DS1806 Digital Sextet Potentiometer www.dalsemi.com FEATURES PIN ASSIGNMENT Six digitally controlled 64-position potentiometers W1 1 20 V CC 3-wire serial port provides for reading and W2 2 19 H1 setting each potentiometer L1-3 3 18 H2 Devices can be cascaded for single processor W3 4 17 H3 multi-device control W4 5 16 H4 Standard resistance values: L4-6 6 15 H5 - DS1806-010 10 k W6 7 14 W5 - DS1806-050 50 k RST 8 13 H6 - DS1806-100 100 k CLK 9 12 D IN Operating Temperature Range: GND 10 11 C - Industrial temperature: -40 C to +85C OUT DS1806 20-Pin DIP (300-mil) PIN DESCIPTION DS1806S 20-Pin SOIC (300-mil) V - 3V or 5V Supply CC DS1806E 20-Pin TSSOP (173-mil) RST - Serial Port Reset Input See Mech. Drawings Section D - Serial Port Data Input IN CLK - Serial Port Clock Input C - Cascade Data Output OUT H1 - H6 - High End terminal of Pot W1 - W6 - Wiper Terminal of Pot GND - Ground L1-3 - Low Terminal Pots 1 through 3 L4-6 - Low Terminal Pots 4 through 6 DESCRIPTION The DS1806 Digital Sextet Potentiometer is a six-channel, digitally controlled, solid-state linear potentiometer. Each potentiometer is comprised of 63 equiresistive sections as illustrated in the block diagram of Figure 1. Each potentiometer has three terminals accessible to the user. These include the high side terminals, H , the wiper terminals, W , and the low-end terminals, L1-3 and L4-6. Potentiometers 1 X X through 3 share the same low-end terminal L1-3 likewise, potentiometers 4 through 6 share the low-end terminal L4-6. Each wipers position is selected via an 8-bit register value. Communication and control of the device is accomplished via a 3-wire serial port interface. This interface in conjunction with a cascade output allows the value of the device wiper settings to be read. 1 of 8 102199DS1806 For multiple device and single processor environments, the DS1806 can be cascaded or daisy-chained. This feature allows a single processor to control multiple devices. The DS1806 is available in 10, 50 and 100-kohm versions and is specified over the industrial temperature range. Packages for the device include 20-lead DIPs, SOICs, and TSSOPs. OPERATION A block diagram of the device is provided in Figure 1. As shown, the DS1806 contains six 64-position potentiometers whose wiper positions are set by an 8-bit value. The DS1806 contains a 48-bit I/O shift register which is used to store the respective wiper position data for each of the six potentiometers. Each potentiometer has three terminals accessible to the user. These include the high side terminals, H , X the wiper terminals, W , and the low-end terminals, L1-3 and L4-6. Potentiometers 1 through 3 share the X same low-end terminal L1-3. And likewise, potentiometers 4 through 6 share the low-end terminal L4-6. Control of the DS1806 is accomplished via a 3-wire serial communication interface which allows the user to set the wiper position value for each potentiometer. The 3-wire serial interface consists of the control signals RST , D , and CLK. On power-up, the wiper positions of each potentiometer are set to the low- IN end terminal L (00000000). X The RST control signal is used to enable 3-wire serial port operation. The RST signal (3-wire serial port) is active when in a high state. Any communication intended to change wiper settings must begin with the transition of the RST from the low state to the high state. The CLK signal input is used to provide timing synchronization for data input and output. Wiper position data is loaded into the DS1806 through the D input terminal. This data is shifted one bit at a time into IN the 48-bit I/O shift register of the part, LSB first. Figure 3 provides an illustration of the 48-bit shift register. Figure 4 provides 3-wire serial port protocol and timing diagrams. As shown, the 3-wire port is inactive when the RST signal input is low. Once RST has transitioned from the low to the high state, the serial port becomes active. When active, data is loaded into the I/O shift register on the low-to-high transition of the CLK. Data is transmitted in order of LSB first. Potentiometers are designated from 1 through 6 and the value for potentiometer-1 will be the first data entered into the shift register, followed by that of potentiometer- 2 and so forth. Each wiper has an 8-bit register which is used for setting the position of the wiper on the resistor array. Because the DS1806 is a 64-position potentiometer, only six bits of information are needed to set wiper position. The remaining two bits of information are used to provide a dont change feature. Wiper position is controlled by bit positions 0 through 5 of each register. The dont change feature is controlled by bits 6 and 7 of each register. When bits 6 and 7 have value 11 xxxxxx, wiper position will not change regardless of the states of bits 0 through 5. If bits 6 and 7 are set to any other value, bits 0 through 5 will be used as the new wiper position. The dont change feature allows the user to change the value of any potentiometer of the DS1806 without affecting or having to remember the remaining positions of the potentiometer wipers. Figure 2 provides the format for a wipers register. 2 of 8 102199