DS2108

DS2108 Differential SCSI Switchable Terminator www.dalsemi.com FEATURES Fully compliant with SCSI, SCSI-2 and SCSI3 standards Conforms to EIA RS-485 standard Provides differential termination for 9 pairs of signal lines Operates with SCSI signal voltages of -7 to +12 Volts Laser-trimmed 330 and 150-ohm termination resistors have ±5% tolerance over full temperature range Switchable power-down mode Low power down capacitance of 6 pF 24-pin plastic SOIC (DS2108S) PIN ASSIGNMENT TPWR R1N R2N R3N R4N R5N R6N R7N R8N R9N TPWR NC 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 PD GND R1P R2P R3P R4P R5P R6P R7P R8P R9P GND DS2108S 24-Pin SOIC (300-mil) DESCRIPTION The DS2108 SCSI Terminator has been specifically designed for High Voltage Differential (HVD) SCSI systems requiring switchable termination. The DS2108 integrates eighteen 330-ohm and nine 150-ohm precise switched termination resistors into a monolithic IC. The surface mount SOIC package saves board space over conventional resistor SIPs. The termination resistors can be isolated from the SCSI bus under software or hardware control. While in the powered down mode, the DS2108 isolates the nine terminator blocks from the bus while adding only 6 pF capacitance to each signal line of the SCSI bus. FUNCTIONAL DESCRIPTION The DS2108 consists of power-down circuitry, eighteen 330-ohm and nine 150-ohm termination resistors (Figure 1). The DS2108 can be removed from the circuit by bringing the power down pin (PD)...