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Texas Instruments UC3903QG3
- Part No.:
- UC3903QG3
- Manufacturer:
- Texas Instruments
- Category:
- Supervisors
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
UC3903QG3.pdf
- Description:
- IC SUPERVISOR 4 CHANNEL 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,341
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Product details
Overview
UC3903QG3 from Texas Instruments is a quad supply and line monitor IC designed for power system supervision in industrial and telecom power supplies. It monitors up to four voltage rails-including one negative rail via internal inverter-with programmable under- and over-voltage thresholds centered on a 2.5-V precision reference, 30-mA open-collector fault outputs, and 8-V to 40-V supply operation.
For engineers reviewing the UC3903QG3 datasheet, UC3903QG3 pinout, UC3903QG3 application, or UC3903QG3 equivalent, this page delivers verified technical context, real-world timing behavior, fault delay scaling, sense input clamping architecture, and design-meaningful comparisons to alternative quad monitor ICs-enabling confident selection for multi-rail power integrity monitoring.
Technical Context
The UC3903QG3 implements a proportional hysteresis architecture where window adjust voltage (Pin 4) linearly scales both OV/UV threshold offsets (±0.25 V/V × VADJ) and hysteresis magnitude (10–30 mV/V), ensuring glitch-free fault detection across temperature. Its dedicated Sense 4 inverter enables direct negative supply monitoring without external components, while the general-purpose op-amp supports auxiliary functions like feedback signal buffering with 20-mA source capability.
Three independent open-collector outputs indicate UV fault, OV fault, and POWER OK status-each with user-programmable delay via external capacitors and internal 60-µA charging current. The line/switcher sense comparator triggers POWER OK deassertion at 2.0 V with 175-mV hysteresis, enabling early detection of AC line or DC-DC converter failures before downstream rail collapse.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Range | 8 V to 40 V - supports wide-input industrial and telecom power supplies without external regulators |
| Reference Voltage | 2.5 V ±15 mV (0°C to +70°C) - stable system reference for all sense thresholds and external divider scaling |
| Fault Threshold Hysteresis | 10–30 mV/V of window width - scales precisely with adjust voltage to maintain consistent % hysteresis across all programmed windows |
| Open-Collector Output Sink | >30 mA per output - drives standard logic-level optocouplers or LED indicators directly without buffer transistors |
| Standby Current | 7 mA typical (no faults) - enables low-power supervision in always-on systems without significant overhead |
| Sense Input Range | –0.3 V to +20 V - accommodates negative rails (via inverter) and high-side positive sensing with robust input clamping |
| Line Sense Threshold | 2.0 V ±60 mV - precise early-warning trigger for AC line dropout or switcher output sag before regulation loss |
Pinout & Package
UC3903QG3 is housed in a 20-pin PLCC (FN package) with gull-wing leads, RoHS-compliant Cu/Sn finish, and JEDEC Level-2 moisture sensitivity rating. Pin numbering follows top-view orientation as defined in TI's SLUS233A datasheet for Q/L packages.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| +VIN | Main supply input | Power source for internal circuitry; enables operation from 8 V to 40 V; powers reference, comparators, and outputs |
| VREF | Precision 2.5-V reference output | Stable, buffered reference used for threshold generation and external resistive divider scaling of sense inputs |
| GND | Analog/digital ground | Common return for all internal circuits; two GND pins (Pins 3 & 4) provide low-impedance grounding for noise-sensitive analog blocks |
| WINDOW ADJUST | Fault window magnitude control | Voltage applied here (0–10 V) sets proportional OV/UV offset and hysteresis; 1 V = ±250 mV offset, 20 mV hysteresis |
| SENSE 1–4 | Monitor inputs for supply voltages | Four high-impedance inputs; SENSE 4 supports inverted mode for negative rail sensing via internal op-amp inverter |
| LINE/SWITCHER SENSE | Early power failure warning input | Comparator referenced to 2.0 V detects line or switcher collapse; 175-mV hysteresis prevents chatter during marginal conditions |
| POWER OK | Active-low "all-rails-in-spec" indicator | Open-collector output asserted low only when no UV/OV/line faults exist; signals system readiness to boot or operate |
