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Analog Devices Inc. LTC3855IUJ#TRPBF
- Part No.:
- LTC3855IUJ#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 40-WFQFN Exposed Pad
- Datasheet:
-
LTC3855IUJ#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 40QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,850
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Product details
Overview
LTC3855IUJ#TRPBF from Analog Devices (formerly Linear Technology) is a dual, 180° out-of-phase, current-mode synchronous step-down DC/DC controller driving all-N-channel MOSFET stages. It features differential remote sensing, programmable current sense thresholds (30/50/75 mV), ±0.75% 0.6 V reference accuracy, and supports up to 12-phase operation via CLKOUT/PHASMD. Used in high-current server VRMs and telecom intermediate bus converters.
For engineers reviewing the LTC3855IUJ#TRPBF datasheet, LTC3855IUJ#TRPBF pinout, LTC3855IUJ#TRPBF application, or LTC3855IUJ#TRPBF equivalent, key selection criteria include input voltage range (4.5 V to 38 V), dual-channel output capability (0.6 V to 12.5 V), phase-lockable frequency (250 kHz–770 kHz), DCR temperature compensation, and QFN-40 package thermal performance.
Technical Context
The LTC3855IUJ#TRPBF implements two independent polyphase current-mode control loops with shared oscillator synchronization and configurable phase relationships (0°/180°/240°). Each channel uses an error amplifier with transconductance of 2 mmho and ITH-based peak current programming, enabling precise load transient response and stable multi-phase interleaving.
Its integrated differential remote sense amplifier (gain = 0.998–1.002 V/V, 3 MHz GBW, 2 V/µs slew rate) enables accurate regulation at the load point, while programmable ILIM pins set maximum sense thresholds per channel. The device supports three light-load modes-Burst Mode®, pulse-skipping, and forced continuous-selected via MODE/PLLIN pin state.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 38 V - supports 5 V, 12 V, 24 V, and 36 V intermediate bus systems without external regulators. |
| Output Voltage Range | 0.6 V to 12.5 V - covers core logic (0.6–1.8 V), I/O (1.2–3.3 V), and auxiliary rails (5 V, 12 V) without external amplification. |
| Reference Voltage Accuracy | ±0.75% at 0.6 V - ensures tight output regulation across temperature and line/load variations for CPU/GPU VRMs. |
| Switching Frequency Range | 250 kHz to 770 kHz - adjustable via FREQ pin current (10 µA); enables optimization of size vs. efficiency in high-density PCB layouts. |
| Current Sense Threshold | Programmable 30/50/75 mV - allows flexible use of DCR sensing (low loss) or discrete shunts (high accuracy) with temperature compensation. |
| Operating Junction Temp | –40°C to +125°C - qualified for industrial and telecom environments; θJA = 33°C/W (UJ package) supports >15 A/channel thermal design. |
| Differential Amplifier Gain | 0.998–1.002 V/V - enables true remote sensing with <0.2% gain error, critical for low-voltage, high-current loads where IR drop exceeds 10 mV. |
Pinout & Package
Package: 40-pin (6 mm × 6 mm) plastic QFN with exposed SGND pad (Pin 41), RoHS-compliant, moisture sensitivity level 3. Thermal resistance θJA = 33°C/W; requires soldering exposed pad to PCB ground plane for thermal and noise integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 26) | Main input supply connection | Accepts 4.5–38 V; must be decoupled locally with 0.1–1 µF ceramic capacitor to PGND. |
| TG1/TG2 (Pins 20, 30) | Top gate driver outputs | Drive N-channel high-side MOSFET gates; require bootstrap capacitors tied to BOOST1/BOOST2. |
| BG1/BG2 (Pins 23, 27) | Bottom gate driver outputs | Drive N-channel low-side MOSFET gates; sourced/sunk with RDS(ON) ≤ 2.4 Ω (pull-up) / ≤ 1.1 Ω (pull-down). |
| SENSE1+/SENSE1– (Pins 39, 40) | Channel 1 current sense inputs | Differential pair for DCR or shunt sensing; bias current ±1 µA enables low-loss layout. |
