TL431ILPR - Adjustable 2.495V Shunt Reference | TI
料号： TL431ILPR ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $0.28 | $0.28 |
| 10 | $0.22 | $2.20 |
| 100 | $0.14 | $14.00 |
| 500 | $0.1 | $50.00 |
| 1,000 | $0.08 | $80.00 |
| 3,000 | $0.06 | $180.00 |
TL431ILPR 概述
An adjustable shunt regulator is a type of voltage reference IC that maintains a programmed voltage across its cathode-anode terminals by sinking current when the sense voltage at its reference pin exceeds an internal bandgap threshold. Within the power-management hierarchy it sits below linear regulators as a precision reference element, and it is widely used as the feedback error amplifier inside isolated and non-isolated switching power supplies.
Key features of the TL431ILPR include a programmable output voltage set anywhere from Vref (approximately 2.5V) to 36V using just two external resistors, a sharp low-dynamic-output-impedance characteristic, low output noise, and a typical temperature coefficient in the low ppm/C range across the specified -40C to +85C industrial operating range. Its 1mA to 100mA sink-current range gives designers wide loop-gain control in optocoupler feedback networks.
Technically, the TL431 combines an internal 2.495V bandgap reference with an open-collector-style error amplifier driving the cathode output. Because the reference input draws only about 2uA typical, high-impedance divider networks are practical. The device is stable with appropriate capacitive loading per the stability boundary in the manufacturer datasheet, and it is specified for thermal stability over automotive, commercial, and military temperature grades across the family.
Typical applications include secondary-side voltage regulation in flyback and forward AC-DC power supplies, adjustable zener replacement in overvoltage protection Crowbar circuits, precision current-source and current-limiter biasing, and set-point generation in battery chargers. Its three-pin simplicity and low cost make it the industry default feedback element driving optocoupler LEDs in isolated converters.
Design-wise, keep the cathode current above the 1mA minimum for regulation and respect the datasheet stability criteria when adding decoupling capacitance at the cathode node; the compensation capacitor interacts with the equivalent series resistance in ways that can destabilize the loop.
This page synthesizes distributor pricing, drop-in cross-brand alternatives, pinout detail, and practical design notes not consolidated in the manufacturer datasheet.
直接替换替代料： TL431ILPR ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： TL431ILPR （相同外形与封装尺寸） ——差异在于 Adjustable Output Range, Operating Temperature Range, Output Type.
快速对比工具——选择替代料号进行并排对比：
TL431AILPR
✅ 直接替换📋 参考替代料（不在目录中）
TL431CLPR
✅ 直接替换📋 参考替代料（不在目录中）
TL431ILP
✅ 直接替换📋 参考替代料（不在目录中）
TL432ILPR
✅ 直接替换📋 参考替代料（不在目录中）
KA431
✅ 直接替换📋 参考替代料（不在目录中）
LM431
✅ 直接替换📋 参考替代料（不在目录中）
AZ431
✅ 直接替换📋 参考替代料（不在目录中）
KIA431
✅ 直接替换📋 参考替代料（不在目录中）
TL431ILPR 规格参数
| 输出类型 | Adjustable Shunt Regulator |
| Reference Voltage (Vref) | 2.495 V |
| Initial Reference Tolerance | 2.2% at 25C (standard grade) |
| Adjustable Output Range | Vref (2.495 V) to 36 V |
| Maximum Cathode Current | 100 mA |
| Maximum Cathode Voltage | 36 V |
| Minimum Cathode Current for Regulation | 1 mA |
| 工作温度范围 | -40C to +85C (I grade) |
| 封装 | TO-92-3 (LP) |
| 安装类型 | Through Hole |
| Packaging | Tape & Reel (R suffix) |
| 输出噪声 | Low output noise (per TI datasheet) |
| RoHS 状态 | Compliant |
| Grade | Standard (I grade, 2% class) |
TL431ILPR 引脚配置
| 引脚 1 | REF — Reference input - connect output divider here (nominal threshold 2.495 V) |
| 引脚 2 | ANODE — Anode - lowest potential terminal, connect to common/ground |
| 引脚 3 | CATHODE — Cathode - output that sinks up to 100 mA; max 36 V |
典型应用
TL431ILPR 适用于 6 应用s: Isolated Flyback Converter Feedback, Overvoltage Protection Crowbar, Adjustable Precision Current Source, Zener Diode Replacement Reference, Battery Charger Voltage Regulation, adjustable Threshold Comparators and Alarm Circuits.
Isolated Flyback Converter Feedback
The TL431ILPR is the de facto industry standard secondary-side error amplifier in isolated flyback and forward AC-DC power supplies. Its 2.495V reference monitors the 5V or 12V output through a resistor divider, while the cathode sinks current through an optocoupler LED (typically with at least 1mA cathode current for regulation and several mA for LED drive). The 36V cathode rating accommodates most low-voltage secondary rails, and the 100mA sink capability provides ample optocoupler LED drive. Loop compensation (a resistor-capacitor network from cathode to REF) is designed per TI application notes; the device's high open-loop gain and low REF input current keep output set-point accuracy limited mainly by divider tolerance and the chosen accuracy grade.
