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参数资料
| 型号： | AD5245BRJ50-R2 |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 数字电位计 |
| 英文描述： | 256-Position I2C Compatible Digital Potentiometer |
| 中文描述： | 50K DIGITAL POTENTIOMETER, 2-WIRE SERIAL CONTROL INTERFACE, 256 POSITIONS, PDSO8 |
| 封装： | 2.90 X 3 MM, MO-178BA, SOT-23, 8 PIN |
| 文件页数： | 12/16页 |
| 文件大小： | 995K |
| 代理商： | AD5245BRJ50-R2 |
AD5245
OPERATION
The AD5245 is a 256-position digitally controlled variable
resistor (VR) device.
Rev. 0 | Page 12 of 16
An internal power-on preset places the wiper at midscale
during power-on, which simplifies the fault condition recovery
at power-up.
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistance of the RDAC between terminals A and
B is available in 5 k, 10 k, 50 k, and 100 k. The final two
or three digits of the part number determine the nominal
resistance value, e.g., 10 k = 10; 50 k = 50. 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. Assume a 10 k part is used, the wiper’s first
connection starts at the B terminal for data 0x00. Since there is a
60
wiper contact resistance, such connection yields a
minimum of 60 resistance between terminals W and B. The
second connection is the first tap point, which corresponds to
99 (R
WB
= R
AB
/256 + R
W
= 39 + 60 ) for data 0x01.
The third connection is the next tap point, representing 177
(2 × 39 + 60 ) for data 0x02, and so on. Each LSB data value
increase moves the wiper up the resistor ladder until the last tap
point is reached at 9961 (R
AB
– 1 LSB + R
W
). Figure 39 shows
a simplified diagram of the equivalent RDAC circuit where the
last resistor string will not be accessed; therefore, there is 1 LSB
less of the nominal resistance at full scale in addition to the
wiper resistance.
B
RDAC
LATCH
AND
DECODER
W
A
R
S
R
S
R
S
R
S
SD BIT
D7
D6
D5
D4
D3
D2
D1
D0
Figure 39. AD5245 Equivalent RDAC Circuit
The general equation determining the digitally programmed
output resistance between W and B is
W
AB
WB
R
R
+
R
D
D
(
×
=
256
)
(1)
where
D
is the decimal equivalent of the binary code loaded in
the 8-bit RDAC register,
R
AB
is the end-to-end resistance, and
R
W
is the wiper resistance contributed by the on resistance of
the internal switch.
In summary, if R
AB
= 10 k and the A terminal is open
circuited, the following output resistance R
WB
will be set for the
indicated RDAC latch codes.
Table 7. Codes and Corresponding R
D (Dec.)
R
WB
()
Output State
255
9,961
Full Scale (R
AB
– 1 LSB + R
W
)
128
5,060
Midscale
1
99
1 LSB
0
60
Zero Scale (Wiper Contact Resistance)
WB
Resistance
Note that in the zero-scale condition a finite wiper resistance of
60 is present. Care should be taken to limit the current flow
between W and B in this state to a maximum pulse current of
no more than 20 mA. Otherwise, degradation or possible
destruction of the internal switch contact can occur.
Similar to the mechanical potentiometer, the resistance of the
RDAC between the wiper W and terminal A also produces a
digitally controlled complementary resistance R
WA
. When these
terminals are used, the B terminal can be opened. Setting the
resistance value for R
WA
starts at a maximum value of resistance
and decreases as the data loaded in the latch increases in value.
The general equation for this operation is
W
AB
WA
R
R
R
D
D
(
+
×
=
256
256
)
(2)
For R
AB
= 10 k and the B terminal open circuited, the
following output resistance R
WA
will be set for the indicated
RDAC latch codes.
Table 8. Codes and Corresponding R
D (Dec.)
R
WA
()
255
99
128
5,060
1
9,961
0
10,060
WA
Resistance
Output State
Full Scale
Midscale
1 LSB
Zero Scale
Typical device to device matching is process lot dependent and
may vary by up to ±30%. Since the resistance element is
processed in thin film technology, the change in R
AB
with
temperature has a very low 45 ppm/°C temperature coefficient.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD5245BRJ50-RL7 | 制造商:Analog Devices 功能描述:Digital Potentiometer 256POS 50KOhm Single 8-Pin SOT-23 T/R |
| AD5245BRJ5-R2 | 制造商:Analog Devices 功能描述:IC DIGITAL POT. 8-BIT I2C |
| AD5245BRJ5-RL7 | 制造商:Analog Devices 功能描述:Digital Potentiometer 256POS 5KOhm Single 8-Pin SOT-23 T/R |
| AD5245BRJZ100 | 制造商:Analog Devices 功能描述:DGTL POT 256POS 100K SOT23-8 制造商:Analog Devices 功能描述:DGTL POT, 256POS, 100K, SOT23-8 |
| AD5245BRJZ100-R2 | 功能描述:IC DGTL POT 256POS SOT-23-8 T/R RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数字电位器 系列:- 标准包装:3,000 系列:DPP 接片:32 电阻（欧姆）:10k 电路数:1 温度系数:标准值 300 ppm/°C 存储器类型:非易失 接口:3 线串行（芯片选择，递增，增/减） 电源电压:2.5 V ~ 6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-WFDFN 裸露焊盘 供应商设备封装:8-TDFN（2x3） 包装:带卷 (TR) |
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