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Analog Devices Inc. LTC3871HLXE#PBF
- Part No.:
- LTC3871HLXE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 48-LQFP Exposed Pad
- Datasheet:
-
LTC3871HLXE#PBF.pdf
- Description:
- IC REG CTRLR BCK/BST SYN 48LQFP
- Quantity:
- Payment:
- Shipping:
Inventory:3,584
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Product details
Overview
LTC3871HLXE#PBF from Analog Devices is a high-performance bidirectional polyphase synchronous buck/boost controller designed for 48V/12V dual-battery automotive systems. It regulates in buck mode (VHIGH→VLOW) or boost mode (VLOW→VHIGH) on demand, supports up to 100V VHIGH and 30V VLOW input ranges, delivers ±1% voltage regulation accuracy over temperature, and features programmable current limits with DCR/RSENSE sensing.
For engineers reviewing the LTC3871HLXE#PBF datasheet, LTC3871HLXE#PBF pinout, LTC3871HLXE#PBF application, or LTC3871HLXE#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed automotive-grade thermal specs (–40°C to 150°C), and real-world bidirectional power conversion use cases in backup power and battery energy transfer systems.
Technical Context
The LTC3871HLXE#PBF implements a proprietary constant-frequency current-mode architecture with independent buck and boost control loops, enabling seamless bidirectional energy flow between two voltage domains. It uses dual current-sense paths (SNSA+/SNSD+) for low-DCR inductor sensing and supports both valley-current (boost) and peak-current (buck) modulation schemes.
Its phase-lockable oscillator operates from 60kHz to 460kHz, supports up to 12-phase multiphase operation via CLKOUT/SYNC, and integrates independent loop compensation networks for buck and boost modes. The device includes dedicated OV/UV monitors for both VHIGH and VLOW rails, programmable current limit foldback (LTC3871 variant), and thermally enhanced 48-lead LQFP packaging qualified per AEC-Q100 Grade H.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VHIGH Range | 5V to 100V - supports wide-input 48V automotive bus with headroom for transients. |
| VLOW Range | 1.2V to 30V - compatible with 12V battery, auxiliary rails, and intermediate bus converters. |
| Voltage Regulation Accuracy | ±1% over –40°C to 150°C - ensures stable output under extreme automotive thermal conditions. |
| Switching Frequency Range | 60kHz to 460kHz - adjustable via FREQ pin resistor; enables optimization of efficiency vs. size. |
| Current Sense Threshold | 10mV to 58.5mV (programmable via ILIM) - supports accurate current limiting with low-DCR inductors or RSENSE. |
| Operating Junction Temp | –40°C to 150°C - AEC-Q100 Grade H qualification for under-hood automotive deployment. |
| Package | 48-lead 7mm × 7mm LQFP with exposed GND pad - optimized thermal resistance (θJA = 36°C/W). |
Pinout & Package
Package: 48-lead plastic LQFP (7mm × 7mm), exposed GND pad (Pin 49), RoHS-compliant, thermally enhanced for automotive-grade reliability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SS (1) | Soft-start ramp input | 1.25µA internal pull-up sets controlled VLOW/VHIGH ramp rate; capacitor-to-ground enables inrush control. |
| VFBLOW (2) | VLOW feedback inverting input | Connects to resistive divider from VLOW; compares against 1.200V reference for regulation. |
| ITHLOW/ITHHIGH (3,4) | Buck/boost current threshold control | Programs max current limit in each mode; ITHLOW = 1.5V for buck, ITHHIGH = 0.5V for boost. |
| VFBHIGH (5) | VHIGH feedback inverting input | Connects to resistive divider from VHIGH; references same 1.200V bandgap for bidirectional stability. |
| V5 (6) | Internal 5.5V regulator output | Powers internal logic; requires ≥4.7µF low-ESR bypass to SGND for noise immunity. |
| SGND (7,28) | Signal ground reference | Low-noise return for feedback, sense, and control circuits; must be star-connected to exposed pad. |
| OVHIGH/UVHIGH (8,9) | VHIGH overvoltage/undervoltage set | Resistor dividers set 1.2V trip points; 5µA hysteresis current enables precise, adjustable fault thresholds. |
| IMON (11) | Average current monitor output | 1.25V = zero average inductor current; scales linearly (38V/V or 19V/V) for system-level current telemetry. |
| SETCUR (12) | Initial current limit programming | Sources 7.5µA to external resistor; sets baseline current limit before ITH-based dynamic adjustment. |
| SNSA1+/SNSD1+ (13,15) | Channel 1 AC/DC current sense inputs | Separate paths enable high-SNR DCR sensing: SNSA+ captures fast AC component, SNSD+ tracks DC. |
| BUCK (16) | Mode selection control | Float or tie to V5 → buck mode; ground → boost mode - direct hardware-selectable directionality. |
| RUN (18) | Enable control input | 1.22V threshold with 80mV hysteresis; internal 2µA→6.5µA pull-up enables controlled startup sequencing. |
| DRVSET (20) | DRVCC output voltage programming | Selects DRVCC level (6V–10V in 1V steps) to optimize gate drive strength and MOSFET switching loss. |
| TG1/TG2 (22,39) | Top gate driver outputs | Floating drivers with 5Ω pull-up / 2.5Ω pull-down; swing = DRVCC + SW voltage for high-side N-MOSFETs. |
| SW1/SW2 (23,38) | Switch node connections | Direct connection to inductor center taps; handles rail-to-rail voltage swing (ground to VHIGH). |
| BOOST1/BOOST2 (24,37) | Bootstrap supply terminals | Charge path for floating top-gate drivers; swings from DRVCC–diode-drop to VHIGH+DRVCC. |
| BG1/BG2 (25,36) | Bottom gate driver outputs | Drives low-side N-MOSFET gates between PGND and DRVCC; matched 5Ω/2.5Ω on-resistance. |
