TL431CDT - Adjustable Precision Shunt Regulator | STMicroelectronics
MPN: TL431CDT ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.1227 | $0.12 |
| 10 | $0.0886 | $0.89 |
| 100 | $0.0784 | $7.84 |
| 500 | $0.075 | $37.50 |
| 1,000 | $0.0716 | $71.60 |
| 2,500 | $0.0697 | $174.25 |
TL431CDT Overview
A shunt regulator is a type of voltage regulator that maintains a stable output voltage by shunting excess current to ground through a variable impedance path. The TL431 is a programmable precision reference that can be configured as a shunt regulator, series regulator, or error amplifier by adding external resistors. It belongs to the family of adjustable precision references, which are fundamental building blocks in power management and analog circuits, sitting between discrete Zener diodes and more complex integrated regulators.
Key features of the TL431CDT include a reference voltage of 2.495 V with ±1% accuracy, a cathode voltage range of 2.5 V to 36 V, and a cathode current range of 1 mA to 100 mA. The device offers a typical dynamic output impedance of 0.2 Ω, ensuring excellent load regulation. It also features a low output noise of 90 nV/√Hz and a fast turn-on response, making it suitable for high-frequency applications.
The TL431CDT is built using a bipolar process technology, providing stable performance over a wide temperature range of -40°C to +105°C. The SOT-23-3 package is lead-free and RoHS compliant, with a compact footprint of 2.9 mm × 1.6 mm, ideal for space-constrained designs. The device is also available in other package options, but the CDT suffix specifically denotes the SOT-23-3 package with tape and reel packaging.
Typical applications include precision voltage references for power supplies, error amplifiers in switching power supplies, voltage monitoring circuits, and adjustable output voltage regulators. The TL431CDT is also widely used in battery chargers, LED drivers, and automotive electronics where accurate voltage regulation is critical.
When designing with the TL431CDT, ensure that the cathode current is maintained within the specified range (1 mA to 100 mA) to guarantee proper regulation. The device requires a minimum cathode current of 1 mA to operate correctly, and an external resistor is needed to set the bias current. For optimal stability, place a bypass capacitor at the cathode to ground, especially in high-frequency applications.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the STMicroelectronics datasheet, providing engineers with a comprehensive resource for selecting and implementing the TL431CDT.
Drop-in alternatives for TL431CDT — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TL431AIDBZR
📋 Reference alternative (not in catalog)
TL431QDBZR
📋 Reference alternative (not in catalog)
TL431IDBZR
📋 Reference alternative (not in catalog)
TL431CDT Maximum Ratings & Electrical Characteristics
| Reference Voltage | 2.495 V ±1% |
| Cathode Voltage Range | 2.5 V to 36 V |
| Cathode Current Range | 1 mA to 100 mA |
| Dynamic Output Impedance | 0.2 Ω typical |
| Output Noise | 90 nV/√Hz typical |
| Operating Temperature Range | -40°C to +105°C |
| Package | SOT-23-3 |
| Mounting Type | Surface Mount |
| Reference Voltage Tolerance | ±1% |
| Minimum Cathode Current | 1 mA |
| Maximum Cathode Current | 100 mA |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| MSL Level | 1 |
| Output Type | Adjustable |
TL431CDT Pin Configuration
| Pin 1 | Cathode (K) — Cathode of the shunt regulator, connected to the load and bias resistor |
| Pin 2 | Reference (REF) — Reference input, connected to the external resistor divider |
| Pin 3 | Anode (A) — Anode of the shunt regulator, typically connected to ground |
Typical Applications
TL431CDT is suitable for 6 applications: Precision Voltage Reference, Error Amplifier in Switching Power Supplies, Voltage Monitoring and Detection, Adjustable Output Voltage Regulator, Battery Charger Control, LED Driver Current Regulation.
Precision Voltage Reference
The TL431CDT provides a stable 2.495V reference voltage with ±1% accuracy, making it ideal for precision voltage references in analog circuits. Its low dynamic impedance of 0.2Ω ensures excellent load regulation, maintaining a constant output voltage even with varying load currents. In a typical application, the TL431CDT is configured with two external resistors to set the desired output voltage, and a bypass capacitor is added to reduce noise. This configuration is widely used in ADC reference circuits, comparator thresholds, and sensor biasing, where accurate and stable voltages are critical for system performance. The device's low output noise of 90nV/√Hz further enhances its suitability for high-precision measurement and instrumentation systems.
Recommended
Error Amplifier in Switching Power Supplies
In switching power supplies, the TL431CDT is used as an error amplifier to regulate the output voltage. It compares the divided output voltage to its internal 2.495V reference and generates a feedback signal that controls the PWM controller. The device's fast response and low output impedance ensure stable loop compensation, minimizing output voltage ripple and improving transient response. For example, in a flyback converter, the TL431CDT is placed on the secondary side, with an optocoupler providing isolation to the primary-side controller. The cathode current range of 1mA to 100mA allows flexible biasing, and the wide cathode voltage range of 2.5V to 36V accommodates various output voltage levels. This application is common in AC-DC adapters, battery chargers, and industrial power supplies.
