TL431ASA-7 - Adjustable Shunt Regulator 36V 1% SOT-23-3 | Diodes Inc.
MPN: TL431ASA-7 ✓ Hoạt độngTL431ASA-7 Tóm tắt
An adjustable shunt regulator is a three-terminal voltage reference device that maintains a precise voltage across its cathode and anode terminals by shunting excess current, controlled by an external resistor divider connected to the reference pin. In the power-management hierarchy, it sits below switching regulators and linear regulators as the precision building block used to set feedback thresholds, and it is one of the most widely used reference ICs in the industry, with the TL431 function being a de-facto industry standard footprint.
Key features of the TL431ASA-7 include the ±1% initial reference accuracy of the A-grade die, a temperature-compensated bandgap reference, and a low dynamic output impedance. According to the Diodes Incorporated datasheet, the TL431 series has the same electrical specifications as the industry-standard '431 and is offered in A (1%) and B (0.5%) accuracy grades. The device operates as either a shunt regulator or an open-collector comparator with a 2.495V threshold, giving engineers two functions in one package.
Technically, the part uses an internal bandgap reference and an output amplifier driving a shunt transistor. When the reference pin voltage exceeds 2.495V, the device sinks current from cathode to anode, holding the reference pin at 2.495V. With two external resistors the output is programmable from 2.495V up to 36V. The primary use case is as the error amplifier and reference in the feedback loop of flyback and buck switching power supplies, optocoupler-coupled feedback networks, and precision comparators.
Typical applications include SMPS feedback regulation, battery chargers, adjustable zener replacement, voltage monitoring thresholds, and constant-current source circuits. Its low cost and small SOT-23-3 footprint make it suitable for both industrial and consumer designs.
A key design consideration is ensuring the cathode current stays above the minimum regulation level (typically ~1mA region) across load and temperature for guaranteed regulation, and choosing divider resistor values that balance accuracy against quiescent loading.
This page adds information gain beyond the datasheet by combining distributor pricing tiers, cross-brand drop-in alternatives, comparison tables, and practical design notes in one place.
Bộ thay thế dễ dàng lắp đặt cho TL431ASA-7 — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Các biến thể trong loạt này
Các mẫu cùng loạt có thể lắp đặt dễ dàng tương thích với TL431ASA-7 (cùng hình factor và footprint) — khác nhau ở Adjustable Output Range, Grade, Package.
TL431BSA-7
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
TL432ASA-7
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
TL431AIDBZR
✅ Drop-In✓ Còn hàng
$0.08 / Đơn vị
Xem tài liệu →TL431AIDBZT
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
TL431QDBZT
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
TL431ASA-7 Tỷ lệ tối đa & tính chất điện
| Kiểu đầu ra | Adjustable shunt |
| Điện áp tham chiếu | 2.495 V |
| Initial Accuracy | ±1% (A grade) |
| Adjustable Output Range | 2.495 V to 36 V |
| Maximum Cathode Current | 100 mA |
| Hộp | SOT-23-3 |
| Kiểu lắp đặt | Surface Mount |
| Grade | A (1%) |
| Số chân | 3 |
| Reel Packaging | Tape and Reel (suffix -7) |
Cấu hình chân TL431ASA-7
| Chân 1 | REF — Reference input (2.495V threshold), connected to output divider |
| Chân 2 | ANODE — Low side of shunt, typically connected to ground |
| Chân 3 | CATHODE — Regulated output / current sink terminal, high side |
Ứng dụng tiêu biểu
TL431ASA-7 phù hợp cho 6 Áp dụngs: SMPS Flyback Feedback Regulation, Adjustable Zener Replacement, Battery Charger Voltage Regulation, Voltage Monitoring and Over-Voltage Threshold, Constant-Current Source, Precision Comparator and Threshold Circuits.
SMPS Flyback Feedback Regulation
The TL431ASA-7 is the de-facto standard error amplifier in isolated flyback power supplies. Its 2.495V reference and ±1% accuracy set the output voltage via a divider across the secondary rail; the cathode sinks current through an optocoupler LED (e.g., PC817) to close the isolated loop back to the PWM controller. The 36V output range supports 5V, 12V, and 24V rails from one BOM item, and the 100mA cathode capability comfortably drives the optocoupler LED at 2-5mA. Compared to a discrete zener-transistor network, the TL431ASA-7 gives far tighter line/load regulation and a compensation-friendly transconductance stage. Loop compensation (a capacitor plus resistor from cathode to REF) trades transient response against stability margin; this is the dominant design task when using this device.
Được đề xuất
Adjustable Zener Replacement
The TL431ASA-7 is the classic precision replacement for zener diodes in clamping and bias applications. Where a zener offers 5% tolerance and a soft knee, the TL431ASA-7 provides a programmable 2.495V-36V breakdown with ±1% accuracy and a sharp regulation knee, improving clamp thresholds and reference stability. In practice the device is wired with a resistor divider from cathode to REF, and the series resistor from the supply is chosen so cathode current stays above the minimum regulation level but below the 100mA maximum. This substitution reduces BOM variance in industrial power supplies, over-voltage protection thresholds, and analog front-end bias circuits. The low dynamic impedance in regulation means the clamped voltage shifts far less with current than an equivalent zener, improving system accuracy across load conditions.
