DS1804_11 datasheet(2/10 Pages) MAXIM

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DS1804

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OPERATION

The DS1804 is a single nonvolatile potentiometer. The device has a total of 100 tap-points including the

L- and H- terminals. A total of 99 resistive segments exist between the L- and H- terminals. These tap-

points are accessible to the W-terminal, whose position is controlled via a three-terminal control port. A

block diagram of the DS1804 is shown in Figure 1.

The three-terminal port of the DS1804 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 100 decoder to

select wiper position. Additionally, this interface provides for a wiper storage operation using the CS and

INC

input control pins. The timing diagram for the three-terminal interface control is shown in Figure 2.

PIN DESCRIPTIONS

VCC - Power Supply. The DS1804 will support supply voltages ranging from +2.7V to +5.5V.

GND - Ground.

H - High-Terminal Potentiometer. This is the high terminal of the potentiometer. It is not required that

this terminal be connected to a potential greater than the L-terminal. Voltage applied to the H-terminal

cannot exceed the power-supply voltage, VCC, or go below ground.

L - Low-Terminal Potentiometer. This is the low terminal of the potentiometer. It is not required that this

terminal be connected to a potential less than the H-terminal. Voltage applied to the L-terminal cannot

exceed the power-supply voltage, VCC, or go below ground.

W - Wiper of the Potentiometer. This pin is the wiper of the potentiometer. Its position on the resistor

array is controlled by the three-terminal control port. Voltage applied to the wiper cannot exceed the

power-supply voltage, VCC, or go below ground.

- Chip Select. The CS input is used to activate the control port of the DS1804. 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 of the W-terminal 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

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 L-terminal.

DS1804 Scheda tecnica(PDF) 2 Page - Maxim Integrated Products