推荐
Overvoltage Protection Crowbar
In crowbar overvoltage-protection circuits, the TL431ILPR acts as a precision threshold detector: a divider scales the supply rail to the REF pin, and when the rail exceeds the programmed trip point, the cathode pulls low and gates a thyristor or MOSFET to short the supply. The 2.495V reference and the programmable divider allow precise trip voltages from 2.5V up to the 36V device maximum, far more accurate than a zener diode whose knee is soft and temperature dependent. Designers must ensure the cathode current stays within the 100mA rating, typically by series-limiting the gate-drive path, and should add slight hysteresis via the divider to prevent chatter near the threshold.
推荐
Adjustable Precision Current Source
The TL431ILPR forms accurate current sources and current limiters by servoing the voltage across a sense resistor to its 2.495V reference. Placing the REF pin across the sense resistor in series with a pass transistor forces a current of approximately 2.495V divided by the sense resistance; values in the milliamp-to-amp range are set by resistor choice. Because the reference tolerance (2.2% for the standard I grade) directly sets current accuracy, designers needing tighter tolerance should select the A (1%) or B (0.5%) grades or trim the sense resistor. The cathode voltage rating up to 36V and -40C to +85C industrial range suit battery chargers, LED bias, and instrumentation current loops.
推荐
Zener Diode Replacement Reference
As a two-resistor-programmable zener replacement, the TL431ILPR outperforms discrete zener diodes with a much sharper knee, lower dynamic impedance, and a far flatter temperature coefficient. Any nominal voltage from 2.495V to 36V is generated by choosing the divider ratio, eliminating the need to stock many zener values. The 1mA minimum cathode current is comparable to low-current zeners, while the 100mA capability covers shunt-bias duties in analog front ends. In ADC and comparator reference applications, adding the datasheet-recommended compensation capacitance at the cathode preserves stability while filtering reference noise, yielding low output noise superior to typical zener references.
推荐
Battery Charger Voltage Regulation
Battery chargers use the TL431ILPR to enforce precise float and termination voltages: the divider from the battery terminal programs the regulation set-point to values such as 4.2V per lithium cell or 13.8V for lead-acid banks, well within the 36V ceiling. The device compares the divided battery voltage to the internal 2.495V reference and drives a pass-transistor or PWM-controller feedback node accordingly. The -40C to +85C industrial temperature range and specified thermal stability keep the charge voltage accurate across environmental extremes. Charger designers commonly pair the TL431 with a PNP or NMOS pass element and rely on its low REF bias current so high-impedance dividers do not drain the battery when unpowered.
推荐
adjustable Threshold Comparators and Alarm Circuits
The TL431ILPR works as a low-cost comparator with an accurate built-in 2.495V trip point: when the REF voltage rises above the internal reference, the cathode snaps from high to low, giving a sharp transition suitable for undervoltage/overvoltage alarms, window detectors, and level sensors. Unlike a generic op-amp comparator, no separate reference IC is needed, cutting BOM cost and board area in the 3-pin TO-92 package. Note the output is open-collector-like and sinks rather than sources current, so a pull-up resistor defines the logic-high level. The 36V cathode rating allows direct monitoring of higher-voltage rails through an appropriate divider, within the industrial temperature span.
推荐
推荐产品汇总
工程参考数据： TL431ILPR ——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 | TL431AILPR | TL431CLPR | KA431 | LM431 | KIA431 |
|---|---|---|---|---|---|---|
| Package | TO-92-3 (LP) | TO-92-3 (LP) - same | TO-92-3 (LP) - same | TO-92-3 - same footprint | TO-92-3 - same footprint | TO-92-3 - same footprint |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | Texas Instruments | KEC |
| Reference Voltage | 2.495 V | 2.495 V | 2.495 V | 2.495 V (nominal 2.5 V) | 2.495 V | 2.495 V |
| Max Cathode Voltage | 36 V | 36 V | 36 V | 36 V | 36 V | 36 V |
| Max Sink Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
关键差异点
- Standard grade cost-optimized accuracy （对比 TL431AILPR)
- Industrial temperature span （对比 TL431CLPR)
- Documented TI thermal stability data （对比 KA431)
设计说明
Always maintain at least 1mA of cathode current for guaranteed regulation; below this the device exits its specified operating region and output accuracy degrades. In optocoupler feedback designs, budget the series LED resistor so the TL431 sinks both the LED current (typically 2-5mA) and the bias resistor current under full-load conditions, while not exceeding the 100mA absolute maximum. Also verify the 36V cathode ceiling with transient overshoot in offline supply start-up conditions.
Capacitive loading at the cathode can destabilize the TL431 loop: the datasheet stability boundary shows that mid-range capacitance values (roughly 0.01uF to a few uF depending on cathode current) form an unstable region, while either very small or deliberately large (10uF with defined ESR) capacitors are stable. When using the TL431 as a zener replacement with a decoupling cap, consult the manufacturer datasheet stability curves and, if in doubt, add a series resistor or choose a capacitor outside the unstable region.
Reference accuracy is set by the internal 2.495V bandgap plus divider resistor tolerance and REF pin bias current error. Use 1% or better divider resistors and keep divider current two to three orders of magnitude above the ~2uA REF input current (e.g., 0.1mA to 1mA) to suppress bias-error. For set-points tighter than 2%, step up to the TL431AILPR (1%) or a B-grade (0.5%) device instead of trimming, since these are drop-in in the same TO-92 LP footprint.
合规信息
RoHS compliance and lead-free status per DigiKey/Mouser distributor listings; REACH, halogen-free and conflict-minerals declarations not present in provided data - consult TI product page.
