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Analog Devices Inc. LTC1731EMS8-8.2#TRPBF
- Part No.:
- LTC1731EMS8-8.2#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Chargers
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LTC1731EMS8-8.2#TRPBF.pdf
- Description:
- IC BATT CHG MULT-CHEM 2CEL 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,095
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Product details
Overview
LTC1731EMS8-8.2#TRPBF from Analog Devices (formerly Linear Technology) is a complete constant-current/constant-voltage linear battery charger controller for 2-cell lithium-ion batteries, featuring 8.2V regulated float voltage, ±1% output voltage accuracy, 7% charge current programming accuracy via external RPROG/RSENSE, and automatic trickle-charge initiation below 4.95V - deployed in portable medical monitors requiring precise, low-quiescent-power battery management.
For engineers reviewing the LTC1731EMS8-8.2#TRPBF datasheet, LTC1731EMS8-8.2#TRPBF pinout, LTC1731EMS8-8.2#TRPBF application, or LTC1731EMS8-8.2#TRPBF equivalent, key selection criteria include its 8-pin MSOP package, C/10 end-of-charge detection, programmable timer termination, sleep-mode battery drain of 15µA, and compatibility with external P-channel MOSFET or high-gain PNP pass devices.
Technical Context
The LTC1731EMS8-8.2#TRPBF implements a dual-loop linear control architecture: a current amplifier servoing the DRV pin to maintain precise IBAT via RSENSE, and a voltage amplifier regulating BAT pin potential to 8.2V using an internal 2.457V reference and precision resistor divider. It operates only within 8.8V–12V input supply range and enters sleep mode when VCC − VBAT falls below 54mV.
Charge sequencing is fully autonomous: trickle charge at 10% IBAT initiates if VBAT < 4.95V; transition to constant-current mode occurs above that threshold; constant-voltage regulation begins as VBAT approaches 8.2V; and termination is enforced either by C/10 detection (after ≥320ms delay) or by external CTIMER-based timeout - with no firmware or host intervention required.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Float Voltage | 8.2V ±1% - ensures safe, full-state-of-charge for 2-cell Li-Ion without overvoltage stress or capacity loss. |
| Charge Current Accuracy | ±7% - set by RPROG/RSENSE ratio; enables repeatable 400mA–500mA charging across production units. |
| Sleep Mode Drain | 15µA typical - minimizes battery self-discharge during standby, extending shelf life in unpowered devices. |
| Input Voltage Range | 8.8V to 12V - matches standard 9V wall adapters and industrial DC supplies; UVLO disables operation below 8.2V. |
| C/10 Detection Threshold | 50mA typical (at 500mA full scale) - provides reliable near-full-charge signal for status indication or system wake-up. |
| Trickle Threshold | 4.95V ±0.15V - prevents forced charging of deeply discharged or defective cells, improving safety compliance. |
| Timer Accuracy | ±10% (with 0.1µF capacitor) - supports predictable 30-hour max charge window for fail-safe battery protection. |
Pinout & Package
Package: 8-lead plastic MSOP (3.0mm × 3.0mm × 0.86mm), RoHS-compliant, moisture-sensitive level 1, 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 8.2V regulation point; bypassed with ≥10µF for loop stability. |
| CHRG (2) | Open-drain charge status output | Pulled low during active charge; switches to 100µA sink at C/10; floats high-impedance after timer expiry or shutdown. |
| TIMER (3) | Timer capacitor & CV disable input | CTIMER to GND sets 30h/µF timeout; tied to VCC forces constant-current-only mode; shorted to GND disables timer/C/10. |
| GND (4) | Analog and power ground reference | Common return for all internal amplifiers, comparators, and current sources; must be low-impedance connection. |
| PROG (5) | Charge current programming & shutdown input | RPROG to GND sets IBAT = (2.457V × 800Ω)/(RPROG × RSENSE); floating triggers 2.457V shutdown threshold. |
| DRV (6) | External pass device drive output | Drives gate of P-MOSFET or base of high-gain PNP; clamped to VCC − 6.5V to protect low-VGS MOSFETs. |
| VCC (7) | Main input supply voltage | Accepts 8.8V–12V; bypassed with 1µF ceramic; UVLO activates at 8.2V with 200mV hysteresis. |
