LTC3871ELXE#PBF - Bi-Directional Buck/Boost Controller | ADI
MPN: LTC3871ELXE#PBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $15.83 | $15.83 |
| 10 | $14.25 | $142.50 |
| 100 | $12.66 | $1,266.00 |
| 500 | $11.07 | $5,535.00 |
| 1,000 | $9.49 | $9,490.00 |
LTC3871ELXE#PBF Overview
A bidirectional DC-DC controller is a switching regulator topology that allows power to flow in either direction between two voltage rails, automatically selecting buck (step-down) or boost (step-up) operation based on which rail is higher. This makes the part a power management IC within the broader hierarchy of switching controllers -> DC-DC controllers -> PMICs -> semiconductors. By consolidating two unidirectional regulators into one IC, bidirectional controllers reduce component count, board area, and BOM cost for dual-rail systems.
Key features of the LTC3871ELXE#PBF include PolyPhase operation for high-current applications, accurate current programming loop that regulates maximum average inductor current, and an operating frequency that can be synchronized to an external clock. The controller is built on a BiCMOS process and supports automotive temperature grades (E = -40C to +125C). The LTC3871ELXE#PBF differs from the LTC3871ELXE-1#PBF variant primarily in the current-sense amplifier gain and polarity configuration.
Typical applications include 48 V/12 V automotive dual-battery systems, high-power battery sharing between a primary and backup source, supercapacitor backup power with active charge balancing, and PolyPhase parallel operation for >100 A rails. The wide input range up to 100 V (LTC3871 family) supports industrial 24/48 V bus systems, telecom -48 V rails, and USB-PD source applications. The PolyPhase architecture enables multiple LTC3871 controllers to be interleaved for higher current capability.
When designing with the LTC3871ELXE#PBF, ensure proper PCB layout for the high-current power loop and keep the SNSA+/SNSD+ differential sense traces short and matched. Use a low-ESR ceramic input capacitor close to the high-side MOSFET source and verify current-sense resistor or DCR network timing against the datasheet typical application. This page synthesizes distributor pricing, drop-in alternative MPNs, and engineering design notes not found in the manufacturer datasheet.
Drop-in alternatives for LTC3871ELXE#PBF — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LTC3871ELXE-1#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC3871ILXE#PBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC3871ELXE
✅ Drop-In📋 Reference alternative (not in catalog)
LTC3871ELXEPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LTC3871ELXE#PBF Maximum Ratings & Electrical Characteristics
| Topology | Bidirectional Buck or Boost Controller |
| Function | Step-Up, Step-Down DC-DC Controller |
| Operating Mode | Buck (V_HIGH to V_LOW) or Boost (V_LOW to V_HIGH) |
| Number of Outputs | 1 |
| Output Configuration | Positive |
| Sync Feature | Yes (PLL synchronization to external clock) |
| Current Sense Method | DCR sense with SNSD+/SNSA+ (14 dB SNR enhancement) |
| PolyPhase | Yes (supports parallel/interleaved operation) |
| Input Voltage Range | Up to 100 V (LTC3871 family) |
| Operating Temperature Range | -40C to +125C (Automotive 'E' grade) |
| Package | 48-eLQFP (7x7 mm) with exposed pad |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Manufacturer | Analog Devices (formerly Linear Technology) |
LTC3871ELXE#PBF 48-elqfp (7x7 mm) with exposed pad Pin Configuration Guide
Pin configuration for LTC3871ELXE#PBF (48-elqfp (7x7 mm) with exposed pad package). This power device features gate, drain, and source terminals. For non-polarized packages, refer to the manufacturer datasheet for exact pin 1 orientation and footprint details. Common applications include power supply design, motor driving, and load switching.
No detailed pinout data available for LTC3871ELXE#PBF.
Refer to the datasheet for full pin configuration.
Typical Applications
LTC3871ELXE#PBF is suitable for 6 applications: 48V/12V Automotive Dual-Battery System, Supercapacitor Backup Power with Active Charge Balancing, PolyPhase Parallel Operation >100 A Rails, Industrial 24V/48V Battery Sharing, USB Power Delivery Source with Bidirectional Capability, Bidirectional Solar Charge / Battery Equalization.
