Analog Devices Inc. LTC2928CUHF#PBF

Overview

LTC2928CUHF#PBF from Analog Devices (acquired Linear Technology) is a four-channel cascadable power supply sequencer and high-accuracy supervisor IC. It performs staged enable/disable sequencing of up to four supplies per device, monitors undervoltage (±1.5% accuracy) and overvoltage conditions, and generates µP reset signals. Used in telecom infrastructure for controlled ramp-up/ramp-down of I/O and core voltages.

For engineers reviewing the LTC2928CUHF#PBF datasheet, LTC2928CUHF#PBF pinout, LTC2928CUHF#PBF application, or LTC2928CUHF#PBF equivalent, key selection criteria include cascading capability for >4 supplies, charge-pumped EN outputs driving N-channel MOSFETs, configurable sequence timing via RT/STMR/PTMR pins, and fault-diagnostic reporting via CMP/FLT pins.

Technical Context

The LTC2928CUHF#PBF implements a state-machine-based sequencing engine with independent time-position decoding per channel (RT1–RT4), dual-phase timing control (STMR for inter-supply delay, PTMR for power-good timeout), and hierarchical fault management that latches CMP outputs and forces all EN pins low on internal/external fault detection. Its HVCC input (7.2V–16.5V) powers an internal regulator delivering 3.3V to VCC, enabling single-rail operation while supporting high-side gate drive.

Supervision uses precision comparators with 0.5V reference-derived thresholds (VSEL-configurable for negative supply monitoring on V1), 1.5% UV accuracy across –40°C to +85°C, and programmable OV thresholds via OVA biasing. RST generation incorporates RTMR-set delay, and DONE signaling enables cascade handshaking between master/slave devices using ON–DONE protocol.

Key Specifications

Pinout & Package

38-lead plastic QFN (5mm × 7mm) with exposed thermal pad (pin 39, optional GND connection). Pinout validated per Linear Technology datasheet 2928fa (Rev. 2012).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power supply sequencing and supervision applications.

Compared with TPS652860RGER and MAX16050ATL+, the LTC2928CUHF#PBF uniquely combines HVCC operation, charge-pumped gate drive, negative rail monitoring, and diagnostic fault latching - making it optimal for high-reliability, externally switched multi-rail systems requiring full hardware autonomy.

Availability

LTC2928CUHF#PBF is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLC backplanes, and network switch ASIC power management requiring stable component supply across extended temperature ranges.

Supply support for LTC2928CUHF#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains its high-performance analog and power management product lines with rigorous qualification standards.

The LTC2928CUHF#PBF belongs to Linear's precision power sequencing and supervision family, designed specifically for complex, multi-rail systems demanding deterministic timing, hardware-level fault diagnosis, and robust operation without software intervention.

FAQ

What is the maximum number of power supplies that can be sequenced using LTC2928CUHF#PBF?

The LTC2928CUHF#PBF supports unlimited supply sequencing through cascading: multiple devices connect via the CAS pin, with master/slave roles configured using MS1/MS2. Each LTC2928CUHF#PBF controls up to four supplies directly, and the DONE–ON handshake protocol allows appending additional time positions across devices without firmware or layout changes.

How does LTC2928CUHF#PBF handle negative voltage monitoring?

The LTC2928CUHF#PBF monitors negative supplies on the V1 input when VSEL is tied to VCC. The buffered REF output (1.189V) serves as an offset reference; a resistor divider connects the negative rail to V1, translating its magnitude into a positive voltage relative to REF. This enables precise undervoltage detection for –1.2V, –2.5V, or –5V rails within the same 1.5% accuracy spec.

Can LTC2928CUHF#PBF drive N-channel MOSFETs directly without external level shifters?

Yes. The LTC2928CUHF#PBF integrates a charge pump that delivers EN1–EN4 outputs at VCC + 5.5V (typical), sufficient to fully enhance standard N-channel MOSFETs used as high-side pass devices. Each EN pin sinks 2.5mA when low and provides regulated gate drive - eliminating external level-shifting circuitry and reducing component count.

What happens to EN outputs during a fault condition detected by LTC2928CUHF#PBF?

Upon detection of any internal or external fault (e.g., UV timeout, OV event, command error), the LTC2928CUHF#PBF immediately pulls all EN1–EN4 outputs low to disable controlled supplies. FLT goes low and CMP outputs latch to indicate fault source. Recovery requires a "return-to-zero" state: all monitored supplies must fall below their sequence-down thresholds while ON remains below 0.97V before re-enabling.

Is external capacitor selection required for basic operation of LTC2928CUHF#PBF?

Yes - three timing capacitors are essential: STMR sets inter-supply delay (8670ms/µF scale), PTMR sets power-good timeout (4000ms/µF), and RTMR sets RST assertion delay (4000ms/µF). Floating STMR/PTMR/RTMR yields minimum delays (~100µs, ~50µs), but stable, repeatable sequencing requires populated capacitors matched to design timing targets.