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Analog Devices Inc. LTC3856IFE#TRPBF
- Part No.:
- LTC3856IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3856IFE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,083
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Product details
Overview
LTC3856IFE#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 - deployed in telecom intermediate bus converters requiring tight regulation and low noise.
For engineers reviewing the LTC3856IFE#TRPBF datasheet, LTC3856IFE#TRPBF pinout, LTC3856IFE#TRPBF application, or LTC3856IFE#TRPBF equivalent, this page delivers verified technical context on dual-phase interleaving, AVP load-line control, Burst Mode vs Stage Shedding trade-offs, and TSSOP-38 thermal design constraints - all grounded in Linear's official LTC3856 datasheet Rev. FA.
Technical Context
The LTC3856IFE#TRPBF implements a constant-frequency current-mode architecture with two independent PWM channels operating up to 180° out-of-phase to reduce input/output ripple and EMI. Its differential amplifier (gain = 0.997–1.003 V/V, PSRR = 100dB) enables ±0.75% output accuracy over temperature via remote sense at the load.
Current sensing supports both RSENSE and DCR methods, with programmable ILIM pin selection (GND/FLOAT/INTVCC) setting max sense thresholds of 23–84mV (I-grade). The ISET pin configures either Burst Mode threshold or Stage Shedding current limit, while PHASMD selects CLKOUT phase (60°/90°/120°) for multi-IC synchronization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4.5V to 38V - supports 5V, 12V, and 24V intermediate bus systems without external pre-regulation. |
| VOUT Range | 0.6V to 3.3V with differential sense - enables precise core voltage regulation for FPGAs and ASICs with AVP load-line compliance. |
| fSW Range | 250kHz to 770kHz - adjustable via FREQ pin resistor; phase-lockable to external clock via PLLIN for synchronized multi-phase systems. |
| Reference Accuracy | ±0.75% at 0.6V - ensures ≤±7.5mV error at 1V output, critical for sub-1V CPU/GPU rails. |
| Current Sense | RSENSE or DCR with tempco compensation - maintains stable current limit across –40°C to 125°C junction range. |
| Efficiency | Up to 95% at 1.5V/50A - achieved via low-RDS(ON) gate drivers (TG RDOWN = 1.5Ω, BG RDOWN = 1.1Ω) and interleaved phase shedding. |
| Package | 38-pin TSSOP (FE) with exposed SGND/PGND pad - θJA = 25°C/W; requires PCB thermal vias for >3W dissipation. |
Pinout & Package
Package: 38-lead plastic TSSOP (FE), 12.5mm × 6.1mm × 1.1mm, exposed pad (Pin 39) soldered to SGND/PGND for thermal and electrical integrity. θJA = 25°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TG1, TG2 | Top gate drivers | Floating N-channel gate outputs; swing from SW node + INTVCC; drive high-side MOSFET gates with 25ns rise/fall time. |
| BG1, BG2 | Bottom gate drivers | N-channel gate outputs referenced to PGND; 25ns transition time; enable synchronous rectification with minimal dead-time loss. |
| SENSE1+, SENSE1− SENSE2+, SENSE2− |
Current sense inputs | Differential inputs for DCR or RSENSE networks; ±1µA bias current; support programmable max threshold (23–84mV). |
| DIFFP, DIFFN, DIFFOUT | Remote sense differential amplifier | True Kelvin sense interface: DIFFP connects to load VOUT, DIFFN to output cap ground, DIFFOUT feeds VFB via divider for ±0.75% accuracy. |
| TK/SS | Soft-start/tracking input | 1.25µA internal pull-up charges external capacitor for linear VOUT ramp; also accepts master supply tracking signal. |
| AVP | Active Voltage Positioning | Programs load-line slope (up to 2.5V drop) when used with DIFFAMP; sinks 250µA / sources 2mA for precise droop control. |
| MODE | Operating mode select | GND = forced continuous; FLOAT = Burst Mode; INTVCC = Stage Shedding - determines light-load efficiency strategy. |
| ILIM | Current limit range | Selects max sense voltage: GND = 23mV, FLOAT = 50mV, INTVCC = 84mV (I-grade) - sets foldback threshold for overload protection. |
