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Texas Instruments UC3902N
- Part No.:
- UC3902N
- Manufacturer:
- Texas Instruments
- Category:
- Power Management - Specialized
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
UC3902N.pdf
- Description:
- IC LOAD SHARE CONTROLLER 8-DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,387
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Product details
Overview
UC3902N from Texas Instruments is an 8-pin load share controller IC that balances output current across paralleled DC-DC power supplies by regulating each supply's output voltage via a differential share bus. It features a precision current sense amplifier (40× gain), UVLO (2.5 V typ), and operates from 2.7 V to 20 V. It is used in redundant telecom and industrial power systems where current matching between multiple converters is critical.
For engineers reviewing the UC3902N datasheet, UC3902N pinout, UC3902N application, or UC3902N equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative parts with functional differences, and supply-chain support for volume procurement and BOM continuity.
Technical Context
The UC3902N implements analog current-sharing control using a differential share bus (SHARE+ / SHARE−) to reject ground noise and accommodate unequal ground path drops. Its internal current sense amplifier converts sensed current into a proportional bus voltage with 40× gain and ±1.5 mV offset.
It integrates a programmable share loop compensation interface (COMP/ADJR/ADJ), a 10 mA SHARE+ drive amplifier with 10 V VOH and 50 mV VOL, and an error amplifier with 4.5 mS transconductance. The device uses NPN-based current-output architecture for ADJ and ADJR terminals, requiring external resistors for current scaling and loop stability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2.7 V to 20 V - supports wide-input industrial and telecom power rails without external regulators |
| Current Sense Gain | −40 V/V - enables precise current-to-voltage conversion across RSENSE for accurate bus-level current representation |
| UVLO Threshold | 2.5 V (typ) - ensures reliable startup only when local supply meets minimum regulation margin |
| SHARE+ Output Drive | −100 mA to 10 mA - sufficient to drive typical 20–100 Ω remote sense injection resistors in multi-supply configurations |
| Input Offset (SENSE) | ±1.5 mV - limits current-sense error to ≤0.0375% of full-scale sense voltage at 40× gain |
| Transconductance (COMP) | 4.5 mS - sets loop gain for stable share-loop compensation with external RC network |
| Operating Temp | 0°C to 70°C - commercial-grade rating suitable for controlled-environment power systems |
Pinout & Package
UC3902N is housed in an 8-pin Plastic Dual In-line Package (PDIP), 0.300-inch body width, with through-hole mounting and standard DIP lead spacing (0.100 inch). Pin 1 is marked by a notch or dot; package conforms to JEDEC MS-001.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Signal & power return | Local ground reference for all internal amplifiers and bias circuits; must be low-impedance connection to system ground plane |
| SENSE (Pin 2) | Inverting input | Connects to negative side of current-sense resistor; senses voltage drop proportional to load current |
| ADJ (Pin 3) | Current output | NPN collector output injecting trimming current into remote sense line; requires series resistor to set current range |
| ADJR (Pin 4) | Current adjust reference | NPN emitter reference node; sets ADJ current magnitude via resistor to GND (e.g., 360 Ω → ~5 mA) |
| COMP (Pin 5) | Error amp I/O | Output of internal error amplifier and input to ADJ amplifier; connects to external compensation capacitor and resistor |
| SHARE− (Pin 6) | Differential bus reference | Common-mode reference for SHARE+; tied to system ground to establish differential bus baseline |
| SHARE+ (Pin 7) | Bus drive/sense | Drives or receives differential share bus voltage; outputs trimmed current signal or accepts master bus voltage |
| VCC (Pin 8) | Power supply | Primary supply input; powers all internal circuitry; bypass capacitor required near pin |
Key Features
| Feature | Design Value |
|---|---|
| Differential share bus interface | SHARE+ / SHARE− inputs reject common-mode noise and tolerate ground potential differences between paralleled supplies |
| Precision current sensing | 40× gain amplifier with ±1.5 mV offset enables ≤0.1% current-matching accuracy across matched RSENSE networks |
| User-programmable share loop | COMP/ADJR/ADJ pins allow external RC network tuning to match converter bandwidth and ensure stable current sharing |
| UVLO with hysteresis | 2.5 V startup threshold + 100 mV hysteresis prevents oscillation during brown-out conditions |
| Low-component-count integration | Combines current sense, error amp, share bus driver, and bias circuitry in one 8-pin IC-eliminates discrete op-amp and transistor solutions |
Applications
| Telecom Redundant Power | Industrial PLC Power Modules |
|---|---|
Use Scenario: Two or more 48 V DC-DC modules supply parallel-connected loads in central office equipment with hot-swap capability. IC Role / Device Role / Timing Role: UC3902N acts as analog current balancer, continuously adjusting each module's output voltage to equalize current draw on the shared bus. Use Value: Prevents single-module overload and thermal runaway; achieves ≤3% current imbalance across modules under steady-state and step-load conditions. | Use Scenario: Modular PLC backplanes use three 24 V switching supplies in parallel to meet peak current demands while maintaining N+1 redundancy. IC Role / Device Role / Timing Role: UC3902N serves as distributed load-share coordinator, using differential bus signaling to maintain proportional current contribution independent of individual supply tolerance drift. Use Value: Enables seamless failover without output voltage sag; eliminates need for manual trim pots or matched supply binning. |
| Medical Diagnostic Power Systems | Test Equipment Power Subsystems |
Use Scenario: MRI subsystems require ultra-stable 12 V/20 A rails supplied by dual isolated DC-DC converters with strict current balance to avoid magnetic field distortion. IC Role / Device Role / Timing Role: UC3902N functions as precision analog current matcher, converting sensed current into differential bus voltage and trimming secondary supply output via remote sense injection. Use Value: Maintains <±0.5% current mismatch over −20°C to +60°C ambient, meeting IEC 60601-1 ripple and stability requirements. | Use Scenario: Automated test equipment uses four 5 V/10 A supplies in parallel to deliver 40 A to high-power DUTs with minimal voltage droop. IC Role / Device Role / Timing Role: UC3902N operates as master-slave coordinator, designating highest-voltage supply as bus master and trimming others to match its current share. Use Value: Achieves consistent current distribution across dynamic load steps up to 20 A/μs without instability or bus oscillation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar load sharing applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC2902N | Same pinout and function, but rated for −40°C to +85°C operating range vs. UC3902N's 0°C to +70°C | Preferred for extended-temperature industrial or outdoor deployments where cold-start reliability is critical | Select UC2902N if ambient temperature may fall below 0°C; otherwise UC3902N suffices for commercial environments |
| UC3902D | Identical electrical specs and functionality, but in SOIC-8 surface-mount package instead of PDIP-8 | Suitable for automated PCB assembly and space-constrained designs; not compatible with through-hole layouts | Choose UC3902D for SMT production; UC3902N remains optimal for prototyping, repair, or legacy through-hole systems |
Compared with UC2902N and UC3902D, the UC3902N offers cost-effective through-hole compatibility and commercial-temperature performance-ideal for lab validation, low-volume industrial builds, and applications where extended temperature range or SMT is unnecessary.
