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Texas Instruments UC3901QTR
- Part No.:
- UC3901QTR
- Manufacturer:
- Texas Instruments
- Category:
- Power Management - Specialized
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
UC3901QTR.pdf
- Description:
- IC ISOLATED FB GENERATOR 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,058
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Product details
Overview
UC3901QTR from Texas Instruments is an isolated feedback generator IC designed for closed-loop regulation across voltage isolation boundaries in switch-mode power supplies. It implements amplitude modulation using an internal 130–180 kHz oscillator (typ. 150 kHz), features a 1.5 V ±1.5% reference, integrated error amplifier with 60 dB CMRR and 100 dB PSRR, and delivers dual emitter-follower driver outputs capable of sourcing ≥15 mA for transformer-coupled feedback paths.
For engineers reviewing the UC3901QTR datasheet, UC3901QTR pinout, UC3901QTR application, or UC3901QTR equivalent, this device serves as a low-cost, transformer-based alternative to optocouplers-offering stable DC-coupled error amplification, loop status monitoring, UVLO protection, and external clock synchronization capability up to 5 MHz.
Technical Context
The UC3901QTR uses an internal amplitude-modulation architecture where the error amplifier output modulates a high-frequency carrier (130–180 kHz) generated by a programmable RC oscillator. This modulated signal drives two complementary emitter-follower outputs (DRIVERA/DRIVERB) for RF transformer coupling, enabling galvanic isolation without optical components.
It includes a dedicated STATUS output that asserts active-low when the error amplifier's differential input stays within ±130–±170 mV of the 1.5 V reference, and incorporates under-voltage lockout (UVLO) that enables drivers only above VIN = 3.9–4.5 V. The compensation terminal (Pin 12) supports unity-gain stable feedback networks with external capacitor coupling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage | 1.5 V ±1.5% over 0°C to +70°C - provides precise DC bias for error amplifier comparison |
| Oscillator Frequency | 130–180 kHz (typ. 150 kHz) - sets carrier frequency for transformer-coupled feedback; adjustable via RT/CT |
| Error Amp CMRR | 60–80 dB - rejects common-mode noise on feedback inputs in noisy SMPS environments |
| Driver Output Sink Current | 700 µA min - sufficient to drive small-signal transformer primary with minimal distortion |
| STATUS Input Window | ±130 to ±170 mV around reference - enables accurate loop-in-regulation detection for system monitoring |
| Supply Range | 4.5 V to 40 V - supports wide-input industrial and telecom power supply rails |
| UVLO Threshold | 3.9–4.5 V - prevents erratic operation during power-up or brownout conditions |
Pinout & Package
UC3901QTR is housed in a 20-lead PLCC (FN package), surface-mount, thermally enhanced ceramic leaded chip carrier with gull-wing leads. The package meets JEDEC Level-2 moisture sensitivity (260°C peak reflow) and is RoHS-compliant with green finish (Pb-free, no Sb/Br).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CR) | Oscillator Timing Capacitor | Connects external CT to set carrier frequency; ties to VIN to disable internal oscillator |
| 2 (CLK) | External Clock Input | Accepts TTL/CMOS clock up to 5 MHz to synchronize carrier with SMPS switching frequency |
| 3 (GND) | Signal Ground Reference | Ground return for all analog and digital circuitry; referenced for all voltage specs |
| 4 (REF) | Precision Reference Output | 1.5 V ±1.5% source for error amplifier non-inverting input or external biasing |
| 5 (EA–) | Error Amp Inverting Input | Receives isolated feedback signal; used with compensation network at Pin 12 |
| 6 (EA+) | Error Amp Non-Inverting Input | Connected to REF or external voltage divider for setpoint comparison |
| 7 (COMP) | Compensation Terminal | Output of error amp; connects to feedback network (capacitor + resistor) for loop stability |
| 8 (DRIVERB) | Modulator Driver Output B | Emitter-follower output; complements DRIVERA for push-pull transformer drive |
| 9 (DRIVERA) | Modulator Driver Output A | Emitter-follower output; sources ≥15 mA; used with small RF transformer primary |