| PGND1/PGND2 (26,35) | Power ground returns | High-current return for bottom MOSFET sources and bootstrap capacitor negatives; must tie to local PGND plane. |
| EXTVCC (27) | External gate driver supply input | Bypasses VHIGH-powered LDO when > (DRVCC – 0.5V); enables efficient use of auxiliary 12V rail for DRVCC. |
| DRVCC (29) | Gate driver LDO output | Programmable 6V–10V output; requires ≥4.7µF low-ESR bypass to PGND for stable high-current drive. |
| VHIGH (31) | Main high-voltage supply input | Primary power source for controller core and gate drivers; bypassed to PGND with 0.1–1µF ceramic. |
| PGATE (33) | Input short protection driver | Drives external PMOS high-side switch during UVHIGH fault; swings from VHIGH to VHIGH–15V. |
| CLKOUT (41) | Phase-locked clock output | Syncs multiple controllers; phase relative to CH1 set by PHSMD (0°–240°); rail-to-rail 5V logic swing. |
| SYNC (42) | External clock synchronization input | Accepts 60–460kHz external clock; internal PLL locks oscillator with integrated compensation network. |
| FREQ (43) | Frequency setting input | Resistor-to-SGND sets nominal frequency (e.g., 51.1kΩ → 200kHz); IFREQ = 20µA typical. |
| MODE (44) | Continuous/discontinuous mode control | SGND = forced CCM; float = DCM in buck / forced CCM in boost; V5 = DCM buck / non-sync boost. |
| PHSMD (45) | Phase mode selection | Configures CH1–CH2 (180°/120°) and CH1–CLKOUT phasing (0°–240°) via 5 voltage levels. |
| GND (49) | Exposed thermal pad | Mandatory PCB solder connection to system GND; primary thermal path and signal ground reference. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional buck/boost control | Hardware-selectable mode (BUCK pin) enables seamless energy transfer between 48V and 12V domains without firmware intervention. |
| Proprietary current-mode architecture | Dual-path (SNSA+/SNSD+) sensing achieves 14dB SNR improvement - enables <10mV current sense thresholds with low-DCR inductors. |
| Independent buck/boost loop compensation | Separate ITHLOW/ITHHIGH pins allow optimized transient response and stability for each power flow direction. |
| Automotive-grade thermal rating | –40°C to 150°C junction operation with AEC-Q100 qualification - validated for under-hood placement in dual-battery systems. |
| Programmable gate drive voltage | DRVSET pin selects DRVCC from 6V to 10V in 1V steps - balances MOSFET RDS(on) reduction against gate charge losses. |
| Multi-phase synchronization | CLKOUT/SYNC/PHSMD pins support up to 12-phase operation with precise phase alignment - reduces input/output ripple and EMI. |
Applications
| Automotive 48V/12V Dual Battery Systems | Backup Power Systems |
|---|---|
|
Use Scenario: Regulating power flow between a 48V starter-generator battery and a 12V accessory battery in mild-hybrid vehicles. IC Role / Device Role / Timing Role: Bidirectional controller managing buck (48V→12V) for infotainment loads and boost (12V→48V) for regenerative braking energy recovery. Use Value: Enables >97% synchronous rectification efficiency across both directions while maintaining ±1% voltage regulation under load transients. |
Use Scenario: Providing uninterrupted power to critical ECUs during main battery disconnect or deep discharge events. IC Role / Device Role / Timing Role: Boost converter drawing from 12V backup battery to maintain 48V rail integrity during engine cranking or cold-start conditions. Use Value: Programmable VHIGH UV/OV thresholds (pins 8,9) and fast fault response (<125µs FAULT assertion) ensure fail-safe operation. |
| High-Efficiency Bidirectional Charger | Energy Storage System (ESS) Interface |
|
Use Scenario: Charging a 48V Li-ion traction battery from a 12V lead-acid service battery in off-grid or marine applications. IC Role / Device Role / Timing Role: Precision current-regulated boost converter (12V→48V) with IMON-based telemetry for state-of-charge monitoring. Use Value: Accurate ±10% IMON current monitoring (pin 11) and programmable SETCUR/ITH limits enable safe, adaptive charging profiles. |
Use Scenario: Interfacing a 48V battery stack with a 12V DC bus in renewable microgrids or telecom backup systems. IC Role / Device Role / Timing Role: Bidirectional power manager transferring excess solar harvest from 48V storage to 12V loads or vice versa. Use Value: Phase-locked multi-controller operation (via SYNC/CLKOUT) ensures balanced current sharing across parallel modules. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional buck/boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MPQ4269-AEC1 | Single-channel, fixed 48V→12V buck-only topology; no boost capability; AEC-Q100 Grade 1 (–40°C to 125°C). | Limited to unidirectional 48V-to-12V conversion; cannot recover energy from 12V side or support backup boost. | Select only for cost-sensitive 48V→12V DC/DC where bidirectionality is unnecessary. |
| LTC3873HDE#PBF | Single-output, non-bidirectional polyphase buck controller; supports up to 60V input; no VLOW regulation or IMON output. | Designed for high-current 48V→12V step-down only; lacks VLOW feedback, BUCK/BOOST pin, or reverse power path. | Choose when only high-efficiency buck conversion is required and thermal margin exceeds 150°C. |
Compared with MPQ4269-AEC1 and LTC3873HDE#PBF, the LTC3871HLXE#PBF uniquely delivers full hardware-controlled bidirectionality, independent dual-loop regulation, and automotive-grade 150°C operation - making it the sole option for true 48V/12V energy recycling architectures.