| UV FAULT / OV FAULT | Dedicated fault indication outputs | Separate open-collector outputs with independent delay timing; enable selective response to under- vs. over-voltage events |
| UV DELAY / OV DELAY | External capacitor connection points | Accept timing capacitors to set fault response delay (20–50 ms/µF); internal 60-µA current source charges capacitor to 1.8 V threshold |
| G.P. OP-AMP OUT/N.I./INV. | Uncommitted operational amplifier | Unity-gain stable op-amp with 20-mA source/40-mA sink; used for feedback buffering, level shifting, or generating tighter fault windows |
Key Features
| Feature | Design Value |
|---|---|
| Quad independent voltage monitoring | Four sense inputs allow simultaneous supervision of +12 V, +5 V, –5 V (via SENSE 4 inverter), and standby +3.3 V rails |
| Proportional hysteresis architecture | Hysteresis scales automatically with window width-ensuring consistent 8% relative hysteresis regardless of programmed threshold spread |
| Internal inverter for negative rail sensing | Eliminates need for external inverting amplifier when monitoring –12 V or –5 V supplies; uses dedicated SENSE 4 path |
| Programmable fault delays | UV/OV delay timing set by external capacitor (e.g., 100 nF → ~3 ms delay); avoids nuisance trips during transient load steps |
| 2.5-V reference with load/line regulation | ±10 mV load regulation (0–10 mA) and ±8 mV line regulation (8–40 V) - maintains accuracy across varying system conditions |
| Line/switcher sense with early warning | Triggers POWER OK deassertion at 2.0 V with 175-mV hysteresis - detects AC line sag or DC-DC controller failure 10–100 ms before output collapse |
Applications
| Telecom Power Shelf Supervision | Industrial PLC Power Management |
|---|---|
Use Scenario: Monitoring +48 V primary, +12 V control, –12 V analog, and +3.3 V logic rails in a carrier-grade power shelf. IC Role / Device Role / Timing Role: UC3903QG3 acts as centralized power-good arbiter, asserting POWER OK only when all rails are within ±5% tolerance with 10-ms delay filtering. Use Value: Prevents system boot on marginal rails; eliminates need for four discrete supervisors and reduces BOM count by 75%. |
Use Scenario: Supervising redundant +24 V DC inputs, isolated +5 V sensor supply, –15 V op-amp bias, and FPGA core voltage in an industrial PLC backplane. IC Role / Device Role / Timing Role: UC3903QG3 provides independent UV/OV fault flags per rail and coordinated POWER OK release after cold-start sequencing. Use Value: Enables deterministic power-up sequence control and field-replaceable module diagnostics via separate fault outputs. |
| Server PSU Redundancy Control | Medical Imaging Power Integrity |
Use Scenario: Detecting early failure of active/standby AC-DC modules in N+1 redundant server PSUs using LINE/SWITCHER SENSE input. IC Role / Device Role / Timing Role: UC3903QG3 monitors rectified transformer output pre-regulation; asserts POWER OK deassertion within 5 ms of line sag >5%. Use Value: Enables seamless switchover to backup PSU before output droop affects CPU or memory subsystems. |
Use Scenario: Ensuring strict voltage stability across high-precision analog rails (+15 V, –15 V, +5 V) powering CT/MRI detector front-ends. IC Role / Device Role / Timing Role: UC3903QG3 uses its precision 2.5-V reference and tight threshold hysteresis to detect sub-1% rail deviations before image artifacts occur. Use Value: Meets IEC 62304 Class C software safety requirements by providing hardware-enforced power integrity verification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad supply monitoring applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM3914N-1 | Single-rail LED driver with 10-segment bar graph; no programmable hysteresis, no negative rail support, no POWER OK output | Limited to visual indication of one rail; lacks fault delay, line sense, or multi-rail coordination | Select only for basic single-rail level display where timing supervision and fault arbitration are unnecessary |
| TPS3808G33 | Single-channel supervisor with fixed 3.3-V threshold, 200-ms reset delay, no reference output or multi-sense capability | Requires four separate devices plus external logic to replicate UC3903QG3 functionality; no shared reference or window scaling | Choose when supervising only one critical rail with simple reset assertion and no multi-rail coordination needed |
Compared with LM3914N-1 and TPS3808G33, the UC3903QG3 uniquely integrates quad sensing, negative rail support, proportional hysteresis, and coordinated POWER OK arbitration in a single PLCC package-reducing board area by >60% and eliminating inter-device timing skew in multi-rail systems.
