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Texas Instruments UC3902D
- Part No.:
- UC3902D
- Manufacturer:
- Texas Instruments
- Category:
- Power Management - Specialized
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC3902D.pdf
- Description:
- IC LOAD SHARE CONTROLLER 8-SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:306
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Product details
Overview
UC3902D from Texas Instruments is an 8-pin SOIC load share controller IC that balances output current across paralleled DC power supplies by regulating a differential share bus. It features a precision 40× current sense amplifier, 2.7–20 V operation, undervoltage lockout (2.5 V typ), and supports remote voltage sensing in redundant telecom and industrial power systems.
For engineers reviewing the UC3902D datasheet, UC3902D pinout, UC3902D application, or UC3902D equivalent, key selection criteria include its differential share bus architecture, ±50 mV current sense offset tolerance, 4.5 mS error amplifier transconductance, slew rate of 0.26 V/μs, and compatibility with standard isolated DC-DC modules requiring precise current balancing without master-slave control logic.
Technical Context
The UC3902D implements a closed-loop analog current-sharing scheme using a dedicated differential SHARE+ / SHARE− interface and a high-gain (40×) current sense amplifier referenced to SENSE. Its error amplifier drives COMP to adjust output voltage via ADJ/ADJR current injection into remote sense lines.
It operates over 0°C to 70°C ambient, requires no external clock, and uses internal UVLO (2.5 V startup, 100 mV hysteresis) and rail-to-rail SHARE+ drive (10 V VOH at 12 V VCC). The share loop compensation is user-programmable via external RC network connected to COMP and ADJR.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2.7 V to 20 V - powers device directly from system rail or auxiliary supply without LDO |
| Current Sense Gain | −40 V/V - converts RSENSE voltage drop to proportional share bus voltage for accurate inter-supply matching |
| UVLO Threshold | 2.5 V typical - prevents erratic operation during brownout or soft-start conditions |
| SHARE+ Output Drive | 10.0 V at 1 mA sink - sufficient headroom to drive long differential buses with >100 mV noise margin |
| Error Amp gM | 4.5 mS - sets gain-bandwidth tradeoff for stable share loop compensation with external CC/RG |
| Slew Rate | 0.26 V/μs - limits transient response to avoid instability while accommodating typical DC-DC bandwidths |
| Input Offset (SENSE) | ±0.5 mV - ensures ≤1.25% current imbalance at full scale when RSENSE = 10 mΩ |
Pinout & Package
UC3902D is housed in an 8-pin SOIC (D) package per JEDEC MS-012AA, 3.94 mm width, 1.75 mm max height, with Gull-wing leads and RoHS-compliant NiPdAu finish. Pin 1 identifier located at top-left corner with beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Signal & power ground reference | Common return for all internal amplifiers and bias circuits; must be low-impedance connection to system star ground |
| SENSE (Pin 2) | Inverting input of current sense amp | Connects to negative side of current sense resistor; senses voltage drop proportional to load current |
| ADJ (Pin 3) | NPN collector output of adjust amplifier | Sinks current into remote sense line to trim output voltage; requires series resistor (20–100 Ω) per application note |
| ADJR (Pin 4) | NPN emitter current range set | Defines maximum ADJ current (e.g., 5 mA with 360 Ω to GND); sets share loop compliance limit |
| COMP (Pin 5) | Error amplifier output / adjust amp input | Node for external compensation (RC network); determines share loop stability and crossover frequency |
| SHARE− (Pin 6) | Differential share bus reference | Return path for SHARE+; connects to system ground to reject common-mode noise on bus |
| SHARE+ (Pin 7) | Share bus input/output terminal | Drives or receives differential voltage representing master supply's current; immune to ground shift up to 1 V |
| VCC (Pin 8) | Positive supply input | Accepts 2.7–20 V; powers all internal circuitry including SHARE+ driver and UVLO comparator |
Key Features
| Feature | Design Value |
|---|---|
| Differential share bus interface | SHARE+/SHARE− pair provides >50 dB CMRR, enabling robust current sharing across non-isolated or transformer-coupled supplies with varying ground potentials |
| Precision current sense amplifier | 40× fixed gain with ±0.5 mV offset ensures ≤1.5% current mismatch between paralleled 50 A supplies using 1 mΩ sense resistors |
| User-programmable share loop compensation | External RC network on COMP/ADJR allows tuning loop bandwidth below DC-DC converter bandwidth to prevent interaction |
| Remote voltage sensing compatibility | ADJ/ADJR current injection method works with standard 2-wire or 4-wire feedback topologies without modifying existing power supply designs |
| Undervoltage lockout with hysteresis | 2.5 V startup + 100 mV hysteresis prevents oscillation during input ramp-up and ensures clean enable/disable sequencing |
Applications
| Telecom Rectifier Systems | Industrial Redundant PSUs |
|---|---|
Use Scenario: Multiple 48 V rectifiers operate in parallel to feed a common DC bus in central office or base station power shelves. IC Role / Device Role / Timing Role: UC3902D acts as analog current balancer, forcing each rectifier to contribute proportionally to total load regardless of unit-to-unit output voltage tolerance (±1%) or thermal drift. Use Value: Enables N+1 redundancy without derating; eliminates need for manual potentiometer trimming or digital communication between units. | Use Scenario: Dual-output 24 V/5 V industrial PSUs supply PLC I/O modules where failure of one unit must not overload the other. IC Role / Device Role / Timing Role: UC3902D monitors current through individual sense resistors and adjusts output voltage via remote sense lines to maintain equal load division. Use Value: Achieves <±3% current imbalance across temperature (0–70°C), extending mean time between failures in continuous-duty applications. |
| Medical Power Distribution | Test Equipment Power Racks |
