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Analog Devices Inc. LT1579CS8-3.3#TRPBF
- Part No.:
- LT1579CS8-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Battery Management
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1579CS8-3.3#TRPBF.pdf
- Description:
- IC BATT PWR MGMT MULTI 1C 8SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT1579CS8-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a dual-input, single-output 3.3V fixed-output low-dropout linear regulator designed for battery backup systems requiring seamless input switchover. It delivers 300mA output current with 0.4V dropout at full load, 3.300V ±0.050V output accuracy, and 50µA quiescent current in active mode. It operates in 8-lead SOIC package and supports automatic priority-based switching between VIN1 (primary) and VIN2 (secondary) inputs.
For engineers reviewing the LT1579CS8-3.3#TRPBF datasheet, LT1579CS8-3.3#TRPBF pinout, LT1579CS8-3.3#TRPBF application, or LT1579CS8-3.3#TRPBF equivalent, key selection criteria include dual-input switchover timing, dropout behavior under 300mA load, backup flag assertion logic, reverse-battery protection integrity, and compatibility with 0.01µF BIASCOMP bypassing for stability during input transition.
Technical Context
The LT1579CS8-3.3#TRPBF implements a single error amplifier controlling two independent pass transistors - one per input - enabling tight regulation (±25mV load regulation) regardless of active input source. Its internal 1.5V reference sets thresholds for both low-battery comparators (LBI1/LBI2) and the dropout detector, ensuring consistent voltage monitoring across VIN1 and VIN2.
Switchover is governed by comparator hysteresis (18mV), secondary select (SS) pin logic (0.25–0.75V threshold for VIN1→VIN2), and status flags (BACKUP, DROPOUT) with open-collector outputs capable of sinking 5mA. The BIASCOMP pin requires mandatory 0.01µF ceramic bypassing to stabilize internal bias during input transitions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 3.300V ±0.050V at 1mA, ±0.100V over full load (1–300mA) and temperature range - ensures stable MCU core or I/O rail supply without external trimming. |
| Max Output Current | 300mA from either VIN1 or VIN2 - sufficient to power microcontrollers, real-time clocks, or small sensor subsystems during primary source failure. |
| Dropout Voltage | 0.60V max at 300mA load - enables operation down to VIN = 3.9V while maintaining 3.3V output, critical for single-cell Li-ion or alkaline backup scenarios. |
| Quiescent Current | 50µA typical in active mode, 7µA in shutdown - minimizes standby drain on backup batteries, extending shelf life in always-on monitoring applications. |
| Low-Battery Threshold | 1.500V ±0.050V on LBI1/LBI2 pins - provides precise, hysteresis-stabilized detection of failing input sources before regulation loss occurs. |
| Reverse-Battery Protection | Integrated - eliminates need for external blocking diodes, reducing BOM count and forward voltage drop in battery-replaceable systems. |
| Logic Flag Drive | Open-collector BACKUP and DROPOUT outputs sinking up to 5mA - directly interfaces with CMOS/TTL inputs or LEDs without level-shifting or current-limiting resistors. |
Pinout & Package
LT1579CS8-3.3#TRPBF is housed in an 8-lead plastic SOIC (SO-8) package with standard JEDEC MS-012AC footprint (4.9mm × 3.9mm, 1.27mm pitch). Pin functions are validated per Linear Technology's official SO-8 top view diagram (Document 1579 • BD, page 11).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN1 | Primary power input | Default source; supplies load until voltage drops below LBI1 threshold or SS pin forces switchover - must be bypassed with ≥1µF capacitor if >6" from bulk capacitance. |
| VIN2 | Secondary power input | Backup source activated automatically on VIN1 failure or manually via low-active SS pin - same bypass requirement as VIN1. |
| OUT | Regulated 3.3V output | Delivers up to 300mA; requires ≥4.7µF output capacitor (tantalum or ceramic) to prevent oscillation and limit transient overshoot. |
| GND | Power and signal reference | Common return for all inputs, output, and logic flags - must be low-impedance connection to minimize ground bounce during switchover. |
| SHDN | Shutdown control input | Active-low enable; pulls device into 7µA shutdown state when ≤0.75V - compatible with 3.3V/5V logic and open-drain drivers. |
| SS | Secondary select input | Active-low manual override; forces immediate switch from VIN1 to VIN2 and reduces VIN1 current to ≤3µA - enables controlled battery replacement. |