| SENSE (8) | Current sense amplifier input | Connected to RSENSE high-side node; senses voltage drop to regulate IBAT; referenced to VCC, not GND. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.457V precision reference | Enables 8.2V float regulation with ±1% total error over temperature and line, eliminating need for external DAC or trimming. |
| Automatic low-voltage trickle charge | Initiates 10% IBAT charging when VBAT < 4.95V and holds for ≤¼ of programmed timer duration - prevents damage to depleted cells. |
| Programmable C/10 end-of-charge indicator | Provides clean, latched digital signal (via CHRG pin state change) at 10% of full-scale current - usable for LED or µC interrupt without analog thresholding. |
| Dual-termination safety logic | Combines timer expiry and C/10 detection to terminate charge - prevents thermal runaway in case of failed cell or sensor fault. |
| Low-power sleep mode | Reduces battery drain to 15µA when input is removed - critical for long-term storage of battery-backed instrumentation. |
Applications
| Portable Medical Monitors | Handheld Diagnostic Scanners |
|---|---|
|
Use Scenario: Battery-powered ECG or pulse oximeter operating 72+ hours between charges, stored for months without maintenance. IC Role / Device Role / Timing Role: Primary linear charger controller managing 2S Li-Ion pack; regulates float voltage to 8.2V and terminates charge via C/10 + timer dual logic. Use Value: ±1% voltage accuracy preserves cell longevity; 15µA sleep drain extends shelf life; MSOP package enables compact PCB layout in space-constrained enclosures. |
Use Scenario: Ruggedized ultrasound probe with hot-swap battery, requiring fast recharge and real-time charge status feedback. IC Role / Device Role / Timing Role: Constant-current/constant-voltage charger with CHRG pin driving status LED and µC GPIO; TIMER pin configured for 4-hour max charge window. Use Value: C/10 detection enables accurate "90% charged" alert; PROG pin programmability allows field calibration of charge rate; 8.2V setting avoids overvoltage stress on aging cells. |
| Industrial Handheld Terminals | Charging Docks for Wearables |
|
Use Scenario: Warehouse inventory scanner used 12h/day, recharged nightly via cradle; requires robust termination against NiMH/Li-Ion misinsertion. IC Role / Device Role / Timing Role: Charger controller supporting both Li-Ion (8.2V CV) and NiMH (CC-only via TIMER-to-VCC) modes; uses external PNP pass transistor for cost-sensitive design. Use Value: Constant-current-only mode eliminates voltage regulation for NiMH; trickle threshold prevents charging of shorted cells; 8-pin MSOP simplifies automated assembly. |
Use Scenario: Multi-bay dock simultaneously charging 4 smartwatches; each bay requires independent, low-noise charging with status reporting. IC Role / Device Role / Timing Role: Standalone charger per bay; BAT pin directly connected to battery; CHRG pin drives discrete LED; SENSE/DRV pins interface with low-RDS(on) P-MOSFET. Use Value: No external op-amps or comparators needed - reduces BOM count; 7% current accuracy ensures consistent charge time across bays; MSOP footprint allows dense multi-channel layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar linear 2-cell Li-Ion charger controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1731EMS8-8.4#TRPBF | Fixed 8.4V float voltage (vs. 8.2V); otherwise identical pinout, specs, and functionality. | Designed for newer 2S Li-Ion cells with higher nominal voltage; not interchangeable without battery chemistry verification. | Select only if battery datasheet specifies 4.20V/cell (8.4V total); avoid for legacy 4.10V/cell (8.2V) packs to prevent overcharge. |
| LTC1732EMS8#TRPBF | Includes AC adapter presence detection, automatic recharge, and thermal regulation; lacks programmable timer and uses different PROG scaling. | Targeted at consumer docks with plug/unplug cycling; requires different RPROG calculation and adds VACOK monitoring circuitry. | Choose when system needs auto-recharge on voltage sag or adapter-in detection; not drop-in - redesign of PROG/TIMER/CHRG interface required. |
Compared with LTC1731EMS8-8.2#TRPBF, the -8.4 variant offers higher float voltage for modern cells but risks overcharging older 8.2V-rated packs, while the LTC1732 adds system-level features at the cost of increased design complexity and non-interchangeable timing/control behavior.
