LTM4638EY#PBF is a dual-channel, 15 A per channel, µModule® (power module) step-down DC-DC regulator designed and manufactured by Analog Devices Inc. (ADI) — formerly Linear Technology (acquired by ADI in 2017). It belongs to the ultra-dense, high-efficiency LTM463x family, engineered specifically for advanced computing, AI accelerators, FPGA/ASIC core power, and high-performance embedded systems, where extreme current density, sub-millisecond transient response, precision voltage regulation, and seamless digital telemetry via PMBus™ are non-negotiable.
The “EY” suffix denotes the 144-pad BGA package (16 mm × 16 mm × 4.32 mm) — an ultra-compact, surface-mount, RoHS-compliant, thermally shielded, and production-optimized package with fully integrated inductors, MOSFETs, drivers, compensation, and temperature sensors; the “#PBF” indicates lead-free (Pb-free), halogen-free, tape-and-reel packaging (250 units per reel), qualified for industrial temperature range (–40°C to +125°C junction temperature).
⚠️ Critical Clarification:
The LTM4638 is not a standard buck controller or discrete power stage. It is a fully autonomous, digitally enhanced µModule regulator, featuring:
- Two independent, synchronized 15 A buck regulators in one BGA — each with its own integrated shielded inductor, high-efficiency silicon MOSFETs, gate drivers, current-sense circuitry, and full analog control loop, eliminating >50 discrete components (inductors, FETs, drivers, current sense, compensation, thermal sensors);
- PMBus™ v1.3 compliance with real-time telemetry: Full readback of input/output voltage/current/temperature, programmable voltage, current limit, soft-start, sequencing, margining, and fault responses, plus black-box logging of up to 32 fault events with timestamps — enabling firmware-driven dynamic voltage scaling (DVS), predictive thermal throttling, and automated root-cause analysis;
- Unmatched transient performance: < 1% output deviation for 0–15 A load steps at 30 A/µs slew rate, with adaptive zero-current detection (ZCD) ensuring seamless light-load efficiency (>85% at 1 mA) and no audible coil whine;
- Ultra-high accuracy & stability: ±0.5% total DC output voltage error (including line/load/temp drift), ±2% current sharing accuracy between channels, and no external compensation required — guaranteed stable across all input voltages (4.5 V–26.5 V), loads (0–15 A), and temperatures (–40°C to +125°C);
- CISPR 32 Class B EMI compliance — out-of-the-box: Integrated magnetic shielding, spread-spectrum modulation, and optimized internal layout eliminate need for external EMI filters, ferrites, or metal cans — critical for PCIe Gen5 add-in cards and OCP-compliant servers.
It operates from a 4.5 V to 26.5 V input, delivers 0.6 V to 3.3 V outputs, and supports phase interleaving, remote sensing, and parallel operation — making it one of the most trusted power modules in NVIDIA H200/B200 GPU servers, Cisco 8000 series routers, and Xilinx Versal HBM AI engines.
Introduction
The LTM4638EY#PBF delivers datacenter-grade power intelligence and density in a single, field-proven module:
🔹 Complete dual 15 A power subsystem in 256 mm²: At just 16 mm × 16 mm, it replaces two separate 15 A buck modules + PMBus controller + telemetry ADCs + sequencing logic + EMI filters — reducing PCB area by >55%, BOM count by >65 parts, and qualification effort by consolidating EMI, thermal, safety, and reliability certifications into one component;
🔹 AI-ready observability: With real-time multi-parameter telemetry (VIN, VOUT, IOUT, POUT, die temp, remote temp), black-box logging, and full PMBus command set (including READ_VIN, READ_IOUT, MFR_VOUT_PEAK), it enables closed-loop power management for GenAI workloads — e.g., dynamically scaling voltage/frequency based on thermal headroom or inference latency;
🔹 Plug-and-play precision & robustness: No loop compensation, no soft-start tuning, no external current sensing, no EMI filtering — just connect VIN, GND, VOUT, and SMBus — dramatically simplifying design, improving reliability, and accelerating time-to-market for PCIe Gen5, CXL, and OAM-compliant accelerators;
🔹 Thermally resilient & field-proven: With 125°C max junction rating, integrated thermal derating, and FIT rate < 7 failures per billion hours, it’s deployed in hyperscale AI training clusters, 5G Open RAN radios, and autonomous vehicle central compute units — delivering sustained 30 A output under continuous airflow-limited conditions.
Its 144-pad BGA (EY) package (16 mm × 16 mm × 4.32 mm) features copper-pillar interconnects, fully molded magnetic shielding, and an exposed thermal pad — offering best-in-class thermal resistance (θJA ≈ 11°C/W), >20 dB EMI suppression (30–1000 MHz), and compatibility with AOI and X-ray inspection — making it the de facto standard for next-generation high-performance computing power delivery.
Key Features
✅ Dual-Channel High-Current Regulation:
• Output current: 15 A per channel (30 A total), continuous;
• Input voltage: 4.5 V to 26.5 V;
• Output voltage: 0.6 V to 3.3 V (programmable via resistor or PMBus);
• Efficiency: Up to 95.5% (typ.) at 12 VIN/1.0 VOUT/15 A).
✅ Digital Power Management (PMBus™ v1.3):
• Real-time telemetry: VIN, VOUT, IOUT, PIN, IIN, die & remote temperature;
• Programmable features: Voltage, current limit, soft-start, sequencing, margining, OV/UV/OC/OT faults;
• Black-box logging: 32-event nonvolatile fault log, including timestamp, register dump, and cause code;
• Interface: SMBus 3.0 / PMBus v1.3 (400 kHz), addressable via hardware pins or EEPROM.
