Four-rail power sequencer for controlled start-up
The LTC2928CUHF#PBF is a four-channel power supply sequencer from Analog Devices that manages the turn-on and turn-off order of up to four independent voltage rails. It monitors each rail against an adjustable threshold and asserts an active-low reset signal when any rail falls outside the programmed window. The 5 ms minimum reset timeout gives downstream logic a clean power-good window before the system starts. This part is built for controlled start-up sequencing in multi-rail systems — think server motherboards, base stations, or industrial controllers where the FPGA core must come up before the I/O banks.
What the ratings mean for the BOM
Four monitored voltages means this single 38-QFN replaces what used to take a handful of reset ICs and a CPLD. The adjustable threshold per channel lets you set each rail's trip point independently — no fixed-voltage variants to stock. The active-low reset output matches the majority of FPGA and processor reset inputs, so no external inverter is needed. The commercial temperature range (0°C to 70°C) limits it to indoor, conditioned environments; if the board sees an engine bay or a rooftop cabinet, you will need the industrial-grade version.
Package and mounting
Housed in a 38-lead WFQFN with an exposed pad (5x7 mm body). The pad must be soldered to a thermal land on the PCB — it is the primary heat path and also ties to the ground plane. Reflow soldering is the intended assembly method; hand-soldering a QFN on site is possible with a hot-air station and a steady hand, but it is not a field-swap part like a DIP or an SOIC. The tube shipping medium is fine for prototype builds; for production, order the tape-and-reel variant if your pick-and-place needs it.
Active production — no LTB risk
The LTC2928CUHF#PBF is listed as Active and ROHS3 compliant. No end-of-life notice, no last-time-buy window to track. For a BOM freeze or a long-production-run design, this part is safe to qualify now. If you are looking for a second-source option, the ADM1186-2ARQZ is a functional peer — same sequencer type, same 4-channel count, but its reset is active high and its operating temperature range extends to -40°C to 85°C. That wider temperature grade makes the ADM1186 a better fit for outdoor or industrial builds, but the polarity difference means a board spin if you swap directly.