DS1802.pdf

DS1802

Dual Audio Taper Potentiometer

with Push–button Control

FEATURES

•

PIN ASSIGNMENT

Ultra–low power consumption

GND

V CC

•

Operates from 3V or 5V supplies

C OUT

VU (UC1)

VD (DC1)

B0 (UC0)

B1 (DC0)

MUTE

AGND

•

Two digitally controlled, 65–position potentiometers

including mute

CLK

RST

•

Logarithmic resistive characteristics (1 dB per step)

ZCEN

•

Zero–crossing detection eliminates noise caused by

wiper movement

MODE

•

Digital or mechanical push–button wiper control

•

Serial port provides means for setting and reading

both potentiometer wipers

20–PIN DIP (300 MIL)

20–PIN SOIC (300 MIL)

20–PIN TSSOP (173 MIL)

See Mech. Drawings

Section

•

20–pin SOIC and 20–pin TSSOP for surface mount

applications

PIN DESCRIPTION

L0, L1

•

Temperature:

– Commercial: 0 ° C to 70 ° C

– Low End of Resistor

H0, H1

– High End or Resistor

W1, W2

– Wiper End of Resistor

V CC

– 3V/5V Power Supply Input

•

Software and hardware mute

RST

– Serial Port Reset Input

– Serial Port Data Input

CLK

– Serial Port Clock Input

MODE

– Mode Select Input

UC0, UC1

– Up Control push–button Inputs

DC0, DC1

– Down Control push–button Inputs

VU, VD

– Volume–Up/Volume–DownInputs

B0, B1

– Balance Pot–0, Pot–1 Inputs

GND

– Digital Ground

MUTE

– Mute

AGND

– Analog Ground

ZCEN

– Zero–Crossing Detect

C OUT

– Cascade Output

DESCRIPTION

The DS1802 is a dual audio taper–potentiometer having

logarithmic resistive characteristics over the device

range. Each potentiometer provides 65 wiper positions

with a 1 dB increment per step and device mute. The

DS1802 has two methods of device control which include

contact closure (push–button) inputs and a 3–wire serial

interface for wiper positioning. The push–button control

inputs provide a simple interface for device control with-

out the need for a CPU. While the 3–wire serial interface,

using a CPU, provides the user the ability of reading or

writing exact wiper positions of the two potentiometers.

The DS1802 can also be configured to operate in either

independent or “stereo” modes, when using push–button

control. Independent mode of operation allows for inde-

pendent wiper control and stereo mode of operation pro-

vides single input control over both potentiometer wiper

positions. The DS1802 is offered in commercial temper-

ature versions. Packages for the part include a 20–pin

DIP, 20–pin SOIC, and 20–pin TSSOP.

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DS1802

OPERATION

The DS1802 provides two 65–position potentiometers

per package; each having a logarithmic resistive charac-

teristic as shown in Table 1. The DS1802 can be con-

trolled either digitally, or mechanically using a 3–wire

serial interface or contact closure input, respectively.

The push–button interface allows for a simple mechani-

cal control method for incrementing or decrementing

wiper position. The 3–wire serial interface is designed for

CPU controlled applications and allows the potentiome-

ter’s exact wiper position to be read or written. Addition-

ally, the DS1802 can be daisy chained for multi–device

environments.

On power–up the serial port is stable and active within 10

microseconds. The contact closure control interface

inputs are active after 50 ms. The wiper position on pow-

er–up will be at position 63, the low end of the potentiome-

ter. Position 64 is the mute level.

RESISTANCE CHARACTERISTICS Table 1

POSITION

OUTPUT LEVEL (dB)

–1

–2

–3

Figure 1 presents a block diagram of the DS1802. As

shown, the inputs from the 3–wire serial interface and

contact closure inputs drive a command/control unit.

The command/control unit interprets these inputs for

control of the two potentiometers.

–4

–5

•

The MODE input is used for contact closure operation.

This input allows the user to choose between indepen-

dent mode control and stereo mode control. The MODE

input is discussed in detail under the contact closure

interface control.

