DS1802 Datasheet, PDF (4/17 Pages) Dallas Semiconductor – Dual Audio Taper Potentiometer With Pushbutton Control

DS1802
Independent mode control allows the user to independently control each potentiometer's 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.
The contact closure inputs which affect independent mode control include UC0, UC1, DC0, and DC1. As
outlined 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. The DC0 and DC1 inputs control movement towards
the low-end terminals (L0, L1). Note that UC0 and DC0 control potentiometer-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
pushbutton operation. Figure 2(a) and (b) illustrates both configurations for single pushbutton and dual
pushbutton operation.
Stereo Mode Control
Stereo mode control allows for the simultaneous positioning 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 functionality available when operating in stereo mode control includes: 1) volume-up, 2) volume-
down, 3) balance-0, and 4) balance-1.
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.
Balance Control Inputs
Balance control inputs allow the user to control the distance or offset between potentiometer-0 and
potentiometer-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.
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 movement 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 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.
In the case where both wiper positions are at position 63, no movement of the wipers will take place
when using the 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 presented in Figure 3.
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