DS1808 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

Part Name

Description

Manufacturer

DS1808

Dual Log Digital Potentiometer

Dallas Semiconductor -> Maxim Integrated 

DS1808

OPERATION

The DS1808 is a dual-channel, digitally controlled, logarithmic potentiometer. Each potentiometer has

three accessible terminals, which include H, L, and W. Between each resistor element is a tap-point that is

multiplexed to the wiper terminal, W. A block diagram of the DS1808 is shown in Figure 1.

Potentiometer Characteristics

The DS1808 is a volatile device and always powers-up with the wiper positions set to the mute position

(33-decimal) with 90-dB of signal attenuation. The resistor section of the DS1808 is composed of two 32-

position resistor arrays that provide a logarithmic attenuation. The resistor section of the DS1808

provides a typical 50kW end-to-end resistance between the H terminal and the L terminal. The wiper

terminal will have a total possible 34 tap positions. The 34th position is considered the mute position and

will provide attenuation in excess of 90dB.

The potentiometers of the DS1808 are closely matched and provide excellent tracking. Interchannel

matching for the device is specified to provide less than 0.5dB. Tap-to-tap tolerances for the device are

specified to provide less than 0.5dB.

Power Supplies

The DS1808 is designed to be powered from dual ±12V supplies. The maximum input signal that can be

placed across the potentiometer sections is ±12V. The device can also be powered using a single +12V

power source. When using the device in a single supply configuration, VB is set to 0V and the maximum

potentiometer input signals are restricted to single supply voltage rails.

Controlling the Potentiometers

All writing and reading to the potentiometers is done with the industry standard 2-wire interface, which

includes pins SDA and SCL.

2-WIRE SERIAL PORT OPERATION

The 2-wire serial port interface supports a bi-directional data transmission protocol with device

addressing. A device that sends data on the bus is defined as a transmitter, and a device receiving data as

a receiver. The device that controls the message is called a master. The devices that are controlled by the

master are slaves. The bus must be controlled by a master device that generates the serial clock (SCL),

controls the bus access, and generates the start and stop conditions. The DS1808 operates as a slave on

the two-wire bus. Connections to the bus are made via the open-drain I/O lines SDA and SCL. The

following I/O terminals control the 2-wire serial port: /CE, SDA, SCL, A0, A1, A2. Timing diagrams for

the 2-wire serial port can be found in Figures 2 and 7.

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