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Analog Devices Inc. LTC3856IUH#TRPBF
- Part No.:
- LTC3856IUH#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3856IUH#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,611
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Product details
Overview
LTC3856IUH#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, polyphase synchronous step-down DC/DC controller driving all-N-channel MOSFET stages for high-current 1.5V/50A power delivery. It features true remote differential voltage sensing, DCR temperature-compensated current monitoring, and phase-lockable 250–770kHz operation across a 4.5V–38V input range - deployed in telecom intermediate bus converters and server VRMs.
For engineers reviewing the LTC3856IUH#TRPBF datasheet, LTC3856IUH#TRPBF pinout, LTC3856IUH#TRPBF application, or LTC3856IUH#TRPBF equivalent, key selection criteria include its ±0.75% 0.6V reference accuracy, dual-phase interleaved timing control, AVP-enabled load-line regulation, and QFN-32 package thermal performance at 125°C junction temperature.
Technical Context
The LTC3856IUH#TRPBF implements a constant-frequency current-mode architecture with independent per-channel peak-current sensing via RSENSE or DCR networks, where ITH voltage directly sets the current threshold. Its differential amplifier (ADA = 0.997–1.003 V/V, PSRR = 100dB) enables precise remote sense with <2mV offset, supporting active voltage positioning (AVP) when used with the DIFFP/DIFFN/DIFFOUT signal chain.
Phase management includes programmable CLKOUT phasing (60°/90°/120° via PHASMD), PLLIN synchronization, and stackable up to 12-phase operation. Burst Mode®, Stage Shedding™, and forced continuous modes are selected via MODE pin logic, while ILIM pin configures three-tier current-sense thresholds (23–84mV) for I-grade operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 38V - supports 5V, 12V, and 24V intermediate bus systems without external regulators. |
| Output Voltage Range | 0.6V to 3.3V with differential amplifier - enables tight-regulation CPU/GPU core supplies with remote sense compensation. |
| Reference Accuracy | ±0.75% at 0.6V - ensures output stability within ±11.25mV at 1.5V under full temperature range (–40°C to 125°C). |
| Switching Frequency | 250kHz to 770kHz, phase-lockable - allows EMI spread-spectrum tuning and multi-phase synchronization across boards. |
| Current Sensing | RSENSE or DCR with programmable tempco - maintains ±5% current limit accuracy over –40°C to 125°C via ITEMP bias current (9–11µA). |
| Thermal Rating | 125°C max junction temperature, θJA = 34°C/W (QFN-32) - requires minimum 4cm² exposed pad copper for rated 50A two-phase operation. |
| Driver Strength | TG RDS(ON) = 2.6Ω (high), BG RDS(ON) = 1.1Ω (low) - drives 30A+ N-MOSFET gates with <30ns transition times at 3300pF load. |
Pinout & Package
Package: 32-pin (5mm × 5mm) plastic QFN with exposed SGND/PGND pad (Pin 33), RoHS-compliant, reflow-compatible (260°C peak).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TK/SS (Pin 1) | Soft-start & tracking control | 1.25µA internal current charges external capacitor for linear VOUT ramp; accepts master supply voltage for rail tracking. |
| VFB (Pin 2) | Error amplifier feedback input | Compares divided output voltage against 0.6V reference; accepts signal from DIFFOUT or direct resistor divider. |
| ITH (Pin 3) | Current threshold & compensation node | Directly sets per-phase peak inductor current; connects to EA output and RC network for loop stability. |
| AVP (Pin 4) | Active voltage positioning slope control | Resistor to DIFFP sets load-line droop (e.g., 0.5mΩ for 1.5V/50A); only functional with differential amplifier enabled. |
| ITEMP (Pin 5) | DCR temperature compensation input | Biases external NTC thermistor; adjusts current limit vs. board temperature to prevent thermal runaway. |
| PHASMD (Pin 6) | CLKOUT phase select | GND/INTVCC/floating selects 60°/120°/90° clock phase for synchronized multi-phase stacking. |
| DIFFP (Pin 9) | Differential amp positive input | Must connect directly to remote load point (e.g., CPU VDD); defines sense reference for AVP and precision regulation. |
| DIFFN (Pin 10) | Differential amp negative input | Connects to local ground plane near output capacitors; completes Kelvin sense path for noise immunity. |
| DIFFOUT (Pin 11) | Differential amp output | Drives VFB through resistive divider; enables remote sensing without adding gain error from PCB trace resistance. |
| ISET (Pin 12) | Stage shedding & burst mode threshold | Resistor to GND programs current foldback point and light-load efficiency mode activation level. |
| ILIM (Pin 13) | Current sense threshold scaling | GND/FLOAT/INTVCC selects 23/50/75mV max sense voltage - matches MOSFET RDS(ON) or DCR value. |
| MODE (Pin 14) | Operating mode control | GND = forced continuous, INTVCC = stage shedding, floating = Burst Mode® - determines light-load efficiency strategy. |
| PGOOD (Pin 15) | Power-good open-drain output | Asserts low after 20µs delay when VOUT deviates >±10% from setpoint - used for system sequencing and fault reporting. |
| SW1/SW2 (Pins 16/26) | Switch node connections | High dv/dt nodes tied to inductor ends; require tight layout to minimize EMI and gate drive ringing. |
| TG1/TG2 (Pins 17/25) | Top gate drivers | Floating outputs referenced to SWx; drive high-side N-MOSFET gates using bootstrap capacitors (CB). |
| BOOST1/BOOST2 (Pins 18/24) | Bootstrap supply inputs | Accept boot capacitor (+) terminals; swing from ~4.3V below INTVCC to VIN + INTVCC during switching. |
