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Analog Devices Inc. LTC1731ES8-8.4#PBF
- Part No.:
- LTC1731ES8-8.4#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1731ES8-8.4#PBF.pdf
- Description:
- IC BATT CHG MULT-CHEM 2CEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:205
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Product details
Overview
LTC1731ES8-8.4#PBF from Analog Devices (formerly Linear Technology) is a complete constant-current/constant-voltage linear charger controller for 2-cell lithium-ion batteries, delivering 500mA typical charge current with 1% float voltage accuracy (8.4V), programmable C/10 termination, and automatic trickle charge for deeply discharged cells - used in handheld computing and charging cradles.
For engineers reviewing the LTC1731ES8-8.4#PBF datasheet, LTC1731ES8-8.4#PBF pinout, LTC1731ES8-8.4#PBF application, or LTC1731ES8-8.4#PBF equivalent, key selection criteria include 8.4V regulated float voltage, external RPROG/RSENSE-based current programming, sleep-mode battery drain ≤30µA, and SO-8 package compatibility with thermal design constraints.
Technical Context
The LTC1731ES8-8.4#PBF implements dual-loop control: a current amplifier servoing an external P-channel MOSFET gate via the DRV pin to regulate charge current through RSENSE, and a voltage amplifier comparing BAT voltage against an internal 2.457V reference scaled by precision resistive divider to maintain ±1% 8.4V float regulation.
Charge sequencing is managed by integrated logic including a C/10 comparator detecting end-of-charge, a timer circuit driven by CTIMER capacitor (3 hours/µF), automatic trickle mode activation below 4.95V battery voltage, and UVLO hysteresis (8.2V turn-on, 200mV hysteresis) ensuring stable startup under marginal input conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Float Voltage | 8.4V ±1% - precisely regulates 2-cell Li-Ion termination at full charge without external feedback components. |
| Charge Current Accuracy | ±7% - set by external RPROG and RSENSE; enables repeatable 400–500mA fast-charge profiles. |
| Sleep Mode Drain | 15µA typical - minimizes battery self-discharge when input supply is removed. |
| C/10 Detection Threshold | 50mA typical (at 500mA full scale) - signals near-full charge via CHRG pin state change after 320ms debounce. |
| Timer Accuracy | ±10% - sets total charge duration using CTIMER capacitor; timeout disables charging and forces CHRG high-Z. |
| Trickle Threshold | 4.95V ±0.15V - initiates 10% reduced current for cells below safe fast-charge voltage. |
| UVLO Threshold | 8.2V rising, 8.8V falling - prevents unstable operation during brown-out or weak adapter conditions. |
Pinout & Package
Package: 8-lead plastic SO (Small Outline, narrow 0.150-inch body), RoHS-compliant, rated for –40°C to +85°C operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BAT (1) | Battery voltage sense input | Connects to battery positive; internal 720Ω/100kΩ divider sets 8.4V regulation point; requires ≥10µF bypass for stability. |
| CHRG (2) | Open-drain charge status output | Pulled low during fast charge; switches to 100µA sink at C/10; goes high-Z at timer expiry or shutdown. |
| TIMER (3) | Timer capacitor & CV-mode disable | CTIMER sets 30-hour/µF timeout; tied to VCC disables voltage regulation and timer for NiMH/NiCd constant-current mode. |
| GND (4) | Analog/digital ground reference | Common return for all internal circuits; must be low-impedance connection to minimize sensing error. |
| PROG (5) | Current programming & shutdown control | RPROG to ground sets charge current; floating triggers 2.457V shutdown threshold and disables charging. |
| DRV (6) | External pass device drive output | Sources gate drive for P-MOSFET; clamped to VCC – 6.5V to protect low-VGS FETs. |
| VCC (7) | Main input supply (8.8V–12V) | Power source for IC and pass device; bypass with 1µF ceramic capacitor; UVLO protects against undervoltage. |
| SENSE (8) | Current sense amplifier input | Connected to low-side of RSENSE; senses voltage drop to close current loop; high common-mode rejection. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.457V precision reference | Enables 1% float voltage accuracy without trimming or external DAC, critical for Li-Ion cell longevity. |
| Automatic trickle-to-fast charge transition | Activates 10% current at VBAT < 4.95V and transitions cleanly above threshold, preventing damage to depleted cells. |
| Programmable C/10 detection with debounced latch | 320ms internal delay prevents false triggering from transient load spikes, ensuring reliable end-of-charge signaling. |
| Dual-mode operation (CV+CC or CC-only) | TIMER pin hardwired to VCC disables voltage regulation and timer, converting IC into programmable current source for NiMH/NiCd. |
| Low-battery sleep mode | Reduces ICC to 15µA when VCC is absent or VCC–VBAT < 54mV, extending standby time in portable systems. |
Applications
| Cellular Handhelds | Charging Docks |
|---|---|
Use Scenario: Portable cellular handset with removable 2-cell Li-Ion pack requiring safe, autonomous charging from USB-powered wall adapter. IC Role / Device Role / Timing Role: Linear charger controller managing full CC/CV cycle, C/10 detection, and thermal-safe termination without host MCU intervention. Use Value: Eliminates need for firmware-based charge management; 1% voltage accuracy ensures cell voltage stays within JEDEC A114-B spec limits. | Use Scenario: Desktop charging cradle for enterprise tablets, supporting simultaneous charge of multiple units with LED status indication. IC Role / Device Role / Timing Role: Primary charge controller per slot, driving discrete P-MOSFETs and feeding CHRG signal to microcontroller for multi-state LED control. Use Value: CHRG open-drain output supports direct LED drive or µC polling; sleep mode prevents battery drain when cradle unplugged. |
| Handheld Computers | Industrial Portable Terminals |
