DS1666
Audio Digital Resistor
www.dalsemi.com
FEATURES
128 position, digitally controlled poten-
tiometer
Operates from a +5 volts power supply with
TTL signal inputs
Wide analog voltage range of ±5 volts
Low-power CMOS
14-pin DIP or 16-pin SOIC for surface
mount applications
Default position on power up sets wiper
position to 10% of active digital taps (3% of
the total end-to-end resistance)
Operating temperature range
– Industrial temp. range: -40°C to +85°C
Resistance/Step
Resistance values Low End High End
DS1666-10 10K
24Ω
152Ω
DS1666-50 50K
122Ω
759Ω
DS1666-100 100K 243Ω
1.519Ω
PIN ASSIGNMENT
NC
U/D
INC
CS
GND
NC
NC
1
2
3
4
5
6
7
14
13
12
11
10
9
8
NC
V
CC
V
B
V
W
V
H
V
L
NC
14-PIN DIP (300 MIL)
See Mech. Drawings Section
U/D
NC
NC
INC
NC
CS
NC
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
NC
V
B
V
W
V
H
NC
NC
V
L
-3dB Point
1.0 MHz
200 kHz
100 kHz
16-PIN SOIC (300 MIL)
See Mech. Drawings Section
PIN DESCRIPTIONS
V
H
V
L
V
W
U/
D
INC
CS
NC
V
CC
GND
V
B
-
-
-
-
-
-
-
-
-
-
High Terminal of Potentiometer
Low Terminal of Potentiometer
Wiper Terminal of Potentiometer
Up/Down Control
Wiper Movement Control
Chip Select for Wiper Movement
No Connection
5V Power Supply Input
Ground
Substrate Bias Voltage (0 to -5V)
DESCRIPTION
The DS1666 Audio Digital Resistor is a solid-state potentiometer composed of 127 digitally controlled
resistive elements. Between each resistive section and both ends of the potentiometer are tap points
multiplexed to the wiper. The position of the wiper on the resistance array is controlled by the
CS
, U/
D
and
INC
inputs. The taper of the DS1666 is shown in Figure 1.
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DS1666
The DS1666 is uniquely designed to provide a potentiometer that is pseudo-logarithmic rather than linear
across its entire range. The lower half of the potentiometer advances 1% of total resistance for each 3%
of scale advanced, providing for precise amplification of low volume signals. The upper half of the
potentiometer advances 2% of resistance for every 1% of scale advanced, providing for the lower
resolution gain required for high volume amplification.
GRAPH OF AUDIO TAPER
Figure 1
OPERATION
The DS1666 has a total of 128 tap-points including the V
L
and V
H
terminals. A total of 127 resistive
segments exist between the V
L
and V
H
terminals. These tap-points are accessible to the V
W
terminal
whose position is controlled via a 3-terminal control port. A block diagram of the DS1666 is shown in
Figure 2.
The 3-terminal port of the DS1666 provides an increment/ decrement interface which is activated via a
chip select input. This interface consists of the input signals
CS
,
INC
, and U/
D
. These input signals
control a 7-bit up/down counter. The output of the 7-bit up/down counter controls a 1 of 128 decoder to
select wiper position. The timing diagram for the 3-terminal interface control is shown in Figure 4.
ANALOG CHARACTERISTICS
The DS1666 has a pseudo-logarithmic resistor array that resembles an audio taper potentiometer as
shown in Figure 1. Taps on the lower portion of the potentiometer increment 0.25% of the total
resistance and are specified to within ±0.5% of the expected value. Taps on the higher portion increment
1.5% of the total resistance and are specified to within ±2.0% of the expected value.
End-to-End Resistance Tolerance = ±20 %
Temperature Coefficient = 750 PPM/°C typical
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DS1666
PIN DESCRIPTIONS
V
CC
-
Power Supply. The DS1666 will support supply voltages ranging from +4.5 to +5.5 volts.
GND -
Ground Terminal.
V
B
- Negative Bias. The DS1666 will support a negative bias ranging from 0 to -5 volts.
H -
High-Terminal of Potentiometer. It is not required that this terminal be connected to a potential
greater than the V
L
terminal. Voltage applied to the V
H
terminal can not exceed the power-supply
voltage, (V
CC
), or go below the negative bias, (V
B
).
V
L
-
Low-Terminal of Potentiometer. It is not required that this terminal be connected to a potential less
than the V
H
terminal. Voltage applied to the V
L
terminal cannot exceed the power-supply voltage, (V
CC
),
or go below the negative bias (V
B
).
V
W
-
Wiper of the Potentiometer. Its position on the resistor array is controlled by the 3-terminal control
port. Voltage applied to the wiper cannot exceed the power-supply voltage, V
CC
, or go below the
negative bias (V
B
).
CS
-
Chip Select. The
CS
input is used to activate the control port of the DS1666. This input is active
low. When in a high-state, activity on the
INC
and U/
D
port pins will not affect or change wiper
position.
INC
-
Wiper Movement Control. This input provides for wiper position changes when the
CS
pin is low.
Wiper position changes will occur one position per high-to-low transition of this input signal. Position
changes will not occur if the
CS
pin is in a high-state.
U/
D
-
Up/Down Control. This input sets the direction of wiper movement. When in a high-state and
CS
is low, any high-to-low transition on
INC
will cause a one position movement of the wiper towards the
V
H
terminal. When in a low-state and
CS
is low, any high-to-low transitions on
INC
will cause the
position of the wiper to move towards the V
L
terminal.
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BLOCK DIAGRAM
Figure 2
MODE SELECTION
Figure 3
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ABSOLUTE MAXIMUM RATINGS*
Voltage on
CS
,
INC
, U/
D
and U/
D
and V
CC
Relative to Ground
Voltage on V
H
, V
L
and V
W
Relative to Ground
Voltage on V
B
Operating Temperature
Storage Temperature
Soldering Temperature
-0.5V to +7.0V
-6.5V to +6.5V
-6.5V to GND
-40° to +85°C
-55°C to +125°C
260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
Supply Voltage
Input Logic 1
Input Logic 0
V
H
, V
L
, V
W
Voltage
V
B
Voltage
SYMBOL
V
CC
V
IH
V
IL
V
R
V
B
MIN
+4.5
2.0
-0.5
V
B
-0.3
-5.5
TYP
5.0
MAX
5.5
V
CC
+0.5
+0.8
V
CC
+0.3
GND
(-40°C to +85°C)
UNITS
V
V
V
V
V
NOTES
1
1
1
1, 3
1
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Supply Current
Input Leakage
Wiper Resistance
Wiper Current
SYMBOL
I
CC
I
LI
R
W
I
W
-1
MIN
(-40°C to +85°C; V
CC
= 5.0V ± 10%)
TYP
0.2
MAX
4.5
+1
350
900
1
UNITS
mA
µA
Ω
mA
2
NOTES
4
CAPACITANCE
PARAMETER
Capacitance
SYMBOL
C
IN
CONDITION
t
A
=25°C
TYP
6
MAX
pF
(t
A
=25°C)
UNITS
NOTES
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