Được đề xuất
Battery Charger Voltage Regulation
In linear and switching battery chargers, the TL431ASA-7 monitors the pack voltage through a precision divider and drives the control element or optocoupler when the set charge voltage is reached. The ±1% initial accuracy of this A-grade part directly tightens charge termination tolerance, which matters for lithium chemistries where overcharge degrades cell life. With its 36V programmable range, a single TL431ASA-7 covers 1S through multi-cell configurations by changing divider ratios only. Temperature drift of the bandgap reference is low enough for indoor charger applications. Designers should allow a small hysteresis or use the charger controller's logic for re-charge thresholds, since the TL431 itself is a proportional shunt element rather than a comparator with built-in hysteresis.
Được đề xuất
Voltage Monitoring and Over-Voltage Threshold
Wired with its open-collector-style cathode pulling a logic or optocoupler node, the TL431ASA-7 acts as a precision 2.495V-threshold comparator for supply supervisory circuits. A divider scales the monitored rail to 2.495V; when the rail crosses the programmed threshold, the cathode snaps high, flagging a microcontroller or gate-driving a protection MOSFET. The ±1% reference accuracy yields roughly ±1% threshold accuracy before divider tolerance, far tighter than a zener-transistor supervisor. Because the device needs only a small minimum cathode current, it can monitor rails continuously without wasting milliwatts, and the SOT-23-3 footprint keeps the supervisor cell under a few square millimeters on dense industrial and consumer boards.
Được đề xuất
Constant-Current Source
With a sense resistor between the REF pin and anode, the TL431ASA-7 forms a 2-terminal constant-current sink that holds Vref/sense across the resistor, giving I = 2.495V/R. This configuration is widely used for LED bias, sensor excitation, and optocoupler LED current regulation where a stable 2-10mA improves CTR consistency. The 36V compliance range allows the current source to operate from high rails, while the 100mA maximum limits it to small-signal loads. Compared to a JFET current regulator, the TL431ASA-7 solution is programmable by resistor choice and cheaper; the trade-off is a higher minimum operating voltage (~2.5V plus headroom) and a startup current path that must be accounted for in low-power designs.
Được đề xuất
Precision Comparator and Threshold Circuits
The TL431ASA-7's internal amplifier makes it an economical precision comparator with a built-in 2.495V reference for sensor threshold detection, window comparators (two devices), and analog limit alarms. The reference input draws minimal current, so high-impedance dividers from thermistor, potentiometer, or photodiode nodes work without significant loading error. Output swing is determined by the pull-up resistor on the cathode, allowing direct interface to 3.3V or 5V logic. Its ±1% reference accuracy removes the need for a separate reference IC plus comparator, cutting BOM count in appliance and industrial sensor boards. For fast edges, a small pull-up keeps rise times adequate; the device is not intended for high-speed switching beyond tens of kilohertz.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho TL431ASA-7 — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | TL431BSA-7 | TL432ASA-7 | TL431AIDBZR | TL431QDBZT |
|---|---|---|---|---|---|
| Package | SOT-23-3 | SOT-23-3 - same | SOT-23-3 - same | SOT-23-3 (DBZ) - same | SOT-23-3 (DBZ) - same |
| Brand | Diodes Incorporated | Diodes Incorporated | Diodes Incorporated | Texas Instruments | Texas Instruments |
| Reference Voltage | 2.495 V | 2.495 V | 1.24 V | 2.495 V | 2.495 V |
| Initial Accuracy | ±1% | ±0.5% | ±1% | ±1% | ±1% (extended temp grades vary) |
| Max Adjustable Output | 36 V | 36 V | 36 V | 36 V | 36 V |
| Max Cathode Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
Bảo phân biệt quan trọng
- Cost leadership at equivalent accuracy (vsTL431AIDBZR)
- Tighter accuracy option within same footprint (vsTL431BSA-7)
- Industry-standard '431 compatibility (vsTL432ASA-7)
Ghi chú thiết kế
Ensure cathode current stays above the device minimum regulation current (on the order of 1mA; verify exact limit in the manufacturer datasheet) at the lowest supply and highest divider current conditions. Below this current the TL431ASA-7 loses regulation and output voltage accuracy degrades sharply. Size the series resistor so worst-case cathode current also stays well below the 100mA maximum rating, with margin for input transients.
Keep the REF pin divider resistors physically close to pin 1 and route the divider sense trace away from the cathode switching node in SMPS feedback layouts to avoid noise coupling into the 2.495V threshold. Add a small compensation network (typically a capacitor with series resistor from cathode to REF) for flyback loop stability; the exact values come from the power controller vendor's design procedure.
The TL431ASA-7 is not a latch-style comparator: around the threshold its cathode operates in linear region and can oscillate with capacitive loads. If used as a supervisor, add a small collector resistor and, if needed, hysteresis via feedback from cathode to REF. Also note the TL432ASA-7 alternative has a 1.24V reference - substituting it without changing divider ratios will double the regulated voltage.
Thông tin tuân thủ
RoHS/REACH/lead-free status not stated in the retrieved verified data; confirm on the official Diodes Incorporated product page before procurement.