–63

64 (Mute)

< –90

DS1802 BLOCK DIAGRAM Figure 1

POTENTIOMETER–0

POTENTIOMETER–1

POS 64

POS 0

POS 64

POS 0

65–TO–1 MULTIPLEXER

b15

16–BIT I/O SHIFT REGISTER

C OUT

(UC1) VU

RST

COMMAND/

CONTROL

UNIT

(DC1) VD

(UC0) B0

(DC0) B1

CLK

MODE SELECT

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DS1802

CONTACT CLOSURE INTERFACE CONTROL

The DS1802 can be configured to operate from contact

closure inputs sometimes referred to as push–button

control. There exist a total of four physical contact clo-

sure terminals on the device package. When combined

with the MODE input, these contact closure inputs pro-

vide a total of eight different contact closure functions.

These eight contact closure functions are listed in

Table 2.

tiometer–0 wiper movement while UC1 and DC1 control

potentiometer–1 movement.

An additional feature of the contact closure interface is

the ability to control both directions of wiper movement

with only the UC0 and UC1 contact closure inputs. This

feature is referred to as single push–button operation.

Figure 2(a) and (b) illustrates both configurations for

single push–button and dual push–button operation.

CONTACT CLOSURE INPUTS Table 2

CONTACT INPUT

DESCRIPTION

Stereo Mode Control

Stereo mode control allows for the simultaneous posi-

tioning of both potentiometer wipers from a single control

input. Stereo mode control is entered when the MODE

select input is in a low state at power–up. The functional-

ity available when operating in stereo mode control

includes: 1) volume–up, 2) volume–down, 3) balance–0,

and 4) balance–1.

UC0*

Up contact potentiometer–0

UC1*

Up contact potentiometer–1

DC0*

Down contact potentiometer–0

DC1*

Down contact potentiometer–1

VU**

Volume–up

Volume Control Inputs

Volume–up and volume–down allow the user to move

both wipers either up or down the resistor array without

changing the relative balance or distance between the

wipers. For example, if potentiometer–0’s wiper is set at

position 28 and potentiometer–1’s wiper is set at position

20, the position distance of eight is maintained when

using either of these functions. Additionally, the balance

between both wipers is preserved if either reaches the

end of its resistor array.

VD**

Volume–down

B0** Balance Pot–0

B1** Balance Pot–1

* independent mode control

** stereo mode control

The MODE input terminal is used to select the mode of

wiper control using contact closure. There exist two

modes of wiper control which include independent mode

control and stereo mode control. As shown in the pin

assignment diagram, the contact closure inputs share

pins. Input functionality is determined by the state of the

MODE input at power–up.

Balance Control Inputs

Balance control inputs allow the user to control the dis-

tance or offset between potentiometer–0 and potentiom-

eter–1 wiper position settings. The two input controls for

balance include B0 and B1. The balance control inputs

attempt to minimize their respective wiper’s attenuation.

When the DS1802 first receives a balance control input,

the position of the wiper closest to the high end terminal,

H X , is stored. Wiper position movement is then governed

by this stored value.

Independent mode control allows the user to indepen-

dently control each potentiometers wiper position. For

independent mode control, the MODE input should be in

a high state. For stereo mode control, the MODE input

should be in a low state. The input should always be tied

to a well defined logic state.

For example, if the B0 input is used, the attenuation of

potentiometer–0 will change only if it is greater than the

attenuation of potentiometer–1. The direction of move-

ment for the potentiometer–0 wiper will be towards the

high end of the resistor array. Movement of wiper–0 will

only stop once its value is equal to that of wiper–1. At this

point, continued input activity on the B0 input will cause

an increase in attenuation of potentiometer–1. Note that

if the wiper of potentiometer–1 peaks at the bottom of its

The contact closure inputs which affect independent

mode control include UC0, UC1, DC0, and DC1. As out-

lined in Table 2, the UC0 and UC1 inputs are used to

move the potentiometers wipers towards the high–end of

the potentiometer (H0, H1) terminals. And the DC0 and

DC1 inputs control movement towards the low–end ter-

minals (L0, L1). Note that UC0 and DC0 control poten-

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DS1802

array, continued B0 input activity will cause no change in

the wiper positions of the device. A B1 input will be

required to change the balance of the two wipers if the

potentiometer wiper peaks in this case.

balance controlled inputs. A volume–up control input is

required to move the wiper positions from the bottom of

the resistor arrays. Balance control operation is pres-

ented in Figure 3.

