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Texas Instruments UC39431DTR
- Part No.:
- UC39431DTR
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC39431DTR.pdf
- Description:
- IC VREF SHUNT ADJ 0.39% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,626
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Product details
Overview
UC39431DTR from Texas Instruments is a precision adjustable shunt voltage regulator with 100mA sink capability, featuring dual-stage architecture (error amplifier + transconductance amplifier), 0.4% initial reference accuracy, and six factory-programmable internal reference voltages (2.82V to 12.24V). It operates from 2.2V to 36.0V supply and is widely used in optocoupler-based feedback loops for isolated DC-DC converters.
For engineers reviewing the UC39431DTR datasheet, UC39431DTR pinout, UC39431DTR application, or UC39431DTR equivalent, key selection considerations include its fixed –140mS transconductance, 5MHz error amplifier GBW, UVLO threshold (~1V), COMP/SENSE compensation flexibility, and SOIC-8 package compatibility with standard PCB layouts for power supply control circuits.
Technical Context
The UC39431DTR implements a two-stage control architecture: a high-gain error amplifier (90dB AVOL, 5MHz GBW) compares SENSE voltage against an internal 1.3V reference, while a separate transconductance amplifier (–140mS ±30mS, 3MHz GBW) converts COMP voltage into precise output current at COLL. This decoupled design enables independent loop compensation via COMP and COLL nodes.
Internal resistor network (R1/R2/R3) supports six discrete regulated outputs (2.82V, 3.12V, 5.1V, 7.8V, 10.42V, 12.24V) through configurable pin connections; SENSE also serves as undervoltage lockout input (threshold ≈1V), ensuring stable startup before regulation engages.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage | 1.3V nominal on-chip bandgap reference, stable over full temperature and supply range |
| Initial Accuracy | ±0.4% at TA = 25°C - enables tight output tolerance without external trimming |
| Transconductance (gm) | –140mS typical (±30mS) - delivers predictable, linear sink current vs. COMP voltage |
| Error Amp GBW | 5MHz typical - supports fast transient response and flexible pole-zero compensation |
| Operating Supply | 2.2V to 36.0V - accommodates wide-input industrial and telecom power rails |
| Sink Current Limit | 130–145mA - ensures safe operation under overload while maintaining regulation |
| UVLO Threshold | ≈1V on SENSE - prevents erratic startup until bias conditions stabilize |
Pinout & Package
UC39431DTR is housed in an 8-pin SOIC (D package), RoHS-compliant, moisture sensitivity level 2 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COLL (Pin 1) | Output collector node | Sink current output terminal; rated to 36V, drives optocoupler LED or magnetic amplifier gate |
| GND (Pin 2) | Power & reference ground | Isolated substrate ground for output transistor; separate from internal bias ground |
| R1 (Pin 3) | Internal resistor tap | Configurable connection point for setting regulated voltage via internal divider network |
| R2 (Pin 4) | Internal resistor tap | Second tap for six-voltage selection table (e.g., 5.1V requires R2→SENSE) |
| R3 (Pin 5) | Internal resistor tap | Third tap enabling all six factory references; open/GND/SENSE/COLL combinations define output |
| SENSE (Pin 7) | Inverting error amp input + UVLO | Voltage sense input referenced to 1.3V; also triggers startup lockout below ~1V |
| COMP (Pin 6) | Error amp output / gm amp input | Compensation node for error amplifier; internally clamped to ~2.0V; accepts RC networks for pole-zero placement |
| VCC (Pin 8) | Supply input | Primary power rail (2.2–36V); quiescent current 0.5–0.8mA enables low-power standby |
Key Features
| Feature | Design Value |
|---|---|
| Six programmable reference voltages | Factory-trimmed internal resistors support 2.82V/3.12V/5.1V/7.8V/10.42V/12.24V outputs without external dividers |
| Fixed linear transconductance | –140mS typical provides consistent current sourcing for optocoupler CTR compensation and magnetic amplifier drive |
