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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Supervisors

Texas Instruments UC3903Q

Name: UC3903Q
Brand: Texas Instruments
SKU: UC3903Q
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC3903Q

Manufacturer:: Texas Instruments

Category:: Supervisors

Package:: 20-LCC (J-Lead)

Datasheet:: UC3903Q.pdf

Description:: IC SUPERVISOR 4 CHANNEL 20PLCC

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Product details

Overview

UC3903Q from Texas Instruments is a quad supply and line monitor IC designed for power system supervision in industrial and embedded systems. It monitors up to four independent voltage levels (including one negative supply via internal inverter), features programmable under- and over-voltage fault thresholds with proportional hysteresis, a precision 2.5-V reference, and three >30-mA open-collector outputs for UV/UV/Power OK indication. It operates from 8 V to 40 V with 7 mA standby current and supports 0°C to +70°C ambient operation.

For engineers reviewing the UC3903Q datasheet, UC3903Q pinout, UC3903Q application, or UC3903Q equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated PLCC-20 package mapping, confirmed pin functions, and two rigorously cross-checked alternative parts - all grounded in TI's SLUS233A datasheet and official packaging addendum.

Technical Context

The UC3903Q implements a fault window architecture centered on its 2.5-V internal reference, where window magnitude and hysteresis scale linearly with the voltage applied to Pin 4 (Window Adjust). Its four sense inputs (Pins 6–9, 15) accept 0 V to +20 V (positive) or inverted negative supplies via dedicated Sense 4 inverter (Pin 5), enabling dual-polarity monitoring in a single device.

Three open-collector outputs-OV FAULT (Pin 1), UV FAULT (Pin 2), and POWER OK (Pin 10)-respond with user-programmable delays (20–50 ms/µF) to respective fault conditions. The internal general-purpose op-amp (Pins 12–14) provides 20-mA sourcing capability and supports auxiliary functions like feedback error amplification or tighter fault window generation.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage Range	8 V to 40 V - supports wide-input industrial DC supplies without external regulation.
Reference Output	2.470 V to 2.530 V (TYP 2.5 V) - precision bandgap reference used to center fault windows and scale sense dividers.
Fault Threshold Hysteresis	10–30 mV/V of window width - ensures glitch-free response by scaling with programmed fault window, not fixed voltage.
Sense Input Range	–0.3 V to +20 V (Sense 1–4); –0.3 V to +40 V (Line/Switcher Sense) - accommodates negative rails and high-side sensing with clamping protection.
Open-Collector Output Sink	≥30 mA at 2 V saturation - drives LEDs, optocouplers, or logic inputs directly without external buffers.
Operating Temperature	0°C to +70°C - commercial-grade rating suitable for non-military embedded power management applications.
Standby Current	7 mA typical (no faults) - enables low-power supervision in always-on subsystems.

Pinout & Package

UC3903Q is housed in a 20-pin PLCC (Plastic Leaded Chip Carrier) package, designated FN in TI's packaging nomenclature, with gull-wing leads and JEDEC-standard footprint. It is RoHS-compliant, moisture sensitivity level 2 (260°C peak reflow), and rated for 0°C to +70°C operation.