Key Features
| Feature | Design Value |
|---|---|
| PolyPhase® dual-channel interleaving | Reduces input RMS current by ~70% and output voltage ripple by ~50% vs single-phase, enabling smaller bulk capacitors and lower EMI filter cost. |
| Programmable Stage Shedding™ | Automatically transitions between 1-phase and 2-phase operation based on load current - extends high-efficiency zone down to <5A without Burst Mode noise. |
| True remote differential sensing | Compensates for PCB IR drop up to 100mV; maintains ±0.75% regulation at point-of-load even with 200mΩ trace resistance. |
| Active Voltage Positioning (AVP) | Generates controlled output droop (VOUT ∝ ILOAD) to prevent current hogging in parallel VRMs and improve transient response stability. |
| DCR temperature compensation | Uses ITEMP pin and external NTC to adjust current sense gain - holds ±5% current limit accuracy across –40°C to 125°C ambient. |
Applications
| Telecom Intermediate Bus Converter | Data Center ASIC Core Supply |
|---|---|
Use Scenario: 12V-to-1.5V conversion delivering 50A to FPGA or network processor with strict <±1% regulation and <10mV ripple. IC Role / Device Role / Timing Role: Dual-phase synchronous buck controller managing interleaved gate timing, current sharing, and remote voltage feedback. Use Value: Interleaving cuts input capacitor RMS current by 70%, reducing 1206 ceramic count from 16 to 6; AVP prevents current imbalance during load transients. |
Use Scenario: High-density server motherboard supplying 0.8V/60A to CPU cores with dynamic voltage scaling and rapid load steps. IC Role / Device Role / Timing Role: PolyPhase controller executing Stage Shedding to maintain >90% efficiency from 5A to full load, synchronized to system clock via PLLIN. Use Value: Stage Shedding eliminates Burst Mode switching noise during light loads while preserving fast transient response - critical for cache-sensitive workloads. |
| Industrial PLC Power Module | Medical Imaging System DC-DC |
Use Scenario: 24V industrial input converted to isolated 3.3V/10A and 1.2V/25A rails in space-constrained DIN-rail enclosure with convection cooling only. IC Role / Device Role / Timing Role: Primary controller for main 1.2V rail; coordinates with secondary controller via CLKOUT/PLLIN for 4-phase total operation. Use Value: Wide 4.5–38V VIN range accommodates brownout conditions; DCR sensing avoids sense resistor power loss in thermally limited enclosures. |
Use Scenario: MRI subsystem requiring ultra-low-noise 1.8V/30A supply with <10µV RMS ripple and guaranteed startup under cold ambient (–40°C). IC Role / Device Role / Timing Role: Dual-channel controller using differential sense and AVP to meet IEC 60601-1 EMI and safety isolation requirements. Use Value: Differential amplifier rejects common-mode noise from gradient coil switching; ±0.75% reference accuracy ensures consistent ADC reference stability. |
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-PR | 4.5–16V VIN, integrated MOSFETs (30A per phase), no DCR tempco, fixed 500kHz fSW | Suitable for compact 12V-input systems where board space > efficiency optimization; lacks remote sense and AVP. | Choose MP2940AGQ-PR for cost-sensitive, lower-power (<30A) designs where integrated FETs simplify layout but remote sensing is not required. |
| ISL95812IRZ | 4.5–24V VIN, supports 3-phase stacking, no differential amplifier, ±1% VREF accuracy | Targeted at laptop VRMs with Intel IMVP-8 compliance; lacks Stage Shedding and AVP but offers SMBus telemetry. | Choose ISL95812IRZ when digital interface (SMBus/PMBus), 3-phase scalability, or IMVP-8 compliance outweigh need for AVP and remote sense precision. |
Compared with MP2940AGQ-PR and ISL95812IRZ, the LTC3856IFE#TRPBF uniquely combines wide VIN (4.5–38V), true differential remote sensing, AVP, and programmable Stage Shedding - making it optimal for high-reliability telecom and industrial 2-phase systems demanding ±0.75% regulation and thermal robustness.