| BG1/BG2 (Pins 19/23) | Bottom gate drivers | Ground-referenced outputs driving low-side N-MOSFET gates; fast turn-on/off (<25ns) minimizes conduction loss. |
| VIN (Pin 22) | Main input supply | 4.5–38V primary power input; requires local 0.1µF ceramic + bulk capacitance decoupling to PGND. |
| INTVCC (Pin 21) | Internal 5V regulator output | Powers control circuitry; must be decoupled with ≥4.7µF low-ESR capacitor to PGND. |
| EXTVCC (Pin 20) | External bias input | Enables bypass of internal LDO when >4.7V applied - improves efficiency in high-current designs. |
| SENSE1+/SENSE1– (Pins 31/32) | Channel 1 current sense inputs | Accept Kelvin connection to DCR network or sense resistor; ±1µA bias current limits trace impedance impact. |
| SENSE2+/SENSE2– (Pins 7/8) | Channel 2 current sense inputs | Independent second channel with identical specs; enables true dual-phase current balancing. |
| PLLIN (Pin 28) | External clock sync input | Accepts 100kHz–1MHz square wave to lock oscillator frequency and phase - critical for multi-rail coherence. |
| CLKOUT (Pin 27) | Synchronized clock output | Provides phase-adjustable clock for cascading LTC3856ICs or coordinating external controllers. |
| RUN (Pin 30) | Enable/disable control | 1.22V threshold with 80mV hysteresis; internal 1µA pull-up enables simple RC soft-start sequencing. |
| FREQ (Pin 29) | Oscillator frequency setting | Resistor to GND or DC voltage (0–2.4V) programs 210–850kHz range - supports dynamic frequency scaling. |
| SGND/PGND (Pin 33) | Exposed thermal pad | Mandatory solder connection to PCB ground plane; provides primary thermal path and low-inductance return for power loops. |
Key Features
| Feature | Design Value |
|---|---|
| PolyPhase® dual-channel interleaving | Reduces input/output ripple current by 50% vs. single-phase, cutting required bulk capacitance by 75% in 50A designs. |
| True remote differential sensing | Compensates for up to 100mV IR drop across PCB traces, enabling ±0.5% regulation at point-of-load without calibration. |
| Programmable Active Voltage Positioning (AVP) | Generates controlled VOUT droop (e.g., 10mV/A) to improve transient response and prevent current hogging in parallel VRMs. |
| DCR temperature compensation | Maintains ±5% current limit accuracy from –40°C to 125°C using external NTC, eliminating need for costly sense resistors. |
| Stackable up to 12-phase operation | Enables scalable 100A+ power delivery using multiple LTC3856IUH#TRPBF ICs with automatic phase alignment via CLKOUT/PLLIN. |
| Three light-load efficiency modes | Burst Mode® (discontinuous), Stage Shedding™ (1→2 phase), or forced continuous - selectable per design trade-off between noise and efficiency. |
Applications
| Telecom Intermediate Bus Converter | Data Center Server VRM |
|---|---|
Use Scenario: 48V-to-12V conversion feeding downstream POL modules in 5G base station power shelves. IC Role / Device Role / Timing Role: Dual-phase controller managing 60A total output with interleaved switching to reduce EMI and input capacitor stress. Use Value: 95% peak efficiency at 50A and 40V input enables passive cooling in space-constrained outdoor enclosures. | Use Scenario: 12V input to 1.5V/50A CPU core supply with strict ±15mV regulation window and <10µs transient response. IC Role / Device Role / Timing Role: Primary VRM controller implementing AVP, remote sensing, and phase shedding to match dynamic CPU load profiles. Use Value: Differential amplifier + AVP delivers ±0.3% load regulation and 30% faster load-step recovery vs. non-AVP solutions. |
| Industrial PLC Power Module | Medical Imaging System PSU |
Use Scenario: 24V battery-backed power supply for programmable logic controllers requiring high reliability and wide temp operation. IC Role / Device Role / Timing Role: Dual-phase buck controller with DCR current sensing and ITEMP-based thermal derating for fanless operation. Use Value: –40°C to 125°C guaranteed operation and 0.75% reference accuracy ensure consistent performance across factory floor environments. | Use Scenario: Precision 3.3V/20A auxiliary supply for FPGA and ADC subsystems in MRI scanner front-end electronics. IC Role / Device Role / Timing Role: Synchronous step-down controller with ultra-low noise Burst Mode® and remote sense for analog signal integrity. Use Value: <10mVpp output ripple in Burst Mode® and 100dB PSRR suppress switching noise coupling into sensitive imaging circuits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2940AGQ-DC | Integrated MOSFET drivers only; no differential amplifier or AVP; 4.5–16V input; 30A max per phase. | Targeted at cost-sensitive industrial SMPS; lacks remote sensing and load-line control for high-end computing. | Select MP2940AGQ-DC when board space and BOM count are prioritized over precision load regulation and thermal robustness. |
| ISL9123IRZ-T | Single-channel, integrated power stage (25A); no phase stacking; 2.5–5.5V input; no DCR sensing or PLL sync. | Designed for portable SoC power rails; incompatible with multi-phase or high-input-voltage telecom/server use cases. | Choose ISL9123IRZ-T only for compact, low-power embedded applications where dual-phase scalability is unnecessary. |
Compared with MP2940AGQ-DC and ISL9123IRZ-T, the LTC3856IUH#TRPBF uniquely combines differential remote sensing, AVP, DCR temperature compensation, and 12-phase stackability - making it the sole option for high-accuracy, high-current, thermally demanding server and telecom VRMs.
