LTM4628 to HG4628: what to verify before a µModule drop-in

Why a µModule is a harder drop-in question than a DRAM

A point-of-load µModule regulator is not a chip in a package — it is a converted power supply squeezed into one: controller, switching elements, inductor and the compensation network that makes the loop stable, all internally connected. That is exactly why µModules are popular (few external parts, predictable layout) and exactly why "same footprint, same pin-out" is a weaker compatibility argument here than it is for memory.

With a DRAM, if the ball map, density, organisation and timings match, the device is very likely to work. With a µModule, the pin map can match perfectly while the behaviour at your load point differs — because the loop, the thermal path and the switching artefacts are all part of the answer. This guide is the checklist we work through with power design teams evaluating an HG-series alternative to an ADI LTM device.

The seven things to verify before you call it a drop-in

• Footprint and pin-out, including the function of every pin you actually use. Not just pad positions: RUN/SS, MODE, VSENSE feedback, clock/synchronise, power-good and compensation pins have to end up in the same place in your netlist, and any pin you currently float must still be safe floated.
• Input and output operating range across your whole worst case, not the nominal rail. Include input under- and over-voltage behaviour and the voltage at which your system must still start.
• Output current class with the thermal headroom your board actually has. A module's continuous current limit is a function of airflow, copper area and ambient — the same module can be fine in one chassis and current-limit in another.
• Switching frequency and synchronisation behaviour if you clock the converter, filter sensitive analog rails nearby, or rely on a specific frequency to avoid a band.
• Loop stability and soft-start with your output capacitance and load profile. Internally compensated modules can still behave differently with a different capacitor bank or a fast-stepping load; this is the check most often skipped.
• Output ripple, noise and transient response at your real load steps, measured on the board — including any sensitive-loads in the same enclosure.
• External component requirements and the physical build-up: what the datasheet expects around the module, plus package height and keep-out in a mechanical assembly where a couple of millimetres can matter.

What our ADI mapping actually records

Our power cross-reference holds 31 entries: 22 in the LTM46xx series, 8 in LTM80xx, and one lead stock line in the LTM36xx family. Three properties of that table matter when you read it:

1. The letter grade is part of the mapping. Our HG4628 is recorded against LTM4628P, not "LTM4628", and HG4630 against LTM4630A. Those suffix letters are not decoration — they mark grade/variant differences inside the same numeric family, so the exact marking on your BOM is what we quote against.

2. One HG part can cover two original variants. HG4644 maps to both LTM4644 and LTM4644T, and each row on our part page states which originals it covers.

3. Where we do not have an equivalent, we say so. For the LTM3605 we hold the original as a stock line and confirm HG-series drop-in status on request rather than implying a mapping we have not characterised.

Each HG part number above links to its own page, where the covered original part numbers are listed explicitly. If your BOM carries a letter grade we do not list, tell us the full marking — the mapping is confirmed line by line.

What we send you, in what order

1. Mapping answer. You send the marking as it appears on the BOM; we confirm which HG part covers it and where no equivalent exists, we say that instead.
2. Datasheet and comparison. Our datasheet for the HG part plus the parameter comparison our Taiwan engineering team runs against the original's public datasheet — pin function, operating ranges, frequency, protection behaviour.
3. Measured evidence. Per-lot inspection and validation records, plus functional/thermal data from the platform class we validated on, so your QA can review evidence rather than adjectives.
4. Samples. 10 pcs to run on your board — loop, transient, thermal and ripple under your real load profile. The sample cost is credited against your first production order.
5. Supply plan. Stock lines dispatch in 48 hours; for long-lifecycle programmes we can agree firm pricing and scheduled shipments. Where the original is still the right answer, we supply the original from stock instead of talking you into a change.

A commercial note, stated plainly: pricing on our stock power lines typically sits 5–10 % below major distributor list prices. That is a procurement argument, not the qualification argument — the qualification argument is the loop, thermal and transient behaviour on your board.

Browse the ADI µModule line, search a marking in the cross-reference tool, or send the BOM line and we will answer with the mapping and the datasheet.