AD5200 데이터 시트보기 (PDF) - Analog Devices
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AD5200 Datasheet PDF : 16 Pages
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AD5200/AD5201
A
SHDN
D7
D6
D5
D4
D3
R
D2
D1
D0
R
RDAC
R
LATCH &
DECODER
SWSHDN
SW2N؊1
SW2N؊2
SW1
SW0
W
R
RAB
2N–1
B DIGITAL CIRCUITRY
OMITTED FOR CLARITY
Figure 2a. AD5200 Equivalent RDAC Circuit. 255 positions
can be achieved up to Switch SW 2N–1.
SHDN
A
SWSHDN
SW2N
D5
R
SW2N؊1
D4
D3
D2
D1
R
SW2N؊2
D0
W
R
SW1
RDAC
R
LATCH &
DECODER
SW0
R
RAB
2N
B DIGITAL CIRCUITRY
OMITTED FOR CLARITY
Figure 2b. AD5201 Equivalent RDAC Circuit. Unlike AD5200,
33 positions can be achieved all the way to Switch SW 2N.
The general equation determining the digitally programmed
output resistance between W and B is:
( ) RWB
D
=
D
255
RAB
+ 50 Ω
for AD5200
(1)
( ) RWB
D
=
D
32 RAB
+ 50
Ω
for AD5201
(2)
where:
D is the decimal equivalent of the data contained in
RDAC latch.
RAB is the nominal end-to-end resistance.
RW is the wiper resistance contributed by the on-resistance
of the internal switch.
Note D in AD5200 is between 0 to 255 for 256 positions. On
the other hand, D in AD5201 is between 0 to 32 so that 33
positions can be achieved due to the slight internal structure
difference, Figure 2b.
Again if RAB = 10 kΩ and A terminal can be opened or tied to
W, the following output resistance between W to B will be set
for the following RDAC latch codes:
D
(DEC)
255
128
1
0
AD5200 Wiper-to-B Resistance
RWB
(⍀)
10050
5070
89
50
Output State
Full-Scale (RAB + RW)
Midscale
1 LSB
Zero-Scale (Wiper Contact Resistance)
AD5201 Wiper-to-B Resistance
D
(DEC)
32
16
1
0
RWB
(⍀)
10050
5050
363
50
Output State
Full-Scale (RAB + RW)
Midscale
1 LSB
Zero-Scale (Wiper Contact Resistance)
Note that in the zero-scale condition a finite wiper resistance of
50 Ω is present. Care should be taken to limit the current flow
between W and B in this state to no more than ± 20 mA to avoid
degradation or possible destruction of the internal switch contact.
Like the mechanical potentiometer the RDAC replaces, it is
totally symmetrical. The resistance between the wiper W and
Terminal A also produces a digitally controlled resistance RWA.
When these terminals are used, the B terminal should be tied to
the wiper. Setting the resistance value for RWA starts at a maxi-
mum value of resistance and decreases as the data loaded in
the latch is increased in value. The general equation for this
operation is:
( ) 255 − D
( ) RWA D = 255 RAB + 50 Ω
for AD5200 (3)
( ) 32 − D
( ) RWA D = 32 RAB + 50 Ω
for AD5201 (4)
Similarly, D in AD5200 is between 0 to 255, whereas D in
AD5201 is between 0 to 32.
For RAB = 10 kΩ and B terminal is opened or tied to the wiper
W, the following output resistance between W and A will be set
for the following RDAC latch codes:
–12–
REV. B
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