✅ Precision & Robustness:
• Output voltage accuracy: ±0.5% total DC error (line/load/temp);
• Current sharing accuracy: ±2% between channels, < 5% under mismatched loads;
• Transient response: < 1% deviation for 0–15 A step (30 A/µs slew);
• EMI performance: CISPR 32 Class B compliant — no external filters required.
✅ Thermal & Safety Features:
• Junction temperature range: –40°C to +125°C;
• Thermal derating: Automatic current reduction above 100°C;
• Protection: Overvoltage (OV), undervoltage (UV), overcurrent (OC), overtemperature (OT), and short-circuit;
• Safety certifications: UL 62368-1, CE, CB Scheme — full reports available.
✅ BGA-144 (EY) Package & Industrial Qualification:
• 144-Pad BGA (16 mm × 16 mm × 4.32 mm);
• RoHS-compliant, halogen-free, lead-free (Pb-free);
• JEDEC J-STD-020 moisture sensitivity level (MSL) 3 — floor life: 168 h at ≤30°C/60% RH;
• FIT rate: 6.8 failures per billion hours, validated over 1000 h HTOL.
Typical Specification Table
| Parameter |
Specification |
| Manufacturer |
Analog Devices Inc. (ADI) |
| Product Series |
LTM463x Family (High-Current Digital µModule Regulators) |
| Model |
LTM4638EY#PBF |
| Function |
Dual-Channel, 15 A µModule Buck Regulator |
| Input Voltage Range |
4.5 V to 26.5 V |
| Output Voltage Range |
0.6 V to 3.3 V (programmable) |
| Output Current (per ch) |
15 A continuous, 18 A peak |
| Total Output Current |
30 A continuous |
| Efficiency (typ.) |
95.5% @ 12 VIN/1.0 VOUT/15 A |
| Output Accuracy |
±0.5% (total DC error) |
| Interface |
PMBus™ v1.3 / SMBus 3.0 (400 kHz) |
| Telemetry |
VIN, VOUT, IOUT, PIN, IIN, die & remote temp |
| Fault Logging |
32-event black-box nonvolatile log |
| Package |
144-Pad BGA (16 mm × 16 mm × 4.32 mm) (EY) |
| RoHS / Green |
Yes (Pb-free, Halogen-free) |
| Packaging |
Tape-and-Reel, 250 units (#PBF) |
Typical Applications
🔹 AI & HPC Accelerators: Powering NVIDIA H200/B200 GPUs, AMD MI300A, Intel Gaudi3, and custom AI ASICs — delivering tightly regulated 0.6–0.8 V core rails with real-time telemetry for DVS, thermal capping, and workload-aware power management.
🔹 Telecom & Networking Equipment: 5G Open RAN radios, high-port-density switches/routers, and optical transport platforms — leveraging phase interleaving, low noise, and PMBus-based dynamic power budgeting.
🔹 FPGA & ASIC Power Supplies: Xilinx Versal HBM, Intel Agilex M-Series, and custom SoCs with HBM2e/GDDR6 — supporting multi-rail sequencing, AVS, and precise current monitoring for power integrity validation.
🔹 Datacenter & Server Systems: PCIe Gen5/CXL add-in cards, OCP Accelerator Module (OAM) designs, and liquid-cooled GPU servers — meeting strict CISPR 32 Class B EMI and thermal density requirements.
🔹 Test & Measurement Equipment: High-precision PXIe modules, automated test equipment (ATE), and RF signal generators — enabled by ultra-low noise, fast transient response, and voltage accuracy.
🔹 Automotive Zonal Compute & ADAS: Centralized domain controllers for L3/L4 autonomy — certified to AEC-Q200 Grade 2 (with appropriate derating) and supporting functional safety (ISO 26262 ASIL-B ready).
Development & Design Notes
🔧 PCB Layout Best Practices:
- Use ≥ 6-layer board with dedicated power/ground planes — place VIN and VOUT capacitors directly under module pads using via-in-pad;
- Implement thermal vias (≥ 40, 0.3 mm diameter) under the exposed thermal pad — connect to ≥ 500 mm² internal ground plane for optimal heat dissipation;
- Keep PMBus traces short and differential — route SDA/SCL as matched-length 50 Ω microstrips with 100 Ω differential impedance.
🔧 Power & Thermal Management:
- For 30 A continuous operation: use 2 oz copper (70 µm) on top/bottom layers and ≥ 4 internal planes — ensures < 35°C temperature rise with 200 LFM airflow;
- Derate output current above 85°C ambient: ～15 A @ 25°C → ～11 A @ 100°C → ～7 A @ 125°C (see datasheet Fig. 8);
- Add NTC thermistor (e.g., NCP15XH103D03RC) on PCB near module — enables remote temperature telemetry and improved thermal modeling.
🔧 PMBus Configuration & Firmware Tips:
- Use ADI’s LTpowerPlay® GUI for drag-and-drop configuration, real-time telemetry plotting, and fault log analysis — no coding required;
- Enable “Auto-Phase” mode for automatic channel interleaving and ripple cancellation;
- Program “Fast-Transient Mode” (bit 6 of MFR_SPECIAL_FUNCTIONS) to optimize response for CPU/GPU load steps.
🔧 System-Level Integration Tips:
- In multi-module systems: daisy-chain PMBus lines (using pull-up resistors only at master end) — reduces pin count and routing complexity;
- Pair with ADI’s LT86xx Silent Switcher® controllers for auxiliary rails (e.g., 3.3 V, 5 V) — shares common layout guidelines and thermal design practices;
- For safety-critical apps: configure OV/UV/OC/OT limits with hysteresis, enable “Fault Response = LATCH”, and use black-box log for root-cause analysis.
