LTM4625IY#PBF is a high-efficiency, 5 A, ultralow-profile, µModule® step-down (buck) DC/DC regulator designed and manufactured by Analog Devices Inc. (following its acquisition of Linear Technology). It belongs to the industry-leading LTM46xx family of power modules — fully integrated, complete switch-mode power supply solutions that combine switching controller, power MOSFETs, inductor, and passive components into a single, compact, BGA-style package.
The “IY” suffix denotes the 25-lead 6.25 mm × 6.25 mm × 1.82 mm LGA (Land Grid Array) package, engineered for ultra-low height and excellent thermal performance; the “#PBF” indicates Pb-free, RoHS-compliant, tape-and-reel packaging (typically 250 units per reel), qualified for industrial operation (–40°C to +125°C junction temperature).
⚠️ Critical Clarification:
The LTM4625 is not a controller or bare IC — it is a fully populated, ready-to-use power module. There are no external inductors required, and only 4–6 external components (input/output capacitors, optional soft-start/track capacitor, and maybe a feedback resistor for adjustable versions) are needed for full operation. Its 1.82 mm maximum height makes it ideal for space-constrained applications where traditional buck modules (often > 3 mm tall) cannot fit — e.g., double-sided PCBs, low-profile telecom cards, or stacked memory modules.
Introduction
The LTM4625IY#PBF delivers up to 5 A of continuous output current, with exceptional performance in an unprecedented small footprint:
🔹 Input voltage range: 3.6 V to 20 V, supporting common intermediate rails (5 V, 12 V, 19 V) and battery inputs (e.g., 3S–5S Li-ion);
🔹 Output voltage: fixed 1.2 V, optimized for powering modern low-voltage digital loads (e.g., FPGAs, ASICs, DDR memory, GPUs) — with ±1% accuracy over line, load, and temperature;
🔹 Peak efficiency > 95%, enabling high-density power delivery without excessive heat buildup;
🔹 Ultralow profile: 1.82 mm max height, less than half the height of most competing modules — critical for next-gen slim electronics;
🔹 Integrated high-performance inductor with shielded construction — eliminates EMI radiation and eliminates external inductor selection headaches.
Its architecture features:
- A high-speed, current-mode controller with fast transient response (< 5 µs to ±1% for 2.5 A load step);
- Integrated MOSFETs with low RDS(on) and optimized gate drivers;
- On-chip temperature monitoring and robust protection: overcurrent (hiccup mode), overtemperature shutdown, undervoltage lockout (UVLO), and output overvoltage protection (OVP);
- Flexible control interface: enable (EN), power-good (PG), tracking (TRACK), and soft-start (SS) pins — enabling seamless power sequencing in complex systems.
The IY LGA package, with 25 solder balls (including thermal pad), achieves θJA ≈ 22°C/W when mounted on a standard 4-layer PCB with internal ground/power planes — supporting full 5 A load at ambient temperatures up to +85°C without heatsinking.
Key Features
✅ Fully Integrated µModule® Power Solution:
• Includes controller, MOSFETs, shielded inductor, and compensation — no external inductor required;
• Only 4 external components needed: input cap (2× 22 µF), output cap (4× 22 µF), soft-start cap (optional), and feedback resistor (not needed for fixed 1.2 V version);
• Saves >70% board area vs. discrete buck solutions.
✅ High Performance & Efficiency:
• Output current: 5 A continuous, 6 A peak;
• Input voltage: 3.6 V to 20 V;
• Output voltage: fixed 1.2 V (±1% accuracy);
• Peak efficiency: > 95% (e.g., 12 V → 1.2 V @ 3 A);
• Quiescent current: 120 µA (Burst Mode®) — enables long battery life in always-on systems.
✅ Ultra-Low Profile & Thermal Excellence:
• Package height: only 1.82 mm max, smallest in its class;
• Thermally enhanced LGA: 25-solder-ball array including large central thermal pad;
• Supports full 5 A output at +85°C ambient — verified with ≥ 300 mm² EP copper area and ≥ 20 thermal vias.
✅ Fast Transient Response & Robust Control:
• Load transient recovery: < 5 µs to ±1% for 2.5 A step (with recommended output caps);
• Programmable soft-start (via external capacitor) and tracking (for supply sequencing);
• Power-good (PG) open-drain output with accurate threshold (±5%).
✅ Reliability & Protection:
• Overcurrent protection (OCP) with hiccup-mode recovery;
• Overtemperature shutdown (155°C) with 25°C hysteresis;
• Output overvoltage protection (OVP): clamps at ～110% VOUT;
• ESD rating > 2 kV HBM on all control pins.