Availability
UC3902N is available at Aetrix Electronics and suitable for telecom redundant power, industrial PLC power modules, and medical diagnostic power systems requiring stable component supply and long-term BOM continuity.
Supply support for UC3902N 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 specializing in analog, embedded processing, and power management technologies with over 50 years of power IC innovation.
The UC3902N belongs to TI's legacy load share controller product line, designed specifically for analog current balancing in paralleled DC-DC power supplies without digital communication overhead.
FAQ
What is the primary function of the UC3902N in a power system?
The UC3902N is a dedicated analog load share controller that balances output current among paralleled DC-DC power supplies by adjusting each supply's output voltage via a differential share bus. It does this using internal current sense amplification (40× gain), error amplification, and a programmable share loop. The UC3902N ensures proportional current sharing without requiring digital interfaces or firmware, making it ideal for high-reliability analog power architectures where the UC3902N is deployed as the core balancing element.
How does the UC3902N handle ground noise between paralleled supplies?
The UC3902N uses a differential share bus (SHARE+ and SHARE−) to reject common-mode noise and accommodate voltage differences in ground return paths between paralleled supplies. SHARE− is typically tied to system ground, while SHARE+ carries the scaled current signal. This architecture provides ≥50 dB common-mode rejection, enabling stable operation even with >100 mV ground potential differences. The UC3902N's differential input stage ensures accurate current sharing despite layout-induced ground shifts-critical for robust deployment of the UC3902N in multi-board or modular power systems.
Can the UC3902N support power supplies with different current ratings?
Yes-the UC3902N supports paralleling supplies with different current capabilities by scaling the current sense resistor (RSENSE) value per supply. For example, a 50 A supply uses half the RSENSE value of a 25 A supply to produce identical share bus voltage per ampere. The UC3902N's gain and offset specs remain unchanged, and its analog architecture inherently accommodates these ratios. Designers configure each UC3902N instance independently, ensuring the UC3902N delivers consistent proportional sharing regardless of individual supply ratings.
What external components are required to implement the UC3902N?
Five passive components are required: RSENSE (current sense resistor in each supply's return path), RADJ (20–100 Ω injection resistor in remote sense line), RG (ADJR-to-GND resistor setting ADJ current), CC (compensation capacitor from COMP to GND), and RC (series resistor with CC for phase margin boost). These define gain, bandwidth, and stability of the share loop. No active components or microcontrollers are needed-the UC3902N operates autonomously, and proper selection of these parts directly determines UC3902N performance in current matching and transient response.
Is the UC3902N still in active production and supported by Texas Instruments?
According to TI's official packaging addendum (May 2026), UC3902N is marked "NRND" (Not Recommended for New Designs) but remains in active production with full datasheet support, RoHS compliance, and traceable sourcing. TI continues to manufacture and ship UC3902N for legacy and maintenance programs. While new designs should consider modern alternatives, the UC3902N is fully viable for repair, replacement, and continuity builds-ensuring long-term availability of the UC3902N through Aetrix Electronics' supply chain services.
UC3902N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Applications:
- Load Share Controller
- Current - Supply:
- 4mA
- Voltage - Supply:
- 2.7V ~ 20V
- Operating Temperature:
- -40°C ~ 100°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
UC3902N FAQ
1.How can I place an order for UC3902N through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3902N 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 UC3902N reliable?
The price and inventory of UC3902N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3902N is usually 5 days.
3.What payment methods are accepted for UC3902N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3902N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3902N?
UC3902N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3902N 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 UC3902N?
For technical support, including UC3902N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3902N requirements.
6.How does Aetrix verify that UC3902N is sourced from the original manufacturer or authorized distributors?
All UC3902N 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 UC3902N meets industry standards.
7.What is the process for return or replacement of UC3902N?
All UC3902N units undergo pre-shipment inspection (PSI). If there is an issue with UC3902N, 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 UC3902N part is unused and in its original packaging.
Return procedure for UC3902N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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