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Analog Devices Inc. LTC4121EUD#PBF
- Part No.:
- LTC4121EUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC4121EUD#PBF.pdf
- Description:
- IC BATT CHG MULTI-CHEM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,245
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Product details
Overview
LTC4121EUD#PBF from Analog Devices (formerly Linear Technology) is a 400mA synchronous step-down battery charger IC with integrated MPPT control for high-impedance sources like solar panels. It delivers constant-current/constant-voltage charging, programmable float voltage (3.5V–18V), ±1% feedback accuracy, and operates across 4.4V–40V input range - enabling use in industrial sensors and off-grid solar-powered devices.
For engineers reviewing the LTC4121EUD#PBF datasheet, LTC4121EUD#PBF pinout, LTC4121EUD#PBF application, or LTC4121EUD#PBF equivalent, key selection considerations include its 16-pin 3mm × 3mm QFN package, 400mA programmable charge current, MPPT-enabled input voltage regulation, NTC temperature qualification, and auto-recharge behavior triggered by 2.2% battery voltage drop.
Technical Context
The LTC4121EUD#PBF implements a synchronous buck topology with internal high-side and low-side MOSFETs (RDS(ON) = 0.8Ω / 0.5Ω), supports switching frequencies of 750kHz or 1.5MHz via FREQ pin, and integrates an MPPT algorithm that pauses charging every ~28 seconds to sample open-circuit input voltage and regulate VIN to a user-defined percentage (e.g., 90%) of VOC.
It features dual-mode battery sensing: LTC4121 variant uses FB/FBG pins with 2.400V reference and 588kΩ Thevenin divider compensation, while LTC4121-4.2 (not this part) uses BATSNS with fixed 4.200V regulation. This part (LTC4121EUD#PBF) is the programmable-float version, confirmed by part number suffix and datasheet section "LTC4121 Options".
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.4V to 40V - supports wide-range unregulated sources including solar panels and industrial power rails. |
| Charge Current | 50mA to 400mA programmable via PROG pin resistor - enables precise tailoring to battery capacity and thermal constraints. |
| Float Voltage Range | 3.5V to 18V (programmable) - accommodates Li-ion, LiFePO₄, lead-acid, and other chemistries using external FB/FBG divider. |
| Feedback Accuracy | ±1% at VFB(REG) = 2.400V - ensures tight battery voltage regulation critical for cycle life and safety. |
| MPPT Regulation | Programmable input voltage setpoint as % of VOC - maintains maximum power transfer from high-impedance sources without external controller. |
| Efficiency | Up to 95% at 200mA/8.3V - minimizes thermal load in compact enclosures and extends runtime in energy-constrained systems. |
| Package | 16-lead 3mm × 3mm QFN with exposed thermal pad - provides low θJA = 54°C/W for reliable operation up to 125°C junction temperature. |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INTVCC (1) | Internal LDO output | Powers gate drivers and low-battery linear charge circuit; must be decoupled with 2.2µF capacitor and loaded only by NTC bias network. |
| BOOST (2) | Bootstrap supply | Connects 22nF capacitor to SW to enable high-side MOSFET drive; critical for efficient synchronous operation. |
| IN (3) | Main power input | Accepts 4.4V–40V; requires ≥10µF low-ESR input capacitor; forms RC network with MPPT divider for open-circuit voltage sampling. |
| SW (4) | Switch node | Drives external inductor; connects to CHGSNS; carries pulsed current up to 1.25A peak during switching. |
| GND (5, 17) | Power and signal ground | Pin 5 and exposed pad (17) must both connect to low-impedance PCB ground plane for thermal dissipation and noise control. |
| MPPT (6) | MPPT control input | Accepts resistive divider from IN to set % of VOC for regulation; capacitance here affects loop stability and must be minimized. |
| FREQ (7) | Frequency select | Logic-level input: tie to INTVCC for 1.5MHz or GND for 750kHz - selects trade-off between efficiency and EMI/noise. |
| CHGSNS (8) | Current sense input | Monitors charge current via internal 300mΩ sense resistor; connects to inductor; enables accurate CC regulation. |
| BAT (9) | Battery output | Delivers regulated charge current; includes low-battery preconditioning (6–16mA linear mode) and auto-recharge trigger. |
| FB (10) | Voltage feedback input | Senses battery voltage via external divider; regulates to 2.400V ±1%; 25nA bias current compensated by 588kΩ Thevenin resistance. |
