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Texas Instruments UC39431D
- Part No.:
- UC39431D
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC39431D.pdf
- Description:
- IC VREF SHUNT ADJ 0.39% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,315
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Product details
Overview
UC39431D from Texas Instruments is an adjustable shunt voltage regulator with 100mA sink capability, precision 1.3V internal reference (±0.4% initial accuracy), 2.2V–36.0V operating supply range, and six factory-programmable output voltages (2.82V to 12.24V) via internal resistor network. It serves as the feedback control element in isolated DC-DC converters using optocouplers or magnetic amplifiers.
For engineers reviewing the UC39431D datasheet, UC39431D pinout, UC39431D application, or UC39431D equivalent, key selection criteria include its fixed transconductance (–140 mS typical), dual-stage compensation architecture (error amp + gm amp), UVLO threshold (~1V), and SOIC-8 package compatibility with industrial power supply feedback loops.
Technical Context
The UC39431D implements a two-stage analog control architecture: a high-gain error amplifier (90 dB AVOL, 5 MHz GBW) compares SENSE voltage against a stable 1.3V bandgap reference, while a separate transconductance amplifier (–140 mS ±30 mS, 3 MHz GBW) converts the COMP node voltage into a linear collector sink current. This decoupled design enables independent loop compensation for both stages.
Its internal R1/R2/R3 resistor network supports six discrete regulated outputs (2.82V, 3.12V, 5.1V, 7.8V, 10.42V, 12.24V) by configuring connections between SENSE, COLL, GND, and open terminals - no external resistors required for these standard voltages. UVLO activation at ~1V on SENSE ensures reliable startup only after reference stabilization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage | 1.30 V ±0.4% initial accuracy - enables precise feedback setpoint without external trimming |
| Sink Current Capability | 100 mA continuous - sufficient to drive optocoupler LEDs or magnetic amplifier reset circuits |
| Operating Supply Range | 2.2 V to 36.0 V - supports wide-input industrial and telecom power supplies |
| Transconductance (gm) | –140 mS typical (±30 mS) - delivers predictable linear current output vs. COMP voltage |
| Error Amp GBW | 5 MHz typical - provides fast transient response and flexible compensation via COMP pin |
| UVLO Threshold | ~1 V on SENSE pin - prevents operation until internal reference is fully biased |
| Package | SOIC-8 (D package) - surface-mount compatible with standard PCB assembly processes |
Pinout & Package
UC39431D is housed in an 8-pin SOIC (D package), 150 mil width, RoHS-compliant with CU NIPDAU finish and JEDEC MSL Level-2-260°C-1 year rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COLL (Pin 1) | Collector output of internal transistor | Sink current path up to 100 mA; max 36 V rating; connects to optocoupler anode or magamp control winding |
| GND (Pin 2) | Power and reference ground | Isolated substrate ground for bias circuitry; separate from output transistor power return |
| R1 (Pin 3) | Connection to internal resistor R1 | Configurable node for selecting one of six internal divider ratios (e.g., tied to SENSE for 2.82V output) |
| R2 (Pin 4) | Connection to internal resistor R2 | Configurable node for internal voltage divider selection (e.g., tied to COLL for 5.1V output) |
| R3 (Pin 5) | Connection to internal resistor R3 | Configurable node enabling full six-voltage selection matrix (e.g., tied to GND for 7.8V output) |
| SENSE (Pin 7) | Inverting input of error amplifier | Voltage sense point; also functions as UVLO input (~1 V threshold); low bias current (–0.2 µA typical) |
| COMP (Pin 6) | Error amp output / gm amp input | Primary compensation node; internally clamped to ~2.0 V; used for pole/zero placement in feedback loop |
| VCC (Pin 8) | Supply input | 2.2–36.0 V operation; quiescent current 0.50–0.80 mA; powers all internal circuitry |
Key Features
| Feature | Design Value |
|---|---|
| Fixed transconductance amplifier | –140 mS typical with ±30 mS tolerance - eliminates CTR variation issues in optocoupler feedback paths |
| Internal programmable reference | Six factory-set outputs (2.82V–12.24V) via R1/R2/R3 configuration - reduces BOM count and layout complexity |
| Dual-stage compensation architecture | Independent COMP (error amp) and COLL (gm amp) nodes - enables stable loop tuning across wide load/transient conditions |
| UVLO with SENSE pin | ~1 V activation threshold - ensures regulator remains inactive until reference stabilizes, preventing erratic startup |
| Precision 1.3 V reference | 0.4% initial accuracy and 0.7% overall tolerance over temperature - maintains tight output regulation without external calibration |
Applications
| Optocoupler-Based Isolated DC-DC Feedback | Magnetic Amplifier Output Regulation |
|---|---|
Use Scenario: Regulating secondary-side output voltage in flyback or forward converters where primary-side sensing is impractical. IC Role / Device Role / Timing Role: Shunt regulator providing precise voltage reference to optocoupler LED; controls feedback current based on output deviation. Use Value: Eliminates CTR dependency and supply-voltage drift effects, improving cross-regulation and line/load transient performance. | Use Scenario: Controlling saturable reactor saturation timing in multi-output DC-DC converters requiring tight cross-regulation. IC Role / Device Role / Timing Role: Generates controlled reset current for magnetic amplifier core reset; regulates output by modulating reset pulse width/duration. Use Value: Enables high-efficiency, low-noise regulation without optocouplers; leverages UC39431D's linear gm stage for accurate current sourcing. |
| Programmable Reference Source | Industrial Power Supply Monitor |
