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Texas Instruments TL431CD
- Part No.:
- TL431CD
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
TL431CD.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:5,044
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Product details
Overview
TL431CD from STMicroelectronics is an AEC-Q100-qualified, adjustable shunt voltage reference IC with 2% initial voltage accuracy (2.5 V nominal), operating over 0 °C to +70 °C and supporting output voltage programming from 2.5 V to 36 V using two external resistors. It delivers 1–100 mA sink current capability, 0.22 Ω typical dynamic impedance, and is packaged in SO-8 for use in feedback loops of isolated DC-DC converters and automotive power supply regulation.
For engineers reviewing the TL431CD datasheet, TL431CD pinout, TL431CD application, or TL431CD equivalent, key selection criteria include its 2% reference voltage tolerance, SO-8 thermal resistance (RthJA = 85 °C/W), cathode-to-anode voltage rating (37 V), minimum regulation current (0.5 mA), and compatibility with capacitive loads up to 10 µF without instability.
Technical Context
The TL431CD implements a precision 2.5 V bandgap reference with an internal error amplifier and NPN transistor output stage configured as a programmable shunt regulator. Its operation relies on external resistor divider feedback to the REF pin, enabling precise voltage setpoint control independent of input variations.
It features low temperature drift (±17 mV over 0–70 °C), high PSRR (−2.7 to −1.4 mV/V vs. cathode voltage), and stable phase margin across load and capacitance conditions-enabling direct integration into secondary-side feedback paths of flyback and forward converters.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage | 2.5 V nominal, ±2% tolerance at 25 °C - sets absolute accuracy of regulated output voltage |
| Voltage Range | 2.5 V to 36 V programmable via external resistors - enables flexible output scaling without redesign |
| Sink Current | 1–100 mA continuous cathode current - supports direct drive of optocoupler LEDs or small-signal loads |
| Dynamic Impedance | 0.22 Ω typical - ensures tight regulation under fast load transients |
| Operating Temp | 0 °C to +70 °C - suitable for commercial and industrial ambient environments |
| Cathode-Anode Max | 37 V - defines maximum isolation barrier voltage in flyback topologies |
| Min Regulation Current | 0.5 mA - determines lowest usable feedback current before dropout |
Pinout & Package
TL431CD is supplied in SO-8 "batwing" plastic micropackage (ECOPACK® compliant), offering improved thermal dissipation (RthJA = 85 °C/W) versus TO-92 and SOT-23 variants. The package supports surface-mount assembly and provides robust mechanical reliability for automated production.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Anode | Low-side return path; connects to ground or common rail in shunt configuration |
| 2 | Cathode | Current-sinking output node; drives optocoupler LED or feedback network |
| 3 | REF | High-impedance reference input (≤5.2 µA); senses divided output voltage for regulation |
| 4–8 | NC | No-connect pins; electrically isolated and must remain unconnected per design |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Reference | 2.5–36 V output via two-resistor divider - eliminates need for multiple fixed-voltage references |
| Low Dynamic Impedance | 0.22 Ω typical - minimizes output voltage deviation during load steps |
| Stable Capacitive Loading | Compatible with ≥10 µF output capacitance - simplifies EMI filter design without compensation |
| Thermal Robustness | RthJA = 85 °C/W (SO-8) - enables >500 mW power dissipation at 70 °C ambient |
| Automotive Qualification | AEC-Q100 qualified - validated for automotive subsystems requiring long-term reliability |
Applications
| Isolated Flyback Converter Feedback | Automotive Cabin Power Supply |
|---|---|
|
Use Scenario: Secondary-side voltage sensing in 12 V/5 V isolated DC-DC converter for infotainment head unit. IC Role / Device Role / Timing Role: Shunt reference providing precise feedback to optocoupler, closing regulation loop across isolation barrier. Use Value: Enables ±2% output accuracy despite primary-side transformer tolerance and line variation, meeting automotive CISPR-25 conducted emission limits. |
Use Scenario: Regulated 5 V rail for USB charging ports and display backlight drivers in vehicle dashboard. IC Role / Device Role / Timing Role: Adjustable shunt reference setting output voltage of linear post-regulator stage after buck converter. Use Value: Maintains stable 5.0 V ±0.1 V under battery voltage swing (9–16 V) and load steps up to 100 mA, ensuring USB-IF compliance. |
| Industrial PLC I/O Module | Programmable Bench Power Supply |
|
Use Scenario: Precision voltage reference for analog input channel calibration in 24 V-powered PLC backplane module. IC Role / Device Role / Timing Role: Stable 2.5 V reference source for 16-bit ADC reference buffer and DAC output scaling. Use Value: Delivers <±1 LSB error contribution over 0–70 °C, enabling true 16-bit measurement resolution without recalibration. |
Use Scenario: User-adjustable output voltage control in lab-grade 0–30 V, 3 A bench supply with digital panel interface. IC Role / Device Role / Timing Role: Programmable shunt reference generating setpoint for main series pass transistor control loop. Use Value: Supports 10 mV resolution adjustment across full 2.5–30 V range using 12-bit DAC and precision resistor ladder. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt reference applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACD | 1% initial voltage accuracy (vs. 2% for TL431CD), otherwise identical SO-8 packaging and electrical specs | Required where tighter output regulation (±1%) is mandated by system specification or safety standard | Select when higher accuracy justifies marginal cost increase and thermal budget allows same SO-8 footprint |
| TL431CL3T | SOT23-3 package, same 2% accuracy, RthJA = 248 °C/W, max cathode current limited to 15 mA | Suitable for space-constrained, low-power applications where SO-8 thermal performance is unnecessary | Choose for compact PCB layouts with ≤15 mA feedback current and no requirement for high-power dissipation |
Compared with TL431ACD, TL431CD trades 1% accuracy for lower cost and broader availability; compared with TL431CL3T, it offers superior thermal handling and 100 mA sink capability-making it optimal for medium-power isolated supplies where stability and margin matter most.
