1. Identify a dynamic reference load rather than only a voltage value
The ADS8860 reference terminal does not behave only as a static voltage input. TI describes binary-weighted capacitors being switched onto REF during conversion. Their charge demand depends on the input and reference conditions, giving the reference path a dynamic load that cannot be fully described by a reference source's nominal voltage or a detached current label.
That demand belongs to the conversion process. The datasheet separately describes acquisition, during which this converter does not take dynamic current from the external reference source. The distinction matters when a requirement refers generally to sampling: the signal-input acquisition path and the conversion-phase reference path have different responsibilities and should not inherit one another's timing assumptions.
Start the reference requirement by identifying the load the source and its driver must support. A precise or low-drift voltage describes useful source properties but does not answer how charge reaches REF during conversion. This gives the buffer question a specific purpose: preserving the reference condition while the converter applies its documented dynamic demand. It is more precise than simply requesting a generally accurate voltage-reference component.
2. Separate source-noise filtering from charge delivery
Noise filtering and dynamic charge delivery address different aspects of the same path. TI discusses filtering broadband noise from the reference source before considering the buffer that drives the converter's reference load. The filtering role limits unwanted source noise, while the downstream drive role supports the charge demand created during conversion.
A reference can therefore need a quiet source and an effective dynamic interface simultaneously. Treating the filter as the entire solution leaves out how the conversion load is supplied. Treating a fast driver as the entire solution leaves out the source-noise condition. The two functions should remain intelligible even where an integrated device performs more than one of them.
Compare the documented path by following the reference from source to REF. Identify where source noise is band-limited and where the conversion-related demand is supported, rather than merging both into a low-noise label. The result is a functional allocation of requirements. It does not select a cutoff, identify a particular buffer as suitable or promise that either function independently establishes the converter's achieved noise or linearity.
3. Read reservoir capacitance and buffer stability together
The reference capacitor has a charge-reservoir role, but its interaction with the buffer is part of the requirement. TI links a substantial reference capacitor with regulation of the reference condition and requires the amplifier driving it to maintain low output impedance without stability problems. The capacitor and driver therefore cannot be assessed as unrelated attractive component entries.
Increasing capacitance is not a substitute for understanding that interface. The driver must handle the capacitive load as well as the converter's changing demand. A comparison that records only the capacitor's nominal size omits the amplifier behaviour needed to use that reservoir. Conversely, a buffer's general bandwidth description does not identify its behaviour with the actual reference capacitance.
Retain the reservoir, drive impedance and stability questions together when defining the reference stage. This describes why a reference-buffer requirement exists without copying TI's circuit or compensation values. It also avoids treating a component category as a result: a reference buffer label cannot establish settling, accuracy or freedom from conversion errors in an unspecified application. Those conclusions require the actual reference interface, not only its named parts.
4. Include first-conversion and physical reference-path behavior
The first conversion can add a requirement beyond repetitive steady operation. TI's reference-drive application discussion explicitly addresses first-conversion behaviour and identifies burst or event-triggered use as relevant contexts. The useful distinction is whether the path must be ready for the first requested conversion, rather than relying only on its description during an established sequence.
The physical path is also part of dynamic delivery. TI's layout prose identifies reference-path inductance as relevant where REF draws changing current. A nominally correct source and reservoir do not erase the impedance of the connection between them and the converter. This is a different issue from the reference source's static voltage accuracy or its long-term drift description.
A complete functional requirement can therefore retain steady reference properties, first-conversion readiness and physical charge delivery as separate questions. The ADS8860 discussion explains why all three can matter without providing a universal layout or a buffer recommendation. Keep those device-specific roles alongside the signal-input acquisition review, so that an acceptable input driver is not mistaken for evidence that the reference path has already been resolved.
Sources and further reading
TI ADS8860 SBAS569B, physical pages 20, 31, 33 and 38: reference-load, driver and physical-path prose. No buffer selection, capacitor/RC/layout values, circuit transfer or guaranteed conversion performance is supplied.