Use Scenario: Providing stable, user-selectable reference voltage for ADCs, DACs, or comparator thresholds in embedded systems. IC Role / Device Role / Timing Role: Adjustable shunt reference delivering 2.82V–12.24V outputs via internal resistor configuration; replaces discrete Zener/resistor networks. Use Value: Reduces component count and improves long-term stability versus Zener diodes; maintains accuracy over –40°C to +85°C. | Use Scenario: Monitoring auxiliary rail voltages (e.g., 5V, 12V) in programmable logic controllers or motor drives for fault detection. IC Role / Device Role / Timing Role: Precision shunt regulator configured as overvoltage/undervoltage detector via SENSE pin monitoring and COLL current sinking. Use Value: Uses built-in UVLO and 0.4% reference to detect deviations >±1% without external comparators or references. |
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; requires external resistors for programming; 2.495V nominal reference | Lacks configurable internal voltages and dual-stage compensation; simpler loop but less flexible for optocoupler/magamp use | Choose TL431ACDR when cost sensitivity outweighs need for internal voltage options or advanced compensation. |
| UC39432D | Provides access to non-inverting error amp input and reference; omits internal R1/R2/R3 resistors; same gm and GBW specs | Better suited for custom reference designs or when external reference injection is needed; not drop-in for UC39431D's resistor-configured outputs | Choose UC39432D when direct reference or error amp input access is required, and internal voltage options are unnecessary. |
Compared with TL431ACDR and UC39432D, UC39431D uniquely combines factory-programmable outputs, dual-stage compensation, and integrated UVLO - making it optimal for high-performance isolated power supply feedback where flexibility and stability are critical.
Availability
UC39431D is available at Aetrix Electronics and suitable for industrial power supplies, telecom DC-DC modules, and programmable logic controller auxiliary rails requiring stable component supply and long-lifecycle support.
Supply support for UC39431D 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, specializing in analog, embedded processing, and power management technologies.
The UC39431D belongs to TI's legacy precision shunt regulator product line, designed specifically for high-stability feedback control in isolated switching power supplies and magnetic amplifier systems.
FAQ
What is the maximum sink current capability of the UC39431D?
The UC39431D provides a continuous sink current capability of 100 mA, with an absolute maximum rating of 140 mA. This current flows through the COLL pin and is used to drive optocoupler LEDs or magnetic amplifier control windings. The device maintains regulation across its full 2.2 V to 36.0 V supply range while delivering this current, and thermal derating applies above 25°C ambient per the 8 mW/°C specification.
How does the UC39431D achieve six different regulated output voltages without external resistors?
The UC39431D integrates three precision internal resistors (R1, R2, R3) connected to pins 3–5. By selectively wiring these pins to SENSE (pin 7), COLL (pin 1), GND (pin 2), or leaving them open, users configure six distinct voltage divider ratios that scale the internal 1.3 V reference to 2.82 V, 3.12 V, 5.1 V, 7.8 V, 10.42 V, or 12.24 V - all without external components.
Can the UC39431D be used in place of a TL431 in existing designs?
The UC39431D is not a pin-compatible replacement for the TL431 due to differing pinouts (8-pin SOIC vs. 3-pin SOT-23/TO-92) and architecture. While both are shunt regulators, UC39431D offers dual-stage compensation, internal voltage options, and UVLO - features absent in TL431. Migration requires PCB redesign and loop compensation re-optimization, though functional equivalence exists in feedback control role.
What is the purpose of the COMP pin on the UC39431D?
On the UC39431D, the COMP pin (pin 6) serves as the output of the error amplifier and the input to the transconductance amplifier. It is the primary node for frequency compensation: connecting RC networks here adds poles or pole-zero pairs to stabilize the error amplifier stage. Internally clamped to ~2.0 V, it enables precise loop shaping independent of the COLL-stage compensation - a key advantage for optocoupler-based feedback systems.
Does the UC39431D require external components to operate at its default 5.1 V output?
No - the UC39431D achieves 5.1 V output without any external resistors by configuring its internal R1/R2/R3 network: connect R1 (pin 3) to COLL (pin 1), R2 (pin 4) to SENSE (pin 7), and leave R3 (pin 5) open. This configuration scales the 1.3 V reference precisely to 5.1 V (±0.1 V tolerance), leveraging factory-trimmed internal resistors for high accuracy and temperature stability.
UC39431D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tube
- 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
UC39431D FAQ
1.How can I place an order for UC39431D through Aetrix?
Please submit a Request for Quotation (RFQ) for UC39431D 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 UC39431D reliable?
The price and inventory of UC39431D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC39431D is usually 5 days.
3.What payment methods are accepted for UC39431D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC39431D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC39431D?
UC39431D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC39431D 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 UC39431D?
For technical support, including UC39431D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC39431D requirements.
6.How does Aetrix verify that UC39431D is sourced from the original manufacturer or authorized distributors?
All UC39431D 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 UC39431D meets industry standards.
7.What is the process for return or replacement of UC39431D?
All UC39431D units undergo pre-shipment inspection (PSI). If there is an issue with UC39431D, 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 UC39431D part is unused and in its original packaging.
Return procedure for UC39431D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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