1. Identify the Logical RF Paths
Begin with the RF paths the released circuit must connect. Ask the design owner to identify the common path, alternative branches and the states that select them. Preserve those logical roles before comparing switch packages. A request that lists only frequency and package can omit the routing decision the replacement must support.
The ADG918/ADG919 documentation describes an SPDT switch and names a common RF port and two branch ports. Its port descriptions provide a logical example. Keep the corresponding names in a topology record rather than turning a physical package resemblance into proof that a candidate connects the required circuit paths.
Distinguish a circuit's logical port name from a board connector, component reference or physical terminal number. They can be related through the engineering record without being interchangeable identifiers. Obtain the applicable device and board documentation for any physical-interface assessment; this checklist provides no pin assignment or footprint interpretation.
Retain the existing switch code beside the logical route requirement. If the circuit's path names are incomplete, ask the RF owner to resolve them instead of reconstructing the topology from a photograph. That keeps an identification question separate from a proposal to change the circuit's switching architecture.
2. Preserve the Unselected-Branch Behavior
Ask what the circuit requires at a branch that is not carrying the selected signal. Keep this question separate from the active route. The purchaser should preserve the engineering description of the unused path rather than assuming that an SPDT designation determines every property of the other branch.
ADI identifies ADG918 as an absorptive, matched switch with terminated shunt legs and ADG919 as a reflective switch. Preserve those variant descriptions when documenting the requirement. Their shared SPDT category does not erase this distinction. The example identifies a field to review, rather than recommending either device for an unknown RF circuit.
Use the exact candidate's description to resolve its termination behavior. Do not substitute a general explanation of absorptive switching for the relevant device documentation. If the reviewer needs further off-path evidence, record that requirement and its source instead of treating the category name as a complete application assessment.
A change in unused-path treatment belongs on the technical exception list even when the proposed device offers familiar routing labels. Ask the RF owner whether the change affects the approved architecture. Keep that decision visible before an alternative is quoted as though it were the released switch.
3. Match Control Meaning Separately
Retain the required relationship between each logical control state and its selected RF path. ADI's truth table associates the control input with the branch connected to the common port. Use that document-specific mapping as a reference for review; do not assume another switch follows it because the control signal has a similar name.
Keep the controller's required state mapping separate from the semiconductor's table. Engineering must reconcile the two within the actual circuit. A candidate can use the same broad switch category while requiring a different control interpretation, so a purchasing comparison should preserve the mapping question rather than copying only the SPDT label.
Startup, power-off or other unreviewed states need their own applicable evidence when the design requires them. An ordinary control table should not silently resolve every such condition. Ask the design owner which states matter and retain their review status without prescribing control levels, power sequencing or a connection procedure.
If the original design reference does not establish how the switch is controlled, keep the candidate pending. Identify the missing controller or circuit information in the review record. A supplier's functional summary can help locate documentation, but it cannot stand in for the design owner's accepted state mapping.
4. Release Topology with RF Operating Requirements
Prepare a switch-specific comparison containing the logical routes, unused-branch description, control mapping and document references. Keep topology differences distinct from performance fields. The comparison should expose whether the candidate is answering the same routing requirement before engineering considers the rest of its RF operating evidence.
Retain the application's frequency, signal-power and bias requirements as separately sourced inputs for the engineer. A suitable topology does not establish all of those limits. This article supplies no insertion-loss or isolation values and no computed RF result; exact-device specifications must support any later performance comparison.
Keep the complete candidate code and proposed changes with the controlled requirement. Once the responsible reviewer accepts a switch and its operating scope, update the BOM reference before suppliers compare it with the original line. An unresolved route, termination or control change remains a proposal rather than a confirmed replacement.
For an ICULTRA RF-switch enquiry, provide the permitted part and authorised topology reference, identifying any candidate still awaiting review. Ask the offer to distinguish the requested code from a proposed variant. The topology decision and confirmation of current quantity, condition and delivery terms belong to separate records.
Sources and further reading
ADI's ADG918/ADG919 Rev.E supplies a limited topology example. Logical port and termination descriptions are used without interpreting physical pin diagrams or claiming RF measurements.