AD5160BRJZ100-RL7 Analog Devices Inc, AD5160BRJZ100-RL7 Datasheet - Page 14

• Manufacturer Part Number: AD5160BRJZ100-RL7
• Description: IC POT DGTL SPI 256POS SOT23-8
• Manufacturer: Analog Devices Inc

Specifications of AD5160BRJZ100-RL7

• Taps: 256
• Resistance (ohms): 100K
• Number Of Circuits: 1
• Temperature Coefficient: 45 ppm/°C Typical
• Memory Type: Volatile
• Interface: SPI, 3-Wire Serial
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-8
• Resistance In Ohms: 100K
• End To End Resistance: 100kohm
• Track Taper: Linear
• No. Of Steps: 256
• Resistance Tolerance: ± 15%
• Supply Voltage Range: 2.7V To 5.5V
• Control Interface: Serial, SPI
• No. Of Pots: Single
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD5160EVAL - BOARD EVAL FOR AD5160
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: AD5160BRJZ100-RL7; AD5160BRJZ100-RL7TR

AD5160
THEORY OF OPERATION
The AD5160 is a 256-position digitally controlled variable
resistor (VR) device.
An internal power-on preset places the wiper at midscale
during power-on, which simplifies the fault condition recovery
at power-up.
PROGRAMMING THE VARIABLE RESISTOR
Rheostat Operation
The nominal resistance of the RDAC between Terminal A and
Terminal B is available in 5 kΩ, 10 kΩ, 50 kΩ, and 100 kΩ. The
final two or three digits of the model number as listed in the
Ordering Guide section determine the nominal resistance value,
for example, in model AD5160BRJZ10, the 10 represents 10 kΩ;
and in AD5160BRJZ50, the 50 represents 50 kΩ.
The nominal resistance (R
accessed by the 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 10 kΩ part is used, the first connection of the wiper
starts at the B terminal for Data 0x00. Because there is a 60 Ω
wiper contact resistance, such connection yields a minimum of
60 Ω resistance between Terminal W and Terminal B.
The second connection is the first tap point, which corresponds
to 99 Ω (R
The third connection is the next tap point, representing 138 Ω
(2 × 39 Ω + 60 Ω) 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 9961 Ω (R
shows a simplified diagram of the equivalent RDAC circuit
where the last resistor string is not accessed; therefore, there is
1 LSB less of the nominal resistance at full scale in addition to
the wiper resistance.
WB
= R
AB
Figure 39. Equivalent RDAC Circuit
D7
D6
D5
D4
D3
D2
D1
D0
DECODER
/256 + R
LATCH
RDAC
AND
AB
W
R
R
R
R
) of the VR has 256 contact points
S
S
S
S
= 39 Ω + 60 Ω) for Data 0x01.
AB
− 1 LSB + R
W
A
B
W
). Figure 39
Rev. B | Page 14 of 16
The general equation determining the digitally programmed
output resistance between W and B is
where:
D is the decimal equivalent of the binary code loaded in the
8-bit RDAC register.
R
R
the internal switch.
In summary, if R
circuited, the following output resistance R
indicated RDAC latch codes.
Table 7. Codes and Corresponding R
D (Dec.)
255
128
1
0
Note that in the zero-scale condition, a finite wiper resistance of
60 Ω is present. Take care 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
these terminals are used, the B terminal can be opened. Setting
the resistance value for R
resistance and decreases as the data loaded in the latch increases
in value. The general equation for this operation is
For R
following output resistance R
latch codes.
Table 8. Codes and Corresponding R
D (Dec.)
255
128
1
0
Typical device-to-device matching is process lot dependent and
may vary by up to ±30%. Because the resistance element is
processed in thin film technology, the change in R
temperature has a very low 45 ppm/°C temperature coefficient.
AB
W
is the wiper resistance contributed by the on resistance of
is the end-to-end resistance.
R
R
AB
WB
WA
= 10 kΩ and the B terminal is open circuited, the
(
(
D
D
R
9961
5060
99
60
)
)
WB
=
=
(Ω)
256
256
AB
D
256
= 10 kΩ and the A terminal is open
R
99
5060
9961
10,060
×
−
WA
R
D
Output State
Full Scale (R
Midscale
1 LSB
Zero Scale (Wiper Contact Resistance)
(Ω)
AB
×
WA
R
+
starts at a maximum value of
AB
R
WA
W
+
is set for the indicated RDAC
R
AB
W
− 1 LSB + R
Output State
Full Scale
Midscale
1 LSB
Zero Scale
WB
WA
Resistance
Resistance
WB
is set for the
W
WA
)
AB
). When
with
(1)
(2)