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Analog Devices Inc. LTC3871ILXE#PBF
- Part No.:
- LTC3871ILXE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 48-LQFP Exposed Pad
- Datasheet:
-
LTC3871ILXE#PBF.pdf
- Description:
- IC REG CTRLR BCK/BST SYN 48LQFP
- Quantity:
- Payment:
- Shipping:
Inventory:122
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Product details
Overview
LTC3871ILXE#PBF from Analog Devices is a bidirectional polyphase synchronous buck/boost controller for automotive 48V/12V dual-battery systems, operating in either buck mode (VHIGH-to-VLOW) or boost mode (VLOW-to-VHIGH) on demand. It delivers up to 100V VHIGH input, supports ±1% voltage regulation accuracy over temperature, enables phase-locked multiphase operation up to 12 phases, and features independent loop compensation for buck and boost modes.
For engineers reviewing the LTC3871ILXE#PBF datasheet, LTC3871ILXE#PBF pinout, LTC3871ILXE#PBF application, or LTC3871ILXE#PBF equivalent, key selection criteria include bidirectional current programming capability, programmable VHIGH/VLOW OV/UV thresholds, selectable CCM/DCM modes, and AEC-Q100 qualification for automotive use.
Technical Context
The LTC3871ILXE#PBF implements a proprietary constant-frequency current-mode architecture with separate peak-current (buck) and valley-current (boost) control loops, enabling dynamic regulation of input/output voltage or current. Its dual-channel design operates 180° or 120° out-of-phase and supports synchronized multi-IC operation via CLKOUT/SYNC pins.
It integrates two independent error amplifiers (EA_VHIGH, EA_VLOW), programmable transconductance amplifiers (gm-buck = 2 mmho, gm-boost = 1 mmho), and dual-path current sensing (SNSA+/SNSD+ for AC/DC signal separation) to achieve low-noise operation with DCR or RSENSE sensing. The controller provides accurate output current monitoring (±10% IMON accuracy) and overcurrent protection with foldback characteristics specific to the LTC3871 variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VHIGH Range | 5V to 100V - supports wide-input 48V automotive rail with headroom for transients. |
| VLOW Range | 1.2V to 30V - compatible with 12V battery systems and intermediate bus voltages. |
| Switching Frequency | 60kHz to 460kHz - programmable via FREQ pin resistor; synchronizable to external clock. |
| Voltage Regulation Accuracy | ±1% over temperature - ensures stable output under thermal stress in engine bay environments. |
| Current Sense Threshold | 10mV to 50mV (RSENSE); 8mV to 50mV (DCR) - enables high-efficiency low-DCR inductor use. |
| Operating Junction Temp | –40°C to 125°C - qualified per AEC-Q100 Grade I for under-hood automotive deployment. |
| Package | 48-lead 7mm × 7mm LQFP with exposed GND pad - thermally enhanced for >97% efficiency operation. |
Pinout & Package
Package: 48-lead plastic LQFP (7mm × 7mm), exposed pad (Pin 49) soldered to PCB ground for thermal performance (θJA = 36°C/W).
| 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 limiting. |
| VFBLOW (2), VFBHIGH (5) | Voltage feedback inputs | Inverting inputs to error amplifiers; reference voltage = 1.200V ±12mV (VLOW), ±15mV (VHIGH). |
| ITHLOW/ITHHIGH (3,4) | Current limit threshold control | Analog programming of max current in buck/boost modes; determines peak/valley inductor current setpoint. |
| BUCK (16) | Mode selection | Float or tie to V5 for buck operation; ground for boost - defines primary regulation direction. |
| SETCUR (12), ILIM (17) | Current limit configuration | SETCUR sources 7.5µA to program initial current limit; ILIM selects sense threshold scaling (100kΩ input). |
| TG1/TG2 (22,39), BG1/BG2 (25,36) | Gate drivers | TG outputs swing DRVCC above SW node; BG drives bottom MOSFETs between PGND and DRVCC (5Ω pull-down). |
| DRVCC (29), EXTVCC (27) | Driver supply management | DRVCC = 6–10V LDO output; EXTVCC bypasses VHIGH-based LDO when > (DRVCC – 0.5V), improving efficiency. |
| CLKOUT (41), SYNC (42), FREQ (43) | Timing interface | CLKOUT enables multi-IC synchronization; SYNC accepts external clock (60–460kHz); FREQ sets nominal frequency via resistor. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional power flow control | Enables energy transfer from 48V to 12V (buck) or 12V to 48V (boost) without hardware change - critical for regenerative braking and load leveling. |
| Independent buck/boost loop compensation | Separate ITHLOW/ITHHIGH pins allow optimized stability margins for both operating modes - eliminates compromise tuning. |
| Programmable VHIGH/VLOW OV/UV thresholds | Resistor-divider-configurable trip points (e.g., VHIGH UV = 1.2V threshold) enable precise battery protection against overcharge/undervoltage. |
| DCR + RSENSE current sensing support | Dual-path sensing (SNSA+/SNSD+) maintains <10mV threshold accuracy with low-DCR inductors or precision shunts - reduces conduction loss. |
| AEC-Q100 Grade I qualification | Validated for –40°C to 125°C operation with automotive reliability testing - meets OEM requirements for under-hood placement. |
Applications
| Automotive Dual-Battery Systems | Backup Power Systems |
|---|---|
|
Use Scenario: Seamless power sharing between 48V starter-generator and 12V accessory battery during engine start-stop cycles. IC Role / Device Role / Timing Role: Bidirectional controller regulating VLOW (12V) from VHIGH (48V) in buck mode and supporting reverse power flow during regenerative braking. Use Value: Eliminates need for separate buck and boost controllers; ±1% regulation maintains stable 12V rail despite 48V transients up to 100V. |
Use Scenario: Uninterruptible power delivery during main supply failure in telecom base stations or industrial PLCs. IC Role / Device Role / Timing Role: Controller managing charge/discharge between primary DC bus and backup battery bank using programmable current limits. Use Value: Accurate IMON output (±10%) enables real-time state-of-charge monitoring; phase-lockable frequency simplifies EMI filtering across redundant modules. |
