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Analog Devices Inc. LTC3871ELXE#PBF
- Part No.:
- LTC3871ELXE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 48-LQFP Exposed Pad
- Datasheet:
-
LTC3871ELXE#PBF.pdf
- Description:
- IC REG CTRLR BCK/BST SYN 48LQFP
- Quantity:
- Payment:
- Shipping:
Inventory:249
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Product details
Overview
LTC3871ELXE#PBF from Analog Devices is a bidirectional polyphase synchronous buck/boost controller for 48V/12V dual-battery automotive systems, supporting VHIGH up to 100V and VLOW up to 30V, ±1% voltage regulation accuracy, and programmable current limits from 10mV to 50mV in buck or boost mode.
For engineers reviewing the LTC3871ELXE#PBF datasheet, LTC3871ELXE#PBF pinout, LTC3871ELXE#PBF application, or LTC3871ELXE#PBF equivalent, key selection criteria include bidirectional current programming, phase-lockable 60kHz–460kHz operation, AEC-Q100 qualification, independent buck/boost loop compensation, and thermally enhanced 48-lead LQFP package with exposed ground pad.
Technical Context
The LTC3871ELXE#PBF implements proprietary constant-frequency current mode control with separate peak-current (buck) and valley-current (boost) modulation schemes, enabling seamless bidirectional power transfer between VHIGH and VLOW rails. It features dual independent error amplifiers (EA_VHIGH, EA_VLOW), two current sensing paths (SNSA+/SNSD+ per channel), and programmable ITH thresholds for precise current regulation in both directions.
Its architecture supports multiphase synchronization across up to 12 phases via CLKOUT and SYNC pins, with selectable 180° or 120° inter-channel phasing controlled by PHSMD. The device integrates independent OV/UV monitors for both VHIGH and VLOW, programmable DRVCC (6V–10V) via DRVSET, and accurate IMON output proportional to average inductor current (±10% error at max current).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VHIGH Range | 5V to 100V - supports wide-input 48V automotive systems with headroom for transients. |
| VLOW Range | 1.2V to 30V - enables regulation of 12V battery rail or intermediate bus voltages. |
| Voltage Regulation Accuracy | ±1% over temperature - ensures stable output under thermal stress in engine bay environments. |
| Switching Frequency Range | 60kHz to 460kHz - adjustable via FREQ pin resistor or external SYNC clock for EMI optimization. |
| Current Sense Threshold | 10mV to 50mV (programmable via ILIM) - supports low-loss DCR or RSENSE sensing with high SNR. |
| Operating Junction Temp | –40°C to 125°C - qualified for under-hood automotive applications per AEC-Q100 Grade E. |
| Package | 48-lead 7mm × 7mm LQFP with exposed GND pad - provides θJA = 36°C/W for thermal management. |
Pinout & Package
Package: 48-lead plastic LQFP (7mm × 7mm), thermally enhanced with exposed GND pad (Pin 49) requiring PCB soldering for rated thermal performance (θJA = 36°C/W, TJMAX = 150°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SS (1) | Soft-start ramp input | 1.25µA internal pull-up sets output voltage slew rate; capacitor to SGND defines soft-start time. |
| VFBLOW (2) | VLOW feedback inverting input | Connects to resistive divider from VLOW; regulates VLOW to 1.200V reference with ±1% accuracy. |
| ITHLOW / ITHHIGH (3,4) | Buck/boost current threshold control | Programs peak (buck) or valley (boost) current limit; voltage determines comparator trip point. |
| VFBHIGH (5) | VHIGH feedback inverting input | Connects to resistive divider from VHIGH; regulates VHIGH to 1.200V reference with ±1% accuracy. |
| V5 (6) | Internal 5.5V regulator output | Powers internal logic; requires ≥4.7µF low-ESR bypass to SGND for stability. |
| SGND (7,28) | Signal ground reference | Low-noise return for feedback, sense, and compensation networks; connects to exposed GND pad. |