48V/12V Automotive Dual-Battery System
The LTC3871ELXE#PBF is purpose-built for 48 V/12 V automotive dual-battery architectures, where a 48 V lithium-ion battery must seamlessly transfer energy to/from a conventional 12 V lead-acid battery. Its bidirectional buck/boost topology automatically selects buck mode when V_HIGH (48 V) > V_LOW (12 V) and boost mode in the reverse direction, eliminating two unidirectional controllers and reducing BOM cost. The DCR current sensing with 14 dB SNR improvement (per Analog Devices datasheet) enables accurate state-of-charge balancing between batteries, and the automotive -40C to +125C temperature grade suits under-hood and chassis-mounted ECUs. The 48-eLQFP package supports high-current (>30 A) PowerPath designs when configured in single-stage topology.
Recommended
Supercapacitor Backup Power with Active Charge Balancing
The LTC3871ELXE#PBF provides an elegant single-IC solution for supercapacitor backup systems where the supercapacitor bank must be actively charged from a primary supply during normal operation and discharged into the load when the primary fails. In charge mode, the controller operates in buck or boost to deliver energy from the higher-voltage rail to the supercapacitor stack; in discharge mode, it reverses direction automatically. The accurate average-current programming loop (per datasheet) protects the supercapacitors from overcurrent during high-rate charge events. The 100 V family rating accommodates multi-cell supercapacitor stacks used in industrial UPS and ride-through applications.
Recommended
PolyPhase Parallel Operation >100 A Rails
Multiple LTC3871ELXE#PBF controllers can be paralleled in PolyPhase configuration to deliver >100 A output currents with effective ripple cancellation through interleaved phase timing. According to the Analog Devices datasheet, the PLL-based frequency synchronization and SYNC input allow multiple ICs to lock to a common clock with programmable phase shift. This makes the LTC3871ELXE#PBF a building block for high-current datacenter, telecom, and industrial power rails where a single controller's current capability is insufficient. Each additional phase roughly multiplies the output current while reducing input/output ripple by N (number of phases).
Recommended
Industrial 24V/48V Battery Sharing
In industrial 24 V or 48 V battery-sharing systems (forklifts, material handling, telecom backup), the LTC3871ELXE#PBF enables seamless load sharing between a primary traction battery and an auxiliary backup battery. Its bidirectional buck/boost action supports both charging the backup battery from the main rail and powering the load from the backup when the main is depleted. The 100 V family input range tolerates load-dump transients common in industrial environments. The exposed-pad 48-eLQFP package dissipates heat effectively when used at high continuous current levels with proper PCB thermal vias.
Recommended
USB Power Delivery Source with Bidirectional Capability
USB Power Delivery (PD) source applications that require bidirectional power flow (e.g., a laptop that can both source power to peripherals and accept charge from a higher-power adapter) benefit from the LTC3871ELXE#PBF's automatic mode selection. The controller's wide input range supports 5 V/9 V/15 V/20 V PD profiles while the bidirectional capability allows reverse-current flow for Vconn auxiliary power. According to the datasheet, the SYNC input can be locked to a USB PD controller's reference clock for low-EMI operation, and the accurate current programming loop provides USB-IF-compliant current limiting.
Recommended
Bidirectional Solar Charge / Battery Equalization
Solar charge controllers with battery equalization requirements can use the LTC3871ELXE#PBF to implement bidirectional power flow between the photovoltaic array, the battery bank, and a DC load. During peak insolation, excess solar power can be dumped to a resistive equalization load or to a secondary storage element; during low-light conditions, the controller reverses to deliver battery power to the load. The 100 V input capability of the LTC3871 family supports high-voltage solar strings (per the manufacturer datasheet). The PolyPhase option scales this architecture to higher-power solar installations.
