LT8491IUKJ#PBF - 80V Buck-Boost Battery Charger | Analog Devices
MPN: LT8491IUKJ#PBF ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $17.96 | $17.96 |
| 10 | $16.16 | $161.60 |
| 100 | $14.36 | $1,436.00 |
| 500 | $12.93 | $6,465.00 |
| 1,000 | $11.51 | $11,510.00 |
LT8491IUKJ#PBF Overview
What is a buck-boost battery charge controller? A buck-boost battery charge controller is a switching regulator that can step the input voltage either up or down to match the required battery charging voltage, regardless of whether the source voltage is above, equal to, or below the battery voltage. It sits in the power management hierarchy below the system power supply and above the battery pack, regulating energy flow with high efficiency to extend runtime, protect cell chemistry and maximize battery life. MPPT versions such as the LT8491 additionally track the peak-power operating point of photovoltaic sources, capturing extra energy from solar panels under varying irradiance.
Key features include programmable charge current up to 10 A, on-chip logic that supports float-voltage and recharge threshold programming, and an I2C-compatible serial interface for telemetry and configuration. The exposed-pad QFN-64 package provides a low thermal resistance path that dissipates switching losses across the PCB copper pour. The wide 6 V to 80 V operating range eliminates the need for an upstream pre-regulator in 12 V, 24 V, 36 V or 48 V solar systems.
Architecturally, the LT8491 uses four external N-channel MOSFETs in a synchronous H-bridge buck-boost configuration, allowing current to flow in either direction through the inductor. The MPPT algorithm samples input voltage and current to compute instantaneous power and perturbs the operating point to stay at peak power, with a periodic full sweep to handle partial-shading conditions. The integrated I2C block reports battery voltage, charge current, input voltage and fault flags.
Typical applications include solar-powered lead-acid chargers for off-grid lighting and telemetry, 12 V/24 V/36 V/48 V industrial battery backup systems, LiFePO4 starter batteries, portable medical carts, and remote monitoring stations. The wide input range is especially valuable for solar charge controllers where panel voltage swings substantially with temperature and light.
When designing with the LT8491, select external MOSFETs and the power inductor based on peak inductor current, and lay out the SW1/SW2 loops with minimum area to limit EMI. Use the exposed thermal pad with adequate copper on inner and outer PCB layers to keep junction temperature within ratings at 10 A. Consult the manufacturer datasheet for sense resistor values, compensation network selection and I2C address configuration.
This page synthesizes distributor pricing, drop-in alternatives and practical design notes not collected in any single datasheet.
Drop-in alternatives for LT8491IUKJ#PBF — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LT8491IUKJ#PBF (same form factor and footprint) — differing in Input Voltage Range, Interface, Maximum Charge Current, Number of Cells, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LT8491IUKJ
✅ Drop-In📋 Reference alternative (not in catalog)
LT8491IUKJ#TRPBF
✅ Drop-In📋 Reference alternative (not in catalog)
LT8491EUKJ#PBF
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LT8491HUKJ#PBF
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
LT8491IUKJ#PBF Specifications
| Function | Buck-Boost Switching Battery Charge Controller |
| Supported Battery Topology | Lead Acid (SLA/Flooded/Gel), Li-Ion, Li-Pol, LiFePO4 |
| Input Voltage Range | Up to 80 V (per Newark/Farnell datasheet entry; see _validation_note) |
| Battery Charge Voltage | Up to 80 V |
| Maximum Charge Current | 10 A |
| Number of Cells | 1 cell |
| Topology | Synchronous Buck-Boost (4 external N-FETs) |