| OVHIGH / UVHIGH (8,9) | VHIGH overvoltage/undervoltage monitor inputs | Resistor dividers set 1.2V trip thresholds; 5µA hysteresis current enables adjustable window. |
| OVLOW (10) | VLOW overvoltage monitor input | Resistor divider sets 1.2V trip; sources 5µA hysteresis current when threshold exceeded. |
| IMON (11) | Average current monitor output | 1.25V = zero average inductor current; gain varies (19–38 V/V) based on VILIM setting. |
| SETCUR (12) | Initial current limit programming | Sources 7.5µA to set initial ITH voltage; used with external resistor for precise current limit calibration. |
| SNSA1+/SNSA2+ (13,48) | AC current sense inputs | Amplify high-frequency inductor current ripple; bandwidth matched to SNSD+ filter for DCR sensing. |
| SNS1–/SNS2– (14,47) | Negative current sense inputs | Connected to VLOW in buck mode; provide common-mode reference for differential current sensing. |
| SNSD1+/SNSD2+ (15,46) | DC current sense inputs | Amplify DC inductor current; filter time constant R•C must match L/DCR for accurate DCR sensing. |
| BUCK (16) | Mode select control | Float or tie to V5 for buck mode (VHIGH→VLOW); ground for boost mode (VLOW→VHIGH). |
| ILIM (17) | Current limit foldback selection | 100kΩ input impedance; selects VSENSE(MAX) threshold (10–50mV) for buck/boost current limiting. |
| RUN (18) | Enable control input | 1.22V turn-on threshold; 2µA pull-up rising, 6.5µA after enable - supports sequenced power-up. |
| FAULT (19) | Open-drain fault indicator | Pulls low during OV/UV faults, overcurrent, or thermal shutdown; 0.3V max at 2mA sink. |
| DRVSET (20) | DRVCC output voltage programming | 100kΩ input impedance; sets DRVCC to 6–10V in 1V steps for optimal gate drive efficiency. |
| TG1/TG2 (22,39) | Top gate driver outputs | Floating drivers with 5Ω pull-up / 2.5Ω pull-down; swing = DRVCC + SW voltage for N-channel high-side. |
| SW1/SW2 (23,38) | Switch node connections | Connect to inductor and high-side MOSFET source; voltage swings from Schottky drop below PGND to VHIGH. |
| BOOST1/BOOST2 (24,37) | Bootstrap supply terminals | Connect (+) terminal of bootstrap capacitor; swings from diode drop below DRVCC to VHIGH + DRVCC. |
| BG1/BG2 (25,36) | Bottom gate driver outputs | Drives N-channel low-side MOSFET gates between PGND and DRVCC; 5Ω pull-up / 2.5Ω pull-down. |
| PGND1/PGND2 (26,35) | Power ground returns | Must connect closely to bottom MOSFET sources and CDRVCC/–CVHIGH; separates power and signal grounds. |
| EXTVCC (27) | External gate driver supply input | Bypasses VHIGH-to-DRVCC LDO when > (DRVCC – 0.5V); requires Schottky protection if connected to VLOW. |
| DRVCC (29) | Gate driver LDO output | 6–10V output (set by DRVSET); requires ≥4.7µF low-ESR bypass to PGND for gate drive stability. |
| VHIGH (31) | Main high-voltage supply input | 5–100V input; bypass with 0.1–1µF capacitor to PGND near IC for transient suppression. |
| PGATE (33) | Input short protection driver | Drives external PMOS high during UVHIGH fault; swing = VHIGH to (VHIGH – 15V) for reverse polarity protection. |
| CLKOUT (41) | Phase-locked clock output | 5.5V logic swing (0–5.5V); used to synchronize multiple controllers with configurable CH1–CH2/CLKOUT phasing. |
| SYNC (42) | External clock synchronization input | 100kΩ internal pull-down; accepts 60–460kHz external clock to lock internal oscillator phase. |
| FREQ (43) | Frequency set input | 20µA current source; resistor to SGND sets nominal frequency (e.g., 51.1kΩ → 200kHz). |
| 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 select | Selects CH1–CH2 (180°/120°) and CH1–CLKOUT phasing (0°–240°) via 5 voltage levels. |
| GND (49) | Exposed thermal pad | Mandatory solder connection to PCB ground plane; primary thermal path and signal ground reference. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional buck/boost control | Enables dynamic power flow from VHIGH to VLOW (buck) or VLOW to VHIGH (boost) without hardware change. |
