Analog Devices Inc. LTC2928CUHF#TRPBF

Comprehensive Summary LTC2928CUHF#TRPBF Power Supply Sequencing and Supervisory IC

The LTC2928CUHF#TRPBF, designed by Analog Devices Inc., is a highly integrated four-channel power supply sequencer and supervisor housed in a 38-lead QFN package. It’s engineered for advanced power management in modern electronics systems, enabling precise coordination and fault supervision across multiple power supplies. Unlike software-intensive sequencing implementations, the LTC2928CUHF#TRPBF allows engineers to define supply sequencing, thresholds, and timing exclusively through external passive components, greatly simplifying design, evaluation, and modification during development cycles.

Supporting both high-performance sequencing and accurate voltage supervision (±1.5% accuracy), the LTC2928CUHF#TRPBF is particularly well-suited to infrastructure, telecom, FPGA/SoC-based platforms, and any application where multi-rail power delivery and robust system reliability are required.

Primary Attributes of the LTC2928CUHF#TRPBF

At the heart of the LTC2928CUHF#TRPBF’s appeal is its suite of versatile features:

Sequencing and supervision for up to four independent power supplies per device (expandable through cascading for unlimited supplies)

Hardware-based staged supply sequencing at user-selectable time positions

Configurable system shutdown in response to detected faults—with in-depth fault event reporting and diagnostics

Undervoltage supervision with high precision (±1.5% accuracy), and independent configuration of both undervoltage and overvoltage thresholds

Enable outputs equipped with internal charge-pumped drivers, suitable for direct N-channel MOSFET gate drive

Rugged input voltage operation: device supply from 2.9V to 16.5V, with selectable high-voltage input (HVcc)

Comprehensive supervisory outputs: RESET, Overvoltage, Fault status signaling

Flexible configuration via resistive dividers and time-position selection resistors—no firmware required

These features ensure that the LTC2928CUHF#TRPBF can be readily adapted to a wide range of sequencing topologies and system requirements, even as project needs evolve.

Operation Mechanisms and Flexibility

The operating logic of the LTC2928CUHF#TRPBF is centered on three sequential power states: sequence-up, voltage monitoring (“supply monitor phase”), and sequence-down.

During power-up (sequence-up phase), the device enables power rails in a pre-defined order determined by user-configured resistors (RT1-RT4). Each enable (EN1–EN4) pin can drive a supply enable input or control the gate of an external N-channel MOSFET switch. The sequencing timing and inter-supply delays are precisely set with STMR, RTMR, and PTMR timing pins, each accepting a user-selected external capacitor.

Monitoring is continuous; voltage sense inputs (V1-V4) track each supply through high-impedance dividers. Transition thresholds (for both sequencing and fault detection) are independently set via SQT inputs and RT resistor choices.

The sequence-down phase is initiated on command (ON pin pulled low), with the device reversing the order of shutdown, ensuring controlled power-down and protection for sensitive subsystems.

Crucially, the supervision circuitry can rapidly transition to fault states, disabling all enables and preserving diagnostic information on comparator outputs for post-fault analysis.

Enhanced Sequencing, Monitoring, and Fault Handling

One of the strengths of the LTC2928CUHF#TRPBF is the breadth of its sequencing and fault management capabilities:

Cascadability: Multiple LTC2928 devices may be interconnected to either expand the number of supplies that can be sequenced simultaneously (CAS pin) or create extended time-position chains (DONE–ON handshake), yielding scalability for both large power trees and complex sequencing requirements.

Fault detection and diagnostics: The unit immediately responds to undervoltage, overvoltage, supply stall (with watchdog-enabled), controller command errors, or externally-asserted faults. Enable outputs are pulled low to shut down all connected supplies. Comprehensive fault type and source information is latched and viewable for easy troubleshooting.

Overvoltage management: All monitored positive supplies are constantly checked for overvoltage excursions. Thresholds for overvoltage can be finely tuned system-wide, and rapid shutdown upon detection is user-configurable by connecting relevant outputs.

Reset management: A true microprocessor-style RESET signal is issued when all monitored rails are in compliance, with propagation delays and hold times controlled by user-selectable timing components.

Debug and test modes: Pin-selectable features enable testing of power-on margining or intentional masking of fault actions during development phases.

LTC2928CUHF#TRPBF Use Cases and Engineering Applications

The LTC2928CUHF#TRPBF is purpose-built for advanced, multi-rail applications where meticulous sequencing and robust monitoring are critical. Key use cases include:

Network and telecom infrastructure equipment, where multiple I/O and core voltages must be brought up and down in tightly controlled order

FPGA and SoC-based designs (such as those employing Xilinx or Altera FPGAs) with critical core and I/O rail dependencies

Power modules or DC-DC converter stacks requiring precise enable sequencing for inrush control or hot-swap management

Systems demanding high reliability and serviceability, benefiting from comprehensive built-in fault logging and diagnostic capabilities

The device’s hardware-defined configuration is especially valuable in environments where firmware changes are costly, or configuration security and reproducibility are major considerations.