Availability
LTC1731EMS8-8.2#TRPBF is available at Aetrix Electronics and suitable for portable medical monitors, handheld diagnostic scanners, industrial handheld terminals, and charging docks requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC1731EMS8-8.2#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 technical support, datasheet archives, and manufacturing continuity for all Linear-branded products including the LTC series.
The LTC1731EMS8-8.2#TRPBF belongs to Linear's precision battery management IC family, designed specifically for space-constrained, low-power, single-chip linear charging of multi-cell Li-Ion systems without microcontroller dependency.
FAQ
What is the maximum input voltage rating for the LTC1731EMS8-8.2#TRPBF?
The LTC1731EMS8-8.2#TRPBF has an absolute maximum input voltage (VCC) of 13.2V. Its recommended operating range is 8.8V to 12V. Operation above 12V may degrade long-term reliability, and exceeding 13.2V risks permanent damage to the VCC pin and internal regulators. Always include transient suppression if used in environments with load-dump or inductive switching noise.
Can the LTC1731EMS8-8.2#TRPBF charge NiMH batteries?
Yes, the LTC1731EMS8-8.2#TRPBF can charge NiMH batteries in constant-current-only mode by connecting the TIMER pin to VCC, which disables voltage regulation, timer, and trickle functions. However, external termination (e.g., −ΔV or temperature cutoff) remains mandatory, as the LTC1731EMS8-8.2#TRPBF provides no NiMH-specific termination logic. The 8.2V float setting is irrelevant in this mode.
How is charge current programmed on the LTC1731EMS8-8.2#TRPBF?
Charge current is set using two external resistors: RPROG from PROG to GND and RSENSE between VCC and SENSE. The formula is IBAT = (2.457V × 800Ω) / (RPROG × RSENSE). For example, RPROG = 19.6kΩ and RSENSE = 0.2Ω yields ~500mA. Both resistors should be 1% tolerance metal film types for best accuracy.
What happens to the LTC1731EMS8-8.2#TRPBF when the input supply is disconnected?
When VCC drops below VBAT + 54mV, the LTC1731EMS8-8.2#TRPBF automatically enters sleep mode, reducing battery drain current to 15µA typical. In this state, the internal resistor divider disconnects from BAT, the DRV pin pulls to VCC (turning off the external pass device), and the CHRG pin goes high-impedance - preserving battery energy during storage or transport.
Does the LTC1731EMS8-8.2#TRPBF support automatic recharge?
No, the LTC1731EMS8-8.2#TRPBF does not support automatic recharge. Once charging terminates (by timer expiry or C/10), it remains idle until VCC is cycled or the PROG pin is momentarily floated and re-grounded. For auto-recharge functionality, consider the pin-compatible LTC1732EMS8#TRPBF, which includes voltage-sag detection and restart logic.
LTC1731EMS8-8.2#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 8.2V
- Voltage - Supply (Max):
- 12V
- Interface:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LTC1731EMS8-8.2#TRPBF FAQ
1.How can I place an order for LTC1731EMS8-8.2#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1731EMS8-8.2#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 LTC1731EMS8-8.2#TRPBF reliable?
The price and inventory of LTC1731EMS8-8.2#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1731EMS8-8.2#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC1731EMS8-8.2#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1731EMS8-8.2#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1731EMS8-8.2#TRPBF?
LTC1731EMS8-8.2#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1731EMS8-8.2#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 LTC1731EMS8-8.2#TRPBF?
For technical support, including LTC1731EMS8-8.2#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1731EMS8-8.2#TRPBF requirements.
6.How does Aetrix verify that LTC1731EMS8-8.2#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1731EMS8-8.2#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 LTC1731EMS8-8.2#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1731EMS8-8.2#TRPBF?
All LTC1731EMS8-8.2#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1731EMS8-8.2#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 LTC1731EMS8-8.2#TRPBF part is unused and in its original packaging.
Return procedure for LTC1731EMS8-8.2#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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