| Proprietary current mode architecture | Separate peak-current (buck) and valley-current (boost) loops with independent compensation for stability. |
| Accurate current monitoring & regulation | IMON output tracks average inductor current (±10% error); SETCUR and ILIM enable precise current limit setup. |
| Programmable DRVCC and EXTVCC switchover | DRVSET configures gate drive voltage (6–10V); EXTVCC bypasses VHIGH LDO above (DRVCC – 0.5V) for efficiency. |
| Automotive-grade reliability | AEC-Q100 qualified (Grade E, –40°C to 125°C), integrated OV/UV protection, and fault reporting via open-drain FAULT. |
| Multiphase synchronization | CLKOUT and SYNC pins support up to 12-phase operation with user-selectable inter-channel phasing (0°–240°). |
Applications
| Automotive 48V/12V Dual Battery Systems | Backup Power Systems |
|---|---|
|
Use Scenario: Regulating power transfer between 48V starter-generator and 12V legacy electrical system in mild hybrid vehicles. IC Role / Device Role / Timing Role: Bidirectional controller managing energy flow direction, voltage regulation, and current limiting in real time based on BUCK pin state. Use Value: Enables regenerative braking energy recovery into 12V battery and cold-cranking assist from 48V rail, improving fuel economy and system redundancy. |
Use Scenario: Providing seamless failover between primary and backup DC power sources in telecom or industrial UPS units. IC Role / Device Role / Timing Role: Synchronous buck/boost controller maintaining stable load voltage during source transitions with <100µs fault response. Use Value: Eliminates need for mechanical relays or diode-ORing; supports bidirectional current sharing and fast switchover with no output droop. |
| High-Efficiency Bidirectional Charger | Energy Storage System (ESS) Interface |
|
Use Scenario: Charging/discharging lithium-ion battery packs from/to variable-voltage DC buses in EV charging stations or grid-tied inverters. IC Role / Device Role / Timing Role: Precision current-regulated bidirectional converter controlling charge/discharge rates via ITHLOW/ITHHIGH voltage programming. Use Value: Achieves up to 97% efficiency with synchronous rectification and programmable CCM/DCM modes for light-load optimization. |
Use Scenario: Interfacing battery energy storage with microgrid DC distribution networks operating at different voltage levels (e.g., 400V DC bus ↔ 48V battery bank). IC Role / Device Role / Timing Role: Polyphase bidirectional DC-DC stage providing galvanic isolation-free voltage translation and active power balancing. Use Value: Supports up to 12-phase interleaving to reduce input/output ripple, thermal stress, and EMI - critical for compact ESS enclosures. |
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 from Monolithic Power Systems | Single-channel, fixed 400kHz frequency, no programmable current sense threshold; supports only 36V max VHIGH. | Limited to lower-voltage automotive subsystems (e.g., ADAS cameras); lacks dual independent current loops and IMON output. | Choose for cost-sensitive, single-rail 24V/12V interfaces where full 100V VHIGH range and precision bidirectional current control are unnecessary. |
| ISL78234 from Renesas | Dual-output synchronous buck controller (not bidirectional); supports 60V max input; includes integrated MOSFET drivers but no boost capability. | Designed for isolated dual-rail supplies (e.g., 12V + 5V) in infotainment systems; cannot regulate power flow from low- to high-voltage rail. | Choose when only unidirectional step-down from 48V to multiple lower rails is required, and bidirectional functionality is not needed. |
Compared with MPQ4269-AEC1 and ISL78234, the LTC3871ELXE#PBF uniquely delivers true bidirectional power flow with independent buck/boost current regulation, 100V VHIGH tolerance, and AEC-Q100 Grade E qualification - making it the only option for demanding 48V/12V automotive energy management.
