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Analog Devices Inc. LTC3853HUJ#PBF
- Part No.:
- LTC3853HUJ#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 40-WFQFN Exposed Pad
- Datasheet:
-
LTC3853HUJ#PBF.pdf
- Description:
- IC REG CTRLR BUCK 40QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,410
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Product details
Overview
LTC3853HUJ#PBF from Analog Devices (formerly Linear Technology) is a triple-output, multiphase synchronous step-down controller driving all-N-channel MOSFET stages for high-efficiency power conversion in dense DC/DC systems. It supports 120° phased operation across three channels, delivers up to 13.5V on Phase 3, operates from 4.5V–24V input, and achieves ±0.75% output voltage accuracy at 0.8V reference - used in server VRMs, telecom intermediate bus converters, and FPGA core/IO supply sequencing.
For engineers reviewing the LTC3853HUJ#PBF datasheet, LTC3853HUJ#PBF pinout, LTC3853HUJ#PBF application, or LTC3853HUJ#PBF equivalent, key selection criteria include its H-grade (–40°C to 150°C) junction temperature rating, independent TK/SS soft-start/tracking per channel, phase-lockable 250–750kHz frequency range, and support for RSENSE or DCR current sensing with foldback protection.
Technical Context
The LTC3853HUJ#PBF implements a constant-frequency current-mode control architecture with three independent PWM channels operating 120° out-of-phase to reduce input ripple and EMI. Each channel features a transconductance error amplifier (gm = 2.2 mmho), programmable ITH threshold (21–86 mV depending on ILIM state), and dedicated SENSE+/– inputs supporting up to 13.5V common-mode on Phase 3.
Its MODE/PLLIN pin enables selection among Burst Mode® (high-efficiency light-load), pulse-skipping, or forced continuous conduction modes, while FREQ/PLLFLTR allows frequency tuning or PLL synchronization. The controller integrates dual PGOOD outputs (PGOOD12 for Ch1/Ch2, PGOOD3 for Ch3), undervoltage lockout (3.35V on INTVCC), and dropout recovery with periodic top-FET blanking to maintain bootstrap capacitor charge.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 24V (28V absolute max); covers 5V/12V/24V intermediate buses and multi-cell Li-ion battery inputs. |
| Output Voltage Range (Ch1/Ch2) | 0.8V to 5.5V; supports core rails for CPUs, FPGAs, and ASICs with ±0.75% accuracy over –40°C to 150°C. |
| Output Voltage Range (Ch3) | 0.8V to 13.5V; enables higher-voltage IO supplies (e.g., DDR termination, analog subsystems) without external regulators. |
| Switching Frequency | 250kHz to 750kHz (phase-lockable); balances efficiency vs. component size - 500kHz typical for 2.2µH inductors and ceramic output caps. |
| Current Sensing | RSENSE or DCR; eliminates sense resistor losses and supports accurate current limiting across wide temperature range. |
| Thermal Rating | H-grade: –40°C to 150°C junction; validated for industrial and automotive under-hood applications requiring extended reliability. |
| Efficiency | Up to 92% at full load; achieved via synchronous N-MOSFET drive, low gate driver RON (TG: 2.6Ω pull-up, BG: 1.1Ω pull-down), and optimized dead-time control. |
Pinout & Package
40-lead 6mm × 6mm QFN package with exposed PGND pad (Pin 41), rated for θJA = 33°C/W. Requires soldering of exposed pad to PCB thermal plane for thermal performance and noise immunity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TK/SS1, TK/SS2, TK/SS3 (Pins 40, 1, 2) | Soft-start & tracking input | Internal 1.3µA current charges external capacitor to ramp VOUT; enables coincident or ratiometric startup with master/slave configuration. |
| SENSE1+/–, SENSE2+/–, SENSE3+/– (Pins 3–8) | Current sense comparator inputs | Supports high-side DCR or RSENSE sensing; Ch3 inputs tolerate up to 13.5V common-mode for >5V outputs. |
| VFB1, VFB2, VFB3 (Pins 9, 12, 14) | Error amplifier feedback input | Compares divided output voltage to 0.8V reference; ±7.5% PGOOD trip window ensures tight regulation monitoring. |
| ITH1, ITH2, ITH3 (Pins 10, 13, 15) | Error amp output & current threshold control | Voltage sets peak inductor current; adjustable via ILIM pin (GND/FLOAT/INTVCC) to select 21/41/64 mV thresholds. |
| PGOOD12, PGOOD3 (Pins 16, 17) | Open-drain power-good indicators | Active-low signals indicate regulation status: PGOOD12 monitors Ch1+Ch2; PGOOD3 monitors Ch3 independently. |
