Configurable 4-Bit To 20-Bit Bus Switch With -2V Undershoot Protection And Selectable Level Shifting And 25?٠Series Resistors In Outputs

The Fairchild Universal Bus Switch FSTUD162450 pro- vides 4-bit, 5-bit, 8-bit, 10-bit, 16-bit, 20-bit of high-speed CMOS TTL-compatible bus switching. The low On Resis- tance of the Switch allows inputs to be connected to out- puts without adding propagation delay or generating additional ground bounce noise. The FSTUD162450 is designed to allow customer config- uration control of the enable connections. The device CAN be organized as either a five 4-bit, four 5-bit, two 10-bit or one 20-bit bus Switch Also available are 8-bit and 16-bit enabled configurations (see Functional Description). The device's bit configuration is controlled through select pin Logic (see Truth Table). When OEx is LOW, Port Ax is con- nected to Port Bx. When OEx is HIGH, the Switch is OPEN. The A and B Ports are protected against undershoot to support an extended range to 2.0V below ground. Fairchild's integrated Undershoot Hardened Circuit (UHC) senses undershoot at the I/O and responds by preventing voltage differentials from developing and turn- ing the Switch on. Another innovative device feature is the addition of a level shifting select pin, S2. When S2 is LOW, the device behaves as a standard N-MOS Switch When S2 is HIGH, a Diode to VCC is integrated into the circuit allowing for level shifting between 5V inputs and 3.3V outputs. By Fairchild Semiconductor