DS1866 OPERATION The DS1866 is a single volatile potentiometer. The device has a total of eight positions providing a resolution of 5 dB per step and giving a total attenuation range of 0 dB to -35 dB. These tap points are accessible to the W-terminal whose position is controlled via a 3-terminal parallel port consisting of input signals P0, P1, and P2. A block diagram of the DS1866 is shown in Figure 1. Wiper position setting of the DS1866 is determined by the states of the P0, P1, and P2 input terminals. Table 1 below outlines position setting versus value of the parallel port inputs. A Position-0 setting places the wiper position at the L-terminal of the potentiometer and provides 35 dB of attenuation. As wiper position increases, attenuation decreases with Position-7 giving 0 dB of attenuation. On power-up, the wiper position of the DS1866 will be set to the P0, P1, and P2 values. P2 P1 P0WiperAttenuation(binary)Position(dB) 000 0 35 dB 001 1 30 dB 010 2 25 dB 011 3 20 dB 100 4 15 dB 101 5 10 dB 110 6 5 dB 111 7 0 dB PIN DESCRIPTIONS VCC - Power Supply Terminal. The DS1866 will support supply voltages ranging from +2.7 to +5.5 volts. GND - Ground Terminal.H - High-end Resistor. This is the high-end terminal of the potentiometer. It is not required that this terminal be connected to a potential greater than the L-terminal. Maximum voltage on the H-terminal can not exceed the power supply voltage, VCC, or go below ground. L - Low-end Resistor. This is the low-end terminal of the potentiometer. It is not required that this terminal be connected to a potential less than the H-terminal. Maximum voltage on the L-terminal can not exceed the power-supply voltage, VCC, or go below ground. W - Wiper of the Potentiometer. This pin is the wiper terminal of the potentiometer. Its position on the resistor array is controlled by the 3-terminal parallel port. Maximum voltage on the W-terminal can not exceed the power supply voltage, VCC, or go below ground. P0 - Bit 0. P0 is the bit 0 data input to the parallel port. P1 - Bit 1. P1 is the bit 1 data input to the parallel port. P2 - Bit 2. P2 is the bit 2 data input to the parallel port. 2 of 5 102199