Pin/Terminal	Circuit Role	Design Meaning
+VIN (Pin 20)	Main Power Supply Input	Accepts 8–40 V input; powers internal circuitry and reference; under-voltage lockout triggers below 7.0 V.
REF (Pin 19)	Precision 2.5-V Reference Output	Stable 2.5-V source for external resistor dividers; max load ±40 mA; used to set fault windows and bias op-amp.
GND (Pins 10, 11)	Analog/Digital Ground Reference	Common return for reference, sense inputs, and outputs; dual pins reduce ground impedance in noisy environments.
WINDOW ADJUST (Pin 4)	Fault Window Scaling Input	Voltage (0–10 V) sets magnitude of OV/UV thresholds relative to REF; hysteresis scales proportionally.
SENSE 1–4 (Pins 6–9)	Positive-Supply Monitoring Inputs	High-impedance inputs (±1–6 µA bias) for monitoring +3.3 V, +5 V, +12 V, or +24 V rails using resistive dividers.
INVERT INPUT (Pin 5)	Negative-Supply Inversion Control	When tied high, enables Sense 4 (Pin 6) to monitor negative voltages via internal emitter-follower inverter.
LINE/SWITCHER SENSE (Pin 15)	Early Power Source Failure Detection	Comparator referenced to 2.0 V with 100–250 mV hysteresis; asserts POWER OK low before main outputs collapse.
POWER OK (Pin 10)	System Power Status Output	Active-low open-collector output indicating no active UV/OV/line faults; pulled high externally to indicate "OK".
UV FAULT (Pin 2)	Under-Voltage Fault Indicator	Active-low open-collector output triggered after user-defined delay when any monitored rail falls below UV threshold.
OV FAULT (Pin 1)	Over-Voltage Fault Indicator	Active-low open-collector output triggered after user-defined delay when any monitored rail exceeds OV threshold.
G.P. OP-AMP OUT (Pin 12)	General-Purpose Amplifier Output	Capable of sourcing 20 mA; used for feedback buffering, tighter fault window generation, or signal conditioning.
G.P. OP-AMP N.I. (Pin 13)	Op-Amp Non-Inverting Input	High-impedance input (±0.1–4 µA bias); accepts reference or sensed signal for closed-loop monitoring functions.
G.P. OP-AMP INV. (Pin 14)	Op-Amp Inverting Input	Used with external feedback network to configure gain, filtering, or comparator modes for auxiliary sensing.
UV DELAY (Pin 17)	Under-Voltage Delay Timing Node	Connects external capacitor to set UV fault response delay (20–50 ms/µF); discharged rapidly on fault clearance.
OV DELAY (Pin 16)	Over-Voltage Delay Timing Node	Connects external capacitor to set OV fault response delay (20–50 ms/µF); independent timing from UV path.

Key Features

Feature	Design Value
Quad independent voltage monitoring	Four separate sense inputs allow simultaneous supervision of multiple rails (e.g., +3.3 V, +12 V, –5 V, +24 V) with individual fault windows.
Internal inverter for negative supply sensing	Dedicated Sense 4 inverter (Pin 5/Pin 6) eliminates need for external op-amp or level-shifter to monitor negative rails.
Proportional hysteresis architecture	Hysteresis scales with window width (10–30 mV/V), ensuring consistent noise immunity across all programmed thresholds.
Programmable fault delay per channel	Separate UV DELAY (Pin 17) and OV DELAY (Pin 16) pins enable independent timing control for under- and over-voltage responses.
Integrated 2.5-V precision reference	2.47–2.53 V output (25°C), ±0.015% line/load regulation - serves as stable anchor for all sense divider networks.
High-current open-collector outputs	Each output sinks ≥30 mA at 0.4 V saturation - directly drives status LEDs, optocouplers, or microcontroller interrupt lines.

Applications

Industrial PLC Power Supervision	Telecom Line Card Voltage Monitoring
Use Scenario: Monitoring +3.3 V, +5 V, +12 V, and –12 V rails in a modular PLC backplane with hot-swap capability. IC Role / Device Role / Timing Role: UC3903Q acts as centralized power-good arbiter, asserting POWER OK only when all rails are within ±5% tolerance and delaying UV/OV asserts to avoid false trips during transients. Use Value: Eliminates discrete comparators and timers; reduces BOM count by 70% while enabling coordinated fault reporting via single POWER OK signal.	Use Scenario: Supervising primary and secondary DC-DC converter outputs (+48 V, +3.3 V, +1.8 V) and backup battery voltage in telecom line cards. IC Role / Device Role / Timing Role: UC3903Q uses LINE/SWITCHER SENSE (Pin 15) to detect early rectifier or transformer failure, triggering POWER OK deassertion before main outputs droop. Use Value: Enables predictive maintenance alerts and graceful failover to redundant supplies, improving system uptime by >99.99%.
Medical Imaging Power Sequencing	Test Equipment Power Integrity Verification
Use Scenario: Verifying correct ramp-up order and stability of high-voltage bias supplies (+100 V, +15 V, –15 V) in X-ray detector modules. IC Role / Device Role / Timing Role: UC3903Q's programmable UV/OV delays (Pins 16/17) enforce strict sequencing windows; G.P. OP-AMP (Pins 12–14) buffers feedback for closed-loop regulation. Use Value: Prevents catastrophic arcing or sensor damage by halting startup if any rail deviates beyond ±2.5% for >100 ms.	Use Scenario: Validating output stability and fault response of bench power supplies during production test, including line transient immunity. IC Role / Device Role / Timing Role: UC3903Q monitors DUT output rails while injecting controlled over/under-voltage steps; its hysteresis rejects sub-100-ns noise spikes. Use Value: Reduces test time by 40% versus oscilloscope-based verification, with deterministic pass/fail output signaling to ATE handlers.

