Comparing LDO dropout voltage: keep the load and test conditions

Published 23 October 2026 (UTC). Manufacturer sources reviewed on 23 October 2026.

Two low-dropout regulators can show different millivolt figures without having been evaluated under comparable conditions. Before carrying a dropout number into a BOM review or quotation comparison, attach its load current, output-voltage option, package, temperature range and definition. A smaller isolated number does not establish that a proposed device meets the project requirement.

Start with what dropout describes

Dropout concerns the input-to-output voltage difference at the edge of an LDO's ability to maintain regulation as its input falls. It is not a second output-voltage setting. TI's LDO seminar and ADI's concepts tutorial explain why the load and pass-element behavior matter when reading this parameter.

For a comparison record, identify the required regulator and intended load first. A curve or a specification at one load should not silently become a statement covering every operating current. Keep an unresolved condition visible instead of filling it from a different device.

Read one complete row, not the headline

The TLV755P example here uses TI document SBVS320D, revised September 2024. In section 5.5, the DYD-package row at 500 mA and an output-voltage range of 3.3 V to below 5.0 V lists a typical dropout of 150 mV; the table defines typical values at a junction temperature of 25 degrees Celsius.

For that package and output range, the maximum is 238 mV over junction temperatures from minus 40 to 85 degrees Celsius, and 258 mV over minus 40 to 125 degrees Celsius. Those conditions belong with the values. This family-level document example does not select a complete ordering code, approve a board design or confirm an offered unit.

Check how the measurement is defined

TI's SLUP239A seminar describes different dropout test methods, including a method that lowers input voltage until the output has fallen by a specified amount from a reference measurement. Its 100 mV output-change example illustrates a test definition; it is not a universal rule for every regulator.

When comparing two datasheets, record each document's stated method or footnote. If the conditions differ or the definition cannot be located, flag that gap for the technical reviewer. Do not normalize the figures by assumption.

Keep headroom and PSRR separate

ADI distinguishes dropout from the headroom used to meet other performance specifications. In the TLV755P electrical table, PSRR is specified with input voltage 1 V above output voltage and a 50 mA load, alongside stated frequencies. A dropout entry alone does not establish the same rejection performance near dropout.

A design owner must assess the relevant operating margins and performance requirements. Purchasing can preserve the evidence and questions without turning a single dropout figure into a compatibility decision.

Keep a short, traceable handoff

The following is a suggested review record, not a manufacturer acceptance procedure:

Required manufacturer and complete ordering code; proposed alternatives on separate lines.
Package and nominal output-voltage option, with the relevant datasheet revision.
Load current, junction-temperature range, units and typical or maximum classification.
Dropout row or curve, measurement definition and applicable footnotes.
Reviewer, project/BOM revision and any conditions still awaiting confirmation.

For a BOM/RFQ enquiry to HongKong Wei Ya Hua Electronic Technology Co.,Limited, supply the full code, quantity and required date together with these technical questions. Stock, batch evidence, price and delivery require separate confirmation; the datasheet discussion makes no supply commitment.

Can a lower-load dropout figure stand in for the required load?

Keep the specified load with the number. Where the required operating point is not established by the cited information, leave the comparison open for engineering review rather than treating the lower-load result as approval.

Does the smaller dropout figure approve an alternative?

No. Preserve the original requirement and review the proposed ordering code through the project's alternative-part process. Dropout is one parameter; it does not replace checks of the complete device and application.

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