AD5255
For example, the following RDAC latch codes set the
corresponding output resistance values, which apply to
For RDAC0 and RDAC1:
D
RAB = 25 kΩ digital potentiometers.
RWB
For RDAC2:
RWB
(
D
)
=
× RAB + RW
(1)
(2)
512
Table 12. RWA(d) at Selected Codes for RAB = 25 kΩ
D (DEC)
RWA(d) (Ω)
148.8
12600
Output State
Full scale
Midscale
1 LSB
511
256
1
D
128
(
D
)
=
× RAB + RW
25051
0
25100
Zero scale
where D is the decimal equivalent of the data contained in the
RDAC register and RW is the wiper resistance.
The typical distribution of RAB from channel-to-channel is
0.1% within the same package. Device-to-device matching is
process lot-dependent, with a worst-case variation of 15%. RAB
temperature coefficient is 35 ppm/°C.
The output resistance values in Table 11 are set for the given
RDAC latch codes with VDD = 5 V, which applies to RAB = 25 kΩ
digital potentiometers.
Table 11. RWB at Selected Codes for RWB_FS = 25 kΩ
PROGRAMMING THE POTENTIOMETER DIVIDER
D (DEC) RWB(d) (Ω)
Output State
Voltage Output Operation
511
256
1
25051
12600
148.8
100
Full scale
Midscale
1 LSB
The digital potentiometer can be configured to generate an
output voltage at the wiper terminal that is proportional to the
input voltages applied to the A and B terminals. Connecting the
A terminal to 5 V and the B terminal to ground produces an
output voltage at the wiper that can vary between 0 V to 5 V.
Each LSB of voltage is equal to the voltage applied across the A
and B terminals divided by the 2N position resolution of the
potentiometer divider.
0
Zero scale (wiper contact resistance)
Note that in the zero-scale condition, a finite wiper resistance of
100 Ω is present. To avoid degradation or possible destruction
of the internal switches, care should be taken to limit the current
flow between W and B to no more than 20 mA intermittently or
2 mA continuously.
Since the AD5255 can operate from dual supplies, the general
equations defining the output voltage at VW with respect to
ground for any given input voltages applied to the A and B
terminals are as follows.
Channel-to-channel RWB matching is better than 0.1%. The
change in RWB with temperature has a 35 ppm/°C temperature
coefficient.
For RDAC0 and RDAC1:
Like the mechanical potentiometer that the RDAC replaces, the
AD5255 parts are totally symmetrical. The resistance between
the W wiper and the A terminal also produces a digitally
controlled complementary resistance, RWA. When RWA is used,
the B terminal can be floating or tied to the wiper. Setting the
resistance value for RWA starts at a maximum value of resistance
and decreases as the data loaded in the latch is increased in
value. The general transfer equations for this operation are as
follows.
D
512
VW
For RDAC2:
VW
(
D
)
=
=
×VAB + VB
(5)
(6)
D
128
(
D
)
×VAB + VB
Equation 5 assumes that VW is buffered so that the effect of
wiper resistance is nulled. Operation of the digital potentiometer
in the divider mode results in more accurate operation over
temperature. In this mode, the output voltage is dependent on
the ratio of the internal resistors, not on the absolute value;
therefore, the drift improves to 15 ppm/°C. There is no voltage
polarity restriction between the A, B, and W terminals as long as
For RDAC0 and RDAC1:
512 − D
(3)
(4)
RWB
For RDAC2:
RWB
(
D
)
)
=
=
× RAB + RW
512
the terminal voltage (VTERM) stays within VSS < VTERM < VDD
.
128 − D
128
(
D
× RAB + RW
Rev. 0 | Page 18 of 20
5秒后页面跳转
MAX7219驱动8段数码管详解及数据手册关键信息
ATMEGA328P技术资料深入分析
AT24C02芯片手册管脚信息、参数分析、应用领域详解
AT24C256芯片手册参数分析、引脚说明、读写程序示例
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