| 10 (STATUS) | Loop Status Indicator | Active-low open-collector output signaling error within ±130–±170 mV of reference |
| 11 (VIN) | Power Supply Input | 4.5–40 V DC input; powers all internal circuits and enables drivers after UVLO threshold |
| 12 (NC) | No Connect | Internally unused; must be left unconnected per datasheet |
| 13 (NC) | No Connect | Internally unused; must be left unconnected per datasheet |
| 14–20 | Ground / Thermal Pad | PLCC thermal pad and surrounding pins are internally tied to GND for heat dissipation |
Key Features
| Feature | Design Value |
|---|---|
| Amplitude-Modulation Feedback Architecture | Enables transformer-based isolation without optocoupler aging or CTR drift, supporting long-term reliability in industrial power supplies |
| 1% Precision Internal Reference | 1.5 V ±1.5% tolerance over full temperature range ensures stable regulation setpoint without external voltage reference |
| Synchronizable Carrier Oscillator | Internal oscillator disables when CR pin tied to VIN, allowing external clock input at CLK pin to align carrier with SMPS switching frequency |
| Loop Status Monitor | STATUS output asserts low when error voltage stays within ±130–±170 mV of reference-enabling real-time fault detection and system-level diagnostics |
| Integrated Error Amplifier with 100 dB PSRR | Rejects supply ripple and noise from VIN rail, maintaining regulation accuracy even under dynamic load or line transients |
Applications
| AC-DC Adapter Regulation | Industrial DC-DC Converter |
|---|---|
|
Use Scenario: Regulating output voltage in universal-input 12 V/24 V AC-DC adapters with reinforced isolation requirements. IC Role / Device Role / Timing Role: Isolated feedback generator providing error signal across transformer barrier via amplitude-modulated carrier. Use Value: Eliminates optocoupler CTR degradation over time, improving long-term output accuracy and reducing field failure rates. |
Use Scenario: Closed-loop control in 48 V input industrial DC-DC modules operating in harsh EMI environments. IC Role / Device Role / Timing Role: Error amplifier + modulator driving RF transformer to transmit feedback while rejecting common-mode noise. Use Value: 80 dB CMRR and 100 dB PSRR maintain regulation stability despite high dv/dt noise on primary side. |
| Telecom Rectifier Module | Server PSU Feedback Path |
|
Use Scenario: Secondary-side voltage regulation in -48 V telecom rectifiers requiring high reliability and 10-year lifetime. IC Role / Device Role / Timing Role: Isolation interface generating synchronized modulated signal referenced to secondary ground. Use Value: STATUS output feeds system supervisor IC to flag loss-of-regulation before OVP/OCP triggers, enabling graceful shutdown. |
Use Scenario: Multi-phase server power supply where feedback latency and noise immunity directly impact transient response. IC Role / Device Role / Timing Role: Low-latency isolated feedback path with 12 dB fixed gain from COMP to DRIVER outputs. Use Value: 25 MHz gain-bandwidth product in driver stage preserves phase margin in fast-response control loops. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated feedback generator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC2901Q | Wider temperature range (–40°C to +85°C); identical pinout, oscillator spec, and functional block diagram | Valid for extended ambient environments (e.g., outdoor telecom cabinets, factory floors) | Select UC2901Q when operation beyond 0°C–70°C is required; otherwise UC3901QTR offers cost-optimized commercial-grade performance |
| UC3846N | No integrated error amp or modulator; requires external optocoupler and compensation; PWM controller with isolation interface | Used in primary-side controlled topologies where secondary-side sensing is impractical | Choose UC3846N only if primary-side regulation architecture is mandated; UC3901QTR provides superior accuracy and simplicity for secondary-side isolation |
Compared with UC2901Q, UC3901QTR trades extended temperature operation for lower cost and tighter production binning in commercial-grade applications; compared with UC3846N, it eliminates external optocoupler dependency and simplifies loop compensation while delivering higher DC accuracy and built-in status monitoring.