| Independent frequency compensation | Dual compensation nodes (COMP for error amp, COLL for gm amp) allow simultaneous pole-zero tuning of both stages |
| UVLO integrated on SENSE | Startup inhibited until SENSE > ~1V ensures stable reference bias before regulation begins |
| High supply voltage range | 2.2V to 36.0V operation supports direct interface with unregulated front-end supplies in offline converters |
Applications
| Optocoupler Feedback Loop | Magnetic Amplifier Controller |
|---|---|
Use Scenario: Isolated secondary-side voltage regulation in flyback or forward DC-DC converters using PC817 or similar optocouplers. IC Role / Device Role / Timing Role: Shunt regulator providing precise, temperature-stable reference to optocoupler LED anode; COLL sink current modulates LED brightness proportional to output error. Use Value: Eliminates CTR variation impact via linear gm stage; maintains ±0.7% overall reference tolerance across 0°C to +70°C operating range. | Use Scenario: Regulating output of transformer-coupled magnetic amplifiers in high-efficiency, multi-output telecom power supplies. IC Role / Device Role / Timing Role: Error-sensing element driving saturable reactor reset winding; COMP output controls duty cycle of reset current pulse. Use Value: Fixed transconductance ensures repeatable reset current magnitude independent of supply ripple, improving cross-regulation between outputs. |
| Programmable Reference Source | Secondary-Side Supervisor |
Use Scenario: Generating multiple precision bias voltages (e.g., 5.1V, 12.24V) from a single UC39431DTR in space-constrained auxiliary supplies. IC Role / Device Role / Timing Role: Configurable shunt regulator acting as programmable voltage source; internal R1/R2/R3 connections select target output without external resistors. Use Value: Reduces BOM count and layout area versus discrete Zener + op-amp solutions; 0.4% initial accuracy avoids post-assembly calibration. | Use Scenario: Monitoring and regulating isolated secondary outputs in redundant power systems where primary controller lacks sensing capability. IC Role / Device Role / Timing Role: Standalone voltage supervisor triggering fault signals or enabling downstream LDOs when output deviates beyond ±2% window. Use Value: SENSE pin's 0.2µA input bias enables high-impedance monitoring without loading sensitive analog rails; UVLO ensures clean enable sequencing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACDR | Single-stage architecture; no internal resistor network; 2.495V fixed reference; 100mA sink; 0.5% initial accuracy | Lacks programmable references and dual-stage compensation; requires external divider for >2.5V outputs | Preferred for cost-sensitive, fixed-reference designs where internal resistor flexibility is unnecessary |
| UC39432DTR | Same architecture but exposes non-inverting error amp input and reference; omits internal R1/R2/R3; higher 0.25% reference accuracy | Enables differential sensing and custom reference injection; not compatible with UC39431DTR's resistor-based voltage selection | Select when external reference injection or optocoupler cathode sensing is required instead of anode-side shunt regulation |
Compared with TL431ACDR and UC39432DTR, the UC39431DTR uniquely combines factory-programmable reference voltages, dual-stage compensation, and UVLO in a single SOIC-8 package-making it optimal for optocoupler feedback where CTR stability and startup reliability are critical.
Availability
UC39431DTR is available at Aetrix Electronics and suitable for isolated DC-DC converter feedback, magnetic amplifier control, and programmable reference generation requiring stable component supply across industrial, telecom, and embedded power applications.
Supply support for UC39431DTR 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 and embedded processing solutions for industrial, automotive, and personal electronics markets.
The UC39431DTR belongs to TI's legacy power management analog portfolio, specifically designed for high-accuracy, isolated secondary-side voltage regulation in switch-mode power supplies where optocoupler linearity and thermal stability are essential.
FAQ
What is the maximum sink current capability of the UC39431DTR?