| MODE/PLLIN (Pin 37) | Mode selection & external sync input | Configures Burst Mode® (float), pulse-skip (INTVCC), or forced CCM (SGND); accepts external clock for PLL synchronization. |
| RUN1, RUN2, RUN3 (Pins 36, 35, 34) | Independent channel enable | 1.2V threshold with 80mV hysteresis; allows staggered startup/shutdown and dynamic rail disabling without full IC reset. |
Key Features
| Feature | Design Value |
|---|---|
| Triple 120° phased control | Reduces input capacitance requirements by ~50% and lowers RMS input ripple current versus single-phase designs. |
| Configurable topology | Supports 3× single-phase, 2+1 dual+single, or true 3-phase output - enabling flexible rail partitioning for mixed-voltage SoCs. |
| Pre-biased output startup | Allows safe turn-on into pre-charged outputs without reverse current flow, critical for hot-swap and power-sequencing applications. |
| Output overvoltage protection | Detects VFB excursion beyond ±7.5% and asserts PGOOD low within 17µs, preventing damage to downstream logic or memory. |
| Independent soft-start/tracking | Each channel's TK/SS pin supports unique ramp rates or precise voltage tracking (e.g., 1.2V core following 3.3V IO). |
Applications
| Server VRM | Telecom Intermediate Bus |
|---|---|
|
Use Scenario: Powering multi-rail processors and memory interfaces in 1U rack servers with strict thermal and space constraints. IC Role / Device Role / Timing Role: Triple-output controller managing CPU core (1.2V), SOC IO (3.3V), and DDR termination (1.35V) with synchronized 120° phasing. Use Value: Reduces input capacitor count by 40% and lowers system-level conducted EMI, easing compliance with CISPR 32 Class A limits. |
Use Scenario: Converting 48V backplane to 12V/5V/3.3V distribution in carrier-grade base station power shelves. IC Role / Device Role / Timing Role: High-reliability controller delivering stable intermediate rails with H-grade thermal margin for uncooled chassis operation. Use Value: Enables use of smaller magnetics and ceramics due to 750kHz max switching frequency, reducing board area by 22% vs. 300kHz alternatives. |
| FPGA Power Sequencing | Industrial PLC I/O Module |
|
Use Scenario: Supplying configurable logic, transceivers, and auxiliary rails in Xilinx/Intel FPGA-based edge AI accelerators. IC Role / Device Role / Timing Role: Independent RUN and TK/SS pins allow precise power-up order (e.g., configuration voltage before core) and voltage tracking. Use Value: Eliminates need for external sequencers or supervisors, reducing BOM cost and improving startup repeatability across temperature. |
Use Scenario: Providing isolated 5V, 3.3V, and 12V rails for microcontroller, analog front-end, and fieldbus interface in factory automation controllers. IC Role / Device Role / Timing Role: H-grade rating and robust current foldback protect against short-circuits in harsh industrial environments with wide ambient swings. Use Value: Maintains regulation during 100ms brownouts (via EXTVCC option) and survives 150°C junction temperatures without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3855IUJ#PBF | Same pinout, wider VIN (4.5V–38V), integrated MOSFET drivers with higher current (±4A), but no H-grade option. | Better suited for 24V/36V industrial inputs; lacks 150°C junction rating for under-hood or high-ambient deployments. | Select when input exceeds 24V or higher gate drive current is needed; avoid where extended temperature validation is required. |
| MP8770GL-Z | Single-chip triple controller (no external MOSFETs), lower IQ (2.5mA), but fixed 500kHz frequency and no PLL sync capability. | Targets cost-sensitive consumer electronics; lacks independent channel control, tracking, and H-grade qualification. | Choose for compact, low-cost designs with fixed frequency and no sequencing complexity; not suitable for mission-critical thermal environments. |
Compared with LTC3853HUJ#PBF, LTC3855IUJ#PBF extends input range and drive strength but sacrifices high-temperature assurance, while MP8770GL-Z integrates power stages at the expense of configurability and thermal ruggedness - making LTC3853HUJ#PBF optimal for thermally demanding, multi-rail industrial and telecom systems requiring field-proven H-grade reliability.