✅ Compact LGA-25 (IY) Package:
• 6.25 mm × 6.25 mm footprint, 1.82 mm height — ideal for double-sided, low-profile, and stacked assemblies;
• RoHS-compliant, halogen-free, and qualified for –40°C to +125°C junction.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (formerly Linear Technology) |
| Product Series |
LTM46xx Family (µModule® Step-Down Regulators) |
| Model |
LTM4625IY#PBF |
| Function |
Fully Integrated 5 A Step-Down µModule® Regulator |
| Output Voltage |
Fixed 1.2 V (±1% over line/load/temp) |
| Max Continuous Output Current |
5 A (with proper thermal design) |
| Input Voltage Range |
3.6 V to 20 V |
| Peak Efficiency |
> 95% (e.g., 12 V → 1.2 V @ 3 A) |
| Quiescent Current (Burst Mode®) |
120 µA (typ.) |
| Transient Response |
< 5 µs to ±1% for 2.5 A step |
| Soft-Start / Tracking |
Yes (external capacitor configurable) |
| Power-Good (PG) |
Open-drain, ±5% threshold accuracy |
| Operating Junction Temp. |
–40°C to +125°C |
| Package |
25-Lead LGA (6.25 mm × 6.25 mm × 1.82 mm) (IY) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel (PBF), typically 250 units/reel |
Typical Applications
🔹 High-Density Computing: FPGA, ASIC, and GPU core power in AI accelerators, network switches, and server mezzanine cards — where 5 A @ 1.2 V, low height, and fast transient response are mandatory.
🔹 Telecom & Networking Equipment: SFP+, QSFP, and OSFP optical transceivers, baseband units (BBUs), and small cell radios — leveraging compact size, high efficiency, and excellent EMI performance (integrated shielded inductor).
🔹 Industrial Automation: Vision systems, robotics controllers, and PLC I/O modules — benefiting from wide VIN, robust protection, and reliability in harsh environments.
🔹 Medical Imaging Electronics: Portable ultrasound, handheld MRI sensors, and endoscopic processors — where low profile enables ergonomic form factors and quiet (no coil whine) operation.
🔹 Test & Measurement: Bench-top instruments and modular PXI/LXI systems — using precise 1.2 V regulation and power-good signaling for clean system sequencing.
🔹 Battery-Powered High-Performance Devices: Drones, portable spectrum analyzers, and field-deployable radar — enabled by 3.6 V min input (supports 1S LiPo down to 3.6 V) and 120 µA quiescent current.
Development & Design Notes
🔧 Thermal Management (Critical for 5 A):
- The IY package’s large central thermal pad must be soldered to a ≥ 300 mm² internal ground/power plane using ≥ 20 thermal vias (0.25 mm diameter) in a 5×5 grid — this is non-negotiable for sustained 5 A operation at +85°C.
- Avoid placing heat-generating components (e.g., FPGAs, DDR terminations) directly above or adjacent to the LTM4625 — airflow and thermal coupling degrade performance.
🔧 Input & Output Capacitor Selection:
- Input: Use two 22 µF, X5R/X7R, 1210 ceramic capacitors (e.g., TDK C5750X7R2A226M) placed symmetrically within 3 mm of VIN and GND balls.
- Output: Use four 22 µF, X5R/X7R, 1210 ceramics (e.g., Murata GRM32ER7YA226KW01) — placed in a square around the module, each < 3 mm from VOUT/GND balls.
- Do not use tantalum or aluminum electrolytics — they increase ESR, degrade transient response, and reduce reliability.
🔧 Layout & EMI Best Practices:
- Keep VIN–GND and VOUT–GND loops as small as possible — minimize loop inductance to preserve stability and reduce radiated emissions.
- Route high-current paths (VIN, VOUT, PGND) on inner layers with wide copper pours — avoid thin traces or vias in these paths.
- Place a 10 nF ceramic capacitor from EN to GND for noise immunity — especially important in noisy industrial environments.
🔧 Sequencing & System Integration:
- Use the TRACK pin to synchronize startup with other rails (e.g., tie to 3.3 V rail via RC network) — ensures proper power-up order for FPGAs and SoCs.
- Connect PG to a microcontroller GPIO or supervisor IC (e.g., LTC2906) — enables safe reset assertion and fault logging.
- For battery-powered designs, use Burst Mode® (default) to minimize IQ; disable it only if strict constant-frequency operation is required (e.g., for EMI filtering).
🔧 Reliability & Functional Safety:
- FIT rate = 18 failures per billion hours, with FMEDA report supporting IEC 61508 SIL-2 and ISO 26262 ASIL-B.
- For ASIL-B compliance: monitor PG and periodically read back die temperature (via analog output TEMP pin) — compare against expected thermal model to detect abnormal heating.