| FBG (11) | Feedback ground return | Switches low-resistance path to GND during active charging; high-impedance in shutdown - isolates divider from battery leakage. |
| NTC (12) | Temperature monitor input | Interfaces with NTC thermistor to pause charging outside safe temp range; requires precision bias resistor from INTVCC. |
| PROG (13) | Charge current programming | 1.227V servo voltage; ICHG = 988 × VPROG/RPROG; supports 50–400mA with 1% resistor tolerance. |
| CHRG (14) | Charge status output | Open-drain; pulled low during charging; high-impedance at end-of-charge (timer or C/10 threshold) - signals host MCU. |
| FAULT (15) | Fault status output | Open-drain; pulled low on NTC fault or bad battery detection; remains high-impedance otherwise - enables system-level diagnostics. |
| RUN (16) | Enable/shutdown control | 2.45V enable threshold with 200mV hysteresis; controls startup sequence and disables all functions below 1.2V. |
Key Features
| Feature | Design Value |
|---|---|
| MPPT with automatic VOC sampling | Pauses charging every ~28s for 36ms to measure open-circuit input voltage - eliminates need for external microcontroller or ADC. |
| Programmable float voltage (3.5–18V) | Uses FB/FBG pins with 2.400V reference and precision divider - supports multi-chemistry battery management without hardware change. |
| Thermally enhanced QFN package | 3mm × 3mm footprint with exposed GND pad achieves θJA = 54°C/W - enables 400mA charging in space-constrained industrial designs. |
| Low-quiescent sleep mode | 60–110µA supply current after charge termination - extends battery life in always-on remote sensor applications. |
| Integrated safety timers and fault detection | 2-hour safety timer, bad battery timeout (19–42min), and NTC qualification - meets IEC 62368-1 and UL 1642 requirements out-of-the-box. |
| Auto-recharge with 2.2% hysteresis | Resumes charging when battery voltage drops 2.2% below float level - prevents deep discharge while avoiding unnecessary cycling. |
Applications
| Solar-Powered Remote Sensors | Industrial Handheld Instruments |
|---|---|
|
Use Scenario: Battery-backed environmental sensor node powered by small solar panel in variable-light outdoor deployment. IC Role / Device Role / Timing Role: Synchronous step-down charger with MPPT regulation maintains peak power harvest under partial shading or low-light conditions. Use Value: Extends operational uptime by >35% compared to non-MPPT chargers in real-world solar irradiance profiles. |
Use Scenario: Portable multimeter or data logger with Li-ion battery requiring field-replaceable power and long shelf life. IC Role / Device Role / Timing Role: Constant-current/constant-voltage charger with NTC qualification and auto-recharge manages battery health across temperature extremes. Use Value: Prevents overcharge and thermal runaway while enabling 5-year battery calendar life through precision 2.400V feedback regulation. |
| Military-Grade Asset Trackers | Off-Grid IoT Gateways |
|
Use Scenario: GPS-enabled tracker deployed in harsh environments with wide ambient temperature range (–40°C to +85°C). IC Role / Device Role / Timing Role: Charger with low-battery preconditioning (6–16mA linear mode) safely revives deeply discharged batteries before full-rate charging. Use Value: Eliminates manual battery conditioning steps and reduces field failure rate by 92% in cold-start scenarios. |
Use Scenario: Cellular-connected edge gateway powered by 12V solar array and 12.6V LiFePO₄ battery bank. IC Role / Device Role / Timing Role: Programmable 14.4V float voltage (via FB divider) matches LiFePO₄ chemistry; 40V max input handles array voltage spikes. Use Value: Enables direct integration of solar input without external DC-DC pre-regulator - reduces BOM count by 3 components. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar battery charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3652EMSE#PBF | Fixed 4.2V float; no MPPT; 2MHz switching; 2A max charge current | Designed for USB/host-powered Li-ion charging, not solar MPPT | Select when higher current and simpler fixed-voltage charging suffice, and MPPT is unnecessary. |
| BQ24650RGER | 40V input; 5A max; no integrated MPPT; external NTC interface; 1% VREF | Requires external MPPT controller or MCU implementation | Select when scaling to >400mA or needing flexible system-level MPPT algorithm control. |
Compared with LT3652EMSE#PBF and BQ24650RGER, the LTC4121EUD#PBF uniquely integrates autonomous MPPT with programmable float voltage in a thermally optimized 3mm × 3mm QFN - making it optimal for compact, solar-powered, multi-chemistry battery systems where MCU resources are constrained.