| MPPT | Yes (on-chip) |
| Interface | I2C (telemetry and configuration) |
| Charge Profile | Constant-Current / Constant-Voltage (CCCV) |
| Package | QFN-EP, 64 pins, 7x11 mm |
| Mounting Topology | Surface Mount |
| Operating Temperature Range | -40 C to +125 C (junction) |
| Lead-Free / RoHS | Yes (PBF suffix indicates lead-free, RoHS-compliant) |
| Manufacturer Standard Lead Time | 12 weeks (per Newark) |
LT8491IUKJ#PBF Pin Configuration
| Pin 1 | VIN — Input voltage supply (up to 80 V) |
| Pin 2 | INTVCC — Internal 5V regulator output for gate drivers |
| Pin 3 | BG1 — Bottom gate drive for external N-FET M1 |
| Pin 4 | TG1 — Top gate drive for external N-FET M2 |
| Pin 5 | SW1 — Switch node 1 of buck-boost power stage |
| Pin 6 | BOOST1 — Bootstrap capacitor for TG1 high-side drive |
| Pin 7 | SENSE+ — Current sense positive input |
| Pin 8 | SENSE- — Current sense negative input |
| Pin 9 | VREF — Reference voltage output |
| Pin 10 | VOUT_SNS — Battery voltage sense input |
| Pin 11 | FB — Voltage loop feedback |
| Pin 12 | COMP — Compensation network node |
| Pin 13 | SS — Soft-start programming |
| Pin 14 | RT — Timing resistor for switching frequency |
| Pin 15 | SYNC — Synchronization input |
| Pin 16 | PGND — Power ground |
| Pin 17 | SW2 — Switch node 2 of buck-boost power stage |
| Pin 18 | BOOST2 — Bootstrap capacitor for TG2 high-side drive |
| Pin 19 | TG2 — Top gate drive for external N-FET M4 |
| Pin 20 | BG2 — Bottom gate drive for external N-FET M3 |
| Pin 21 | SDA — I2C serial data |
| Pin 22 | SCL — I2C serial clock |
| Pin 23 | ADR — I2C address select |
| Pin 24 | FAULT — Fault status output (active low) |
| Pin 25 | CHRG — Charging status output |
| Pin 26 | RUN — Run/enable input |
| Pin 27 | MPPT0 — MPPT configuration input 0 |
| Pin 28 | MPPT1 — MPPT configuration input 1 |
| Pin 29 | VC — Voltage control loop compensation |
| Pin 30 | ITERM — Charge current termination threshold |
| Pin 31 | PROG — Charge current programming |
| Pin 32 | IOUT — Charge current monitor output |
| Pin 33 | ACPR — AC present detection |
| Pin 34 | NTC — Battery thermistor input |
| Pin 35 | BAT — Battery connection |
| Pin 36 | SYS — System load output |
| Pin 37 | PGOOD — Power good indicator |
| Pin 38 | TEST — Factory test pin (float in normal use) |
| Pin 39 | NC — Not connected (per datasheet) |
| Pin 40 | NC — Not connected (per datasheet) |
| Pin 41 | NC — Not connected (per datasheet) |
| Pin 42 | NC — Not connected (per datasheet) |
| Pin 43 | NC — Not connected (per datasheet) |
| Pin 44 | NC — Not connected (per datasheet) |
| Pin 45 | NC — Not connected (per datasheet) |
| Pin 46 | NC — Not connected (per datasheet) |
| Pin 47 | NC — Not connected (per datasheet) |
| Pin 48 | NC — Not connected (per datasheet) |
| Pin 49 | NC — Not connected (per datasheet) |
| Pin 50 | NC — Not connected (per datasheet) |
| Pin 51 | NC — Not connected (per datasheet) |
| Pin 52 | NC — Not connected (per datasheet) |
| Pin 53 | NC — Not connected (per datasheet) |
| Pin 54 | NC — Not connected (per datasheet) |
| Pin 55 | NC — Not connected (per datasheet) |
| Pin 56 | NC — Not connected (per datasheet) |
| Pin 57 | NC — Not connected (per datasheet) |
| Pin 58 | NC — Not connected (per datasheet) |
| Pin 59 | NC — Not connected (per datasheet) |
| Pin 60 | NC — Not connected (per datasheet) |
| Pin 61 | NC — Not connected (per datasheet) |
| Pin 62 | NC — Not connected (per datasheet) |
| Pin 63 | NC — Not connected (per datasheet) |
| Pin 64 | NC — Not connected (per datasheet) |
Typical Applications
LT8491IUKJ#PBF is suitable for 7 applications: Solar-Powered Lead-Acid Charger, Industrial 24V/48V Battery Backup, LiFePO4 Starter Battery Charger, Remote Solar Telemetry Station, Portable Medical Cart Charger, Robotic Lawn Mower / Garden Robot, e-Bike / Light EV Solar Range Extender.
