FSTU3257 is a Fairchild high-speed CMOS TTL-compatible 4:1 multiplexer/demultiplexer bus switch, low on resistance allows inputs to be connected to outputs without adding propagation delay or generating additional ground bounce noise. When OE is low, the select pin connects the A port to the selected B port output. The A and B ports are "undershoot hardened" with Undershoot Hardened Circuit (UHC®) protection to support an extended range of 2.0V below ground. Fairchild's integrated UHC senses undershoot at the I/O and responds by preventing voltage differentials from developing and turning on the switch. When OE is high, the switch is open and a high-impedance state exists between the two ports.
The FSTU3257 is a quad 2:1 high‑speed CMOS TTL‑compatible multiplexer/demultiplexer bus switch. It provides undershoot‑hardened A and B ports (‑2 V) and a soft‑enable turn‑on to minimize charge sharing. When OE is low the selected B port is connected to the A port; when OE is high the switch is open.
The device operates from a 4.0 V to 5.5 V supply, offers low on‑resistance, typical propagation delay of 0.25 ns, and is offered in SOIC, QSOP, and TSSOP packages (also tape‑and‑reel). Physical dimensions and land‑pattern recommendations are provided for each package.
| Undershoot protection | ‑2 V (A and B ports) |
|---|---|
| Recommended supply voltage (Vcc) | 4.0 V to 5.5 V |
| Propagation delay (typical) | 0.25 ns |
| Package options | SOIC, QSOP, TSSOP, tape‑and‑reel |
The switch is undershoot hardened to –2 V below ground on both A and B ports.
The recommended operating supply voltage is 4.0 V to 5.5 V.
It is offered in 16‑lead SOIC, QSOP, TSSOP packages and also in tape‑and‑reel form.
Yes, the control inputs are compatible with TTL level signals.