Texas Instruments UC5608QP

Overview

UC5608QP from Texas Instruments is an 18-line active SCSI terminator IC designed for parallel SCSI-2 and SPI-2 bus termination. It delivers ±650mA sourcing/sinking capability, 104.5–115.5Ω trimmed termination impedance (±5%), 6pF channel capacitance in disconnect mode, 100µA standby supply current, and integrated thermal shutdown. It enables hot-pluggable, low-noise SCSI backplanes in server storage controllers.

For engineers reviewing the UC5608QP datasheet, UC5608QP pinout, UC5608QP application, or UC5608QP equivalent, key selection criteria include its PLCC-28 package, 4.0–5.25V Termpwr range, active negation sinking current (200mA), regulator output voltage (2.9V typ), and compliance with SCSI hot-plug requirements.

Technical Context

The UC5608QP integrates a precision 2.9V linear regulator with dropout voltage ≤1.2V and line regulation ≤20mV, powering 18 matched termination channels. Each channel provides bidirectional current control: −22.4mA sourcing at 0.5V line voltage and +200mA sinking capability under active negation.

Its disconnect logic disables all terminators and shuts down the regulator when DISCNCT exceeds 1.7V, reducing supply current to 100µA while maintaining high-impedance outputs-even without Termpwr applied. Internal trimming ensures ±5% tolerance on both impedance and output current, maximizing noise margin in Fast SCSI operation.

Key Specifications

Pinout & Package

UC5608QP is housed in a 28-pin PLCC (Plastic Leaded Chip Carrier) package with pins 12–18 serving as dual-function heatsink and signal ground terminals. The package features low thermal resistance suitable for continuous 2W operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SCSI active termination applications.

Compared with UC5602QP and AMCC 53C810, the UC5608QP offers superior noise margin (±5% vs ±3%), enhanced safety (thermal shutdown), and true hot-plug readiness-making it the preferred choice for modern SCSI backplane designs requiring reliability and compliance.

Availability

UC5608QP is available at Aetrix Electronics and suitable for SCSI RAID controller backplanes, hot-swappable server storage modules, and industrial motion control buses requiring stable component supply and long-term obsolescence management.

Supply support for UC5608QP includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, delivering analog and embedded processing solutions across industrial, automotive, and communications markets.

The UC5608QP belongs to TI's legacy SCSI interface product line, engineered specifically for high-reliability parallel bus termination in enterprise storage systems where signal integrity, thermal resilience, and hot-plug compliance are critical.

FAQ

What is the primary function of the UC5608QP in a SCSI system?

The UC5608QP serves as an 18-line active terminator for SCSI-2 and SPI-2 parallel buses. It replaces passive resistor networks by providing precisely trimmed 110Ω termination impedance and regulated current sourcing/sinking. Its role is to maintain signal integrity at both ends of the SCSI bus, reduce reflections, and ensure reliable high-speed data transfers up to 10MB/s. The UC5608QP achieves this while supporting hot-plug operations and thermal protection-key requirements in enterprise storage environments.

Does the UC5608QP require an external regulator?

No, the UC5608QP integrates a precision linear regulator that outputs 2.9V ±0.1V from a 4.0–5.25V Termpwr input. This internal regulator powers the termination circuitry and eliminates the need for external regulation. Its dropout voltage is ≤1.2V and line regulation is ≤20mV, ensuring stable operation across the specified input range. The UC5608QP's self-contained regulation simplifies PCB layout and improves system-level reliability compared to discrete regulator + terminator solutions.

How does the UC5608QP support SCSI hot-plug functionality?

The UC5608QP supports SCSI hot-plug through its logic-controlled DISCNCT input: when driven high (>1.7V), it simultaneously disconnects all 18 termination lines and shuts down the internal regulator, reducing supply current to just 100µA. Outputs remain high-impedance even without Termpwr applied-preventing bus contention during insertion/removal. This behavior complies with SCSI-2 hot-plug timing and electrical requirements. The UC5608QP's 6pF channel capacitance in disconnect mode further minimizes signal disturbance during live swaps.

What thermal protection features does the UC5608QP include?

The UC5608QP incorporates thermal shutdown that activates at 170°C with 10°C hysteresis, preventing permanent damage during sustained overload or poor heatsinking. It also includes current-limit protection on the regulator output, limiting short-circuit current to −950mA. These protections operate independently of external circuitry and are factory-trimmed for accuracy. In high-power 2W operation-enabled by its PLCC-28 package with pins 12–18 as heatsink/ground-the UC5608QP maintains safe junction temperatures without external heatsinks under typical airflow conditions.

Is the UC5608QP pin-compatible with earlier UC56xx series devices?

Yes, the UC5608QP is pin-for-pin compatible with UC5601QP and UC5602QP in the same PLCC-28 package. However, functional differences exist: the UC5608QP increases sinking current from 20mA to 200mA, removes low-side clamps, and tightens impedance and current tolerances to ±5% (vs ±3% in UC5601/02). While PCB layout remains unchanged, firmware or system-level timing may require validation due to the enhanced active negation capability and updated disconnect behavior of the UC5608QP.