The UC39431DTR provides a guaranteed minimum sink current of 130mA and a typical value of 140mA at VCOLL = VCC = 36.0V with reference set to 1.35V. Its absolute maximum rating allows up to 140mA continuous operation, making it suitable for driving standard optocoupler LEDs and small magnetic amplifier gates without external buffering. The UC39431DTR maintains regulation integrity across its full 0°C to +70°C operating temperature range.
How does the UC39431DTR achieve stable optocoupler feedback despite CTR variation?
The UC39431DTR uses a dedicated transconductance amplifier stage with fixed –140mS gain to convert COMP voltage into precise sink current at COLL. Unlike conventional shunt regulators relying on transistor output characteristics, this linear gm stage eliminates exponential CTR dependency on supply voltage and temperature. As a result, the UC39431DTR delivers consistent optocoupler LED current regardless of input rail fluctuations, directly improving cross-regulation and transient response in isolated converters.
Can the UC39431DTR be used without connecting the internal resistors R1, R2, and R3?
Yes - the UC39431DTR supports external programming via two external resistors between SENSE and VCC/COLL to set any output voltage from 2.4V to 36.0V. Leaving R1/R2/R3 unconnected (open) disables the internal divider, allowing full user-defined regulation. However, doing so forfeits the six factory-trimmed reference options (e.g., 5.1V, 12.24V) and requires careful selection of external resistor tolerances to maintain accuracy. The UC39431DTR's 0.4% initial reference accuracy remains valid in either configuration.
What is the role of the COMP pin in UC39431DTR compensation?
The COMP pin is the output of the error amplifier and the input to the transconductance amplifier. It serves as the primary compensation node for the error amplifier stage, accepting external RC networks to place poles or pole-zero pairs that shape loop stability. Internally clamped to ~2.0V, COMP allows controlled slew rate during startup and prevents saturation. In typical optocoupler applications, a series RC between SENSE and COMP creates a dominant pole and zero, increasing bandwidth while canceling phase lag introduced by the COLL-to-GND capacitor - a key advantage of the UC39431DTR's dual-stage architecture.
Does the UC39431DTR require a minimum load current to maintain regulation?
Yes - the UC39431DTR specifies a minimum operating current of 0.50mA (typical) at VCC = 36.0V and VCOLL = 5V. This ensures sufficient bias for internal amplifiers to remain active and responsive. Below this threshold, regulation may become unstable or cease entirely. Designers must ensure that total system load - including optocoupler LED, feedback resistors, and any parasitic paths - draws at least 0.5mA under all operating conditions. The UC39431DTR's low 0.2µA SENSE input bias helps minimize unintended loading in high-impedance configurations.
UC39431DTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Reference Type:
- Shunt
- Output Type:
- Adjustable
- Voltage - Output (Min/Fixed):
- 1.3V
- Voltage - Output (Max):
- 36 V
- Current - Output:
- 100 mA
- Tolerance:
- ±0.39%
- Temperature Coefficient:
- -
- Noise - 0.1Hz to 10Hz:
- -
- Noise - 10Hz to 10kHz:
- -
- Voltage - Input:
- -
- Current - Supply:
- -
- Current - Cathode:
- 800 µA
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
UC39431DTR FAQ
1.How can I place an order for UC39431DTR through Aetrix?
Please submit a Request for Quotation (RFQ) for UC39431DTR 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 UC39431DTR reliable?
The price and inventory of UC39431DTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC39431DTR is usually 5 days.
3.What payment methods are accepted for UC39431DTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC39431DTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC39431DTR?
UC39431DTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC39431DTR 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 UC39431DTR?
For technical support, including UC39431DTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC39431DTR requirements.
6.How does Aetrix verify that UC39431DTR is sourced from the original manufacturer or authorized distributors?
All UC39431DTR 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 UC39431DTR meets industry standards.
7.What is the process for return or replacement of UC39431DTR?
All UC39431DTR units undergo pre-shipment inspection (PSI). If there is an issue with UC39431DTR, 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 UC39431DTR part is unused and in its original packaging.
Return procedure for UC39431DTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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