Texas Instruments TL1431QDREP

Overview

TL1431QDREP from Texas Instruments is a precision-programmable shunt voltage reference IC with 0.4% initial voltage tolerance, 0.2 Ω typical output impedance, and adjustable output voltage from 2.5 V to 36 V via two external resistors. It operates across –40°C to 125°C and serves as a Zener diode replacement in onboard regulation and switching power supply feedback loops.

For engineers reviewing the TL1431QDREP datasheet, TL1431QDREP pinout, TL1431QDREP application, or TL1431QDREP equivalent, this device requires attention to cathode current ≥1 mA, reference input current (≤4 µA), thermal stability over military-grade temperature range, and anode pin multiplicity (Pins 2, 3, 6, 7 internally tied) for precision layout.

Technical Context

The TL1431QDREP implements a precision bandgap-based reference amplifier with internal error amplifier and NPN output stage, enabling sharp turnon (500 ns) and low dynamic impedance. Its reference input (REF) senses voltage at the cathode–anode junction, while the cathode (CATHODE) sinks 1–100 mA of regulated current.

Operation depends on external resistor divider between cathode and anode, setting output voltage per V_KA = V_REF(1 + R1/R2). The device exhibits –1.1 mV/V cathode voltage coefficient below 10 V and –1.5 mV/V above, with reference voltage drift ≤17 mV over full temperature range.

Key Specifications

Pinout & Package

TL1431QDREP is housed in an SOIC-8 (D package) with nominal body size 3.91 mm × 4.90 mm and maximum height 1.75 mm. Pins 2, 3, 6, and 7 are internally connected to ANODE and must be externally shorted for optimal precision.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt reference applications.

Compared with TL1431QDREP, TL431ACDR trades accuracy and thermal stability for lower cost in benign environments, while TL1431MDREP extends operational range downward to –55°C for aerospace deployment - both share identical pinout and basic functionality but differ in qualification scope and reliability documentation.

Availability

TL1431QDREP is available at Aetrix Electronics and suitable for switching power supplies, precision current limiters, overvoltage protection circuits, and adjustable linear regulators requiring stable component supply across extended temperature ranges.

Supply support for TL1431QDREP includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company designing analog and embedded processing chips for industrial, automotive, and communications markets.

The TL1431-EP product line delivers enhanced-plastic packaged precision references engineered for high-reliability applications in defense, aerospace, and medical systems where extended temperature operation and long-term stability are critical.

FAQ

What is the minimum cathode current required for regulation in TL1431QDREP?

The TL1431QDREP requires a minimum cathode current of 0.45 mA at 25°C to maintain regulation, rising to 1 mA across its full operating temperature range. This ensures the internal amplifier remains biased correctly; insufficient current causes reference voltage collapse and loss of regulation. Always verify I_K ≥1 mA under worst-case conditions including lowest input voltage and highest output load.

How does the TL1431QDREP reference input current affect resistor-divider accuracy?

The TL1431QDREP reference input current (I_REF) is ≤4 µA over temperature and flows into the REF pin, creating unequal currents in the R1–R2 divider. This introduces gain error unless compensated: R2 must be sized so that (I_REF + I_FB) × R2 ≈ V_REF. For 0.1% accuracy, use R2 ≤12.7 kΩ when I_FB = 0.2 mA, as derived in TI's SLVS529D application example.

Can TL1431QDREP replace a standard Zener diode directly?

Yes, TL1431QDREP can directly replace Zener diodes in shunt regulator configurations, but requires two external resistors to set voltage and proper anode pin handling. Unlike Zeners, it provides 0.4% initial tolerance, 0.2 Ω impedance, and stable performance from –40°C to 125°C - however, the anode pins (2,3,6,7) must be shorted externally to minimize parasitic inductance and ensure specified accuracy.

What is the significance of the TL1431QDREP's cathode voltage coefficient (ΔV_REF/ΔV_K)?

The TL1431QDREP exhibits a cathode voltage coefficient of –1.1 mV/V below 10 V and –1.5 mV/V above 10 V, meaning its reference voltage decreases linearly as cathode voltage increases. This effect must be included in precision designs: for a 12 V output, V_REF shifts by –8.25 mV (from 2.5 V to 10 V) plus –3 mV (from 10 V to 12 V), totaling –11.25 mV - a correction applied before calculating R1/R2 values.

Is TL1431QDREP pin-compatible with other TL1431 variants like TL1431MDREP?

Yes, TL1431QDREP is pin-compatible with TL1431MDREP and all SOIC-8 TL1431-EP variants. Both share identical pinout (CATHODE, ANODE×4, NC, REF, NC), package dimensions, and electrical interface. Differences lie solely in temperature rating (–40°C to 125°C vs –55°C to 125°C), part marking (1431QE vs 1431ME), and qualification documentation - no PCB changes are needed when substituting within same package.