TSSOP-24 |
| 文件页数： | 17/20页 |
| 文件大小： | 626K |
| 代理商： | AD5255BRU250 |
AD5255
POWER-UP SEQUENCE
Since the ESD protection diodes limit the voltage compliance at
the A, B, and W terminals (Figure 30), it is important to power
V
DD
/V
SS
before applying any voltage to the A, B, and W
terminals. Otherwise, the diode is forward-biased such that
V
DD
/V
SS
are powered unintentionally, which affects the rest of
the circuit. The ideal power-up sequence is as follows: GND,
V
DD
, V
SS
, digital inputs, and V
A/B/W
. The order of powering V
A
,
V
B
, V
W
, and the digital inputs is not important as long as they
are powered after V
DD
/V
SS
.
Rev. 0 | Page 17 of 20
LAYOUT AND POWER SUPPLY BIASING
It is always a good practice to use compact, minimum lead
length layout design. Make the leads to the input as direct as
possible with a minimum conductor length. Make sure that
ground paths have low resistance and low inductance.
Similarly, it is also good practice to bypass the power supplies
with quality capacitors. Use low equivalent series resistance
(ESR) 1 μF to 10 μF tantalum or electrolytic capacitors at the
supplies to minimize any transient disturbance and filter low
frequency ripple. Figure 31 illustrates the basic supply-
bypassing configuration for the AD5255.
V
DD
V
SS
V
DD
V
SS
GND
AD5255
C3
10
μ
F
C4
10
μ
F
C1
C2
+
+
0.1
μ
F
0.1
μ
F
0
Figure 31. Power Supply Bypassing
RDAC STRUCTURE
The patent pending RDAC contains a string of equal resistor
segments, with an array of analog switches. The switches act as
the wiper connection.
The AD5255 has two RDACs with 512 connection points
allowing it to provide better than 0.2% set-ability resolution.
The AD5255 also contains a third RDAC with 128-step
resolution.
Figure 32 shows an equivalent structure of the connections
between the two terminals that make up one channel of an
RDAC. The SW
B
switch is always on, while one of the switches,
SW(0) to SW(2
N
1), may or may not be on at any given time
depending on the resistance position decoded from the data bits
in the RDAC register.
Since the switches are nonideal, there is a 100 wiper
resistance, R
W
. Wiper resistance is a function of supply voltage
and temperature; lower supply voltages and higher temperatures
result in higher wiper resistances. Consideration of wiper
resistance dynamics is important in applications in which
accurate prediction of output resistance is required.
0
RDAC
WIPER
REGISTER
AND
DECODER
DIGITAL
CIRCUITRY
OMITTED FOR
CLARITY
R
S
= R
AB
/2
N
R
S
R
S
R
S
A
X
W
X
B
X
SW
B
SW(0)
SW(1)
SW(2
N
–1)
SW(2
N
–2)
SW
A
Figure 32. Equivalent RDAC Structure
CALCULATING THE PROGRAMMABLE RESISTANCE
The nominal resistance of the RDAC between the A and B
terminals is available in 25 k or 250 k. The final two or three
digits of the part number determine the nominal resistance
value, for example, 25 k = 25 and 250 k = 250.
The following discussion describes the calculation of resistance
R
WB
(d) at different codes of a 25 k part for RDAC0. The 9-bit
data word in the RDAC latch is decoded to select one of the 512
possible settings.
The first wiper connection starts at the B terminal for data 0x000.
R
WB
(0) is 100 of the wiper resistance and it is independent of
the full-scale resistance. The second connection is the first tap
point where R
WB
(1) becomes 48.8 + 100 = 148.8 for data
0x001. The third connection is the next tap point representing
R
WB
(2) = 97.6 + 100 = 197.6 for data 0x002, 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
(511) = 25051 . See
Figure 32 for a simplified diagram of the equivalent RDAC
circuit.
These general equations determine the programmed output
resistance between W and B.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD5255BRU250-RL7 | 制造商:Analog Devices 功能描述:DGTL POTENTIOMETER 512POS 250KOHM TRIPLE 24TSSOP - Tape and Reel |
| AD5255BRU25-RL7 | 制造商:Analog Devices 功能描述:DGTL POTENTIOMETER 512POS 25KOHM TRIPLE 24TSSOP - Tape and Reel |
| AD5255BRUZ25 | 制造商:Analog Devices 功能描述:Digital Potentiometer 512POS 25KOhm Triple 24-Pin TSSOP 制造商:Analog Devices 功能描述:DGTL POTENTIOMETER 512POS 25KOHM TRIPLE 24TSSOP - Rail/Tube 制造商:Analog Devices 功能描述:DIGIPOT I2C NV MEMORY 5K SMD 5255 |
| AD5255BRUZ250 | 制造商:Analog Devices 功能描述:Digital Potentiometer 512POS 250KOhm Triple 24-Pin TSSOP 制造商:Analog Devices 功能描述:DGTL POTENTIOMETER 512POS 250KOHM TRIPLE 24TSSOP - Rail/Tube 制造商:Analog Devices 功能描述:DIGIPOT I2C NV MEMORY 250K 5255 |
| AD52579 | 制造商:Analog Devices 功能描述: |
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