Analog Devices Inc. LTM4691EY#PBF

Product Summary LTM4691EY#PBF Dual DC/DC μModule Regulator

The LTM4691EY#PBF from Analog Devices is a compact, high-efficiency, dual output step-down DC/DC μModule regulator optimized for point-of-load (PoL) applications. With an input voltage range from 2.25V to 3.6V and two independently programmable outputs each capable of delivering up to 2A continuous current, the device integrates nearly all necessary components into a small 24-lead LGA or BGA surface mount package (3mm × 4mm × 1.18mm LGA, or 3mm × 4mm × 1.48mm BGA). Designed for telecom, networking, industrial, FPGA, and ASIC core supplies, the LTM4691EY#PBF simplifies power architecture and minimizes board space.

Main Features and Technical Details of the LTM4691EY#PBF

At the heart of the LTM4691EY#PBF are its robust features:

Input voltage range: 2.25V to 3.6V

Dual outputs: each programmable from 0.5V to 2.5V, up to 2A per channel

±1.5% total output voltage regulation

Surface mount 24-LGA/BGA package for compactness

Adjustable output with remote sense capability

Internal current mode control and compensation for fast transient response

External frequency synchronization (1MHz to 3MHz) and selectable operating modes

Integrated protection functions: overvoltage, overcurrent, overtemperature, and short-circuit protection

Wide operating temperature: -40°C to 125°C (with derating)

RoHS compliant and Pb-free

These features individually and collectively support reliability, ease of design, and high performance in demanding environments, making the LTM4691EY#PBF an ideal PoL regulator.

Circuit Design and Integrated Elements of LTM4691EY#PBF

The LTM4691EY#PBF comes as a fully integrated μModule solution, incorporating dual switching regulators, power MOSFETs, inductors, and supporting passive components within a single package. Only external bulk input and output capacitors are needed, reducing BOM complexity. The module implements current mode control with internal feedback loop compensation, ensuring system stability and fast transient behavior with minimal external components.

Operation Modes and Frequency Coordination in LTM4691EY#PBF

Flexibility in operating modes allows the LTM4691EY#PBF to fit diverse applications and load profiles:

Pulse-Skipping Mode for efficient operation at light loads

Forced Continuous PWM Mode for minimal output ripple and predictable switching frequency

Burst Mode® for lowest input power consumption at light loads

The mode is selected via the MODE/SYNC pin. Additionally, the module’s internal oscillator (default 2MHz) can be externally synchronized to clocks from 1MHz to 3MHz, which is particularly valuable for EMI management and system-level timing alignment. Both buck channels operate 180° out of phase, reducing input ripple currents and enhancing overall performance.

Electrical and Thermal Performance of LTM4691EY#PBF

Electrical robustness comes from a wide operating temperature range, precise voltage regulation (±1.5%), and current mode control. Key absolute maximum ratings include VIN up to 4V and VOUT up to 2.5V. Rigorous thermal management is supported by detailed thermal resistance values (θJA, θJCbot, θJCtop) and derating curves, enabling engineers to predict device behavior under varying loads, ambient temperatures, and airflow conditions. Integrated overtemperature protection ensures shutdown above 165°C, safeguarding the device and system.

Setting Output Voltages and Choosing Capacitors for LTM4691EY#PBF

Output voltages are set via external resistor dividers, referencing the internal 0.5V feedback voltage. Using 1% resistors preserves output accuracy, and optional phase lead capacitors can optimize transient response. For reliable operation, input decoupling is achieved with low-ESR ceramic capacitors positioned close to VIN pins, and output ripple is minimized with a single 22μF low-ESR ceramic capacitor per channel. Engineers may augment capacitors if system requirements demand additional filtering for voltage droop or overshoot during transient load steps.

Protection Features, Monitoring, and Power-Up Sequencing of LTM4691EY#PBF

Integrated protection mechanisms make LTM4691EY#PBF highly fault tolerant:

Overvoltage protection: turns off internal PMOS immediately upon detecting FB pin voltage exceeding 110% of regulation

Overcurrent and short-circuit protection: cycle-by-cycle peak current limiting and secondary valley current limits

Thermal shutdown: disables output when junction exceeds 165°C

Status monitoring is provided through the PGOOD pin, which delivers feedback on power failure and overvoltage conditions with built-in delays to prevent false reporting during transient events. The RUN pin’s precision threshold enables event-based power sequencing, allowing cascading startup between rails or synchronized enabling depending on system needs.

PCB Design and Packaging Guidelines for LTM4691EY#PBF

Achieving optimal electrical and thermal performance requires thoughtful PCB layout:

Use large copper areas for VIN, VOUT, and GND to minimize resistance and thermal stress

Place high-frequency ceramic capacitors close to power pins

Employ dedicated power ground layers under the module

Utilize multiple vias for high-current paths

Separate SGND for sensitive signal routing and connect beneath module

Provide signal pin test points

Both LGA and BGA packages offer minimum height profiles, supporting high-density board design with reliable surface mount assembly. Package pinout must be referenced for correct implementation.

Typical Applications for the LTM4691EY#PBF

The LTM4691EY#PBF is applicable in a range of high-performance systems:

FPGAs and ASICs demanding low voltage, high current core supplies

Telecommunications and networking equipment with tight space and efficiency constraints

Industrial equipment requiring robust regulation across wide temperature ranges

Typical configurations include dual 1.5V, 1.8V, 1.2V, and 0.8V outputs at 2A per channel, tailored to specific system requirements through external component selection and mode configuration.

Alternative or Replacement Options for LTM4691EY#PBF

When considering alternatives or replacements for LTM4691EY#PBF, engineers should focus on devices that offer similar input voltage ranges, dual output capabilities, integrated protection, and compact μModule packaging. Related product families within Analog Devices such as the LTM4643, LTM4672, or LTM4676 may serve as suitable candidates. The selection should be dictated by required output currents, voltage ranges, integration level, and form factor to match system design needs.

Conclusion

The LTM4691EY#PBF μModule regulator offers a highly integrated, efficient, and flexible solution for dual 2A output DC/DC conversion in demanding applications. Its small footprint, robust protection, versatile operating modes, and thorough thermal design considerations make it a compelling choice for engineers seeking reliability and performance with minimal design complexity. Evaluating its features, implementation strategies, and potential alternatives ensures optimized system power delivery in commercial and industrial electronics.