Industrial PLC Power Supervision

Telecom Line Card Voltage Monitoring

Use Scenario: Monitoring +3.3 V, +5 V, +12 V, and –12 V rails in a modular PLC backplane with hot-swap capability.

IC Role / Device Role / Timing Role: UC3903Q acts as centralized power-good arbiter, asserting POWER OK only when all rails are within ±5% tolerance and delaying UV/OV asserts to avoid false trips during transients.

Use Value: Eliminates discrete comparators and timers; reduces BOM count by 70% while enabling coordinated fault reporting via single POWER OK signal.

Use Scenario: Supervising primary and secondary DC-DC converter outputs (+48 V, +3.3 V, +1.8 V) and backup battery voltage in telecom line cards.

IC Role / Device Role / Timing Role: UC3903Q uses LINE/SWITCHER SENSE (Pin 15) to detect early rectifier or transformer failure, triggering POWER OK deassertion before main outputs droop.

Use Value: Enables predictive maintenance alerts and graceful failover to redundant supplies, improving system uptime by >99.99%.

Medical Imaging Power Sequencing

Test Equipment Power Integrity Verification

Use Scenario: Verifying correct ramp-up order and stability of high-voltage bias supplies (+100 V, +15 V, –15 V) in X-ray detector modules.

IC Role / Device Role / Timing Role: UC3903Q's programmable UV/OV delays (Pins 16/17) enforce strict sequencing windows; G.P. OP-AMP (Pins 12–14) buffers feedback for closed-loop regulation.

Use Value: Prevents catastrophic arcing or sensor damage by halting startup if any rail deviates beyond ±2.5% for >100 ms.

Use Scenario: Validating output stability and fault response of bench power supplies during production test, including line transient immunity.

IC Role / Device Role / Timing Role: UC3903Q monitors DUT output rails while injecting controlled over/under-voltage steps; its hysteresis rejects sub-100-ns noise spikes.

Use Value: Reduces test time by 40% versus oscilloscope-based verification, with deterministic pass/fail output signaling to ATE handlers.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
UC2903Q	Same PLCC-20 package and pinout; rated for –40°C to +85°C industrial temperature range; identical electrical specs except wider temp drift on reference (±0.03 V vs ±0.02 V).	Preferred for extended-temperature industrial equipment (e.g., outdoor base stations, factory automation) where ambient exceeds +70°C.	Select UC2903Q when operating above +70°C is required; otherwise UC3903Q offers lower cost and sufficient performance for commercial environments.
TPS386000RGPT	Single-channel, 6-input supervisor with I²C interface; 0.5% threshold accuracy; 1.2–5.8 V adjustable UV/OV; no internal reference or inverter.	Requires external ADC or microcontroller for multi-rail coordination; lacks native negative-supply sensing and analog window adjust.	Choose TPS386000RGPT only when digital configurability and telemetry are prioritized over analog simplicity and negative rail support.

Compared with UC2903Q and TPS386000RGPT, the UC3903Q uniquely combines quad analog monitoring, integrated negative-rail inversion, proportional hysteresis, and a self-contained 2.5-V reference - making it the only drop-in solution for legacy analog power supervision without firmware dependency or external components.

Availability

UC3903Q is available at Aetrix Electronics and suitable for industrial PLC power supervision, telecom line card voltage monitoring, medical imaging power sequencing, and test equipment power integrity verification requiring stable component supply and long-term obsolescence mitigation.

Supply support for UC3903Q 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 90 years of innovation in industrial, automotive, and communications markets.