Availability
LTC3871ELXE#PBF is available at Aetrix Electronics and suitable for automotive 48V/12V dual battery systems, backup power systems, and high-efficiency bidirectional chargers requiring stable component supply, long-term lifecycle support, and AEC-Q100 compliance.
Supply support for LTC3871ELXE#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving automotive, industrial, communications, and healthcare markets.
The LTC3871 product line was designed specifically for high-reliability bidirectional DC-DC conversion in automotive dual-battery architectures, emphasizing precision current control, thermal robustness, and functional safety readiness.
FAQ
What is the maximum VHIGH input voltage supported by the LTC3871ELXE#PBF?
The LTC3871ELXE#PBF supports a VHIGH supply voltage range of 5V to 100V, with absolute maximum rating of –0.3V to 100V. This allows operation in 48V automotive systems with sufficient margin for load-dump transients up to 100V, as confirmed in the Absolute Maximum Ratings table. The device maintains regulation and protection functions across this full range when properly biased and thermally managed.
How does the LTC3871ELXE#PBF switch between buck and boost modes?
The LTC3871ELXE#PBF switches between buck and boost modes using the BUCK pin: tying BUCK to V5 or leaving it floating configures buck mode (VHIGH → VLOW), while grounding BUCK selects boost mode (VLOW → VHIGH). The internal logic reconfigures the current sensing path, error amplifier reference, and PWM modulation scheme (peak-current for buck, valley-current for boost) automatically upon mode change.
Does the LTC3871ELXE#PBF support multiphase interleaving, and how is it implemented?
Yes, the LTC3871ELXE#PBF supports multiphase interleaving up to 12 phases via its CLKOUT and SYNC pins. CLKOUT provides a phase-locked clock output whose relative phase to Channel 1 is set by PHSMD voltage (0°–240°), while SYNC accepts an external clock to synchronize multiple controllers. Channel-to-channel phasing is fixed at 180° or 120° depending on PHSMD setting, enabling ripple cancellation and thermal spreading.
What current sensing methods does the LTC3871ELXE#PBF support, and how are they configured?
The LTC3871ELXE#PBF supports both DCR-based and RSENSE-based current sensing using dual positive inputs per channel: SNSA+ (AC path) and SNSD+ (DC path). For DCR sensing, SNSD+ filter time constant must match L/DCR, and SNSA+ bandwidth is 5× higher. For RSENSE, SNSD+ connects directly to the resistor and SNSA+ filter bandwidth is 4× higher than L/RSENSE. Both methods use the same ILIM pin to program VSENSE(MAX) thresholds from 10mV to 50mV.
Is the LTC3871ELXE#PBF qualified for automotive applications, and what grade does it meet?
Yes, the LTC3871ELXE#PBF is AEC-Q100 qualified for automotive applications and meets Grade E specifications (–40°C to +125°C operating junction temperature). This qualification is explicitly stated in the FEATURES section and confirmed in the ORDER INFORMATION table, which lists LTC3871ELXE#PBF as a standard temperature grade part suitable for under-hood deployment in dual-battery systems.
LTC3871ELXE#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 ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 48-eLQFP (7x7)
LTC3871ELXE#PBF FAQ
1.How can I place an order for LTC3871ELXE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3871ELXE#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 LTC3871ELXE#PBF reliable?
The price and inventory of LTC3871ELXE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3871ELXE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3871ELXE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3871ELXE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3871ELXE#PBF?
LTC3871ELXE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3871ELXE#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 LTC3871ELXE#PBF?
For technical support, including LTC3871ELXE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3871ELXE#PBF requirements.
6.How does Aetrix verify that LTC3871ELXE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3871ELXE#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 LTC3871ELXE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3871ELXE#PBF?
All LTC3871ELXE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3871ELXE#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 LTC3871ELXE#PBF part is unused and in its original packaging.
Return procedure for LTC3871ELXE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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