| DIFFP/DIFFN (Pins 10, 11) | Differential remote sense inputs | Connect directly to load point (+) and output capacitor (–); reject common-mode noise up to 13 V. |
| CLKOUT (Pin 32) | Synchronization clock output | Phase-adjustable (60°/90°/120°) signal for cascading up to 12-phase systems with minimal jitter. |
| ILIM1/ILIM2 (Pins 14, 15) | Current limit threshold select | GND/float/INTVCC configures max sense voltage to 30/50/75 mV per channel independently. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 180° phased controllers | Reduces input ripple current by ~70%, cutting required bulk capacitance and lowering EMI filter cost. |
| Programmable DCR temperature compensation | Uses ITEMP1/ITEMP2 pins with NTC thermistors to maintain current-sense accuracy over –40°C to +125°C. |
| True remote sensing differential amplifier | 0.998–1.002 V/V gain and 100 dB PSRR enable sub-10 mV regulation error at 1.2 V/15 A loads. |
| Adjustable soft-start or tracking | 1.2 µA internal TK/SS current enables linear ramp control or precise power-rail sequencing with external dividers. |
| Foldback output current limiting | Automatically reduces current limit as VFB drops below 0.6 V, protecting against short-circuit and pre-biased start-up faults. |
Applications
| Server VRM | Telecom Intermediate Bus Converter |
|---|---|
|
Use Scenario: Dual-output 1.8 V/15 A and 1.2 V/15 A power delivery for multi-core CPUs in 1U rack servers. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing gate timing, current sharing, and remote voltage feedback. Use Value: 95% peak efficiency at full load and <10 mV load-step deviation enable compliance with Intel VR14 specs. |
Use Scenario: 48 V to 12 V/30 A conversion in 5G base station power shelves with strict EMI limits. IC Role / Device Role / Timing Role: Primary controller synchronizing multiple LTC3855 units into 12-phase topology for ripple cancellation. Use Value: Interleaved 180° phasing cuts input RMS current by 41%, reducing bulk capacitor size and heat generation. |
| Industrial PLC Power Supply | Medical Imaging FPGA Core Rail |
|
Use Scenario: 24 V input to isolated 3.3 V/10 A and 5 V/5 A outputs powering real-time I/O and communication modules. IC Role / Device Role / Timing Role: Dual-channel controller with independent RUN/TK/SS pins enabling staggered startup and fault isolation. Use Value: ±0.75% reference accuracy and differential remote sensing ensure <±15 mV regulation across 0–85°C ambient. |
Use Scenario: Low-noise 1.0 V/20 A core supply for high-speed medical FPGA processing image reconstruction algorithms. IC Role / Device Role / Timing Role: Burst Mode® controller minimizing standby power while maintaining fast transient response via ITH loop. Use Value: Sub-100 µA shutdown current and 92% efficiency at 100 mA load extend system uptime in battery-backed diagnostics mode. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2950GQ-Z (Monolithic Power) | Integrated MOSFETs (40 V, 12 A), fixed 600 kHz fSW, no differential remote sense, smaller QFN-32 package. | Lower BOM count but limited to ≤12 A/channel; unsuitable for >30 A or precision remote sensing needs. | Select when board space and component count outweigh need for ultra-low VOUT drift and multi-phase scalability. |
| ISL91302BIRZ-T7A (Renesas) | Dual 4-phase controller, 2.5–5.5 V input, 0.3–1.5 V output, integrated telemetry, no DCR tempco or ILIM pin programming. | Optimized for mobile SoC power (e.g., APUs), lacks wide VIN range and industrial temp grade (only –10°C to +85°C). | Select for portable/embedded applications requiring PMBus telemetry and ultra-low quiescent current, not for 24/48 V infrastructure. |
Compared with MP2950GQ-Z and ISL91302BIRZ-T7A, the LTC3855IUJ#TRPBF uniquely combines wide 4.5–38 V input, programmable current sense, differential remote sensing, and –40°C to +125°C operation-making it the only choice for high-reliability, high-current, high-accuracy industrial and telecom power systems.