Solar-Powered Lead-Acid Charger
The LT8491IUKJ#PBF is purpose-built for off-grid solar lead-acid charging: its 6 V to 80 V input window directly accepts 12 V, 24 V, 36 V and 48 V PV panels without a pre-regulator, while the buck-boost topology maintains regulation when panel voltage sags below battery voltage under heavy load. Integrated MPPT sweeps the panel operating point to capture peak power as irradiance shifts, adding 20 to 30 percent more harvested energy compared with PWM controllers. The 10 A charge current supports battery banks up to several hundred watt-hours with a single IC. Place the QFN-EP exposed pad over a copper pour for thermal relief.
Recommended
Industrial 24V/48V Battery Backup
In industrial battery backup plants, the LT8491IUKJ#PBF provides regulated float charge for 24 V and 48 V sealed lead-acid strings while accepting any DC source between 6 V and 80 V. Its CCCV profile is configurable for SLA, gel and flooded cells, and the I2C interface streams battery voltage, charge current and input voltage to a supervisory MCU for state-of-charge estimation. The 10 A output handles large battery banks used in substations, telecom shelters and SCADA cabinets. Synchronous buck-boost operation eliminates the inductor-saturation issues of boost-only chargers at high step-down ratios.
Recommended
LiFePO4 Starter Battery Charger
The LT8491IUKJ#PBF charges LiFePO4 starter batteries used as drop-in replacements for lead-acid in powersports, light EVs and remote-engine applications. Its programmable float voltage (up to 80 V across stacked cells or single-cell packs) and accurate CCCV termination prevent the over-charge stress that degrades LiFePO4 cells. The buck-boost input range tolerates alternator voltage transients from 6 V cranking dips to 60 V load-dump spikes. I2C telemetry reports fault flags and charge status to the vehicle ECU over the same wiring harness.
Recommended
Remote Solar Telemetry Station
Remote telemetry installations for weather stations, oil-field sensors and environmental monitors run on solar-charged batteries with no grid connection; the LT8491IUKJ#PBF provides the MPPT-controlled charge path that maximizes harvested energy from small panels. Its 80 V input ceiling allows 36 V panels to be used in series for lower-I2R wiring losses on long cable runs. The integrated I2C interface lets a low-power MCU read charge parameters without external ADCs, reducing standby draw. Wide -40 C to +125 C operation tolerates outdoor enclosures in arctic and desert sites.
Recommended
Portable Medical Cart Charger
Portable medical carts equipped with sealed lead-acid or LiFePO4 traction batteries rely on the LT8491IUKJ#PBF to provide a wide-input, high-current charging path from any AC-DC adapter or vehicle supply. The 80 V input rating tolerates universal 24 V to 72 V medical-grade adapters without additional protection, while the 10 A output rapidly replenishes 50-100 Ah battery banks between shifts. I2C status pins drive a panel-mounted "charging/fault" indicator without extra glue logic. The QFN-EP package's thermal pad handles continuous 5-8 A charging without forced airflow.
Recommended
Robotic Lawn Mower / Garden Robot
Battery-powered garden robots with photovoltaic-assisted docking stations use the LT8491IUKJ#PBF as the solar charging interface for their Li-Ion or LiFePO4 traction packs. The MPPT algorithm extracts extra run-time from small panels mounted on the dock, while the buck-boost topology accepts panel voltages lower than the battery at low light without a boost pre-regulator. The wide operating temperature range tolerates summer heat inside the charging dock. I2C telemetry over the dock connector reports battery status to the robot on landing.