Availability
UC3903QG3 is available at Aetrix Electronics and suitable for telecom power shelves, industrial PLCs, server PSUs, and medical imaging equipment requiring stable component supply with long-term lifecycle support.
Supply support for UC3903QG3 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 high-reliability power supervision ICs.
The UC3903QG3 belongs to TI's UCx903 family of quad supply monitors, engineered specifically for mission-critical power integrity in telecom, industrial, and medical systems where coordinated multi-rail fault detection and early failure warning are essential.
FAQ
What is the operating temperature range for the UC3903QG3?
The UC3903QG3 is specified for 0°C to +70°C ambient operation, matching its catalog-grade qualification. This range supports commercial and industrial environments where ambient temperatures remain within standard enclosure limits. Unlike the military-grade UC1903 (–55°C to +125°C) or industrial UC2903 (–40°C to +85°C), the UC3903QG3 targets cost-sensitive applications with moderate thermal profiles. All electrical parameters-including reference voltage accuracy, fault threshold hysteresis, and delay timing-are guaranteed across this full range.
How does the UC3903QG3 support negative voltage monitoring?
The UC3903QG3 supports negative voltage monitoring exclusively through its dedicated SENSE 4 inverter circuit. When configured, the internal op-amp inverter accepts a negative supply at its non-inverting input (Pin 5) and produces a positive-emitter-follower output referenced to GND, allowing the main SENSE 4 comparator to evaluate the inverted signal against the 2.5-V reference. This eliminates external components required by most supervisors. The inverter's input offset voltage is ≤10 mV and open-loop gain ≥65 dB, ensuring accurate translation of –12 V or –5 V rails into usable positive thresholds for fault detection.
Can the UC3903QG3's POWER OK output be used as a system reset signal?
Yes, the UC3903QG3's POWER OK output can drive a system reset circuit, but requires external pull-up and conditioning. As an open-collector output sinking >30 mA, it must be pulled up to a logic-compatible voltage (e.g., +3.3 V or +5 V) via a resistor (typically 4.7 kΩ). Its active-low assertion occurs only when all monitored rails are within specification and no line/switcher faults exist. To meet processor reset timing requirements, designers should verify that the combined delay of UV/OV comparators, internal logic, and external RC filtering satisfies minimum reset pulse width-typically 10–100 ms depending on the host MCU.
What is the maximum capacitive load the UC3903QG3's 2.5-V reference can drive?
The UC3903QG3's 2.5-V reference output is specified for ±10 mA load current with ≤15 mV deviation across that range. At 0–10 mA, load regulation is ≤10 mV; beyond 10 mA, output voltage drops nonlinearly and is not guaranteed. For driving multiple external resistor dividers (e.g., for four independently scaled sense windows), total current must remain ≤10 mA. If higher current is needed-for example, to drive an ADC reference input or op-amp buffer-the UC3903QG3's reference should feed a unity-gain buffer amplifier rather than connect directly to heavy loads.
How does the window adjust pin (Pin 4) affect hysteresis and threshold accuracy?
The UC3903QG3's window adjust pin (Pin 4) sets both fault threshold offset and hysteresis magnitude proportionally: a 1-V input yields ±250 mV threshold offset and 20 mV hysteresis; 2 V yields ±500 mV and 40 mV, etc. Critically, hysteresis remains fixed at 8% of the total window width across all settings due to internal current mirroring. Input bias current is ±12 µA/V, so a 10-kΩ divider from VREF introduces <1 mV error-well within the 15-mV reference tolerance. This architecture ensures predictable, scalable fault detection without recalibration.
UC3903QG3 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)
UC3903QG3 FAQ
1.How can I place an order for UC3903QG3 through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3903QG3 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 UC3903QG3 reliable?
The price and inventory of UC3903QG3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3903QG3 is usually 5 days.
3.What payment methods are accepted for UC3903QG3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3903QG3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3903QG3?
UC3903QG3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3903QG3 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 UC3903QG3?
For technical support, including UC3903QG3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3903QG3 requirements.
6.How does Aetrix verify that UC3903QG3 is sourced from the original manufacturer or authorized distributors?
All UC3903QG3 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 UC3903QG3 meets industry standards.
7.What is the process for return or replacement of UC3903QG3?
All UC3903QG3 units undergo pre-shipment inspection (PSI). If there is an issue with UC3903QG3, 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 UC3903QG3 part is unused and in its original packaging.
Return procedure for UC3903QG3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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