M74HCT126B1R

Overview

The M74HCT126B1R is a high-speed CMOS quad bus buffer with three-state outputs, manufactured using silicon gate C2MOS technology. It operates within a supply voltage range of 4.5V to 5.5V and supports an operating temperature from -55°C to +125°C. The device features balanced propagation delays (tPLH ≈ tPHL) and symmetrical output impedance with |IOH| = IOL = 6mA minimum. Typical propagation delay is 13ns at VCC = 4.5V, with maximum values reaching 32ns across the extended temperature range. Quiescent supply current is 4μA maximum at 25°C.

Feature Summary

• Provides four independent non-inverting buffers with three-state control for bidirectional data bus management.
• Designed for direct interface between HSC2MOS systems and TTL or NMOS components.
• Includes protection circuits on all inputs against static discharge and transient excess voltage.

Applications

• Data bus driver applications requiring controlled signal directionality
• Interface buffering between different logic families such as HSC2MOS and TTL
• Memory address/data bus drivers in embedded systems

Procurement Notes

Verify component obsolescence status before procurement planning. Confirm package type availability, as tube and tape-and-reel options may differ. Ensure design compatibility with 4.5V to 5.5V supply requirements. Check for pin-to-pin compatible replacements if long-term supply stability is required.

Selection Notes

Select this component when interfacing high-speed CMOS logic with TTL-compatible levels is necessary. The three-state capability allows multiple devices to share a common bus without contention. Verify that the 6mA drive strength meets load requirements. Consider thermal derating for power dissipation above 65°C.

Part Context

The M74HCT126 belongs to the 74HCT series of high-speed CMOS logic devices. It is functionally and pin-compatible with the standard 74LS126 TTL quad bus buffer. The 'B1R' suffix indicates a specific DIP-14 tube packaging variant produced by STMicroelectronics.

Replacement Considerations

Direct substitutes include other manufacturers' 74HCT126 equivalents in DIP-14 packages. Verify electrical specifications match the original requirements, particularly propagation delay and output drive current under similar load conditions.