AD5260BRU200-REEL7 Analog Devices Inc, AD5260BRU200-REEL7 Datasheet - Page 9

• Manufacturer Part Number: AD5260BRU200-REEL7
• Description: IC DGTL POT SNGL 256POS 14-TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5260BRU200-REEL7

• Rohs Status: RoHS non-compliant
• Taps: 256
• Resistance (ohms): 200K
• Number Of Circuits: 1
• Temperature Coefficient: 35 ppm/°C Typical
• Memory Type: Volatile
• Interface: 4-Wire SPI Serial
• Voltage - Supply: 4.5 V ~ 16.5 V, ±4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Resistance In Ohms: 200K
• Other names: AD5260BRU200REEL7

PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistances of the RDAC between terminals A and B
are available with values of 20 kW, 50 kW, and 200 kW. The final
three digits of the part number determine the nominal resistance
value, e.g., 20 kW = 20; 50 kW = 50; 200 kW = 200. The nominal
resistance (R
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.
Assuming a 20 kW part is used, the wiper’s first connection starts
at the B terminal for data 00
resistance, such connection yields a minimum of 60 W resistance
between terminals W and B. The second connection is the first tap
point corresponds to 138 W (R
for data 01
ing 216 W (78
value increase moves the wiper up the resistor ladder until the last
tap point is reached at 19982 W [R
does not directly connect to the B terminal. See Figure 11 for a
simplified diagram of the equivalent RDAC circuit.
The general equation determining the digitally programmed
output resistance between W and B is:
where D is the decimal equivalent of the binary code which is
loaded in the 8-bit RDAC register, and R
to-end resistance.
For example, R
open circuit, the following output resistance values R
set for the following RDAC latch codes. The result will be the
same if terminal A is tied to W:
REV. 0
R
D
(DEC)
256
128
1
0
WB
( )
D
Figure 11. Simplified RDAC Architecture
H
. The third connection is the next tap point represent-
=
AB
R
(W)
19982
10060
138
60
SHDN
256
) of the VR has 256 contact points accessed by the
WB
D
DIGITAL CIRCUITRY
OMITTED FOR CLARITY
AB
D7
D6
D5
D4
D3
D2
D1
D0
2
DECODE
= 20 kW, when V
LATCH
¥
RDAC
AND
R
60) for data 02
AB
Output State
Full-Scale (R
Mid-Scale
1 LSB
Zero-Scale (wiper contact resistance)
+
H
R
R
R
R
R
WB
. Since there is a 60 W wiper contact
S
S
S
S
W
= R
AB
AB
B
R
AB
H
S
= 0 V and A–terminal is
/256
= R
and so on. Each LSB data
– 1 LSB + R
1 LSB
AB
AB
/2
N
is the nominal end-
R
W
Ax
Wx
Bx
= 78 W
R
W
]. The wiper
W
WB
)
will be
60 W)
(1)
–9–
Note that in the zero-scale condition a finite wiper resistance of
60 W 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 switches.
Like the mechanical potentiometer the RDAC replaces, the
AD5260/AD5262 parts are totally symmetrical. The resistance
between the wiper W and terminal A also produces a digitally
controlled complementary resistance R
symmetrical programmability of the various terminal connections.
When R
wiper. Setting the resistance value for R
value of resistance and decreases as the data loaded in the latch
is increased in value. The general equation for this operation is:
For example, R
the following output resistance R
RDAC latch codes. The result will be the same if terminal B is
tied to W:
The typical distribution of the nominal resistance R
channel to channel matches within ±1%. Device-to-device match-
ing is process lot dependent with the worst case of ±30% variation.
On the other hand, since the resistance element is processed in
thin film technology, the change in R
low 35 ppm/∞C temperature coefficient.
R
Figure 12. AD5260/AD5262 Equivalent RDAC Circuit
WA
( )
WA
D
20
16
12
8
4
0
0
is used, the B–terminal can be let floating or tied to the
=
D
(DEC)
256
128
1
0
256
AB
256
R
= 20 kW, when V
WA
-
D
64
¥
R
(W)
60
10060
19982
20060
R
D – CODE in decimal
WA
AB
+
WA
128
R
A
W
= 0 V and B–terminal is open,
R
AD5260/AD5262
will be set for the following
Output State
Full-Scale
Mid-Scale
1 LSB
Zero-Scale
AB
AB
WA
= 20K
WA
with temperature has a
. Figure 12 shows the
starts at a maximum
192
R
WB
AB
from
256
(2)