Availability
UC3901QTR is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, telecom rectifiers, and server PSUs requiring stable component supply, long-lifecycle support, and RoHS-compliant PLCC packaging.
Supply support for UC3901QTR 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 headquartered in Dallas, Texas, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The UC3901QTR belongs to TI's legacy power management analog interface family, engineered specifically to replace optocouplers in isolated feedback paths of offline and DC-DC power converters-prioritizing precision, noise immunity, and long-term stability.
FAQ
What is the primary function of the UC3901QTR in a power supply design?
The UC3901QTR functions as an isolated feedback generator that transmits error signals across a transformer barrier using amplitude modulation. It replaces optocouplers by integrating a precision 1.5 V reference, error amplifier, carrier oscillator, and dual driver outputs-enabling stable closed-loop regulation in AC-DC and DC-DC converters without optical components. Its design directly supports secondary-side sensing in UC3901QTR-based power systems.
Does the UC3901QTR support synchronization with an external clock signal?
Yes, the UC3901QTR supports external clock synchronization via Pin 2 (CLK). When the internal oscillator is disabled by connecting Pin 1 (CR) to VIN, the device accepts an external TTL/CMOS clock up to 5 MHz at CLK. This allows the modulated carrier frequency to align precisely with the SMPS switching frequency-reducing beat frequencies and EMI in UC3901QTR-based designs.
What is the purpose of the STATUS output on the UC3901QTR?
The STATUS output on the UC3901QTR is an active-low, open-collector indicator that asserts when the error amplifier's differential input remains within ±130–±170 mV of the 1.5 V reference-signaling that the power supply is operating within regulation tolerance. This feature enables real-time loop health monitoring in UC3901QTR applications such as telecom rectifiers and server PSUs.
Can the UC3901QTR operate with a supply voltage below 4.5 V?
No, the UC3901QTR incorporates under-voltage lockout (UVLO) with activation thresholds between 3.9 V and 4.5 V. Below this range, the DRIVERA, DRIVERB, and STATUS outputs remain disabled to prevent unstable operation. Therefore, UC3901QTR requires a minimum VIN of 4.5 V for functional operation-consistent with its specified 4.5–40 V supply range.
How does the UC3901QTR differ from the UC2901Q in terms of temperature rating and use cases?
The UC3901QTR is rated for 0°C to +70°C operation, targeting commercial-grade power supplies like AC-DC adapters and server PSUs, whereas the UC2901Q supports –40°C to +85°C for industrial and telecom applications. Both share identical pinout, oscillator specs, and functional architecture-so UC2901Q serves as a drop-in upgrade for wider ambient needs, but UC3901QTR remains optimal for cost-sensitive, temperature-controlled environments.
UC3901QTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-LCC (J-Lead)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Applications:
- Feedback Generator
- Current - Supply:
- 5mA
- Voltage - Supply:
- 4.5V ~ 40V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-PLCC (9x9)
UC3901QTR FAQ
1.How can I place an order for UC3901QTR through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3901QTR 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 UC3901QTR reliable?
The price and inventory of UC3901QTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3901QTR is usually 5 days.
3.What payment methods are accepted for UC3901QTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3901QTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3901QTR?
UC3901QTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3901QTR 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 UC3901QTR?
For technical support, including UC3901QTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3901QTR requirements.
6.How does Aetrix verify that UC3901QTR is sourced from the original manufacturer or authorized distributors?
All UC3901QTR 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 UC3901QTR meets industry standards.
7.What is the process for return or replacement of UC3901QTR?
All UC3901QTR units undergo pre-shipment inspection (PSI). If there is an issue with UC3901QTR, 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 UC3901QTR part is unused and in its original packaging.
Return procedure for UC3901QTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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