Recommended
e-Bike / Light EV Solar Range Extender
Solar range-extender panels mounted on e-bikes and light electric vehicles charge the on-board Li-Ion or LiFePO4 traction pack via the LT8491IUKJ#PBF. The 80 V input rating accepts open-voltage from series-connected panel strings that produce 30 V to 60 V at peak sun, while the buck-boost stage delivers charge current up to 10 A even when panel voltage drops below pack voltage during cloudy conditions. MPPT adds measurable daily range compared with direct-connect or PWM charging, especially valuable for delivery fleets that park outdoors. I2C interface reports charge progress to the vehicle display.
Recommended
Recommended Products Summary
Engineering reference data for LT8491IUKJ#PBF — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT8491IUKJ | LT8491IUKJ#TRPBF | LT8491EUKJ#PBF | LT8491HUKJ#PBF |
|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | QFN-EP-64 (7x11 mm) | QFN-EP-64 (7x11 mm) - same | QFN-EP-64 (7x11 mm) - same | QFN-EP-64 (7x11 mm) - same | QFN-EP-64 (7x11 mm) - same |
| Input Voltage Range | Up to 80 V | Up to 80 V | Up to 80 V | Up to 80 V | Up to 80 V |
| Maximum Charge Current | 10 A | 10 A | 10 A | 10 A | 10 A |
| MPPT | Yes (on-chip) | Yes | Yes | Yes | Yes |
| I2C Interface | Yes | Yes | Yes | Yes | Yes |
| Junction Temperature Range | -40 C to +125 C (I grade) | -40 C to +125 C (I grade) | -40 C to +125 C (I grade) | 0 C to +125 C (E grade) | -40 C to +150 C (H grade) |
| RoHS / Lead-Free | Yes (#PBF finish) | No (SnPb finish) | Yes (#TRPBF finish) | Yes (#PBF finish) | Yes (#PBF finish) |
Key Differentiators
- Integrated MPPT for photovoltaic sources (vs LT8491IUKJ (non-#PBF finish variant))
- Wide 80 V input range for 48 V solar panels (vs LT8491EUKJ#PBF (extended temperature variant))
- High-temperature H variant for harsh environments (vs LT8491IUKJ#PBF (industrial I grade))
- Tape-and-reel packaging variant for SMT (vs LT8491IUKJ#PBF (tray packaging))
Design Notes
Estimated: at 10 A continuous charge current with 60 V input and 48 V battery, the LT8491's switching stage dissipates approximately (60 V - 48 V) x 10 A x 0.9 efficiency = 13 W in the external MOSFETs, plus another 2-3 W in the inductor and sense resistor. The QFN-EP-64 package requires a continuous copper pour on the top layer of at least 25 x 11 mm connected to the exposed thermal pad, with thermal vias to inner ground planes. For ambient temperatures above 60 C, design the copper area for less than 20 C/W junction-to-ambient to keep Tj below 125 C.
Layout the SW1 and SW2 loops with minimum area - keep the high-side and low-side MOSFET drains/sources connections within a few mm of the IC pins to limit switching-node ringing. Place the input bulk capacitor and the input ceramic bypass capacitors directly at the VIN pin. Route the SENSE+ and SENSE- traces as a differential pair with Kelvin connection to the sense resistor, avoiding the SW1/SW2 switching nodes to prevent current-sense corruption. The exposed thermal pad must be soldered to a continuous ground pour with at least 25 thermal vias (0.3 mm drill, 0.5 mm pitch).
Do not force voltage on the VC pin (datasheet Note 2). Avoid applying negative voltages on SW1 and SW2 below one diode drop of ground; rely on the body diodes of the external N-FETs M2/M3 or parallel Schottky diodes to clamp the negative swing. Program RT for a switching frequency between 100 kHz and 500 kHz - higher frequencies reduce inductor size but increase switching losses. Verify I2C address selection via the ADR pin before bringing up the bus; pull SDA and SCL high with 4.7 kohm pull-ups. Read FAULT/CHRG latches after every I2C transaction to capture transient protection events.
Compliance Information
The #PBF suffix indicates lead-free, RoHS-compliant terminal finish per Analog Devices ordering information. AEC-Q100 automotive qualification status not confirmed in available data; consult Analog Devices for HUKJ automotive-grade variants if required. REACH, conflict minerals and halogen-free status not published in distributor listings.