Recommended
Voltage Monitoring and Detection
The TL431CDT is widely used in voltage monitoring circuits to detect over-voltage or under-voltage conditions. By setting a threshold voltage with external resistors, the device can trigger an alarm or shutdown signal when the monitored voltage crosses the threshold. Its precise 2.495V reference and ±1% tolerance ensure accurate detection, which is critical in battery management systems, power supply supervision, and automotive electronics. The device's low quiescent current and small SOT-23-3 package make it suitable for portable and space-constrained applications. In a typical circuit, the TL431CDT is connected as a comparator, with the reference pin tied to the threshold voltage and the cathode driving a logic signal or LED indicator.
Recommended
Adjustable Output Voltage Regulator
The TL431CDT can be configured as an adjustable shunt regulator to provide a stable output voltage from 2.5V to 36V. By selecting appropriate external resistors, the output voltage can be set to any value within this range, making it a versatile building block for custom power supplies. The device's low dynamic impedance ensures good load regulation, and its wide cathode current range allows it to drive loads up to 100mA. In a typical application, the TL431CDT is used with a pass transistor to create a linear regulator with higher output current capability. This configuration is common in bench power supplies, battery chargers, and LED drivers, where adjustable and precise output voltages are required.
Recommended
Battery Charger Control
The TL431CDT is used in battery charger circuits to regulate the charging voltage and current. Its precise 2.495V reference allows accurate voltage setpoints, ensuring that batteries are charged safely without overcharging. In a typical charger, the TL431CDT is used as an error amplifier to compare the battery voltage to a reference and adjust the charging current accordingly. The device's low output noise and stable operation over temperature make it suitable for various battery chemistries, including Li-ion, NiMH, and lead-acid. The SOT-23-3 package is ideal for compact charger designs, such as those found in portable electronics and power tools.
Recommended
LED Driver Current Regulation
The TL431CDT is used in LED driver circuits to regulate the current flowing through LEDs, ensuring consistent brightness and preventing damage from overcurrent. By using the TL431CDT as a shunt regulator, the current can be precisely controlled by setting a reference voltage across a sense resistor. The device's low dynamic impedance and fast response help maintain stable current even with variations in input voltage and LED forward voltage. This application is common in LED lighting, backlighting, and automotive lighting systems. The TL431CDT's small package and low cost make it an attractive choice for high-volume LED driver designs.
Recommended
Recommended Products Summary
Engineering reference data for TL431CDT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TL431AIDBZR | TL431QDBZR | TL431IDBZR |
|---|---|---|---|---|
| Package | SOT-23-3 | SOT-23-3 | SOT-23-3 | SOT-23-3 |
| Reference Voltage | 2.495 V ±1% | 2.495 V ±1% | 2.495 V ±1% | 2.495 V ±1% |
| Cathode Voltage Range | 2.5 V to 36 V | 2.5 V to 36 V | 2.5 V to 36 V | 2.5 V to 36 V |
| Cathode Current Range | 1 mA to 100 mA | 1 mA to 100 mA | 1 mA to 100 mA | 1 mA to 100 mA |
| Dynamic Output Impedance | 0.2 Ω typical | 0.2 Ω typical | 0.2 Ω typical | 0.2 Ω typical |
| Output Noise | 90 nV/√Hz | 90 nV/√Hz | 90 nV/√Hz | 90 nV/√Hz |
| Operating Temperature Range | -40°C to +105°C | -40°C to +105°C | -40°C to +125°C | -40°C to +85°C |
| Automotive Grade | No | No | Yes (AEC-Q100) | No |
Key Differentiators
- Wide operating temperature range of -40°C to +105°C (vs TL431IDBZR)
- Automotive grade option available (vs TL431QDBZR)
- Low output noise of 90 nV/√Hz (vs TL431AIDBZR)
Design Notes
Ensure the cathode current is at least 1 mA for proper regulation. If the current is too low, the TL431CDT may not regulate correctly, leading to output voltage drift. Use an appropriate bias resistor to set the current within the 1 mA to 100 mA range.
Place a bypass capacitor (typically 0.1 µF) close to the cathode pin to ground to reduce noise and improve stability. For high-frequency applications, a small resistor in series with the capacitor may be needed to prevent oscillation.
The SOT-23-3 package has limited thermal dissipation capability. If the TL431CDT is used at high cathode currents (e.g., 100 mA) with a large voltage drop, power dissipation can be significant. Ensure adequate PCB copper area for heat sinking to keep the junction temperature within limits.
Compliance Information
RoHS compliant and lead-free per STMicroelectronics. Not AEC-Q100 qualified; choose TL431QDBZR for automotive.
