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Texas Instruments UCC1921J
- Part No.:
- UCC1921J
- Manufacturer:
- Texas Instruments
- Category:
- Supervisors
- Package:
- -
- Datasheet:
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UCC1921J.pdf
- Description:
- IC SUPERVISOR PWR SUP SUPPORT
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Product details
Overview
UCC1921J from Texas Instruments is a latchable negative floating hot swap power manager IC referenced to the negative input rail, designed for high-reliability -48V telecom and industrial power systems. It provides programmable average power limiting, linear current control, overcurrent threshold (50mV), fault time control via external CT capacitor, and automatic retry or latched fault response modes.
For engineers reviewing the UCC1921J datasheet, UCC1921J pinout, UCC1921J application, or UCC1921J equivalent, this device supports precise fault management in negative-rail hot-swap circuits where MOSFET gate drive, duty-cycle-limited FET power dissipation, and VSS-referenced operation are critical design requirements.
Technical Context
The UCC1921J operates with VDD current-driven from ground through an external resistor and features an internal 10V shunt regulator referenced to VSS. Its fault detection uses a fixed 50mV overcurrent threshold across the sense resistor, while CT pin charging (36µA base + IPL) determines fault timing and duty cycle modulation.
Power limiting is implemented via the PL pin, which sources current proportional to (VFET – 5V)/RPL when VFET exceeds 5V, enabling average MOSFET power control independent of load voltage. The SDFLTCH pin serves triple function: fault output indication, shutdown control, and latched/retry mode selection via external resistor or active toggle.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temperature Range | –55°C to +125°C - qualified for extended-temperature industrial and telecom environments |
| Overcurrent Threshold | 46–53.5mV - sets precise fault trip point across current sense resistor |
| VDD Regulator Voltage | 9.15–10.15V at 10mA - provides stable reference for IMAX programming and gate drive |
| CT Fault Threshold | 2.2–2.6V - triggers output shutdown when timing capacitor reaches this voltage |
| Output Duty Cycle (Fault) | 1.7–3.7% - limits average FET power dissipation during sustained faults |
| SDFLTCH Filter Delay | 250–1000µs - rejects noise on fault/shutdown signal line |
| Shutdown Threshold | 3–VDD+1V - defines voltage level required to assert active-high shutdown |
Pinout & Package
UCC1921J is housed in an 8-pin SOIC package (J package per TI nomenclature), with pins arranged for negative-rail referenced layout and minimal parasitic coupling in high-current hot-swap paths.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CT | Fault timing capacitor connection | Charges at 36µA + IPL to set fault timeout; discharge resets retry cycle |
| IMAX | Maximum sourcing current programming input | Voltage divider from VDD sets current limit: IOUT(max) = VIMAX / RSENSE |
| OUT | MOSFET gate driver output | Drives NMOS pass FET gate; high-impedance when latched off |
| PL | Power limiting current input | Sources current proportional to (VFET – 5V)/RPL to reduce duty cycle under high FET stress |
| SENSE | Current sense amplifier input | Compares voltage across RSENSE to 50mV threshold to detect overcurrent |
| SDFLTCH | Fault output / shutdown / mode select | Open-drain fault indicator; >250µA in >1ms enables shutdown; 5k–250kΩ to VSS selects latched mode |
| VDD | Current-driven supply input | Connected via resistor to ground; regulated at ~10V above VSS by internal shunt |
| VSS | Negative supply reference | System's most negative voltage node; all internal circuitry referenced to this rail |
Key Features
| Feature | Design Value |
|---|---|
| Latchable fault response | Enables fail-safe shutdown in safety-critical systems; requires explicit reset via SDFLTCH toggle or power cycle |
| Programmable average power limiting | Uses PL pin feedback to dynamically reduce duty cycle as FET voltage rises, capping average power without thermal sensors |
| 250µs glitch filter on SDFLTCH | Prevents false fault latching from transient noise in noisy telecom backplane environments |
| Negative floating architecture | Operates with VSS as system ground reference, enabling direct control of negative-rail power paths without level shifters |
| Undervoltage lockout (UVLO) | Disables operation below 6–8V on VDD to prevent erratic behavior during brownout or startup |
Applications
| Telecom -48V Hot Swap | Industrial Negative-Rail Power Distribution |
|---|---|
Use Scenario: Insertion of line cards into live -48V telecom shelves with zero interruption to upstream power. IC Role / Device Role / Timing Role: UCC1921J controls NMOS pass FET to limit inrush, detect short circuits, and enforce safe current ramp-up before full load engagement. Use Value: Prevents bus collapse and protects upstream DC/DC converters using programmable 50mV fault threshold and CT-based timing. | Use Scenario: Modular PLC I/O modules requiring field-replaceable power inputs with fault isolation. IC Role / Device Role / Timing Role: UCC1921J acts as intelligent negative-side switch controller, managing MOSFET gate drive and responding to overloads with configurable retry or latch behavior. Use Value: Enables maintenance without system shutdown via latched-off state, with manual reset via SDFLTCH toggle. |
| Redundant Power Supply ORing | High-Reliability Test Equipment Power Rails |
Use Scenario: Dual -48V supplies feeding common load with automatic switchover on failure. IC Role / Device Role / Timing Role: UCC1921J manages each supply's NMOS pass element, using SDFLTCH to signal fault status to system supervisor and disable failed path. Use Value: Provides clean, low-loss ORing with fast fault detection (sub-µs delay) and coordinated shutdown signaling. | Use Scenario: Precision calibration equipment requiring stable, fault-protected negative bias rails. IC Role / Device Role / Timing Role: UCC1921J serves as protected negative rail switch, enforcing strict current limits and preventing damage from probe shorts or DUT faults. Use Value: Maintains measurement integrity by limiting fault energy to <3.7% duty cycle and providing repeatable, programmable trip thresholds. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative-rail hot swap power management applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC2921J | Rated for –40°C to +85°C operating range; lower temperature grade than UCC1921J | Suitable for commercial/industrial enclosures without extended thermal exposure | Select UCC2921J when ambient temperature stays within –40°C to +85°C and cost sensitivity outweighs extended temp qualification |
| UCC3921J | Rated for 0°C to +70°C; lacks military/extended temperature support; identical pinout and feature set | Targeted at cost-sensitive telecom line cards with controlled thermal environment | Choose UCC3921J for non-mission-critical applications where full –55°C to +125°C qualification is unnecessary |
Compared with UCC1921J, UCC2921J and UCC3921J share identical functionality and pinout but differ in qualified temperature range-UCC1921J supports the widest operating envelope, making it the only choice for aerospace, under-hood automotive, or uncontrolled industrial deployments requiring guaranteed operation down to –55°C.
