AD5258BRMZ1 Analog Devices Inc, AD5258BRMZ1 Datasheet - Page 14
AD5258BRMZ1
Manufacturer Part Number
AD5258BRMZ1
Description
IC POT DGTL I2C1K 64P 10MSOP
Manufacturer
Analog Devices Inc
Specifications of AD5258BRMZ1
Memory Type
Non-Volatile
Temperature Coefficient
200 ppm/°C Typical
Taps
64
Resistance (ohms)
1K
Number Of Circuits
1
Interface
I²C, 2-Wire Serial
Voltage - Supply
2.7 V ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
10-MSOP, Micro10™, 10-uMAX, 10-uSOP
Resistance In Ohms
1.00K
End To End Resistance
1kohm
Resistance Tolerance
± 30%
No. Of Steps
64
Supply Voltage Range
2.7V To 5.5V
No. Of Pots
Single
Control Interface
I2C
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
AD5258EVAL - BOARD EVAL FOR AD5258 DGTL POT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant, Lead free / RoHS Compliant
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AD5258
THEORY OF OPERATION
The AD5258 is a 64-position digitally controlled variable
resistor (VR) device. The wiper’s default value, prior to
programming the EEPROM, is midscale.
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistance (R
and Terminal B is available in 1 kΩ, 10 kΩ, 50 kΩ, and 100 kΩ.
The nominal resistance of the VR has 64 contact points
accessed by the wiper terminal. The 6-bit data in the RDAC
latch is decoded to select one of 64 possible settings.
The general equation determining the digitally programmed
output resistance between Wiper W and Terminal B is
where:
D is the decimal equivalent of the binary code loaded in the
6-bit RDAC register.
R
R
each internal switch.
Note that in the zero-scale condition, there is a relatively low
value finite wiper resistance. Care should be taken to limit the
current flow between Wiper W and Terminal B in this state to a
maximum pulse current of no more than 20 mA. Otherwise,
degradation or destruction of the internal switch contact can
occur.
AB
W
is the wiper resistance contributed by the on resistance of
is the end-to-end resistance.
R
WB
( )
D
A
B
=
Figure 38. AD5258 Equivalent RDAC Circuit
64
Figure 37. Rheostat Mode Configuration
D
D5
D4
D3
D2
D1
D0
DECODER
W
LATCH
RDAC
×
AND
R
AB
+
A
B
AB
2
) of the RDAC between Terminal A
×
R
R
R
R
S
S
S
S
R
W
W
A
B
A
W
B
W
Rev. 0 | Page 14 of 24
(1)
Similar to the mechanical potentiometer, the resistance of the
RDAC between Wiper W and Terminal A produces a digitally
controlled complementary resistance, R
setting for R
decreases as the data loaded in the latch increases in value. The
general equation for this operation is
Typical device-to-device matching is process lot dependent and
may vary by up to ±30%. For this reason, resistance tolerance is
stored in the EEPROM such that the user will know the actual
R
PROGRAMMING THE POTENTIOMETER DIVIDER
Voltage Output Operation
The digital potentiometer easily generates a voltage divider at
Wiper W-to-Terminal B and Wiper W-to-Terminal A propor-
tional to the input voltage at Terminal A to Terminal B. Unlike
the polarity of V
across Terminal A to Terminal B, Wiper W to Terminal A, and
Wiper W to Terminal B can be at either polarity.
If ignoring the effect of the wiper resistance for approximation,
connecting the A terminal to 5 V and the B terminal to ground
produces an output voltage at Wiper W-to-Terminal B starting
at 0 V up to 1 LSB less than 5 V. The general equation defining
the output voltage at V
input voltage applied to Terminal A and Terminal B is
A more accurate calculation, which includes the effect of wiper
resistance, V
Operation of the digital potentiometer in the divider mode
results in a more accurate operation over temperature. Unlike
the rheostat mode, the output voltage is dependent mainly on
the ratio of the Internal Resistors, R
absolute values.
AB
within 0.1%.
V
V
R
W
W
WA
(
(
D
(
D
D
)
)
WA
)
=
=
W
Figure 39. Potentiometer Mode Configuration
=
, is
64
D
R
starts at a maximum value of resistance and
64
WB
DD
R
V
AB
64
(
A
to GND, which must be positive, voltage
−
D
+
)
D
64
W
V
V
I
×
A
with respect to ground for any valid
64
−
+
R
D
AB
R
V
WA
A
B
R
+
B
AB
(
2
W
D
×
)
WA
V
R
B
W
and R
V
WA
O
. The resistance value
WB
, and not the
(2)
(3)
(4)