78Q8392LA03-CHR/F

Overview

The 78Q8392LA03-CHR/F is a low power Ethernet coaxial transceiver designed as a replacement for the 78Q8392L/A02. It provides the interface between single-ended coaxial cable signals and Manchester-encoded differential logic signals, supporting IEEE 802.3 10Base5 and 10Base2 standards. The device integrates analog transmit/receive buffers, a 10 MHz oscillator, collision detection, jabber timer, and heartbeat functions. It operates on a -9V supply with non-transmitting current of 6 to 8 mA and transmitting current of 50 to 65 mA. Differential output voltage ranges from ±550 mV to ±1200 mV, with receiver startup delay at 400 to 500 ns.

Feature Summary

• Integrates all transceiver functions including receiver, transmitter, collision detection, and jabber timer while minimizing external component count.
• Features externally selectable collision detect (CED) heartbeat functionality for compatibility with IEEE 802.3 compatible repeaters.
• Includes squelch circuitry at all inputs to reject noise based on average DC level, pulse width, and transition period criteria.

Applications

• Internal or external Medium Access Unit (MAU) environments
• IEEE 802.3 compliant 10Base5 thick coaxial networks
• IEEE 802.3 compliant 10Base2 thin coaxial networks

Procurement Notes

Verify the specific package configuration required for the design, as the datasheet lists 16-pin DIP and 28-pin PLCC options. Confirm that the ordering suffix corresponds to the intended lead-free plastic package variant. Ensure the source document matches the Teridian Semiconductor Corporation specification for the 78Q8392L/A03 revision 1.3 to guarantee functional compatibility with existing designs.

Selection Notes

Select this component when upgrading from the 78Q8392L/A02, requiring only a single resistor value change. Choose the appropriate package based on board space constraints, noting the thermal dissipation requirements for the VEE pins. Verify that the system supports the -9V supply voltage and accommodates the necessary isolation transformers for the AUI interface connections.

Part Context

Originally manufactured by Teridian Semiconductor Corporation, this device serves as a legacy Ethernet physical layer component. Analog Devices Inc./Maxim Integrated branding may appear in distributor listings due to corporate acquisitions, but the technical specifications remain defined by the original Teridian documentation. It is distinct from modern high-speed PHYs, focusing specifically on legacy coaxial bus architectures.

Replacement Considerations

The datasheet explicitly identifies the 78Q8392L/A03 as a direct replacement for the SSI/TDK/Teridian 78Q8392L/A02. Upgrading requires changing only one external resistor value. No other major circuit modifications are necessary for migration.

FAQ

How does the device handle noise rejection on the transmission media?

The receiver utilizes squelch circuitry that determines valid data via three criteria: average DC level, pulse width greater than 20 ns, and transition period less than 200 ns. Invalid signals are rejected to prevent false triggering.

What is the function of the HBE pin?

The Heartbeat Enable (HBE) pin controls the collision detect heartbeat function. Grounding or leaving it open enables the heartbeat, while connecting it to VEE disables it.

How is the internal operating current established?

A fixed 976 Ω 1% resistor connected between the RR+ and RR- pins establishes the internal operating currents. This differs from the previous generation which used a 1kΩ resistor.