Use Scenario: Ruggedized handheld computer used in warehouse logistics, powered by hot-swappable 2-cell Li-Ion battery. IC Role / Device Role / Timing Role: Embedded charger IC enabling field-replaceable battery operation with automatic preconditioning of deeply discharged packs. Use Value: Trickle charge initiation at 4.95V allows recovery of batteries stored at low voltage; PROG pin shutdown supports battery removal detection. | Use Scenario: Battery-backed industrial data logger operating in remote locations with intermittent solar/battery charging. IC Role / Device Role / Timing Role: Standalone linear charger interfacing with external solar regulator, providing regulated 8.4V float to maintain battery health during long-term storage. Use Value: 15µA sleep current preserves battery capacity over months of idle time; SO-8 package supports conformal coating for harsh environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar linear battery charger controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1731EMS8-8.4 | Same functionality and specs; MSOP-8 package instead of SO-8; θJA = 200°C/W vs 125°C/W. | Better suited for space-constrained PCBs; requires tighter thermal layout due to higher thermal resistance. | Select when board area is limited and thermal management via copper pour or heatsink is feasible. |
| LTC4050EDD-4.2#PBF | Single-cell Li-Ion controller (4.2V), integrates thermistor interface and AC adapter detection; no TIMER or PROG pin for current programming. | Designed for consumer electronics with temperature-aware charging; lacks programmable current and dual-cell support. | Choose only for 1-cell systems requiring thermal monitoring; not a functional substitute for LTC1731ES8-8.4#PBF's 2-cell 8.4V capability. |
Compared with LTC1731EMS8-8.4, the LTC1731ES8-8.4#PBF offers lower thermal resistance in SO-8 packaging for higher ambient reliability, while LTC4050EDD-4.2#PBF serves fundamentally different single-cell, thermally adaptive use cases - neither provides pin-compatible or functional drop-in replacement capability.
Availability
LTC1731ES8-8.4#PBF is available at Aetrix Electronics and suitable for handheld computing, charging docks, and industrial portable terminals requiring stable component supply, long-lifecycle support, and RoHS-compliant linear charging control.
Supply support for LTC1731ES8-8.4#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 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LTC1731 series.
The LTC1731 family was designed specifically for cost-sensitive, space-efficient linear charging of 2-cell Li-Ion batteries in portable electronics where simplicity, accuracy, and low quiescent current are prioritized over switching efficiency.
FAQ
What is the maximum input voltage rating for the LTC1731ES8-8.4#PBF?
The LTC1731ES8-8.4#PBF has an absolute maximum input supply voltage (VCC) rating of 13.2V. Its operational range is specified from 8.8V to 12V for reliable constant-current/constant-voltage charging. Exceeding 13.2V risks permanent damage to internal circuitry, especially the DRV clamp and voltage amplifier stages.
How does the LTC1731ES8-8.4#PBF handle deeply discharged batteries?
The LTC1731ES8-8.4#PBF automatically enters trickle charge mode when the BAT pin voltage is below 4.95V, delivering 10% of the programmed full-scale current until the cell voltage rises above threshold. If the low-voltage condition persists for one quarter of the total timer duration, the IC terminates charging and places CHRG in high-impedance state.
Can the LTC1731ES8-8.4#PBF be used to charge NiMH batteries?
Yes - the LTC1731ES8-8.4#PBF can charge NiMH batteries by connecting the TIMER pin to VCC, which disables constant-voltage regulation and the internal timer, configuring the IC as a pure constant-current source. External temperature or ΔV/dt termination must be implemented, as the IC does not provide NiMH-specific termination logic.
What external components are required for basic operation of the LTC1731ES8-8.4#PBF?
Four minimum external components are required: RPROG (to ground from PROG pin) sets charge current; RSENSE (between VCC and SENSE) senses current; CTIMER (from TIMER to GND) sets charge duration; and a 1µF capacitor on VCC. A 10µF capacitor on BAT is strongly recommended for stability when battery is disconnected.
Is the LTC1731ES8-8.4#PBF pin-compatible with other variants in the LTC1731 family?
Yes - all LTC1731 variants (including -8.2, -8.4, -4.1, -4.2) share identical 8-pin SO and MSOP footprints and pin functions. Only the internal voltage divider ratio differs to set 8.2V or 8.4V float; no changes to PCB layout or external circuitry are needed when substituting between -8.2 and -8.4 versions.
LTC1731ES8-8.4#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Battery Chemistry:
- Multi-Chemistry
- Number of Cells:
- 2
- Current - Charging:
- Constant - Programmable
- Programmable Features:
- Timer
- Fault Protection:
- -
- Charge Current - Max:
- 500mA
- Battery Pack Voltage:
- 8.4V
- Voltage - Supply (Max):
- 12V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC1731ES8-8.4#PBF FAQ
1.How can I place an order for LTC1731ES8-8.4#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1731ES8-8.4#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 LTC1731ES8-8.4#PBF reliable?
The price and inventory of LTC1731ES8-8.4#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1731ES8-8.4#PBF is usually 5 days.
3.What payment methods are accepted for LTC1731ES8-8.4#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1731ES8-8.4#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1731ES8-8.4#PBF?
LTC1731ES8-8.4#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1731ES8-8.4#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 LTC1731ES8-8.4#PBF?
For technical support, including LTC1731ES8-8.4#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1731ES8-8.4#PBF requirements.
6.How does Aetrix verify that LTC1731ES8-8.4#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1731ES8-8.4#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 LTC1731ES8-8.4#PBF meets industry standards.
7.What is the process for return or replacement of LTC1731ES8-8.4#PBF?
All LTC1731ES8-8.4#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1731ES8-8.4#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 LTC1731ES8-8.4#PBF part is unused and in its original packaging.
Return procedure for LTC1731ES8-8.4#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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