Availability
UCC1921J is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, redundant power supplies, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for UCC1921J 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 logic solutions with emphasis on reliability, precision, and power efficiency.
The UCC1921J belongs to TI's hot-swap power manager product line, engineered specifically for negative-rail, floating-point power control in high-availability systems where fault containment and programmable current limiting are mandatory.
FAQ
What is the operating temperature range specified for the UCC1921J?
The UCC1921J is rated for operation from –55°C to +125°C. This extended temperature range is explicitly defined in the Electrical Characteristics table and distinguishes it from the UCC2921J (–40°C to +85°C) and UCC3921J (0°C to +70°C). The specification ensures reliable performance in harsh environments such as industrial control cabinets, outdoor telecom shelters, and aerospace power subsystems where thermal extremes are present.
How does the UCC1921J implement average power limiting for the external MOSFET?
The UCC1921J implements average power limiting via the PL pin, which sources current proportional to (VFET – 5V)/RPL when the voltage across the NMOS pass FET exceeds 5V. This current adds to the CT capacitor charging current, reducing the output duty cycle from its nominal 3% maximum down to as low as 0.045% depending on IPL magnitude. As a result, average MOSFET power dissipation becomes independent of VFET and is determined solely by IMAX, RPL, and the 1µA discharge current, enabling predictable thermal design without external sensors.
What is the function of the SDFLTCH pin on the UCC1921J?
The SDFLTCH pin on the UCC1921J serves three integrated functions: (1) open-drain fault output indicator (drives high during fault or UVLO), (2) active-high shutdown input (requires >250µA sourced for >1ms), and (3) latched/retry mode selector (5k–250kΩ resistor to VSS enables latched operation). Its 250–1000µs internal glitch filter prevents false triggering, and level-shifting circuitry (e.g., optocouplers or discrete transistors) is typically used to interface with system controllers referenced to different ground domains.
Can the UCC1921J be used in positive-rail hot-swap applications?
No-the UCC1921J is specifically designed as a negative floating hot swap power manager and must be referenced to the most negative system voltage (VSS). Its internal architecture-including the 10V shunt regulator, sense amplifier, and OUT driver-is optimized for controlling NMOS FETs in the negative rail. For positive-rail applications, TI offers complementary devices such as the UCCx922 family, which are not pin-compatible or functionally interchangeable with the UCC1921J.
What is the minimum external component required to configure basic overcurrent protection with the UCC1921J?
The minimum external components for basic overcurrent protection with the UCC1921J are: (1) a current sense resistor (RSENSE = 50mV / IFault) between SENSE and VSS, (2) a timing capacitor (CT) from CT to VSS to set fault timeout, and (3) a resistor from VDD to ground to establish ~10V regulation. No IMAX programming or PL network is required for fundamental fault cutoff-only the SENSE resistor and CT capacitor are essential to activate the 50mV threshold and CT-based shutdown sequence in the UCC1921J.
UCC1921J Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- -
- Number of Voltages Monitored:
- -
- Voltage - Threshold:
- -
- Output:
- -
- Reset:
- -
- Reset Timeout:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
UCC1921J FAQ
1.How can I place an order for UCC1921J through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC1921J 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 UCC1921J reliable?
The price and inventory of UCC1921J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC1921J is usually 5 days.
3.What payment methods are accepted for UCC1921J?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC1921J transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC1921J?
UCC1921J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC1921J 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 UCC1921J?
For technical support, including UCC1921J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC1921J requirements.
6.How does Aetrix verify that UCC1921J is sourced from the original manufacturer or authorized distributors?
All UCC1921J 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 UCC1921J meets industry standards.
7.What is the process for return or replacement of UCC1921J?
All UCC1921J units undergo pre-shipment inspection (PSI). If there is an issue with UCC1921J, 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 UCC1921J part is unused and in its original packaging.
Return procedure for UCC1921J:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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