| BACKUP | Status flag output | Open-collector; pulls low when VIN2 is active - signals backup mode to host controller or LED indicator without external pull-up for ≤20µA loads. |
| BIASCOMP | Bias compensation node | Internal bias point requiring mandatory 0.01µF ceramic capacitor to ground - prevents instability during VIN1→VIN2 transition. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-input priority switchover | Automatic, seamless transfer between VIN1 and VIN2 with no output interruption - maintains RTC or SRAM retention during main power loss. |
| Integrated reverse-battery protection | Eliminates need for external series diode - preserves 0.4V dropout margin and avoids 300–500mV conduction loss in battery-replaceable designs. |
| Two independent low-battery comparators | LBI1/LBI2 monitor each input against 1.5V reference with 18mV hysteresis - enables predictive battery health alerts before system reset. |
| Early-warning dropout flag | DROPOUT pin asserts low when both inputs fall below regulation threshold - provides time-critical warning to initiate graceful shutdown or data save. |
| Hot-swap capable architecture | Supports "remove, recharge and replace" battery operation without loss of regulation - verified in LT1579-5 transient response testing (Fig 1579 G34). |
Applications
| Real-Time Clock (RTC) Backup | Industrial PLC I/O Module |
|---|---|
Use Scenario: Maintaining accurate timekeeping during AC mains failure using a coin-cell battery as VIN2 while main 5V rail serves as VIN1. IC Role / Device Role / Timing Role: Dual-input LDO providing uninterrupted 3.3V supply to RTC IC and associated SRAM, with BACKUP flag signaling battery takeover. Use Value: Ensures <1ppm time drift during switchover; eliminates need for external diode-or circuitry and reduces board area by 30% vs discrete solution. | Use Scenario: Powering isolated digital I/O channels in programmable logic controllers where 24V DC field power (VIN1) and onboard supercapacitor (VIN2) provide redundant supply. IC Role / Device Role / Timing Role: Regulating clean 3.3V for FPGA configuration memory and level-shifters, with DROPOUT flag triggering watchdog reset before brownout. Use Value: Guarantees 300ms hold-up time at full I/O load; enables deterministic fail-safe behavior without software intervention. |
| Medical Patient Monitor Battery Pack | Automotive Telematics ECU |
Use Scenario: Supporting critical sensor acquisition during lithium-polymer battery replacement in portable diagnostic devices, using VIN2 as hot-swap buffer. IC Role / Device Role / Timing Role: Providing regulated 3.3V to analog front-end and ADC, with SS pin asserted during battery swap to force VIN2 sourcing and reduce VIN1 leakage to ≤3µA. Use Value: Prevents data corruption during 2-second battery exchange; meets IEC 60601-1 leakage current limits (<10µA) in patient-connected modes. | Use Scenario: Supplying infotainment and GPS modules in vehicle telematics units where 12V battery (VIN1) and backup supercap (VIN2) ensure continuous GNSS lock during engine cranking. IC Role / Device Role / Timing Role: Delivering low-noise 3.3V to RF receivers, with ripple rejection >55dB at 120Hz enabling reliable signal acquisition during alternator ripple events. Use Value: Sustains GNSS position fix through 500ms 6V battery dip; eliminates need for separate LDO for RF section, reducing thermal stress. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-input backup regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX8632ETA+T | Fixed 3.3V output, 200mA max, no BACKUP/DROPOUT flags, requires external diodes for reverse protection | Lacks integrated switchover status signaling and reverse-battery protection - necessitates additional discretes for equivalent functionality | Select only if cost sensitivity outweighs feature completeness and board space constraints are minimal. |
| TPS63020DSJR | Buck-boost topology, 3.3V adjustable, 2.5A output, no dual-input priority logic or dedicated backup flags | Provides wider input range (1.8–5.5V) but lacks automatic VIN1/VIN2 arbitration - requires external microcontroller supervision for switchover | Prefer for high-current, wide-input applications where firmware-controlled power management is acceptable. |
Compared with MAX8632ETA+T and TPS63020DSJR, the LT1579CS8-3.3#TRPBF uniquely integrates priority-based dual-input switchover, reverse-battery protection, and four dedicated logic flags (BACKUP, DROPOUT, LBO1, LBO2) in a single SO-8 package - eliminating design complexity and validation effort for battery backup integrity.
