Programmable shunt reference · reference, cathode and anode connections · feedback divider
An adjustable shunt voltage reference sinks current between cathode and anode while sensing a feedback divider at its reference terminal. The circuit designer sets the output with the divider and supplies current through an upstream impedance. Selection therefore includes the bias circuit and capacitive load as well as the initial voltage tolerance.
Three-terminal adjustable shunt references with an external feedback divider, illustrated by TL431-family circuits and their cathode-current and stability requirements. The Voltage reference (reference voltage source IC) page (4263) covers the broader category, including series-output and fixed shunt references. Fixed two-terminal references, buffered series references and laboratory voltage standards are separate products.
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01
TI describes TL431 and TL432 as three-terminal adjustable shunt regulators, set with two external resistors from Vref (approximately 2.5 V) to 36 V. At 25 °C the initial reference tolerances are 0.5% for B grade, 1% for A grade and 2% for the standard grade. Select the complete part number and resistor network together. [1]
TI characterizes its C versions over 0–70 °C, I versions over −40 to +85 °C, and Q versions over −40 to +125 °C. The same sheet states TL431 and TL432 have different pinouts in the DBV, DBZ and PK packages despite matching functionality and electrical specifications. Check the pin drawing for the ordered device. [1]
State output voltage, supply range, load current, divider values and tolerances, temperature grade and package pin mapping. Keep initial tolerance separate from full-temperature deviation.
02
Diodes DS35050 lists recommended cathode current of 1–100 mA and cathode voltage from Vref to 36 V for its TL431/TL432. Its absolute maximum table instead lists 150 mA and 40 V. The absolute maximum ratings are stress limits, not the design operating range. [3]
TI SLVA482A explains that a capacitor across cathode and anode introduces an output pole that can reduce phase margin and cause oscillation. Select the stability chart for the device, package or grade, then use the actual cathode voltage and current; the report warns that a boundary chart describes a representative device without design margin. [2]
In a test on one randomly selected TL431AILP sample, TI observed approximately 35 mV peak-to-peak oscillation with a 5 nF capacitor after cathode current was reduced from 12 mA to 10 mA. This is a reported sample and operating point, not a universal oscillation threshold. [2]
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| Circuit element | Function or source requirement | Check |
|---|---|---|
| Cathode and anode | Shunt current path, with operating-current limits. [1] [3] | Bias at minimum supply and maximum load |
| Reference input and divider | External resistors set the regulated cathode voltage. [1] | Ratio, tolerance and reference-input current |
| Cathode capacitance | Added pole can affect phase margin. [2] | Capacitance, ESR, current and voltage |
| Package pins | TL431/TL432 pinouts differ in specified TI packages. [1] | Pin drawing and board footprint |
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| Record | Named-source detail | Specify |
|---|---|---|
| Initial tolerance | TI: 0.5%, 1% or 2% at 25 °C by grade. [1] | Manufacturer, grade and full order code |
| Temperature grade | TI C: 0–70 °C; I: −40 to +85 °C; Q: −40 to +125 °C. [1] | Applicable version and circuit temperature |
| Cathode operating range | Diodes: 1–100 mA; Vref to 36 V. [3] | Worst-case bias and load |
| Stability | TI application report ties chart selection to device and operating point. [2] | Circuit validation with actual load capacitor |
| Product lifecycle | Diodes document marks its TL431/TL432 as not recommended for new design and directs readers to AS431/AS431H. [3] | Current availability and approved replacement review |
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Device: [maker; order code; grade; pinout] Output: [target; permitted deviation] Supply and load: [minimum; maximum; transients] Divider: [values; tolerance; temperature coefficient] Cathode: [minimum and maximum current] Capacitive load: [capacitance; ESR; cable] Verification: [temperature; startup; transient stability] Quantity: [prototype; production]
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TI explains that cathode capacitance can reduce phase margin. Validate the selected device at the actual voltage, current and capacitive load. [2]
Diodes lists recommended current of 1–100 mA separately from its 150 mA absolute maximum. Use the recommended conditions for circuit design. [3]
Sources checked 2026-10-16. TI supplies the programmable-reference specifications and circuit-stability report. Diodes supplies a separately identified operating-versus-stress comparison and a product-lifecycle notice.
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