Availability
LTC3856IFE#TRPBF is available at Aetrix Electronics and suitable for telecom intermediate bus converters, data center ASIC core supplies, and industrial PLC power modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3856IFE#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 full product support, datasheet documentation, and application engineering for legacy Linear parts including the LTC3856 series.
The LTC3856 belongs to Linear's high-performance PolyPhase® controller family, designed specifically for high-current, low-voltage DC/DC conversion in infrastructure equipment where efficiency, thermal management, and multi-phase synchronization are critical.
FAQ
What is the maximum output current supported by the LTC3856IFE#TRPBF in a dual-phase configuration?
The LTC3856IFE#TRPBF itself does not set a hard current limit - it controls external N-channel MOSFETs. In typical 1.5V/50A designs (e.g., Linear's DC1707A demo board), each phase delivers ~25A continuously with proper thermal design. Peak current capability depends on MOSFET selection, inductor DCR, and PCB copper area. The controller's current sense threshold (up to 84mV for I-grade) and thermal shutdown via ITEMP ensure safe operation under overload.
Does the LTC3856IFE#TRPBF support both RSENSE and DCR current sensing, and how is DCR temperature compensation implemented?
Yes, the LTC3856IFE#TRPBF supports both methods. DCR compensation uses the ITEMP pin: an external NTC thermistor near the power inductor feeds temperature data to an internal circuit that adjusts the current sense gain. This maintains accurate current limiting across –40°C to 125°C, as confirmed in Electrical Characteristics Table (ITEMP = 9–11µA at VITEMP = 0.3V) and Figure 3856 G11.
How does Active Voltage Positioning (AVP) function on the LTC3856IFE#TRPBF, and what external components are required?
AVP on the LTC3856IFE#TRPBF generates a controlled output voltage droop proportional to load current. It requires connection between AVP and DIFFP pins via a resistor (e.g., 1kΩ for nominal slope). When enabled, AVP sinks 250µA or sources 2mA depending on SENSE+ voltage, creating a programmable load line up to 2.5V maximum drop. AVP only operates when the differential amplifier is active - i.e., DIFFP/DIFFN are properly connected.
What are the key differences between Burst Mode operation and Stage Shedding mode on the LTC3856IFE#TRPBF?
Burst Mode (MODE = float) pulses full 2-phase operation at low frequency during light loads, minimizing switching losses but introducing audible noise and higher output ripple. Stage Shedding (MODE = INTVCC) dynamically disables one phase below ~25% load, maintaining continuous conduction in the active phase - delivering >90% efficiency from 5A to 50A with no burst noise. Both are configured via the MODE pin and use the same ISET programming.
Is the LTC3856IFE#TRPBF pin-compatible with other variants like the LTC3856EUH#TRPBF, and what are the thermal implications of the TSSOP package?
No - the LTC3856IFE#TRPBF (38-pin TSSOP) and LTC3856EUH#TRPBF (32-pin QFN) have different pin counts, layouts, and thermal characteristics. The TSSOP package has θJA = 25°C/W (vs 34°C/W for QFN) but requires careful PCB layout: Pin 39 (exposed pad) must be soldered to a large SGND/PGND copper area with ≥6 thermal vias. Under 3W dissipation, junction temperature rise is ~75°C above ambient - necessitating airflow or heatsinking in sealed enclosures.
LTC3856IFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) 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:
- 38-TSSOP-EP
LTC3856IFE#TRPBF FAQ
1.How can I place an order for LTC3856IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3856IFE#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 LTC3856IFE#TRPBF reliable?
The price and inventory of LTC3856IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3856IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3856IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3856IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3856IFE#TRPBF?
LTC3856IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3856IFE#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 LTC3856IFE#TRPBF?
For technical support, including LTC3856IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3856IFE#TRPBF requirements.
6.How does Aetrix verify that LTC3856IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3856IFE#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 LTC3856IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3856IFE#TRPBF?
All LTC3856IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3856IFE#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 LTC3856IFE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3856IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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