TL431BVDR2G - 36V Adjustable Shunt Regulator | onsemi
料号： TL431BVDR2G ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $0.25 | $0.25 |
| 10 | $0.21 | $2.10 |
| 100 | $0.168 | $16.80 |
| 500 | $0.145 | $72.50 |
| 1,000 | $0.12 | $120.00 |
TL431BVDR2G 概述
A shunt regulator (also called a programmable zener or voltage reference diode) is a three-terminal device that regulates voltage by shunting current through itself in parallel with the load. Unlike a series regulator, the shunt regulator operates as a low temperature coefficient zener whose breakdown voltage is programmable via an external resistor divider. In the power management hierarchy, it spans the voltage reference, shunt regulator, and error amplifier roles, and it is a building block of virtually every SMPS feedback loop.
Key features of the TL431BVDR2G include the B-grade reference accuracy of roughly ±0.4% (2.48 V to 2.52 V), a typical temperature coefficient of 54.51 ppm/C, and operation from -40C to +125C. The internal reference and output stage enable sharp turn-on characteristics and low dynamic output impedance, making feedback isolation in optocoupled flyback converters simple and inexpensive.
Technically, the TL431 integrates a 2.495 V bandgap reference, an error amplifier, and an open-collector output transistor. When the REF pin exceeds the internal reference, the cathode current increases to pull the cathode voltage down, closing the regulation loop. With two external resistors setting the output to any value between Vref and 36 V, the device behaves as a precision zener with programmable breakdown.
Typical applications include the voltage feedback network of optocoupled AC-DC flyback power supplies, adjustable precision references for analog measurement front ends, ADC/DAC reference rails in instrumentation, and calibration or control circuits. The 36 V cathode rating covers offline and 24 V industrial bus systems.
Design tip: ensure a minimum cathode current of 1 mA for guaranteed regulation, and use a small compensation network (for example, a resistor-capacitor combination around the optocoupler) to stabilize the feedback loop, since the TL431 has a defined stability criterion.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
直接替换替代料： TL431BVDR2G ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
快速对比工具——选择替代料号进行并排对比：
TL431ACDR2G
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
TL431BIDR2G
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
TL431BIDR
✅ 直接替换📋 参考替代料（不在目录中）
TL431ACDR
✅ 直接替换📋 参考替代料（不在目录中）
LM431ACMX/NOPB
✅ 直接替换📋 参考替代料（不在目录中）
LM431CIM
✅ 直接替换📋 参考替代料（不在目录中）
TL431BID
✅ 直接替换📋 参考替代料（不在目录中）
TL431BVDR2G 最大额定值与电气特性
| 拓扑 | Three-terminal programmable shunt regulator |
| Reference Voltage (Vref) | 2.48 V to 2.52 V (typical 2.495 V) |
| Adjustable Output Range | 2.495 V to 36 V |
| Cathode Current Range | 1 mA to 100 mA |
| Temperature Coefficient | 54.51 ppm/C |
| Grade | B (precision) |
| 工作温度 | -40C to +125C |
| 封装 | SOIC-8 (lead-free plastic) |
| 安装类型 | Surface Mount |
| Minimum Cathode Current for Regulation | 1 mA |
| Programmability | Vref to 36 V via two external resistors |
| Turn-On Characteristics | Sharp turn-on, low dynamic impedance |
| Lead Finish | Lead-free (G suffix) |
| Reel Suffix | R2 (tape and reel) |
| RoHS 状态 | Lead-free / RoHS-compatible variant |
| 功能 | Voltage reference / shunt regulator / error amplifier |
TL431BVDR2G 引脚配置
| 引脚 1 | REF — Reference input (2.495 V internal reference comparator input) |
| 引脚 2 | ANODE — Anode (lowest potential terminal) |
| 引脚 3 | ANODE — Anode (bonded, current handling) |
| 引脚 4 | CATHODE — Cathode (regulated shunt terminal) |
| 引脚 5 | ANODE — Anode (bonded, current handling) |
| 引脚 6 | ANODE — Anode (bonded, current handling) |
| 引脚 7 | ANODE — Anode (bonded, current handling) |
| 引脚 8 | CATHODE — Cathode (bonded, current handling) |
典型应用
TL431BVDR2G 适用于 6 应用s: Optocoupled SMPS Feedback, Adjustable Precision Voltage Reference, ADC/DAC Reference Rails, Industrial Control and Instrumentation, Battery Charger Voltage Regulation, Constant Current Sources.
Optocoupled SMPS Feedback
The TL431BVDR2G is the de facto standard error amplifier in optocoupler-isolated feedback loops of AC-DC flyback, forward, and offline converters. A resistor divider senses the output rail and compares it against the internal 2.495 V reference; the cathode drives the optocoupler LED, transmitting the error signal across the isolation barrier to the PWM controller. With a 1 mA minimum cathode current and 36 V cathode rating, it fits both 5 V and 24 V output rails. A resistor-capacitor compensation network around the REF pin is essential to satisfy the device's stability criteria and prevent output oscillation in the closed loop.
推荐
Adjustable Precision Voltage Reference
In analog measurement front ends, the TL431BVDR2G provides an adjustable precision reference from 2.495 V to 36 V using only two resistors, replacing discrete zener diodes that have high temperature drift. The B-grade VREF of 2.48 V to 2.52 V and temperature coefficient of about 54.51 ppm/C deliver far better stability than standard zeners, while the sharp turn-on characteristic and low dynamic impedance keep the reference clean under load transients. This makes it well suited to calibration sources, comparator thresholds, and bias networks in industrial control and test equipment where reference accuracy directly affects measurement error.