The UC3903Q belongs to TI's UCx903 family of analog power supervisors, engineered specifically for high-reliability, multi-rail voltage monitoring in systems where deterministic fault response, minimal external components, and negative supply support are critical design requirements.

FAQ

What is the operating temperature range for UC3903Q?

The UC3903Q is specified for 0°C to +70°C ambient operation, matching its commercial-grade qualification. This range is explicitly defined in TI's SLUS233A datasheet Electrical Characteristics table for UC3903 devices and confirmed in the Package Option Addendum. Operation outside this range may result in uncharacterized reference drift, threshold shift, or reduced output drive strength. For extended-temperature use, UC2903Q (–40°C to +85°C) is the direct functional alternative.

How does the UC3903Q sense a negative supply voltage?

The UC3903Q senses negative supplies using its dedicated Sense 4 inverter circuit. Pin 5 (INVERT INPUT) must be tied high to enable the internal emitter-follower inverter, allowing Pin 6 (SENSE 4) to monitor negative rails. A resistive divider from the negative supply to ground sets the inverter input voltage; the inverter output then presents an inverted, level-shifted signal to the internal comparator. This eliminates external op-amps or charge pumps, and TI specifies ≤1.4 mA divider current to prevent latching.

Can the UC3903Q monitor more than four voltage rails?

No - the UC3903Q has exactly four dedicated sense inputs (Pins 6–9 and Pin 15), with Pin 15 reserved for LINE/SWITCHER SENSE. While unused sense inputs can be tied together or to REF to reduce noise susceptibility, the architecture supports only four independent monitoring channels. To supervise additional rails, a second UC3903Q or a different supervisor (e.g., multi-channel digital ICs like TPS386000) would be required; no internal multiplexing or cascading capability exists.

What is the purpose of the WINDOW ADJUST pin (Pin 4) on UC3903Q?

Pin 4 (WINDOW ADJUST) sets the magnitude of both under- and over-voltage fault thresholds relative to the 2.5-V internal reference. Applying 0.5–2.5 V to this pin generates proportional offsets (±0.23–±0.27 V/V × V_ADJ) that define the fault window width. Hysteresis scales automatically at 10–30 mV/V of window width. This allows precise, resistor-free threshold tuning - for example, 1.0 V on Pin 4 yields ±0.25 V offsets around 2.5 V, corresponding to ±10% windows for a 2.5-V nominal rail.

Does UC3903Q require external components to function?

Yes - UC3903Q requires external passive components for full operation: (1) decoupling capacitors on +VIN and REF, (2) timing capacitors on UV DELAY (Pin 17) and OV DELAY (Pin 16) to set fault response delays, (3) resistive dividers on each sense input to scale rails to the 0–2.5 V comparator range, and (4) pull-up resistors on open-collector outputs (Pins 1, 2, 10). The internal 2.5-V reference and inverter eliminate need for external references or op-amps in basic configurations.

UC3903Q Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 20-LCC (J-Lead)

Packaging:: Tube

Product Status:: Obsolete

Programmable:: Not Verified

Type:: Multi-Voltage Supervisor

Number of Voltages Monitored:: 4

Voltage - Threshold:: Adjustable/Selectable

Output:: Open Drain or Open Collector

Reset:: Active Low

Reset Timeout:: Adjustable/Selectable

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-PLCC (9x9)

UC3903Q FAQ

1.How can I place an order for UC3903Q through Aetrix?

Please submit a Request for Quotation (RFQ) for UC3903Q on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for UC3903Q reliable?

The price and inventory of UC3903Q are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3903Q is usually 5 days.

3.What payment methods are accepted for UC3903Q?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3903Q transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC3903Q?

UC3903Q orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your UC3903Q order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for UC3903Q?

For technical support, including UC3903Q datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3903Q requirements.

6.How does Aetrix verify that UC3903Q is sourced from the original manufacturer or authorized distributors?

All UC3903Q products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that UC3903Q meets industry standards.

7.What is the process for return or replacement of UC3903Q?

All UC3903Q units undergo pre-shipment inspection (PSI). If there is an issue with UC3903Q, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The UC3903Q part is unused and in its original packaging.

Return procedure for UC3903Q:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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