In the case where both wiper positions are at position 63,

no movement of the wipers will take place when using the

SINGLE PUSH–BUTTON CONFIGURATION Figure 2(a)

DS1802

GND

V CC

C OUT

VU (UC1)

CLK

VD (DC1)

3–WIRE

SERIAL PORT

B0 (UC0)

RST

B1 (DC0)

ZCEN

MUTE

MODE

AGND

DUAL PUSH–BUTTON CONFIGURATION Figure 2(b)

DS1802

GND

V CC

C OUT

VU (UC1)

CLK

VD (DC1)

3–WIRE

SERIAL PORT

B0 (UC0)

RST

B1 (DC0)

ZCEN

MUTE

MODE

AGND

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DS1802

Contact closure is defined as the transition from a high

level to a low level on the contact closure input terminals.

The DS1802 interprets input pulse widths as the means

of controlling wiper movement. A single pulse input over

the UCx or DCx input terminals will cause the wiper to

move one position. A transition from high to low on these

inputs is considered the beginning of pulse activity or

contact closure. A single pulse is defined as being

greater than 1 ms but lasting no longer than a second.

This is shown is Figure 4(a).

in the single push–button configuration but must be con-

nected to the posit ive s upply voltage (V CC ). The 3–wire

serial port inputs (RST, CLK, and D) must be grounded

when not used.

On device power–up, the configuration shown in Figure

2(a) must exist in order to enter the single contact closure

mode of operation; especially and specifically, the (DC0,

DC1, VD, and B1) input’s connection to the positive sup-

ply voltage (V CC ).

Repetitive pulsed inputs can be used to step through

each resistive position of the device in a relatively fast

manner (see Figure 4(b)). The requirement for repetitive

pulsed inputs is that pulses must be separated by a mini-

mum time of 1 ms. If not, the DS1802 will interpret repeti-

tive pulses as a single pulse.

The direction of wiper movement, in single push–button

operation, is determined by prior activity; with the direc-

tion of wiper movement being opposite to that of the pre-

vious activity.

Changing the direction of wiper movement in single

push–button configuration is accomplish by a period of

inactivity on the controlling input of a (minimum) 1 second

or greater. For example, when operating from indepen-

dent mode control, an inactivity of 1 second or greater on

the UC0 input will cause the direction of the potentiome-

ter–0 wiper to reverse. The same is true for the UC1

input. Also, in independent mode control and single

push–button configuration, as the wiper reaches the end

of the potentiometer range its direction of movement

reverses. This will occur regardless if the input is a con-

tinuous pulse, a sequence of repetitive pulses or a single

pulse.

Pulse inputs lasting longer than 1 second will cause the

wiper to move one position every 100 ms following the ini-

tial 1 second hold time. The total time to transcend the

entire potentiometer using a continuous input pulse is

given by the formula below:

1 (second) + 63 X 100 ms =7.3 (seconds)

Single Contact Closure

Single contact closure operation allows the user to con-

trol wiper movement in either direction from a single

push–button input. Figure 2(a), as mentioned, presents

a typical single push–button configuration.

In stereo mode control, the VU input is responsible for

both directions of wiper movement. Again, a period of

inactivity will allow the direction of volume to be reversed.

Additionally, if either wiper reaches a peak position, the

direction of movement will automatically reverse.

In independent mode control, the UC0 and UC1 inputs

are used to increment and decrement each respective

wiper position for single push–button mode of operation.

The DC0 and DC1 inputs provide no functionality in the

single push–button configuration but must be connected

to the positive supply voltage (V CC ). In stereo mode con-

trol, the VU and B0 inputs are used to control volume and

balance. The VD and B1 inputs provide no functionality

For balance mode control, the B0 input will be responsi-

ble for wiper movement. A period of inactivity lasting 1

second or more will cause a switch in balance movement

(i.e., balance–0 to balance–1).

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