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Analog Devices Inc. LT3651IUHE-8.4#TRPBF
- Part No.:
- LT3651IUHE-8.4#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LT3651IUHE-8.4#TRPBF.pdf
- Description:
- IC BATT CHG LI-ION 2CELL 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,664
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Product details
Overview
LT3651IUHE-8.4#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 4A, 2-cell Li-Ion/Polymer battery charger IC with average current mode synchronous step-down architecture. It operates from 9V to 32V input, delivers ±0.5% float voltage accuracy at 8.4V, supports C/10 or programmable timer termination, and integrates NTC-based temperature monitoring for automotive cradle chargers and industrial handheld instruments.
For engineers reviewing the LT3651IUHE-8.4#TRPBF datasheet, LT3651IUHE-8.4#TRPBF pinout, LT3651IUHE-8.4#TRPBF application, or LT3651IUHE-8.4#TRPBF equivalent, this page provides verified functional identity, validated QFN-36 package mapping, confirmed 8.4V float voltage and 4A charge capability, real-world thermal fault behavior, and two rigorously cross-checked alternative parts for 2-cell high-voltage Li-Ion charging systems.
Technical Context
The LT3651IUHE-8.4#TRPBF implements an average current mode control loop using dual error amplifiers: V-EA compares BAT voltage against an internal 8.4V reference, while C-EA regulates inductor current via SENSE–BAT differential sensing. Charge current is clamped at 95mV across RSENSE, corresponding to 4A full-scale output.
It features integrated safety logic including preconditioning below 5.8V, auto-recharge at 97.5% of float voltage (8.2V), bad battery detection after 22.5 minutes of precondition timeout, and thermal foldback triggered above 125°C. Input current limiting is implemented via CLP/CLN sense resistor feedback controlled by ILIM pin voltage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 9V to 32V - supports direct connection to 12V/24V automotive and industrial rails without pre-regulation. |
| Battery Float Voltage | 8.4V ±0.5% - precisely targets 2-cell Li-Ion nominal 8.4V fully charged state with minimal overvoltage risk. |
| Max Charge Current | 4A - delivered via synchronous switcher with <480mV top-switch on-drop and –140mV bottom-switch on-drop. |
| Charge Termination | C/10 detection or programmable timer (default 3 hours) - enables top-off charging or strict time-limited cycles. |
| NTC Monitoring Range | 0.27V to 1.45V input range - compatible with standard 10kΩ B3380 thermistors for 0°C–40°C safe-charge window. |
| Standby Supply Current | <85µA - minimizes parasitic drain when battery is fully charged and system is idle. |
| Package | 36-lead 5mm × 6mm QFN with exposed SW (Pin 38) and GND (Pin 37) pads - requires PCB soldering for thermal integrity. |
Pinout & Package
LT3651IUHE-8.4#TRPBF uses a 36-lead plastic QFN package (5mm × 6mm, 0.75mm profile) with two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW). Both must be soldered to PCB copper for electrical continuity and thermal dissipation. Pin 37 connects internally to Pins 6, 23, and 31; Pin 38 connects internally to Pins 7, 11–18, and 22.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| NTC (1) | Battery temperature monitor input | Sources 50µA into external 10kΩ NTC; voltage readout determines safe-charge window (0.27V–1.45V = 0°C–40°C). |
| ACPR (2) | Open-collector AC present status | Sinks current when VIN is valid and charger enabled; used for system power-good signaling. |
| BAT (3) | Kelvin battery voltage sense | Direct connection to battery anode; enables precise 8.4V float regulation and 2.5% auto-recharge hysteresis. |
| SENSE (4) | Charge current sense return | Connects to low-side of RSENSE; 95mV differential = 4A max current; sets CC/CV transition point. |
| BOOST (5) | High-side gate drive bootstrap supply | Requires ≥1µF capacitor to SW; enables low RDS(on) operation of top MOSFET for >90% efficiency. |
| GND (6,23,31,37) | Power and signal ground reference | Pins 31/37 must be tied together; exposed Pad 37 is primary thermal path and mandatory PCB solder connection. |
| SW (7,11–18,22,38) | Synchronous switch node | Drives external inductor; exposed Pad 38 is primary thermal path and mandatory PCB solder connection. |
| TIMER (24) | Programmable charge cycle timer | 0.68µF to GND = 3-hour timeout; grounding disables timer, enabling C/10-only termination. |
| FAULT (25) | Open-collector fault indicator | Pulled low during NTC out-of-range, bad battery detection, or thermal shutdown; sinks up to 10mA. |
| CHRG (26) | Open-collector charge status | Pulled low during active charging; high-impedance when terminated or in standby; sinks up to 10mA. |
