Rainbow Electronics DS1666S User Manual

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DS1666

Audio Digital Resisto

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 -3dB Point
DS1666-10 10K 24ȍ 152ȍ 1.0 MHz
DS1666-50 50K 122ȍ 759ȍ 200 kHz
DS1666-100 100K 243ȍ 1.519ȍ 100 kHz

PIN ASSIGNMENT

1

NC

2

U/D

3

INC

4

CS

GND

See Mech. Drawings Section

U/D

NC

NC

INC

NC

CS

NC

GND

See Mech. Drawings Section

5

6

NC

7

NC

14-PIN DIP (300 MIL)

1

2

3

4

5

6

7

8

16-PIN SOIC (300 MIL)

14

13

12

11

10

16

15

14

13

12

11

10

NC

V

CC

V

B

V

W

V

H

9

V

L

8

NC

V

CC

NC

V

B

V

W

V

H

NC

NC

9

V

L

PIN DESCRIPTIONS

V

H

V

L

V

W

U/ D - Up/Down Control

INC - Wiper Movement Control
CS - Chip Select for Wiper Movement

NC - No Connection
V

CC

GND - Ground
V

B

- High Terminal of Potentiometer

- Low Terminal of Potentiometer

- Wiper Terminal of Potentiometer

- 5V Power Supply Input

- 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 VL and VH terminals. A total of 127 resistive
segments exist between the VL and VH terminals. These tap-points are accessible to the VWterminal
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

VCC - Power Supply. The DS1666 will support supply voltages ranging from +4.5 to +5.5 volts.

GND - Ground Terminal.

VB- 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
voltage, (V

), or go below the negative bias, (VB).

CC

VL - Low-Terminal of Potentiometer. It is not required that this terminal be connected to a potential less
than the V

terminal. Voltage applied to the VLterminal cannot exceed the power-supply voltage, (VCC),

H

or go below the negative bias (VB).

V

- Wiper of the Potentiometer. Its position on the resistor array is controlled by the 3-terminal control

W

port. Voltage applied to the wiper cannot exceed the power-supply voltage, VCC, or go below the
negative bias (VB).

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.

terminal. Voltage applied to the VHterminal can not exceed the power-supply

L

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
VH 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 VL terminal.

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