Availability
LTC3856IUH#TRPBF is available at Aetrix Electronics and suitable for telecom intermediate bus converters, data center server VRMs, and industrial PLC power modules requiring stable component supply, long-term lifecycle support, and guaranteed –40°C to 125°C operation.
Supply support for LTC3856IUH#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 power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3856IUH#TRPBF belongs to Linear's PolyPhase® controller family, engineered specifically for high-efficiency, multi-phase DC/DC conversion in computing, networking, and industrial infrastructure where precision regulation and thermal resilience are critical.
FAQ
What is the maximum supported input voltage for the LTC3856IUH#TRPBF?
The LTC3856IUH#TRPBF has an absolute maximum input voltage rating of 40V on the VIN pin, but its specified operating range is 4.5V to 38V. Operation above 38V risks violating the recommended conditions in the datasheet and may compromise long-term reliability or cause premature failure. Always observe the 4.5–38V functional range for guaranteed performance across temperature.
Does the LTC3856IUH#TRPBF support remote voltage sensing with the differential amplifier?
Yes, the LTC3856IUH#TRPBF supports true remote sensing via its dedicated differential amplifier (DIFFP/DIFFN/DIFFOUT pins). This circuit achieves 0.997–1.003 V/V gain and <2mV offset, enabling accurate regulation at the load point despite PCB trace resistance. The amplifier must be used with the AVP function when load-line droop is required.
How does the ILIM pin affect current limit configuration on the LTC3856IUH#TRPBF?
The ILIM pin on the LTC3856IUH#TRPBF selects one of three maximum current sense thresholds: grounding sets 23mV (I-grade), floating sets 50mV, and connecting to INTVCC sets 75mV. This directly scales the peak inductor current trip point for both channels, allowing optimization for different MOSFET RDS(ON) or DCR values without changing sense resistor networks.
Can the LTC3856IUH#TRPBF be synchronized to an external clock source?
Yes, the LTC3856IUH#TRPBF supports external synchronization via the PLLIN pin, which accepts a 100kHz–1MHz square wave to lock the internal oscillator frequency and phase. This capability is essential for reducing beat frequencies in multi-rail systems and enabling deterministic timing across stacked controllers in 12-phase configurations.
What thermal considerations apply to the LTC3856IUH#TRPBF in high-current applications?
The LTC3856IUH#TRPBF uses a 32-pin QFN package with θJA = 34°C/W. For reliable 50A dual-phase operation, the exposed SGND/PGND pad (Pin 33) must be fully soldered to ≥4cm² of inner-layer copper pour. Thermal vias (≥8×0.3mm) to internal ground planes are mandatory to maintain TJ ≤ 125°C under full load and ambient temperatures up to 85°C.
LTC3856IUH#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 32-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):
- 94%
- 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:
- 32-QFN (5x5)
LTC3856IUH#TRPBF FAQ
1.How can I place an order for LTC3856IUH#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3856IUH#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 LTC3856IUH#TRPBF reliable?
The price and inventory of LTC3856IUH#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3856IUH#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3856IUH#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3856IUH#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3856IUH#TRPBF?
LTC3856IUH#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3856IUH#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 LTC3856IUH#TRPBF?
For technical support, including LTC3856IUH#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3856IUH#TRPBF requirements.
6.How does Aetrix verify that LTC3856IUH#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3856IUH#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 LTC3856IUH#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3856IUH#TRPBF?
All LTC3856IUH#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3856IUH#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 LTC3856IUH#TRPBF part is unused and in its original packaging.
Return procedure for LTC3856IUH#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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