Texas Instruments UC2903QTRG3

Overview

UC2903QTRG3 from Texas Instruments is a quad supply and line monitor IC designed for industrial power system supervision. It monitors up to four independent voltage rails-including one negative rail via internal inverter-with programmable under- and over-voltage thresholds centered on a 2.5-V precision reference, ±10 mV typical output voltage accuracy, and three >30 mA open-collector fault outputs (UV/OK/OV) for power sequencing in telecom and embedded control systems.

For engineers reviewing the UC2903QTRG3 datasheet, UC2903QTRG3 pinout, UC2903QTRG3 application, or UC2903QTRG3 equivalent, key selection considerations include its –40°C to +85°C operating range, PLCC-20 package with dedicated LINE/SENSE input for early switcher-fault detection, proportional hysteresis scaling (10–30 mV/V), and integrated general-purpose op-amp capable of sourcing 20 mA for auxiliary feedback conditioning.

Technical Context

The UC2903QTRG3 implements a fault window architecture where OV and UV thresholds are generated as symmetric offsets around the 2.5-V reference, with magnitude and hysteresis both proportional to the voltage applied at Pin 4 (WINDOW ADJUST). Its dedicated Sense 4 inverter enables direct monitoring of negative supplies without external components.

Three open-collector outputs-UV FAULT, OV FAULT, and POWER OK-respond with user-programmable delays (20–50 ms/µF) to respective fault conditions; the POWER OK output is active-low and deasserts only when all monitored rails and the line sense input are within valid windows.

Key Specifications

Pinout & Package

UC2903QTRG3 is housed in a 20-pin PLCC (FN) package with gull-wing leads, RoHS-compliant CU-SN finish, and moisture sensitivity level (MSL) Level-2 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad supply monitoring applications.

Compared with UC3903Q and TPS3431DBVR, UC2903QTRG3 uniquely integrates quad rail monitoring, negative supply sensing, and early line-failure detection in a single PLCC-20 package-reducing component count by ≥75% versus discrete alternatives while supporting industrial temperature requirements.

Availability

UC2903QTRG3 is available at Aetrix Electronics and suitable for telecom power shelves, industrial PLCs, medical imaging subsystems, and automated test equipment requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for UC2903QTRG3 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 leader specializing in analog, embedded processing, and power management technologies with over 50 years of innovation in industrial and automotive electronics.

The UC2903QTRG3 belongs to TI's UC1903/UC2903/UC3903 family of precision supply monitors, engineered specifically for high-reliability power integrity supervision in harsh industrial environments where rail stability, fault isolation, and long-term availability are critical.

FAQ

What is the operating temperature range of the UC2903QTRG3?

The UC2903QTRG3 is rated for operation from –40°C to +85°C, making it suitable for industrial applications exposed to wide ambient temperature swings. This range is confirmed in the Electrical Characteristics table for UC2903 devices and aligns with its PLCC-20 packaging and green (RoHS & no Sb/Br) finish. The UC2903QTRG3 maintains specified performance-including 2.5-V reference accuracy and fault threshold hysteresis-across this full range without derating.

How does the UC2903QTRG3 sense a negative supply voltage?

The UC2903QTRG3 senses negative supplies using its dedicated internal inverter connected to the SENSE 4 input. By applying the negative rail to the inverter's input (Pin 5) and referencing the emitter follower output to ground, the inverter produces a positive-swing signal proportional to the negative voltage magnitude. This eliminates the need for external level-shifting circuitry. The UC2903QTRG3 datasheet confirms this function in Figure 6 and specifies input protection for SENSE 4 down to –0.3 V.

Can the UC2903QTRG3 monitor more than four voltage rails?

No-the UC2903QTRG3 has exactly four dedicated sense inputs (SENSE 1 through SENSE 4), and its internal fault window circuitry is architecturally limited to those four channels. Unused inputs must be tied to the 2.5-V reference or another active sense input per datasheet guidance. While the general-purpose op-amp can condition additional signals, it does not feed into the core UV/OV comparators or POWER OK logic; thus, true multi-rail supervision beyond four rails requires cascading or parallel UC2903QTRG3 devices.

What is the purpose of the WINDOW ADJUST pin on the UC2903QTRG3?

The WINDOW ADJUST pin (Pin 4) on the UC2903QTRG3 sets the magnitude of the fault window around the 2.5-V reference-and simultaneously scales the hysteresis proportionally. Applying 0.5 V to 2.5 V at this pin yields fault windows from ±0.115 V to ±0.625 V (±4.6% to ±25% of nominal sensed voltage), with hysteresis ranging from 10 mV/V to 30 mV/V. This allows precise, resistor-divider-based tuning of trip points for each rail without recalibrating the reference.

Does the UC2903QTRG3 require external components to operate?

Yes-the UC2903QTRG3 requires external timing capacitors on UV DELAY and OV DELAY pins to set fault response delays, and resistive dividers on SENSE 1–4 inputs to scale monitored voltages to the 0–2.5 V window. The WINDOW ADJUST pin also typically uses a divider from the REF output. However, no external transistors or op-amps are needed for basic quad monitoring or negative rail sensing, as those functions are integrated. All required external parts are passive and low-cost.