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Analog Devices Inc. LT3651IUHE-4.1#PBF
- Part No.:
- LT3651IUHE-4.1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LT3651IUHE-4.1#PBF.pdf
- Description:
- IC BATT CHG LI-ION 1CELL 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,168
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Product details
Overview
LT3651IUHE-4.1#PBF from Analog Devices (formerly Linear Technology) is a monolithic 4A synchronous step-down Li-ion battery charger IC for single-cell applications, supporting 6.5V–32V input and delivering 4.1V float voltage with 0.5% accuracy, ±7.5% charge current accuracy, and NTC-based temperature monitoring. It enables automotive cradle chargers, industrial handhelds, and notebook power systems requiring high-efficiency CC/CV charging with programmable termination.
For engineers reviewing the LT3651IUHE-4.1#PBF datasheet, LT3651IUHE-4.1#PBF pinout, LT3651IUHE-4.1#PBF application, or LT3651IUHE-4.1#PBF equivalent, key selection criteria include its 36-pin QFN package, 4A max charge current, 4.1V fixed float voltage, C/10 or timer-based termination, and integrated thermal foldback protection - all validated across –40°C to 125°C operating range.
Technical Context
The LT3651IUHE-4.1#PBF implements average current mode control using dual error amplifiers (V-EA and C-EA) to regulate both battery voltage and inductor current via SENSE–BAT sensing. Its synchronous switcher uses bootstrapped high-side drive (BOOST pin) and low-side MOSFET switching (SW pins), achieving up to 86% efficiency at 24VIN/3.9VBAT.
It integrates precision references for float voltage (4.1V ±0.5%), C/10 detection (8.6mV sense threshold), preconditioning (2.85V BAT threshold), and input current limiting (95mV CLP–CLN threshold), all referenced to internal 50µA bias currents on RNG/SS, ILIM, and NTC pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 6.5V to 32V - supports 12V/24V automotive and industrial supplies; 40V absolute max prevents damage during transients. |
| Float Voltage | 4.1V ±0.5% - precisely regulates single-cell Li-ion/polymer battery end-of-charge voltage; ensures safe full charge without overvoltage stress. |
| Max Charge Current | 4A - set by external SENSE–BAT resistor; enables fast charging of high-capacity batteries in portable equipment. |
| Charge Termination | C/10 detection or programmable timer (up to 3 hours) - provides flexibility between current-based safety and time-based top-off for capacity optimization. |
| NTC Monitoring | 0.29V–1.36V input range with 10% hysteresis - supports standard 10kΩ B3380 thermistors for 0°C–40°C safe-charge window enforcement. |
| Operating Temp Range | –40°C to 125°C - qualified for automotive under-hood and industrial embedded environments; junction temp monitored with thermal foldback. |
| Package | 36-pin QFN (5mm × 6mm, 0.75mm height) - exposes SW and GND pads for low-thermal-resistance PCB mounting and high-current routing. |
Pinout & Package
LT3651IUHE-4.1#PBF is housed in a 5mm × 6mm, 0.75mm low-profile plastic QFN with 36 leads and two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW), both requiring solder connection to PCB copper for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NTC (1) | Battery temperature monitor input | Sources 50µA into external thermistor; voltage readback enables 0°C–40°C charge enable/disable with hysteresis. |
| ACPR (2) | Open-collector AC present status | Sinks current when VIN valid; used to signal system power-good to host controller or LED driver. |
| BAT (3) | Kelvin battery voltage sense | Direct connection to battery anode; enables accurate float regulation and auto-recharge at 97.5% VFLT. |
| SENSE (4) | Charge current sense input | Connects to low-side of RSENSE; 95mV full-scale corresponds to 4A max current; enables CC/CV transition. |
| BOOST (5) | High-side gate drive bootstrap supply | Requires ≥1µF capacitor to SW; maintains >2V gate drive margin for low RDS(on) operation at high duty cycles. |
| GND (6,23,31,37) | Power and signal ground reference | Pins 37 (exposed pad) must be soldered to PCB ground plane for thermal dissipation and noise immunity. |
| SW (7,11–18,22,38) | Synchronous switch node | Multiple parallel pins reduce trace inductance; Pin 38 (exposed pad) must be soldered for high-current conduction path. |
| TIMER (24) | Programmable charge cycle timer | 0.68µF to GND sets 3-hour timeout; fault triggers if precondition fails within 22.5 minutes. |
| FAULT (25) | Open-collector fault indicator | Pulled low on NTC out-of-range, bad battery, or thermal shutdown; sinks up to 10mA for direct LED or microcontroller interface. |
| CHRG (26) | Open-collector charge status | Pulled low during active charging; high-impedance after termination - enables LED or GPIO monitoring without pull-up loading. |