| High-Efficiency Bidirectional Chargers | Server Rack Power Distribution |
|
Use Scenario: Two-way charging of Li-ion battery packs in EV onboard chargers or energy storage systems. IC Role / Device Role / Timing Role: Synchronous buck/boost controller implementing CC/CV charge profiles with independent current/voltage loops. Use Value: Selectable CCM/DCM modes optimize light-load efficiency; 97% peak efficiency reduces thermal load in compact enclosures. |
Use Scenario: Dynamic voltage translation between 48V intermediate bus and 12V/5V server sub-rails in AI accelerator racks. IC Role / Device Role / Timing Role: Polyphase controller distributing load across multiple LTC3871ILXE#PBF units synchronized via CLKOUT/SYNC. Use Value: 12-phase scalability supports >1000A output; programmable VHIGH UV/OV prevents bus collapse during fault propagation. |
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 |
|---|---|---|---|
| MPQ8875A-AEC1 | Single-channel, 40V max VHIGH, no VLOW OV/UV monitoring, fixed 600kHz frequency | Limited to lower-voltage automotive subsystems; lacks independent buck/boost compensation | Choose for cost-sensitive 24V/12V systems where 100V VHIGH headroom and dual-loop tuning are unnecessary. |
| ISL78234 | 40V VHIGH max, integrated gate drivers only (no DRVCC/EXTVCC flexibility), no IMON output | Suitable for simpler 12V/48V converters without current monitoring or multi-phase sync | Prefer when board space is constrained and external current sensing/monitoring is handled separately. |
Compared with MPQ8875A-AEC1 and ISL78234, the LTC3871ILXE#PBF offers wider VHIGH range (100V), full bidirectional current programming, and AEC-Q100-compliant thermal performance - making it uniquely suited for demanding 48V automotive front-end applications requiring robust fault protection and system-level coordination.
Availability
LTC3871ILXE#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 and long-term lifecycle support.
Supply support for LTC3871ILXE#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 delivers high-efficiency, bidirectional DC/DC control for next-generation automotive electrification and energy storage systems - designed specifically for 48V mild-hybrid architectures and scalable power distribution.
FAQ
What is the maximum VHIGH input voltage supported by the LTC3871ILXE#PBF?
The LTC3871ILXE#PBF supports a VHIGH supply voltage range of 5V to 100V, as specified in its Absolute Maximum Ratings. This allows robust operation in automotive 48V systems with transient overvoltage tolerance up to 100V, ensuring reliability during load-dump events. The device remains functional across this full range when configured with appropriate external components.
How does the LTC3871ILXE#PBF implement bidirectional operation without external mode switching?
The LTC3871ILXE#PBF uses the BUCK pin to determine operational mode: floating or tied to V5 enables buck regulation (VHIGH→VLOW), while grounding it enables boost regulation (VLOW→VHIGH). Internal logic automatically configures peak-current (buck) or valley-current (boost) control, independent loop compensation, and gate timing - eliminating need for external mode-change circuitry.
Can the LTC3871ILXE#PBF be used with low-DCR inductors, and how is current sensing achieved?
Yes, the LTC3871ILXE#PBF supports low-DCR current sensing via dual-path inputs SNSA+ (AC component) and SNSD+ (DC component), which are internally processed to emulate a high-SNR DCR signal. With proper RC filter matching (R1•C1 = L/DCR; R2•C2 = R1•C1/5), it achieves accurate current limit thresholds down to 8mV - enabling efficient, low-loss designs.
What is the purpose of the IMON pin on the LTC3871ILXE#PBF, and what accuracy does it provide?
The IMON pin on the LTC3871ILXE#PBF outputs a voltage proportional to the average inductor current of both channels (1.25V = zero current). It provides ±10% accuracy over temperature and load, enabling real-time current monitoring, system-level power management, and fault detection without adding external sense amplifiers or ADC resources.
Is the LTC3871ILXE#PBF pin-compatible with the LTC3871-1 variant?
No, the LTC3871ILXE#PBF (LTC3871) and LTC3871ILXE-1#PBF (LTC3871-1) are not pin-compatible replacements due to differing current limit foldback characteristics and internal current-sense threshold mapping. While sharing identical pinout and package, their ITH-to-current-limit behavior differs - requiring separate layout validation and compensation tuning for each variant.
LTC3871ILXE#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)
LTC3871ILXE#PBF FAQ
1.How can I place an order for LTC3871ILXE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3871ILXE#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 LTC3871ILXE#PBF reliable?
The price and inventory of LTC3871ILXE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3871ILXE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3871ILXE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3871ILXE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3871ILXE#PBF?
LTC3871ILXE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3871ILXE#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 LTC3871ILXE#PBF?
For technical support, including LTC3871ILXE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3871ILXE#PBF requirements.
6.How does Aetrix verify that LTC3871ILXE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3871ILXE#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 LTC3871ILXE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3871ILXE#PBF?
All LTC3871ILXE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3871ILXE#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 LTC3871ILXE#PBF part is unused and in its original packaging.
Return procedure for LTC3871ILXE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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