The TL431 and TL432 from Texas Instruments (TI) are industry-standard programmable precision shunt voltage references. These devices are designed to provide an accurate, adjustable reference voltage for a variety of applications such as voltage regulation, current limiting, and feedback control in power systems. Their combination of high accuracy, low temperature drift, and broad operating range has made them a go-to solution in both linear and switching power supply designs for decades.
1 Features
• Reference voltage tolerance at 25°C– 0.5% (B grade)– 1% (A grade)– 2% (Standard grade)
• Adjustable output voltage: Vref to 36V
• Operation from −40°C to 125°C
• Typical temperature drift (TL43xB)– 6mV (C temp)– 14mV (I temp, Q temp)
• Low Output Noise
• 0.2Ω Typical output impedance
• Sink-current capability: 1mA to 100mA
2 Applications
• Rack server power
• Industrial AC/DC
• AC inverter & VF drives
• Servo drive control module
• Notebook PC power adapter design
3 Description
The TL431 and TL432 devices are three-terminal adjustable shunt regulators, with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5V) and 36V, with two external resistors. These devices have a typical output impedance of 0.2Ω. Active output circuitry provides a very sharp turn on characteristic, making these devices excellent replacements for Zener diodes in many applications, such as on-board regulation, adjustable power supplies, and switching power supplies. The TL432 device has exactly the same functionality and electrical specifications as the TL431 device, but has different pinouts for the DBV, DBZ, and PK packages. Both the TL431 and TL432 devices are offered in three grades, with initial tolerances (at 25°C) of 0.5%, 1%, and 2%, for the B, A, and standard grade, respectively. In addition, low output drift versus temperature verifies good stability over the entire temperature range. The TL43xxC devices are characterized for operation from 0°C to 70°C, the TL43xxI devices are characterized for operation from –40°C to 85°C, and the TL43xxQ devices are characterized for operation from –40°C to 125°C
4 Key Technical Specifications
| Parameter | TL431 | TL432 | Description |
| Reference Voltage (Vref) | 2.495 V | 2.495 V | Internal precision reference |
| Output Voltage Range | 2.495 V – 36 V | 2.495 V – 36 V | Adjustable using external resistors |
| Reference Accuracy (25°C) | ±0.5% (A grade) / ±1% (B grade) | ±0.5% | High precision tolerance |
| Operating Cathode Current | 1 mA – 100 mA | 1 mA – 100 mA | Wide dynamic range |
| Temperature Range | –40°C to +125°C | –40°C to +125°C | Industrial and extended range |
| Package Types | TO-92, SOT-23, SOIC-8 | TO-92, SOT-23, SOIC-8 | Multiple mounting options |
5 Design Tips
Add a bypass capacitor (0.1 µF) between REF and cathode to improve stability in high-frequency circuits. Ensure minimum cathode current (≥1 mA) for proper regulation. For low-load or noisy systems, include a compensation capacitor across the divider network.
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