Availability
LTC3853HUJ#PBF is available at Aetrix Electronics and suitable for server VRMs, telecom power shelves, and industrial PLCs requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LTC3853HUJ#PBF 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 full product support, documentation, and manufacturing continuity for the LTC portfolio.
The LTC3853 belongs to Linear's high-performance polyphase controller family, designed specifically for high-density, multi-rail DC/DC conversion in datacenter, communications, and industrial equipment where thermal resilience and precise sequencing are critical.
FAQ
What is the maximum output voltage supported by LTC3853HUJ#PBF on Channel 3?
LTC3853HUJ#PBF supports up to 13.5V on Channel 3, enabled by SENSE3+ and SENSE3– inputs rated for 14V common-mode voltage. This allows direct generation of higher-voltage rails like DDR VTT (1.35V), analog subsystems (5V/12V), or industrial I/O without post-regulation - verified across the full –40°C to 150°C junction temperature range for the H-grade variant.
How does the ILIM pin affect current limit behavior in LTC3853HUJ#PBF?
The ILIM pin on LTC3853HUJ#PBF selects one of three maximum current sense thresholds: 21 mV (ILIM = GND), 41 mV (ILIM = FLOAT), or 64 mV (ILIM = INTVCC) - all specified for H-grade operation. This directly scales the peak inductor current limit without changing external sense components, enabling flexible overcurrent protection tuning for different MOSFET RDS(on) or DCR values.
Can LTC3853HUJ#PBF operate with pre-biased outputs during startup?
Yes, LTC3853HUJ#PBF supports pre-biased output startup. Its current-mode architecture and reverse-current comparator (IREV) prevent negative inductor current flow, allowing safe turn-on into existing output voltages - confirmed in the Applications Information section and validated in typical circuits with 2V pre-bias conditions.
What thermal advantages does the H-grade rating provide for LTC3853HUJ#PBF?
LTC3853HUJ#PBF is guaranteed over –40°C to 150°C junction temperature, with full electrical specifications validated across this range. This eliminates derating in high-ambient environments (e.g., sealed industrial enclosures or automotive under-hood locations) and ensures reliable operation where standard E/I-grade parts would fail or require oversized heatsinking.
How is phase synchronization implemented on LTC3853HUJ#PBF?
LTC3853HUJ#PBF uses its MODE/PLLIN pin as a phase detector input and FREQ/PLLFLTR as the loop filter node to synchronize internal oscillators to an external clock. When an external signal is applied to MODE/PLLIN, the controller enters forced continuous mode and locks phase with jitter < ±1ns - enabling coherent multi-controller operation in large-scale power systems.
LTC3853HUJ#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 40-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 3
- Output Phases:
- 3
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 24V
- Frequency - Switching:
- 250kHz ~ 750kHz
- Duty Cycle (Max):
- 98%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 40-QFN (6x6)
LTC3853HUJ#PBF FAQ
1.How can I place an order for LTC3853HUJ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3853HUJ#PBF 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 LTC3853HUJ#PBF reliable?
The price and inventory of LTC3853HUJ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3853HUJ#PBF is usually 5 days.
3.What payment methods are accepted for LTC3853HUJ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3853HUJ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3853HUJ#PBF?
LTC3853HUJ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3853HUJ#PBF 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 LTC3853HUJ#PBF?
For technical support, including LTC3853HUJ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3853HUJ#PBF requirements.
6.How does Aetrix verify that LTC3853HUJ#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3853HUJ#PBF 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 LTC3853HUJ#PBF meets industry standards.
7.What is the process for return or replacement of LTC3853HUJ#PBF?
All LTC3853HUJ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3853HUJ#PBF, 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 LTC3853HUJ#PBF part is unused and in its original packaging.
Return procedure for LTC3853HUJ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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