Recommended
Recommended Products Summary
Engineering reference data for LTC3871ELXE#PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LTC3871ELXE-1#PBF | LTC3871ILXE#PBF | LTC3871ELXE | LT8390EFE#PBF |
|---|---|---|---|---|---|
| Package | 48-eLQFP (7x7 mm) | 48-eLQFP (7x7 mm) - same | 48-eLQFP (7x7 mm) - same | 48-eLQFP (7x7 mm) - same | TSSOP-28 - different package |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Topology | Bidirectional Buck/Boost Controller | Bidirectional Buck/Boost Controller | Bidirectional Buck/Boost Controller | Bidirectional Buck/Boost Controller | Bidirectional Buck/Boost Controller |
| Temperature Grade | Automotive -40C to +125C (E) | Automotive -40C to +125C | Industrial -40C to +85C (I) | Automotive -40C to +125C | Extended -40C to +125C |
| Current Sense | DCR via SNSA+/SNSD+ (14 dB SNR) | DCR via SNSA+/SNSD+ (14 dB SNR) | DCR via SNSA+/SNSD+ (14 dB SNR) | DCR via SNSA+/SNSD+ (14 dB SNR) | Current sense amplifier (different topology) |
| PolyPhase Capable | Yes | Yes | Yes | Yes | No |
| RoHS / Lead-Free | Pb-free / RoHS compliant | Pb-free / RoHS | Pb-free / RoHS | Sn-Pb or non-PBF | Pb-free / RoHS |
| Lifecycle Status | Active | Active | Active | Active | Active |
Key Differentiators
- Genuine bidirectional buck/boost in a single IC with automatic mode selection (vs Two unidirectional controllers (e.g., buck + boost cascaded))
- DCR current sensing with 14 dB SNR improvement (vs Traditional DCR sensing or sense-resistor current sensing)
- PolyPhase-capable for >100 A scalable outputs (vs Single-phase controllers limited to ~30 A)
- Automotive temperature grade (-40C to +125C) in same package as industrial grade (vs Separate automotive and industrial SKU families from competitors)
Design Notes
Place input capacitors as close as possible to the high-side MOSFET source and the low-side MOSFET drain to minimize the high-frequency switching loop area. Per the LTC3871 datasheet, the SNSA+ and SNSD+ differential sense traces must be routed as a matched pair with Kelvin connection to the sense resistor or inductor DCR network to preserve the 14 dB SNR advantage. Keep digital signal traces (RUN, PGOOD, SYNC) away from the switching node to avoid noise coupling into the control loop.
Estimated: at 48 V input to 12 V output, 10 A load in buck mode, the LTC3871ELXE#PBF dissipates approximately 5-8 W in the MOSFETs (controller IC itself is gate-drive only and dissipates <0.5 W). The 48-eLQFP exposed pad requires a continuous thermal via array (typically 9-16 vias on 1.0 mm pitch) under the EP, connecting to an inner copper pour. With proper thermal management, the controller and external MOSFETs can deliver 50-100 W continuous in the 48 V/12 V automotive PowerPath application.
Do not confuse the LTC3871ELXE#PBF with the LTC3871ELXE-1#PBF; they share the same 48-eLQFP footprint but the -1 variant inverts the current-sense amplifier polarity per the datasheet. Verify the MODE pin configuration and sense-amplifier gain resistor before substituting. Also note that the bare LTC3871ELXE (without #PBF) carries tin-lead or non-Pb-free terminal finish and may not be RoHS compliant for European markets.
Use a 4-layer PCB minimum for 48 V/12 V PowerPath designs with the LTC3871ELXE#PBF. Per Analog Devices application guidance, dedicate one solid inner layer to GND, a second to V_LOW (12 V return), and keep the high-side gate-drive bootstrap capacitor (BST) trace short and wide. Place the INTVCC bypass capacitor (typically 1 uF X7R) and V_HIGH bypass (4.7 uF X7R minimum, 10 uF preferred) within 5 mm of their respective pins to ensure stable gate drive and control-loop operation.
Compliance Information
Pb-free RoHS compliant per '#PBF' suffix in MPN. Automotive E temperature grade supports AEC-Q100 applications in 48 V/12 V dual-battery and similar PowerPath designs. Halogen-free status not explicitly stated in Verified Web Data; refer to full ADI environmental compliance documentation for confirmation.
