TL431CDBZR - Adjustable 2.495V Shunt Reference 100mA SOT-23-3 | TI
MPN: TL431CDBZR ✓ Hoạt độngTL431CDBZR Tóm tắt
An adjustable shunt regulator (also called a programmable shunt reference) is a type of voltage reference IC that regulates voltage by sinking current from a supply rail through its cathode when the reference pin senses a voltage above an internal bandgap threshold. In the power-management hierarchy, it sits between a fixed zener diode and a full linear regulator: more precise and temperature-stable than a zener, yet far cheaper and simpler than an LDO. Because the output is set by just two external resistors, the shunt reference family is a fundamental building block in analog circuit design.
Key features include a wide adjustable output range set by two external resistors, approximately 2.495 V internal reference with 2.2% (standard C grade) initial tolerance, 0.2 ohm to 0.5 ohm order typical dynamic output impedance, and a maximum cathode current of 100 mA. The C-grade device is specified over the 0 C to 70 C commercial temperature range, and its low minimum cathode current of roughly 1 mA allows operation in low-power systems.
Technically, the TL431 combines an internal 2.495 V bandgap reference with an operational amplifier and an open-collector output transistor. When the REF pin exceeds the internal threshold, the output transistor conducts and sinks current from cathode to anode, forming the basis of error-amplifier action in isolated flyback and forward power supplies, where the TL431 is frequently paired with an optocoupler such as the PC817 for secondary-side feedback.
Typical applications include secondary-side voltage regulation and feedback in AC-DC and DC-DC switch-mode power supplies, adjustable zener replacement and overvoltage crowbar sensing, battery charger voltage monitoring, and precision threshold comparators in industrial instrumentation.
A critical design consideration is temperature drift: the C grade (2.2% at 25 C) drifts more than the A or B grades over temperature, so precision systems should select TL431ACDBZR or TL431BDBZR instead. Always provide at least the minimum cathode current for regulation.
This page adds distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Bộ thay thế dễ dàng lắp đặt cho TL431CDBZR — 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 TL431CDBZR (cùng hình factor và footprint) — khác nhau ở Package, Minimum Cathode Current for Regulation, Operating Temperature Range, Reference Voltage (Vref), Adjustable Output Range.
TL431ACDBZR
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →TL431QDBZR
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →TL431IDBZR
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →TL431BDBZR
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
KA431AZTA
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AZ431AZ-ATRE1
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
TL431CDBZR Thông số kỹ thuật
| Kiểu đầu ra | Adjustable Shunt |
| Reference Voltage (Vref) | 2.495 V |
| Initial Reference Tolerance | ±2.2% at 25 C |
| Adjustable Output Range | 2.495 V to 36 V |
| Maximum Cathode Current | 100 mA |
| Maximum Cathode Voltage | 36 V |
| Dynamic Output Impedance | 0.2 ohm typical |
| Minimum Cathode Current for Regulation | 1 mA (typical, max 4 mA) |
| Grade | C (standard, 2.2%) |
| Khoảng nhiệt độ hoạt động | 0 C to +70 C |
| Hộp | SOT-23-3 (DBZ) |
| Kiểu lắp đặt | Surface Mount |
| Configuration | TL431 pinout (REF, Anode, Cathode) |
| Trạng thái RoHS | Compliant |
| Packaging | Tape & Reel (R suffix) |
Cấu hình chân TL431CDBZR
| Chân 1 | REF — Reference input (2.495 V threshold, connected to resistor divider) |
| Chân 2 | ANODE — Anode, connected to system ground / lowest potential |
| Chân 3 | CATHODE — Cathode, current sink terminal (up to 100 mA, 36 V max) |
Ứng dụng tiêu biểu
TL431CDBZR phù hợp cho 6 Áp dụngs: SMPS Secondary-Side Feedback, Adjustable Zener / Voltage Clamping, Battery Charger Voltage Monitoring, Precision Comparator / Threshold Detection, Constant-Current Sources, Instrumentation Voltage Reference.
SMPS Secondary-Side Feedback
The TL431CDBZR is the industry-standard error amplifier for secondary-side regulation in isolated flyback and forward AC-DC converters. Its 2.495 V bandgap reference and open-collector output drive an optocoupler LED, closing the feedback loop across the isolation barrier with the REF divider sensing the output rail. The 36 V cathode rating covers most 5 V, 12 V, and 24 V power supplies, and its approximately 0.2 ohm dynamic impedance keeps loop gain stable. Typical designs use 1% feedback resistors plus a 10 nF to 100 nF compensation capacitor at REF, achieving load regulation below 1% across the commercial 0 C to 70 C range.
Được đề xuất
Adjustable Zener / Voltage Clamping
Replacing fixed zener diodes, the TL431CDBZR provides any clamping voltage from 2.495 V to 36 V using two resistors, with far sharper knee characteristics and ±2.2% accuracy versus typical ±5% zeners. Its regulation begins at only about 1 mA of cathode current, whereas zeners need several milliamps for stable breakdown, making the TL431 more efficient in low-power clamp and threshold-detection circuits. In overvoltage protection, the TL431 triggers a crowbar SCR or gate-drive shutdown when the sensed rail crosses the programmed threshold. Designers should respect the 100 mA maximum cathode current and add series resistance when clamping high-energy rails.