Availability
TL431CD is available at Aetrix Electronics and suitable for isolated DC-DC converters, automotive cabin power modules, and industrial PLC analog I/O requiring stable component supply, long-lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for TL431CD 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and analog components for automotive, industrial, and consumer markets.
TL431CD belongs to ST's precision analog reference product line, engineered specifically for high-reliability feedback control in power conversion systems where accuracy, thermal stability, and qualification rigor are critical.
FAQ
What is the maximum cathode-to-anode voltage for TL431CD?
The absolute maximum cathode-to-anode voltage (VKA) is 37 V. Operation beyond this risks permanent damage. In practice, the device is typically used with VKA between VREF (2.5 V) and 36 V during normal regulation, as specified in operating conditions. Derating is recommended for long-term reliability in high-temperature environments.
Can TL431CD replace TL431ACD in an existing design?
Yes, TL431CD is pin- and function-compatible with TL431ACD in SO-8 packages, but with ±2% reference voltage tolerance instead of ±1%. System-level validation is required to confirm that the looser tolerance does not degrade output regulation beyond acceptable limits-especially under worst-case temperature and line conditions.
How does TL431CD behave with capacitive loads on the cathode?
TL431CD remains stable with ≥10 µF capacitive loads on the cathode, as verified in Figure 21 of the datasheet. This eliminates need for series resistance or complex compensation networks when driving optocouplers with large LED capacitance or filtering capacitors in feedback paths.
What is the minimum cathode current needed for regulation?
The minimum cathode current (IMIN) is 0.5 mA at 25 °C, rising to 1 mA over the full 0–70 °C operating range. Below this threshold, the device exits regulation and VKA rises toward the input voltage. Designers must ensure feedback network draws sufficient current-even at light loads-to maintain regulation.
TL431CD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tube
- Product Status:
- Active
- Reference Type:
- Shunt
- Output Type:
- Adjustable
- Voltage - Output (Min/Fixed):
- 2.495V
- Voltage - Output (Max):
- 36 V
- Current - Output:
- 100 mA
- Tolerance:
- ±2.2%
- Temperature Coefficient:
- -
- Noise - 0.1Hz to 10Hz:
- -
- Noise - 10Hz to 10kHz:
- -
- Voltage - Input:
- -
- Current - Supply:
- -
- Current - Cathode:
- 1 mA
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
TL431CD FAQ
1.How can I place an order for TL431CD through Aetrix?
Please submit a Request for Quotation (RFQ) for TL431CD 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 TL431CD reliable?
The price and inventory of TL431CD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TL431CD is usually 5 days.
3.What payment methods are accepted for TL431CD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TL431CD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for TL431CD?
TL431CD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your TL431CD 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 TL431CD?
For technical support, including TL431CD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TL431CD requirements.
6.How does Aetrix verify that TL431CD is sourced from the original manufacturer or authorized distributors?
All TL431CD 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 TL431CD meets industry standards.
7.What is the process for return or replacement of TL431CD?
All TL431CD units undergo pre-shipment inspection (PSI). If there is an issue with TL431CD, 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 TL431CD part is unused and in its original packaging.
Return procedure for TL431CD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
TL431CD Tags
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TL431AIDBZR
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TL431BQDBZR
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LM4040CYM3-2.5-TR
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LM4040EIM3-2.5/NOPB
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AZ431LBNTR-G1
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LM4040D20IDBZR
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LM4041DIM3-ADJ/NOPB
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LM4040DIM3X-2.5/NOPB
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LM4040DIM3-2.5/NOPB
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AZ431LANTR-G1
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