| SHDN (27) | Enable/disable control with UVLO | 1.20V threshold with 95mV hysteresis; pulls VIN supply current to 17µA in shutdown mode. |
| ILIM (28) | Input current limit programming | Voltage sets max input current via CLP/CLN sense resistor; 50µA sourced to RILIM for gain of 11.5 V/V. |
| CLP/CLN (29/30) | System input current sense inputs | Differential pair monitors input rail current; enables constant-input-current mode by throttling charge current. |
| VIN (32–34) | Main input power supply | Accepts 9V–32V; supplies internal circuitry and battery charging path; pins must be shorted on PCB. |
| RNG/SS (35) | Charge current range and soft-start | 0–1V input controls max charge current (95mV = 4A); 50µA sourced to RRNG/SS for gain of 10.8 V/V. |
| RT (36) | Oscillator frequency set | 54.9kΩ to GND sets 1MHz switching frequency; supports 250kHz–1.1MHz range for EMI optimization. |
Key Features
| Feature | Design Value |
|---|---|
| Dynamic charge rate programming | RNG/SS pin accepts 0–1V analog input to scale max charge current from 0% to 100% of 4A in real time. |
| Auto-preconditioning below 5.8V | Reduces charge current to 15% of programmed value until battery reaches safe voltage threshold. |
| Bad battery detection with auto-reset | Triggers FAULT if battery fails to reach 5.8V within 22.5 minutes; clears automatically upon battery replacement. |
| Thermal foldback protection | Reduces charge current above 125°C junction temperature; prevents thermal runaway during overload. |
| User-programmable switching frequency | RT pin resistor sets frequency from 250kHz to 1.1MHz - enables layout optimization for size vs. EMI trade-offs. |
Applications
| Industrial Handheld Instruments | 12V to 24V Automotive Systems |
|---|---|
|
Use Scenario: Portable test equipment powered by removable 2-cell Li-Ion packs requiring field-replaceable batteries and robust thermal management. IC Role / Device Role / Timing Role: Primary battery charger IC managing CC/CV profile, NTC-based temperature cutoff, and auto-recharge on voltage sag. Use Value: Enables 4A fast charging from 12V vehicle power while maintaining ±0.5% float accuracy and preventing overtemperature faults in sealed enclosures. |
Use Scenario: In-vehicle cradle charger for tablets or ruggedized mobile computers operating across wide ambient temperatures. IC Role / Device Role / Timing Role: High-voltage battery charger interfacing directly to 24V truck/bus electrical system with input current limiting to avoid fuse tripping. Use Value: CLP/CLN-based input current regulation maintains stable 2A system load while delivering up to 4A to battery under cold-start conditions. |
| Desktop Cradle Chargers | Notebook Computers |
|
Use Scenario: Docking station providing simultaneous power delivery to host device and charging of auxiliary battery pack. IC Role / Device Role / Timing Role: Standalone 2-cell charger IC with open-collector CHRG/FAULT outputs for host microcontroller status polling. Use Value: 85µA standby current minimizes overnight energy loss; C/10 + timer dual-termination ensures full capacity without overcharge risk. |
Use Scenario: Embedded battery charging subsystem in thin-and-light notebooks where space and thermal density are constrained. IC Role / Device Role / Timing Role: Monolithic synchronous charger IC replacing discrete buck controller + external MOSFETs and sense circuitry. Use Value: 5mm × 6mm QFN package with dual exposed thermal pads achieves >90% efficiency at 4A while fitting tight board area budgets. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 2-cell Li-Ion charging applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4162-L8.4 | Integrated USB PD interface, 3.2A max charge current, I2C programmability, no external RT resistor needed. | Requires USB-C PD source; lacks CLP/CLN input current limiting; better suited for portable consumer devices than industrial 24V inputs. | Select LTC4162-L8.4 when USB PD compliance and digital configuration are required; LT3651IUHE-8.4#TRPBF remains optimal for high-current 12V–24V direct-input systems. |
| BQ24618RGER | 4A capable, 8.4V float, but uses peak current mode control; no NTC monitoring; only C/10 termination (no timer option). | No built-in temperature safety; requires external thermistor circuit; less suitable for automotive or unattended charging environments. | Choose BQ24618RGER for cost-sensitive, non-safety-critical applications where NTC monitoring and timer termination are unnecessary. |
Compared with LTC4162-L8.4 and BQ24618RGER, the LT3651IUHE-8.4#TRPBF uniquely combines 4A synchronous switching, dual C/10+timer termination, integrated NTC monitoring, and CLP/CLN input current limiting - making it the only option qualified for demanding 24V automotive cradle and industrial handheld use cases requiring full safety autonomy.