Availability
LTC3871HLXE#PBF is available at Aetrix Electronics and suitable for automotive dual-battery systems, backup power supplies, and bidirectional energy storage interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3871HLXE#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, Inc. is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial, automotive, and communications markets.
The LTC3871 product line is engineered for high-reliability bidirectional DC/DC conversion in automotive and industrial energy management systems, emphasizing thermal robustness, noise-immune current sensing, and hardware-configurable power flow directionality.
FAQ
What is the maximum operating junction temperature for the LTC3871HLXE#PBF?
The LTC3871HLXE#PBF is rated for continuous operation from –40°C to 150°C junction temperature and is AEC-Q100 qualified for Grade H automotive applications. This specification is explicitly defined in the "ORDER INFORMATION" table of the datasheet, distinguishing it from lower-grade variants (e.g., LTC3871ELXE#PBF, rated to 125°C). Thermal derating applies above 125°C per Note 2.
How does the LTC3871HLXE#PBF implement bidirectional control without microcontroller intervention?
The LTC3871HLXE#PBF uses the hardware BUCK pin (Pin 16) to select direction: floating or tied to V5 enables buck mode (VHIGH→VLOW), while grounding enables boost mode (VLOW→VHIGH). No firmware or digital interface is required - mode selection is purely analog and immediate, supporting fail-safe operation in safety-critical automotive systems.
Can the LTC3871HLXE#PBF support both DCR and RSENSE current sensing simultaneously?
No - the LTC3871HLXE#PBF supports either DCR-based sensing (using SNSA+/SNSD+ with matched RC filters) or RSENSE-based sensing (SNSD+ connected directly to resistor), but not both concurrently. The choice is determined by circuit layout and filter design per Figures 3 and 4 in the datasheet; mixing configurations compromises accuracy and noise rejection.
What is the purpose of the IMON pin on the LTC3871HLXE#PBF, and how is its output scaled?
The IMON pin (Pin 11) outputs a voltage proportional to the average inductor current across both channels, with 1.25V representing zero current. Its gain is programmable: 38V/V when VILIM = 0V or 1/4 VV5, and 19V/V when VILIM = 3/4 VV5 or VV5. This enables system-level current telemetry without external amplifiers, directly usable by ADCs or monitoring ICs.
Does the LTC3871HLXE#PBF require external components for phase synchronization across multiple ICs?
No - the LTC3871HLXE#PBF integrates all necessary PLL compensation circuitry internally. Connecting the SYNC pin of slave devices to the CLKOUT pin of a master LTC3871HLXE#PBF achieves full synchronization without external op-amps, capacitors, or resistors. Phase offset between channels is controlled solely by the PHSMD pin voltage level.
LTC3871HLXE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 48-LQFP Exposed Pad
- Packaging:
- Tray
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up, Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck, Boost
- Number of Outputs:
- 2
- Output Phases:
- Programmable
- Voltage - Supply (Vcc/Vdd):
- 1.2V ~ 100V
- Frequency - Switching:
- 60kHz ~ 460kHz
- Duty Cycle (Max):
- 98%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Phase Control, Soft Start
- Operating Temperature:
- -40°C ~ 150°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 48-eLQFP (7x7)
LTC3871HLXE#PBF FAQ
1.How can I place an order for LTC3871HLXE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3871HLXE#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 LTC3871HLXE#PBF reliable?
The price and inventory of LTC3871HLXE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3871HLXE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3871HLXE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3871HLXE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3871HLXE#PBF?
LTC3871HLXE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3871HLXE#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 LTC3871HLXE#PBF?
For technical support, including LTC3871HLXE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3871HLXE#PBF requirements.
6.How does Aetrix verify that LTC3871HLXE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3871HLXE#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 LTC3871HLXE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3871HLXE#PBF?
All LTC3871HLXE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3871HLXE#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 LTC3871HLXE#PBF part is unused and in its original packaging.
Return procedure for LTC3871HLXE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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