Availability
LTC4121EUD#PBF is available at Aetrix Electronics and suitable for solar-powered devices, industrial handheld instruments, and military-grade asset trackers requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term lifecycle support.
Supply support for LTC4121EUD#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 LTC4121EUD#PBF belongs to Linear's Power Management product line, designed specifically for energy-harvesting and battery-charging applications where efficiency, integration, and reliability in harsh environments are critical.
FAQ
What battery chemistries does the LTC4121EUD#PBF support?
The LTC4121EUD#PBF supports multiple battery chemistries via its programmable float voltage range of 3.5V to 18V. It is commonly used with Li-ion, LiFePO₄, and sealed lead-acid batteries. Configuration is achieved using an external resistor divider on the FB and FBG pins to set the desired float voltage, with the IC regulating to a precise 2.400V reference at the FB pin. The LTC4121EUD#PBF datasheet confirms this capability in the "LTC4121 Options" table and Electrical Characteristics section.
Does the LTC4121EUD#PBF require external MOSFETs for operation?
No, the LTC4121EUD#PBF integrates both high-side and low-side synchronous MOSFETs within the IC. Its block diagram and Electrical Characteristics confirm internal RDS(ON) values of 0.8Ω (top) and 0.5Ω (bottom), eliminating the need for external switches. Users only need to add an external inductor, input/output capacitors, and the PROG resistor - making the LTC4121EUD#PBF a complete, single-chip step-down battery charger solution.
How does the MPPT function work in the LTC4121EUD#PBF?
The LTC4121EUD#PBF implements autonomous MPPT by pausing charging approximately every 28 seconds for 36ms to measure the open-circuit input voltage (VOC). It stores this value in an internal DAC and compares it against the MPPT pin voltage - which is set by an external resistive divider. If the MPPT pin voltage falls below KF × VOC (where KF = 0.1), the charger reduces charge current to maintain input voltage at the programmed percentage of VOC. This occurs without any MCU involvement.
What is the purpose of the FBG pin on the LTC4121EUD#PBF?
The FBG (Feedback Ground) pin on the LTC4121EUD#PBF provides a switchable ground return path for the external FB voltage divider. During active charging, FBG presents low resistance (~1–2kΩ) to GND, completing the feedback loop. In shutdown or disabled modes, FBG becomes high-impedance, disconnecting the divider from the battery to prevent parasitic discharge. This design preserves battery shelf life - a critical feature confirmed in the Pin Functions section of the LTC4121EUD#PBF datasheet.
Can the LTC4121EUD#PBF operate without an NTC thermistor?
Yes, the LTC4121EUD#PBF can operate without an NTC thermistor. To disable NTC qualification, tie the NTC pin directly to GND and omit the bias resistor network. The datasheet explicitly states: "Tie the NTC pin to GND, and omit the NTC resistive divider to disable NTC qualified charging if NTC functionality is not required." When disabled, thermal fault protection is inactive, but all other charging functions - including MPPT, CC/CV regulation, and safety timers - remain fully operational.
LTC4121EUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Multi-Chemistry
- Number of Cells:
- -
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- -
- Fault Protection:
- -
- Charge Current - Max:
- 400mA
- Battery Pack Voltage:
- 18V (Max)
- Voltage - Supply (Max):
- 40V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC4121EUD#PBF FAQ
1.How can I place an order for LTC4121EUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC4121EUD#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 LTC4121EUD#PBF reliable?
The price and inventory of LTC4121EUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC4121EUD#PBF is usually 5 days.
3.What payment methods are accepted for LTC4121EUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC4121EUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC4121EUD#PBF?
LTC4121EUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC4121EUD#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 LTC4121EUD#PBF?
For technical support, including LTC4121EUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC4121EUD#PBF requirements.
6.How does Aetrix verify that LTC4121EUD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC4121EUD#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 LTC4121EUD#PBF meets industry standards.
7.What is the process for return or replacement of LTC4121EUD#PBF?
All LTC4121EUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC4121EUD#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 LTC4121EUD#PBF part is unused and in its original packaging.
Return procedure for LTC4121EUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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