Được đề xuất
Battery Charger Voltage Monitoring
In charger ICs and battery packs, the TL431CDBZR senses cell or pack voltage against its 2.495 V reference and indicates or terminates charge when the divider crosses threshold. The 36 V cathode rating supports multi-cell packs, and the C grade ±2.2% tolerance suits lead-acid and NiMH chargers where a final trim is acceptable; lithium applications needing tighter cutoff should select TL431ACDBZR (±1%) or TL431BDBZR (±0.5%) on the same footprint. Because the device draws under 1 mA in regulation, it adds negligible self-discharge burden to battery-powered monitoring circuits across the commercial temperature range.
Được đề xuất
Precision Comparator / Threshold Detection
The TL431CDBZR functions as a comparator with a built-in precision reference: when the REF pin rises above 2.495 V, the cathode pulls low sharply, sinking up to 100 mA. This lets one small SOT-23 device both detect a threshold and directly drive a relay, LED, or microcontroller input without a separate op-amp. Designers set the threshold with a resistor divider from the monitored rail and use a small hysteresis resistor from cathode to REF for clean switching in noisy environments. Compared with a discrete reference-plus-comparator pair, the TL431CDBZR saves board area and BOM cost in industrial sensor and alarm circuits.
Được đề xuất
Constant-Current Sources
By forcing a fixed 2.495 V across a sense resistor placed between the cathode and REF pin, the TL431CDBZR forms a two-terminal constant-current sink; for example, a 12.4 ohm resistor yields approximately 200 mA, scaled by the resistor value. The tight bandgap reference gives far better current accuracy than a zener-based circuit, and the SOT-23 package suits compact LED driver and bias-current applications within the 100 mA cathode limit and package power dissipation. Thermal design matters at higher currents: keep (Vcathode - Vref) times current within the small package capability, or move to a larger package variant.
Được đề xuất
Instrumentation Voltage Reference
Bench instruments, data-acquisition front ends, and industrial meters use the TL431CDBZR to generate a local, adjustable reference rail or offset voltage from a higher system supply. Programming to any value from 2.495 V to 36 V with two resistors eliminates custom reference values, and the approximately 0.2 ohm dynamic impedance provides good ripple rejection when fed from a switching supply. Where the ±2.2% C-grade tolerance is too loose for ADC reference duties, pin-compatible TL431ACDBZR (±1%) or TL431BDBZR (±0.5%) upgrades drop onto the same footprint, allowing one PCB layout to serve multiple accuracy and cost tiers.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho TL431CDBZR — 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 | TL431ACDBZR | TL431QDBZR | KA431AZTA | AZ431AZ-ATRE1 |
|---|---|---|---|---|---|
| Package | SOT-23-3 (DBZ) | SOT-23-3 (DBZ) - same | SOT-23-3 (DBZ) - same | SOT-23-3 - same | SOT-23-3 - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | Diodes Incorporated |
| Reference Tolerance | ±2.2% (C grade) | ±1% (A grade) | ±2% (automotive grade) | ±2% (AZ grade) | ±1% (A grade) |
| Reference Voltage | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.495 V |
| Max Cathode Voltage | 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
- Widest same-brand grade selection on one footprint (vsTL431ACDBZR)
- Commercial temperature range optimized for cost (vsTL431QDBZR)
- Cross-brand second sourcing available (vsKA431AZTA)
- Honest trade-off: not for precision lithium cutoff (vsAZ431AZ-ATRE1)
Ghi chú thiết kế
Do not substitute the TL432CDBZR for the TL431CDBZR without checking pinout: TI states the two devices have different pin assignments in the DBZ package (cathode and REF swapped). Also do not confuse the DBZ and DBV packages - TL431CDBVR uses a different SOT-23 footprint pinout. Always verify the complete ordering code, since grade suffix (C, A, B, I, Q) changes tolerance and temperature range on an otherwise identical die.
Estimated: ensure cathode current stays above the 1 mA typical (4 mA max) minimum for regulation and below the 100 mA absolute maximum. For a 12 V rail clamped to 5 V at 10 mA, series resistor = (12 V - 5 V) / 10 mA = 700 ohm, dissipating 70 mW - safe for SOT-23. Stable regulation requires the feedback loop bias current through the resistor divider to be large relative to REF pin input current; use divider current of 0.5 mA or more.
In optocoupler feedback loops, the TL431 REF pin is sensitive to capacitance: per TI application guidance, capacitance directly on REF can destabilize the internal amplifier. Place a small series resistance (about 1 kOhm to 10 kOhm) between divider and REF when compensation is needed, and use a ceramic capacitor from cathode to REF (typically 10 nF to 100 nF) to set loop crossover. Keep divider resistors within 1% tolerance for best output accuracy.
Place the cathode-to-anode decoupling path short and keep the REF divider close to pin 1 to minimize noise pickup. The SOT-23-3 thermal path is limited; Estimated: at 100 mA and 30 V cathode voltage the device would dissipate 3 W - far beyond SOT-23 capability - so restrict worst-case dissipation to a few hundred milliwatts with adequate copper area on the anode trace.
Thông tin tuân thủ
RoHS compliant and lead-free per TI product page and distributor listings. AEC-Q100 qualification applies to the TL431QDBZR automotive variant, not this C-grade commercial part. REACH and halogen-free status should be confirmed via the TI material declaration page.
