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参数资料
| 型号： | AD5247EVAL |
| 厂商： | Analog Devices, Inc. |
| 元件分类： | 数字电位计 |
| 英文描述： | 128-Position I2C Compatible Digital Potentiometer |
| 中文描述： | 128位置I2C兼容数字电位器 |
| 文件页数： | 13/20页 |
| 文件大小： | 1181K |
| 代理商： | AD5247EVAL |
AD5247
OPERATION
The AD5247 is a 128-position, digitally controlled variable
resistor (VR) device. An internal power-on preset places the
wiper at midscale during power-on, which simplifies the default
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 128 contact points accessed by
the wiper terminal, plus the B terminal contact. The 7-bit data
in the RDAC latch is decoded to select one of the 128 possible
settings.
Assuming a 10 k part is used, the wiper’s first connection
starts at the B terminal for data 0x00. Since there is a 50 wiper
contact resistance, such a connection yields a minimum of
100 (2 × 50 ) resistance between terminals W and B. The
second connection is the first tap point, which corresponds to
178 (R
WB
= R
AB
/128+ R
W
= 78 + 2 × 50 ) for data 0x01.
The third connection is the next tap point, representing 256
(2 × 78 + 2 × 50 ) 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 10,100 (R
AB
+ 2 × R
W
).
Figure 34
circuit where the last resistor string will not be accessed.
Figure 34. AD5247 Equivalent RDAC Circuit
shows a simplified diagram of the equivalent RDAC
Bx
Wx
Ax
D6
D5
D4
D3
D2
D1
D0
RDAC
LATCH
AND
DECODER
R
S
R
S
R
S
0
The general equation determining the digitally programmed
output resistance between W and B is
W
AB
WB
R
R
D
D
R
×
+
×
=
2
128
)
(
(1)
where
D
is the decimal equivalent of the binary code loaded in
the 7-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 output resistance
R
WB
shown in
will be set for the indicated RDAC latch codes.
Table 7
Table 7. Codes and Corresponding R
WB
Resistance
D (Dec.)
R
WB
()
Output State
127
10,100
Full Scale (R
AB
+ 2 × R
W
)
64
5,100
Midscale
1
178
1 LSB
0
100
Zero Scale (Wiper Contact Resistance)
Note that in the zero-scale condition, a finite resistance of
100 between terminals W and B 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
D
D
R
×
+
×
=
2
128
–
128
)
(
(2)
For
R
AB
= 10 k and the B terminal open circuited, the output
resistance
R
WA
shown in
RDAC latch codes.
will be set for the indicated
Table 8
Table 8. Codes and Corresponding R
WA
Resistance
D (Dec.)
R
WA
()
127
178
64
5,100
1
9,961
0
10,100
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.
Output State
Full Scale
Midscale
1 LSB
Zero Scale
Rev. 0 | Page 13 of 20
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| AD5248BRM10 | 功能描述:IC DGTL POT DUAL 10K I2C 10-MSOP RoHS:否 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) |
| AD5248BRM100 | 功能描述:IC DGTL POT DUAL 100K I2C 10MSOP RoHS:否 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) |
| AD5248BRM100-RL7 | 功能描述:IC DGTL POT DUAL 100K I2C 10MSOP RoHS:否 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) |
| AD5248BRM10-RL7 | 功能描述:IC DGTL POT DUAL 10K I2C 10-MSOP RoHS:否 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) |
| AD5248BRM2.5 | 功能描述:IC DGTL POT DUAL 2.5K I2C 10MSOP RoHS:否 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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