| SHDN (27) | Shutdown enable with UVLO | 1.20V threshold with 95mV hysteresis; reduces VIN current to 17µA in shutdown - supports battery-backed sleep modes. |
| ILIM (28) | Input current limit programming | 0–1V input sets max CLP–CLN voltage (95mV = 1V); enables dynamic input current limiting and soft-start. |
| CLP/CLN (29/30) | System input current sense inputs | Differential pair monitors input current via external shunt; allows charge current reduction to hold total system load constant. |
| VIN (32–34) | Main power input | Three parallel pins handle high input current; connects to bulk capacitor and upstream DC source (e.g., 12V/24V supply). |
| RNG/SS (35) | Charge current range and soft-start | 0–1V input sets max SENSE–BAT voltage (95mV = 1V); capacitor to GND enables controlled current ramp-up. |
| RT (36) | Oscillator frequency set | 54.9kΩ to GND sets 1MHz switching frequency; adjusts for EMI or efficiency trade-offs in layout-constrained designs. |
Key Features
| Feature | Design Value |
|---|---|
| Auto-preconditioning below 2.85V | Reduces charge current to 15% of programmed value until battery reaches safe voltage - prevents lithium plating in deeply discharged cells. |
| Thermal foldback protection | Automatically scales back charge current above 125°C junction temperature - avoids thermal runaway while maintaining partial functionality. |
| Dynamic input current limiting | Adjusts battery charge rate in real time to maintain constant total system input current - critical for USB-PD or limited-supply applications. |
| Low standby current (85µA) | Minimizes parasitic drain when battery is fully charged and system is idle - extends shelf life in always-connected devices. |
| Bad battery detection with auto-reset | Triggers FAULT if battery fails to reach 2.85V within 22.5 minutes; clears automatically upon battery replacement - eliminates manual reset requirement. |
Applications
| Industrial Handheld Instruments | 12V to 24V Automotive Systems |
|---|---|
Use Scenario: Ruggedized data collectors and field meters powered by removable Li-ion packs. IC Role / Device Role / Timing Role: Primary CC/CV charger managing battery health, temperature, and input current under variable vehicle voltage (12V–28V). Use Value: Enables reliable hot-swap battery operation with auto-recharge at 97.5% float voltage and NTC-based cold-weather charge suspension. | Use Scenario: In-vehicle cradle chargers for tablets and mobile radios in trucks, construction equipment, and agricultural machinery. IC Role / Device Role / Timing Role: High-input-voltage battery management IC interfacing directly with alternator-fed 24V bus. Use Value: Withstands 40V transients and delivers 4A charge current while maintaining <0.5% float accuracy - ensures long battery cycle life in harsh environments. |
| Desktop Cradle Chargers | Notebook Computers |
Use Scenario: Docking stations that simultaneously power and charge portable devices via universal DC input. IC Role / Device Role / Timing Role: Standalone charger IC providing isolated battery regulation independent of system power rail. Use Value: Programmable C/10 or timer termination allows OEMs to optimize charge time vs. capacity retention for different battery chemistries. | Use Scenario: Embedded battery charging subsystem in thin-and-light notebooks where space and thermal headroom are constrained. IC Role / Device Role / Timing Role: Monolithic synchronous charger integrating sense, control, and switching in compact QFN package. Use Value: 0.75mm profile and exposed SW/GND pads enable high-density layout with minimal thermal resistance - sustains 4A charge without external heatsink. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Li-ion battery charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BQ24610RGER | Fixed 4.2V float; no NTC input; requires external MOSFETs; 3A max current | Lacks integrated synchronous switches and battery temperature monitoring - needs additional components for automotive-grade safety. | Select when cost-sensitive designs accept external FETs and omit thermal monitoring. |
| MP2617GQZ | 4.2V float; 3.5A max; integrated NTC but no programmable timer; smaller 20-pin QFN | Lower current rating and missing timer-based termination limits use in high-capacity or safety-critical top-off applications. | Select for space-constrained consumer devices where 3.5A suffices and timer-based bad-battery detection is not required. |
Compared with BQ24610RGER and MP2617GQZ, the LT3651IUHE-4.1#PBF uniquely combines 4A synchronous switching, 4.1V precision float, integrated NTC interface, and dual-mode (C/10 + timer) termination in a single 36-pin QFN - making it optimal for industrial and automotive applications demanding robustness and configurability.