Availability
LTC3855IUJ#TRPBF is available at Aetrix Electronics and suitable for server VRMs, telecom power shelves, and industrial PLCs requiring stable component supply, long-lifecycle support, and guaranteed industrial temperature grading.
Supply support for LTC3855IUJ#TRPBF 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 portfolio with rigorous automotive and industrial qualification standards.
The LTC3855IUJ#TRPBF belongs to Linear's PolyPhase® controller family, designed specifically for high-efficiency, multi-phase DC/DC conversion in datacenter, telecom, and industrial infrastructure where precision regulation, thermal robustness, and phase scalability are critical.
FAQ
What is the operating temperature range of the LTC3855IUJ#TRPBF?
The LTC3855IUJ#TRPBF is rated for –40°C to +125°C junction temperature, with the "I" grade indicating full specification guarantee across this range. Its 40-pin QFN package has θJA = 33°C/W, requiring proper PCB copper area and exposed pad soldering to sustain 15 A/channel continuous operation at elevated ambient temperatures.
How does the LTC3855IUJ#TRPBF implement differential remote sensing?
The LTC3855IUJ#TRPBF uses dedicated DIFFP (Pin 10) and DIFFN (Pin 11) inputs feeding an integrated differential amplifier (gain = 0.998–1.002 V/V, 3 MHz GBW). The DIFFOUT (Pin 12) connects to VFB1 or VFB2 via a resistive divider, enabling true Kelvin sensing at the load with <2 mV offset and 100 dB PSRR-critical for sub-1.2 V, high-current rails.
Can the LTC3855IUJ#TRPBF operate in single-channel mode?
Yes-the LTC3855IUJ#TRPBF supports independent channel enable/disable via RUN1 (Pin 37) and RUN2 (Pin 13). Either channel can be disabled while the other remains active; unused pins should be pulled to INTVCC or left floating per datasheet guidance. Both channels share the same oscillator but may be configured with different frequencies using separate FREQ networks.
What are the supported light-load operating modes for the LTC3855IUJ#TRPBF?
The LTC3855IUJ#TRPBF supports three selectable light-load modes via the MODE/PLLIN (Pin 34) pin: Burst Mode® (pin floating), pulse-skipping (pin tied to INTVCC), and forced continuous conduction (pin tied to SGND). Each mode trades off efficiency, output ripple, and audio noise-Burst Mode® achieves <30 µA quiescent current, while forced continuous ensures lowest ripple for noise-sensitive analog circuits.
How is the switching frequency programmed on the LTC3855IUJ#TRPBF?
The LTC3855IUJ#TRPBF sets switching frequency via a resistor from FREQ (Pin 35) to SGND. A precision 10 µA current flows from this pin, generating a voltage that programs fSW from 250 kHz (0 V) to 770 kHz (≥2.4 V). Alternatively, a DC voltage source (0–2.5 V) may drive FREQ directly for dynamic frequency scaling in adaptive power systems.
LTC3855IUJ#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 40-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 38V
- Frequency - Switching:
- 250kHz ~ 770kHz
- Duty Cycle (Max):
- 95%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Phase Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 40-QFN (6x6)
LTC3855IUJ#TRPBF FAQ
1.How can I place an order for LTC3855IUJ#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3855IUJ#TRPBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LTC3855IUJ#TRPBF reliable?
The price and inventory of LTC3855IUJ#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3855IUJ#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3855IUJ#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3855IUJ#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3855IUJ#TRPBF?
LTC3855IUJ#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3855IUJ#TRPBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LTC3855IUJ#TRPBF?
For technical support, including LTC3855IUJ#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3855IUJ#TRPBF requirements.
6.How does Aetrix verify that LTC3855IUJ#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3855IUJ#TRPBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LTC3855IUJ#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3855IUJ#TRPBF?
All LTC3855IUJ#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3855IUJ#TRPBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LTC3855IUJ#TRPBF part is unused and in its original packaging.
Return procedure for LTC3855IUJ#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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