Highlighted Electrical Specs and Pin Descriptions

The LTC2928CUHF#TRPBF provides four supply monitor channels, each with complementary enable and comparator outputs. It can directly interface with N-channel MOSFETs or power supply enable/shutdown inputs, and its internal charge pump ensures appropriate gate drive.

Key pin functions include:

HVcc and Vcc supply input flexibility (2.9V–6V for Vcc, 7.2V–16.5V for HVcc)

Dedicated comparator (CMP1–CMP4) and status outputs (RST, OV, FLT, DONE)

Cascade and handshake lines (CAS, DONE, ON) for multi-device systems

Reference output for negative supply monitoring

External capacitor timing pins for sequencing, delay, and watchdog

Easy mask or test configuration via three-state mode pins (MS1, MS2) and enable override pins (RT1–RT4)

Absolute maximum ratings, as well as recommended operating conditions, are consistent with advanced digital and power supply environments, and the device is robustly protected against overstress.

Best Practices for System Integration and PCB Layout

For optimal LTC2928CUHF#TRPBF system integration, engineers should consider:

Proper grounding and minimal trace loops, especially for timing capacitors, reference, and sense lines, to minimize noise pickup and preserve sequence accuracy.

Use of external pull-up resistors (particularly for status and comparator outputs) where faster rise times or higher voltage compatibility are required.

Careful assignment of RT resistors to precisely define time positions and supply order, with attention to thresholds and required sequencing logic.

Tight coupling of supply monitor dividers at the rails to avoid IR drop errors or false trips, especially in high-current domains with remote sense feedback.

Clear separation and appropriate bypassing for HVcc and Vcc if operating at elevated input voltages.

Adherence to recommended resistor and capacitor values for all timing and divider networks (detailed tables and calculations are available in the datasheet).

Use of the asynchronous OFF (RT to GND) or ON (RT to Vcc) modes for system bring-up, individual channel testing, or burn-in cycling.

When cascading, ensure CAS and DONE–ON connections use direct, low-inductance traces with no added capacitive loading.

In-depth Design Walkthrough Using LTC2928CUHF#TRPBF

To illustrate real-world deployment, consider a typical dual-supply DSP and FPGA system:

Four voltage rails must be sequenced: 3.3V, 2.5V, 1.8V, and 1.5V (assigned to V4, V1, V3, and V2 inputs, respectively).

All sequencing decisions—order, timing, thresholds—are set via RT and dividing components.

EN outputs drive external N-FETs on two critical rails, ensuring supply inrush control, while the others connect directly.

Power-good and reset timing is selected via appropriate PTMR and RTMR capacitors (e.g., 0.1 μF for a 400ms watchdog, 0.047 μF for a 190ms reset delay).

Overvoltage thresholds are set globally by leaving the OVA pin open or by resistively dividing as necessary.

The system is designated MASTER-FIRST-LAST via MS1/MS2 selection (grounded), ensuring autonomous, single-device operation while preserving expandability.

This approach delivers deterministic sequencing, reliable supply monitoring, and detailed post-fault analysis—without software.

Alternate and Compatible Devices for LTC2928CUHF#TRPBF

In evaluating alternatives to the LTC2928CUHF#TRPBF, engineers may consider the following families and models, depending on required channel count, features, and packaging:

LTC2930 / LTC2931 (Analog Devices): Similar multi-rail supervisors with sequencing but more emphasis on I²C programmable configuration.

LTC2923 / LTC2929 (Analog Devices): Earlier or simpler versions for twoor four-channel sequencing without some of the advanced monitoring features of the LTC2928.

UCD9090 (Texas Instruments): Offers 10-rail power supply sequencing and monitoring with digital interface and advanced telemetry—suitable for larger, digitally managed platforms.

ADM1066 (Analog Devices): Specialty programmable super sequencer with analog and digital supervision, as an alternative in complex, programmable environments.

Maxim MAX16046/MAX16049: Four-or-eight-channel power supply sequencers with margining and flexible event management.

Selection will depend on the need for analog vs. digital configuration, desired monitoring granularity, and system integration requirements.

Conclusion

The LTC2928CUHF#TRPBF from Analog Devices stands out as an engineer-centric, flexible, and robust multichannel power supply sequencer and supervisor. With its configuration by hardware and passive components, the device dramatically simplifies both design and troubleshooting compared to microcontroller or firmware-based sequencers, while maintaining diverse fault management and expandability for complex power architectures. Its high voltage accuracy, staged sequencing, and diagnostic functions make it an ideal choice for mission-critical, high-uptime, and infrastructure applications. By understanding its configuration, system integration, and alternative options, engineers and procurement decision makers can confidently select the LTC2928CUHF#TRPBF for the most demanding power supply sequencing requirements.