DS1807 Addressable Dual Audio Taper Potentiometer www.dalsemi.com FEATURES PIN ASSIGNMENT Operates from 3V or 5V Power Supplies GND 1 14 V Ultra-low power consumption CC Two digitally controlled, 65-position A2 2 13 SCL potentiometers A1 3 12 SDA Logarithmic resistor characteristics (1 dB per A0 4 11 AGND step) W0 5 10 H1 Zero-crossing detection eliminates noise L0 6 9 L1 caused by discrete wiper changes H0 7 8 W1 Addressable using 3-Chip Select Inputs Serial/Synchronous Bus Inputs DS1807 14-Pin DIP (300-mil) Operating Temperature Range: DS1807E 14-Pin TSSOP (173-mil) - Industrial: -40C to +85C Standard Resistance Value: 45 k GND 1 16 V CC A2 2 15 NC A1 3 14 SCL NC 4 13 SDA PIN DESCIPTION L0, L1 - Low End of Resistor A0 5 12 AGND H0, H1 - High End of Resistor W0 6 11 H1 W0,W1 - Wiper Terminal of Resistor L0 7 10 L1 V - 3V/5V Power Supply Input CC H0 8 9 W1 A0..A2 - Chip Select Inputs SDA - Serial Data I/O DS1807S 16-Pin SOIC (300-mil) SCL - Serial Clock Input See mech. Drawings Section GND - Ground AGND - Analog Ground NC - No connection DESCRIPTION The DS1807 Addressable Dual Audio Taper Potentiometer is a dual audio taper potentiometer having a logarithmic resistive characteristic. Each potentiometer has a total of 65 wiper positions including the mute position. Adjacent wiper positions are separated by 1 dB giving a total attenuation range of 64 dB. When the wipers are in the mute position, attenuation in excess of 90 dB is achieved. The DS1807 also provides a zero-crossing detection capability. This capability eliminates noise caused by discrete wiper position changes. The DS1807 is controlled via a two-input, serial synchronous interface that provides the capability of addressing up to eight different DS1807s. Addressability is obtained via communication protocol and three (3) address select inputs A0, A1, and A2. Communication protocol allows for the exact positioning of the DS1807 wipers position. Additionally, communication protocol allows for independent or simultaneous setting of the two potentiometers wipers. Wiper positions can also be read via the 2-wire serial interface. 1 of 13 110499DS1807 The DS1807 is available in 14-pin DIP, SOIC, and TSSOP packages. The DS1807 is offered in industrial temperature grades. The standard resistance of the DS1807 is 45 k. DEVICE OPERATION The DS1807 is an addressable, digitally controlled device that has two 65-position potentiometers. The DS1807 potentiometers are logarithmic tapers providing a resolution or step size of 1 dB per step from th positions 0 through 63. The 64 position is the mute position and provides attenuation in excess of 90 dB. Moving the potentiometers wiper from position 63 (or 63 dB of attenuation) to position 64 will provide a step size in excess of 30 dB. A functional block diagram of the part is shown in Figure 1. As stated, each potentiometer is composed of a 65 position resistor array. Two 8-bit registers, each assigned to a respective potentiometer, are used to set wiper position on the resistor array. The wiper terminal is multiplexed to one of 65 positions on the resistor array based on its corresponding 8-bit register value. Because the DS1807 has 65 positions, only seven bits of data are needed to set a wipers position. Bits 0 through 5 of the register are used to set the position on the resistor array. Bit 6 is used to set the wiper position to the mute position and bit 7 is a dont care. If the value of bit 6 is set equal to 1, regardless of all other bit values, the wiper position of the respective potentiometer will be set to the mute position. An example diagram of the wiper register and associated bit function is provided in Figure 2. The DS1807 is designed to operate as an attenuator. (see Figure 3) As such, wiper position values are set with respect to the amount of attenuation desired. For example, if the user wishes to attenuate an incoming signal by 6 dB, the wiper position register value(s) should be set to binary (0000 0110). The H0 and H1 terminals of the DS1807 have wiper position values (binary) 0000 0000. These terminals provide 0 dB of attenuation for the input signal. The L0 and L1 terminals provide the greatest attenuation of the input signal. They represent the mute positions for the DS1807 and have wiper position values (binary) 0100 0000 or greater. On power-up, the serial port is stable and active within 10 microseconds. Additionally, DS1807 wiper positions will be set to position 63 or (binary) 0011 1111, one position above mute. The user may then set the wiper register to a desired value. Communication with the DS1807 takes place over the 2-wire serial interface consisting of the bi- directional data terminal, SDA, and the serial clock input, SCL. The 2-wire serial interface and chip select inputs A0, A1, and A2 allow operation of up to eight devices in a bus topology with A0, A1, and A2 being the physical address of the device. Complete details of the 2-Wire interface are discussed in the section entitled 2-Wire Serial Data Bus. 2 of 13 110499