推荐
ADC/DAC Reference Rails
Precision converters are sensitive to reference noise and drift, and the TL431BVDR2G supplies a clean, programmable reference rail for ADC and DAC systems at very low cost. With output voltage settable from 2.495 V upward and B-grade accuracy of roughly ±0.4%, it establishes bias rails and comparison thresholds for converter circuits in instrumentation and data acquisition. Placed with appropriate decoupling and followed by a buffer amplifier if dynamic current is required, the device contributes minimal additional error; its 54.51 ppm/C drift is small compared with typical converter INL budgets over the -40C to +125C industrial range.
推荐
Industrial Control and Instrumentation
Industrial systems operating from 24 V buses benefit from the TL431BVDR2G's 36 V cathode rating and -40C to +125C operation. It serves as a level-sensitive threshold detector, voltage monitor, and adjustable reference in PLC I/O modules, sensor transmitters, and calibration circuits. The 1 mA to 100 mA wide cathode current range allows it to function both as a low-power reference and as a modest shunt regulating element. Its low cost permits use in every channel of multi-channel instrumentation, and the B-grade reference tolerance simplifies accuracy budgets when the reference error is a direct term in overall system calibration.
推荐
Battery Charger Voltage Regulation
Battery chargers and battery-powered systems use the TL431BVDR2G as the precision element regulating charge termination voltage. The divider network is chosen so the output battery voltage maps to the 2.495 V reference point, and the shunt regulator pulls down the charging drive when the target voltage is reached, typically through an optocoupler or transistor. The 36 V rating supports multi-cell and 24 V battery stacks, while the tight B-grade reference ensures charge voltage accuracy, which directly affects battery life and safety. Its ability to operate from minimal headroom current makes it practical even in low-quiescent charger designs.
推荐
Constant Current Sources
By placing a sense resistor between the cathode circuit and the REF pin, the TL431BVDR2G forms a precision constant current source regulated at approximately 2.495 V across the sense resistor, yielding currents on the order of tens of milliamps with good temperature stability. This topology is used for LED bias, sensor excitation, and transistor biasing networks. The 100 mA maximum cathode current bounds the achievable output current, and the low temperature coefficient of about 54.51 ppm/C keeps the set current stable across the -40C to +125C range, outperforming discrete zener-based current source designs at similar cost.
推荐
推荐产品汇总
工程参考数据： TL431BVDR2G ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | TL431ACDR2G | TL431BIDR2G | TL431BIDR | LM431ACMX/NOPB |
|---|---|---|---|---|---|
| Package | SOIC-8 | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Brand | onsemi | onsemi | onsemi | Texas Instruments | Texas Instruments |
| Reference Voltage (Vref) | 2.495 V typ (2.48-2.52 V) | 2.495 V typ (wider A-grade tolerance) | 2.495 V typ (2.48-2.52 V) | 2.495 V typ | 2.5 V typ |
| Adjustable Output Range | Vref to 36 V | Vref to 36 V | Vref to 36 V | Vref 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 | 1 mA to 100 mA |
| Grade / VREF Accuracy | B grade (approx ±0.4%) | A grade (approx ±1.4%) | B grade | B grade | A grade |
| Operating Temperature | -40C to +125C | -40C to +125C | -40C to +125C | -40C to +125C | -40C to +125C |
关键差异点
- B-grade tight reference tolerance （对比 TL431ACDR2G)
- Same footprint across grades and brands （对比 TL431BIDR)
- Cost per accuracy point （对比 LM431ACMX/NOPB)
设计说明
Ensure a minimum continuous cathode current of 1 mA for guaranteed regulation; below this the TL431BVDR2G may not fully turn on and output accuracy degrades. At regulation, size the bias resistor so the cathode current stays between 1 mA and 100 mA including the optocoupler LED current in SMPS feedback designs. Estimated: with a 12 V rail feeding a 1 kOhm bias resistor, cathode current is about (12 V - V_KA)/1 kOhm, which must stay within limits across line and load transients.
Loop stability is the most common failure mode in TL431-optocoupler feedback circuits. The device datasheet specifies stability criteria depending on load capacitance and cathode resistance; omitting the recommended compensation network (series R-C from REF to cathode) can cause output oscillation, particularly in flyback converters with continuous conduction mode. Verify phase margin over line, load, and temperature corners on the bench before release to production.
Use 1% or better tolerance resistors in the output divider, since divider error adds directly to the B-grade reference tolerance of 2.48-2.52 V. Keep the divider trace to REF pin short and away from switching nodes to avoid injected noise; a small capacitor (for example 10 nF, subject to the datasheet stability curves) directly from REF to anode filters switching transients picked up by the divider.
The device dissipates power as V_KA x I_KA. Estimated: at 36 V cathode and 100 mA cathode current, dissipation reaches 3.6 W, which exceeds SOIC-8 capability without derating; in practice shunt operation is at low duty or low voltage. For continuous high-current shunt use, reduce cathode voltage or current, and rely on the SOIC-8 copper pour to conduct heat; verify junction temperature stays within the -40C to +125C rating.
合规信息
Lead-free plastic SOIC-8 package per datasheet-derived specifications (G suffix denotes lead-free). Full RoHS/REACH declarations should be confirmed via the onsemi product page.