Availability
LT1579CS8-3.3#TRPBF is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive telematics, and battery-backed real-time clock applications requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT1579CS8-3.3#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.
The LT1579CS8-3.3#TRPBF belongs to Linear Technology's legacy Smart Battery Regulator product line, engineered specifically for mission-critical backup power applications demanding zero-interruption switchover, ultra-low quiescent current, and integrated fault signaling.
FAQ
What is the minimum input voltage required for LT1579CS8-3.3#TRPBF to maintain regulation?
The LT1579CS8-3.3#TRPBF requires a minimum input voltage of 3.2V on either VIN1 or VIN2 to sustain the internal 1.5V reference and low-battery comparator operation. Below this threshold, regulation degrades and the DROPOUT flag asserts. This value is confirmed in Electrical Characteristics Table (Note 8) and Typical Performance Curve G14.
Does LT1579CS8-3.3#TRPBF require external diodes for reverse-battery protection?
No, the LT1579CS8-3.3#TRPBF includes fully integrated reverse-battery protection - no external diodes are needed. This is explicitly stated in the Features list and Absolute Maximum Ratings section, and eliminates ~0.4V forward drop and associated heat dissipation in battery-replaceable systems.
How does the BACKUP flag behave during automatic versus forced switchover?
The BACKUP flag pulls low identically in both cases: during automatic switchover (when VIN1 falls below LBI1 threshold) and during forced switchover (when SS pin is pulled low). Its assertion indicates VIN2 is actively supplying the load, regardless of trigger mechanism - verified in Block Diagram (page 11) and PIN FUNCTIONS description (page 10).
What capacitor value is mandatory on the BIASCOMP pin of LT1579CS8-3.3#TRPBF?
A 0.01µF ceramic capacitor is mandatory between BIASCOMP and GND for stability during VIN1-to-VIN2 switchover. This requirement is specified in the PIN FUNCTIONS section (page 10) and Applications Information (page 12), and omission causes oscillation or erratic flag behavior per typical performance validation.
Can LT1579CS8-3.3#TRPBF operate with only one input connected?
Yes - LT1579CS8-3.3#TRPBF operates normally with only VIN1 connected (VIN2 left open or grounded), or only VIN2 connected (with SS pin held low). The device draws bias current only from the active input, and unused inputs may float without damage, as confirmed in Absolute Maximum Ratings and Applications Information sections.
LT1579CS8-3.3#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Power Management
- Battery Chemistry:
- Multi-Chemistry
- Number of Cells:
- 1
- Fault Protection:
- Over Current, Over Temperature, Reverse Battery, Reverse Current
- Interface:
- -
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1579CS8-3.3#TRPBF FAQ
1.How can I place an order for LT1579CS8-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1579CS8-3.3#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 LT1579CS8-3.3#TRPBF reliable?
The price and inventory of LT1579CS8-3.3#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1579CS8-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1579CS8-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1579CS8-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1579CS8-3.3#TRPBF?
LT1579CS8-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1579CS8-3.3#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 LT1579CS8-3.3#TRPBF?
For technical support, including LT1579CS8-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1579CS8-3.3#TRPBF requirements.
6.How does Aetrix verify that LT1579CS8-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1579CS8-3.3#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 LT1579CS8-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1579CS8-3.3#TRPBF?
All LT1579CS8-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1579CS8-3.3#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 LT1579CS8-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT1579CS8-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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