QT49S-4.000MAHJ-T

Overview

The QT49S-4.000MAHJ-T is a surface-mount crystal oscillator from the QT49S series manufactured by QST. It operates at a fundamental frequency of 4 MHz with a load capacitance of 18 pF. The component exhibits a frequency stability and tolerance of ±30 ppm. It utilizes an HC-49/US package style, featuring physical dimensions of 12.7 mm x 4.8 mm x 3.8 mm. The equivalent series resistance is specified as 150 Ohms. This device is designed for precise timing applications requiring compact surface-mount integration.

Feature Summary

• Surface-mount design compatible with automated assembly processes
• HC-49/US form factor adapted for PCB mounting
• Stable frequency performance with ±30 ppm tolerance

Applications

• Microcontroller clock sources
• Communication interface timing circuits
• Digital signal processing systems

Procurement Notes

Verify the manufacturer designation matches QST rather than TXC, as some listings may contain conflicting branding data. Confirm the suffix HAJ-T corresponds to the specific surface-mount variant with 18 pF load capacitance. Ensure the operating temperature range meets system requirements, typically extending to -40°C. Cross-reference the 150 Ohm ESR specification against circuit design constraints to guarantee proper oscillation startup conditions.

Selection Notes

Select this component when a 4 MHz reference is required in a low-profile surface-mount configuration. The 18 pF load capacitance must match the external capacitors used in the oscillator circuit to maintain accuracy. Consider the 150 Ohm impedance level for driver strength compatibility. The ±30 ppm stability suits general-purpose digital logic timing where high-precision atomic standards are unnecessary.

Part Context

This part belongs to the QT49S series of quartz crystals, which provides various frequency options in a standardized SMD footprint. The series offers alternatives ranging from lower to higher frequencies while maintaining consistent package dimensions. The QT49S line serves as a cost-effective solution for consumer electronics and industrial control boards requiring reliable clock signals.

Replacement Considerations

Direct substitutes include other 4 MHz SMD crystals with identical 18 pF load capacitance and similar ESR values. Verify that alternative parts support the same HC-49/US mechanical envelope. Check if competitor components offer comparable ±30 ppm stability. Ensure the replacement maintains the same fundamental mode operation without requiring circuit modification.