Availability
LT3651IUHE-4.1#PBF is available at Aetrix Electronics and suitable for industrial handheld instruments, 12V to 24V automotive systems, and desktop cradle chargers requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LT3651IUHE-4.1#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3651 product line delivers monolithic, wide-input synchronous battery chargers optimized for rugged, high-current applications where reliability across –40°C to 125°C and integrated safety features (NTC, thermal foldback, bad-battery detection) are mandatory.
FAQ
What is the exact float voltage specification for LT3651IUHE-4.1#PBF?
The LT3651IUHE-4.1#PBF has a nominal float voltage of 4.1V with guaranteed accuracy of ±0.5% over the full –40°C to 125°C operating junction temperature range. This is confirmed in the Electrical Characteristics table (Page 3) where VBAT(FLT) for LT3651-4.1 is specified as 4.08V (min), 4.10V (typ), and 4.12V (max) at TJ = –40°C to 125°C.
Does LT3651IUHE-4.1#PBF support automatic recharge, and at what threshold?
Yes, the LT3651IUHE-4.1#PBF supports automatic recharge when the battery voltage drops to 97.5% of its float voltage - i.e., 4.0V (97.5% of 4.1V). This behavior is explicitly documented in the "DESCRIPTION" section and verified in the block diagram (Page 9), where VBAT(FLT) – VRECHRG is shown as 4.0V for LT3651-4.1.
What is the maximum allowable input voltage for LT3651IUHE-4.1#PBF, and what protection exists beyond that?
The absolute maximum input voltage for LT3651IUHE-4.1#PBF is 40V, as stated in the Absolute Maximum Ratings table (Page 2). Input overvoltage lockout (OVLO) activates at 32V (rising), with 1.1V hysteresis, ensuring safe shutdown before reaching the 40V absolute limit - protecting against automotive load-dump transients.
How does LT3651IUHE-4.1#PBF implement preconditioning for deeply discharged batteries?
The LT3651IUHE-4.1#PBF initiates preconditioning when BAT voltage falls below 2.85V (VBAT(PRE)). During this mode, charge current is clamped to 15% of the programmed maximum via ITH reduction to 0.15V. Preconditioning terminates automatically once VBAT exceeds 2.85V, and a 70mV hysteresis prevents oscillation.
Can LT3651IUHE-4.1#PBF operate without an NTC thermistor, and what is the default behavior?
Yes, LT3651IUHE-4.1#PBF operates without an NTC thermistor: the NTC pin (Pin 1) may be left unconnected. In this configuration, temperature monitoring is disabled and charging proceeds regardless of battery temperature. No fault is generated, and all other functions (CC/CV, termination, status outputs) remain fully operational.
LT3651IUHE-4.1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Lithium Ion/Polymer
- Number of Cells:
- 1
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- Current, Timer
- Fault Protection:
- Over Temperature
- Charge Current - Max:
- 4A
- Battery Pack Voltage:
- 4.1V
- Voltage - Supply (Max):
- 32V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3651IUHE-4.1#PBF FAQ
1.How can I place an order for LT3651IUHE-4.1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3651IUHE-4.1#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 LT3651IUHE-4.1#PBF reliable?
The price and inventory of LT3651IUHE-4.1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3651IUHE-4.1#PBF is usually 5 days.
3.What payment methods are accepted for LT3651IUHE-4.1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3651IUHE-4.1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3651IUHE-4.1#PBF?
LT3651IUHE-4.1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3651IUHE-4.1#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 LT3651IUHE-4.1#PBF?
For technical support, including LT3651IUHE-4.1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3651IUHE-4.1#PBF requirements.
6.How does Aetrix verify that LT3651IUHE-4.1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3651IUHE-4.1#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 LT3651IUHE-4.1#PBF meets industry standards.
7.What is the process for return or replacement of LT3651IUHE-4.1#PBF?
All LT3651IUHE-4.1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3651IUHE-4.1#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 LT3651IUHE-4.1#PBF part is unused and in its original packaging.
Return procedure for LT3651IUHE-4.1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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