Availability
LT3651IUHE-8.4#TRPBF 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 (–40°C to 125°C), and long-term production continuity.
Supply support for LT3651IUHE-8.4#TRPBF 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 and maintains full product support, datasheet documentation, and application engineering for all LT® parts including the LT3651 family.
The LT3651 product line was designed specifically for high-voltage, high-current 2-cell Li-Ion charging in automotive, industrial, and computing applications where input ranges exceed 12V and thermal reliability is critical.
FAQ
What is the exact float voltage setting for LT3651IUHE-8.4#TRPBF?
The LT3651IUHE-8.4#TRPBF has a factory-trimmed float voltage of 8.4V with ±0.5% accuracy over –40°C to 125°C. This value is fixed per part number suffix "-8.4" and cannot be adjusted externally. The LT3651IUHE-8.4#TRPBF achieves this precision using laser-trimmed internal references and is validated in production test across temperature and line regulation.
Does LT3651IUHE-8.4#TRPBF support both C/10 and timer-based charge termination?
Yes, the LT3651IUHE-8.4#TRPBF supports dual termination modes. C/10 detection triggers when sensed current falls to 10% of programmed maximum; timer termination is set via external capacitor on TIMER pin (e.g., 0.68µF = 3 hours). The LT3651IUHE-8.4#TRPBF defaults to timer mode unless TIMER pin is grounded, enabling flexible safety-critical or time-constrained charging profiles.
What thermal protection mechanisms does LT3651IUHE-8.4#TRPBF implement?
The LT3651IUHE-8.4#TRPBF includes junction temperature monitoring with automatic charge current reduction above 125°C, NTC-based battery temperature supervision (0°C–40°C window), and thermal shutdown at TJMAX = 125°C. These functions are independent and concurrently active - the LT3651IUHE-8.4#TRPBF halts charging and asserts FAULT if either die or battery temperature exceeds safe limits.
Can LT3651IUHE-8.4#TRPBF operate from a 12V automotive supply?
Yes, the LT3651IUHE-8.4#TRPBF operates across 9V to 32V input, making it fully compatible with 12V automotive systems including cold-crank (down to 6V) and load-dump (up to 40V absolute max) transients. Its 40V absolute maximum VIN rating and integrated input overvoltage lockout (32V–35V threshold) ensure robustness in automotive environments without external protection circuitry.
What is the purpose of the CLP and CLN pins on LT3651IUHE-8.4#TRPBF?
The CLP and CLN pins on LT3651IUHE-8.4#TRPBF form a differential input that monitors total system input current via an external sense resistor. When combined with the ILIM pin, they enable constant-input-current mode - dynamically reducing battery charge current to maintain a user-defined maximum input draw. This prevents upstream fuse blowing or adapter overload in multi-load systems, a feature not found in most competing 2-cell chargers.
LT3651IUHE-8.4#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Battery Chemistry:
- Lithium Ion/Polymer
- Number of Cells:
- 2
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- Current, Timer
- Fault Protection:
- Over Temperature
- Charge Current - Max:
- 4A
- Battery Pack Voltage:
- 8.4V
- 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-8.4#TRPBF FAQ
1.How can I place an order for LT3651IUHE-8.4#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3651IUHE-8.4#TRPBF 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-8.4#TRPBF reliable?
The price and inventory of LT3651IUHE-8.4#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3651IUHE-8.4#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3651IUHE-8.4#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3651IUHE-8.4#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3651IUHE-8.4#TRPBF?
LT3651IUHE-8.4#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3651IUHE-8.4#TRPBF 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-8.4#TRPBF?
For technical support, including LT3651IUHE-8.4#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3651IUHE-8.4#TRPBF requirements.
6.How does Aetrix verify that LT3651IUHE-8.4#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3651IUHE-8.4#TRPBF 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-8.4#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3651IUHE-8.4#TRPBF?
All LT3651IUHE-8.4#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3651IUHE-8.4#TRPBF, 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-8.4#TRPBF part is unused and in its original packaging.
Return procedure for LT3651IUHE-8.4#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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