Use Scenario: Paralleled medical-grade AC-DC converters feed critical patient monitoring equipment requiring zero single-point failure. IC Role / Device Role / Timing Role: UC3902D serves as passive analog load share controller, independent of microcontroller or firmware, ensuring fail-safe current distribution. Use Value: Meets IEC 60601-1 creepage/clearance requirements by eliminating digital control lines; supports Class I and II isolation schemes. | Use Scenario: Modular bench power supplies are combined to deliver high-current test profiles (e.g., 100 A @ 12 V) for automotive ECU validation. IC Role / Device Role / Timing Role: UC3902D interfaces with standard lab PSU remote sense terminals to dynamically rebalance load during step-current transients. Use Value: Maintains <±2% current sharing during 10 A/μs slew events, preventing individual supply current limiting and enabling seamless current scaling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar load share controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC2902D | Same architecture and pinout; rated for −40°C to 85°C industrial temp range vs. UC3902D's 0°C to 70°C | Preferred for extended temperature environments such as outdoor telecom cabinets or factory floors with wide ambient swings | Select UC2902D when operating beyond 70°C ambient or requiring wider VCC UVLO hysteresis (140 mV vs. 100 mV) |
| LTC4370CMS#PBF | Wide-input (2.5–36 V), integrated MOSFET drivers, automatic master selection, but requires external MOSFETs and has different compensation structure | Suited for hot-swap-capable systems needing fault isolation; not drop-in compatible due to different pin functions and control methodology | Choose LTC4370 when board space allows discrete FETs and design requires reverse-current blocking or fault flag outputs |
Compared with UC2902D and LTC4370, the UC3902D offers lowest BOM count for basic analog current sharing in cost-sensitive, temperature-stable environments-requiring only five passive components versus eight for LTC4370 and no change in layout versus UC2902D.
Availability
UC3902D is available at Aetrix Electronics and suitable for telecom rectifier systems, industrial redundant PSUs, medical power distribution, and test equipment power racks requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for UC3902D 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.
The UC3902D belongs to TI's legacy power management analog controller family, designed specifically for passive, low-component-count current balancing in paralleled DC power supplies without digital supervision.
FAQ
What is the operating temperature range specified for the UC3902D?
The UC3902D is rated for an operating free-air temperature range of 0°C to 70°C, as confirmed in the SLUS232E datasheet ordering table and absolute maximum ratings section. This distinguishes it from the UC2902D variant, which supports −40°C to 85°C. The UC3902D's thermal performance remains stable within this range, with parameters like current sense offset and SHARE+ drive voltage validated across the full span.
Can the UC3902D be used with power supplies that have different output current ratings?
Yes, the UC3902D supports paralleling supplies with unequal current capabilities. By scaling the current sense resistor (RSENSE) value inversely to each supply's maximum output current, the UC3902D ensures each contributes the same percentage of its rated capacity. For example, a 30 A and 60 A supply can share load equally when their RSENSE values are 2 mΩ and 1 mΩ respectively-enabling flexible system scalability without redesigning the UC3902D interface.
What is the function of the ADJR pin on the UC3902D?
The ADJR pin on the UC3902D sets the maximum current sourced by the ADJ pin through an external resistor to ground. It defines the compliance limit for the adjust amplifier's output current, directly influencing how aggressively the UC3902D trims slave supply output voltages. A typical 360 Ω resistor yields ~5 mA ADJ current, balancing drive strength against power dissipation and remote sense resistor heating in the final UC3902D implementation.
Does the UC3902D require external compensation components?
Yes, the UC3902D requires external compensation on the COMP pin-specifically a capacitor (CC) and optional series resistor (RC)-to stabilize the share loop. Equation (4) in the SLUS232E application information defines CC based on desired crossover frequency, error amplifier transconductance (4.5 mS), and known resistances. Without proper compensation, the UC3902D may exhibit oscillation or slow settling, especially when interfacing with high-bandwidth DC-DC converters.
How does the UC3902D handle master/slave designation among paralleled supplies?
The UC3902D automatically designates the supply with the highest regulated output voltage as the master, which drives the share bus voltage. All other UC3902D-equipped supplies act as slaves, adjusting their output voltage downward to match the bus-derived current reference. This self-organizing behavior accommodates thermal drift and line/load variations-allowing the master role to shift dynamically while maintaining stable current sharing across the UC3902D network.
UC3902D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Applications:
- Load Share Controller
- Current - Supply:
- 4mA
- Voltage - Supply:
- 2.7V ~ 20V
- Operating Temperature:
- -40°C ~ 100°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
UC3902D FAQ
1.How can I place an order for UC3902D through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3902D 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 UC3902D reliable?
The price and inventory of UC3902D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3902D is usually 5 days.
3.What payment methods are accepted for UC3902D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3902D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3902D?
UC3902D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3902D 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 UC3902D?
For technical support, including UC3902D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3902D requirements.
6.How does Aetrix verify that UC3902D is sourced from the original manufacturer or authorized distributors?
All UC3902D 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 UC3902D meets industry standards.
7.What is the process for return or replacement of UC3902D?
All UC3902D units undergo pre-shipment inspection (PSI). If there is an issue with UC3902D, 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 UC3902D part is unused and in its original packaging.
Return procedure for UC3902D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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