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Analog Devices Inc. LT1308BCF#PBF
- Part No.:
- LT1308BCF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LT1308BCF#PBF.pdf
- Description:
- IC REG BST SEPIC ADJ 2A 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,103
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Product details
Overview
LT1308BCF#PBF from Analog Devices (formerly Linear Technology) is a micropower, fixed-frequency 600kHz step-up DC/DC converter optimized for single-cell battery operation (1V–10V input), delivering up to 5V/1A from Li-ion or 5V/800mA in SEPIC mode from NiCd stacks. It features continuous switching at light loads, 2.5mA quiescent current, 36V switch rating, and integrated low-battery detection with ±2% 200mV reference.
For engineers reviewing the LT1308BCF#PBF datasheet, LT1308BCF#PBF pinout, LT1308BCF#PBF application, or LT1308BCF#PBF equivalent, key selection factors include its TSSOP-14 package thermal performance (θJA = 80°C/W), 2A switch current limit, 300mV VCE(SAT) at 2A, Burst Mode absence (vs. LT1308A), and compatibility with ceramic output capacitors via external VC compensation.
Technical Context
The LT1308BCF#PBF implements a current-mode PWM architecture with fixed 600kHz oscillator and ramp compensation to suppress subharmonic oscillation above 50% duty cycle. Its error amplifier drives the VC pin to regulate output voltage via external resistor divider on FB, while internal 0.03Ω sense resistor enables precise switch current limiting.
Unlike the LT1308A, the LT1308B variant omits hysteresis in the enable comparator, ensuring continuous switching down to ~100mA inductor current-eliminating low-frequency output ripple but increasing light-load quiescent current to 2.5mA. The LBI/LBO pins provide ±2% accurate low-battery monitoring independent of VIN, with open-collector LBO sinking 50μA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 600kHz typical; enables compact magnetics and EMI filtering with predictable spectral content. |
| Input Voltage Range | 1V to 10V; supports direct operation from single Li-ion (2.7–4.2V), NiCd/NiMH (1.2V/cell), or alkaline cells. |
| Output Voltage Range | Up to 34V; achieved via external feedback divider; enables 5V, 12V, or higher bias supplies. |
| Switch Current Limit | 2A minimum; sustains heavy transient loads and start-up into full output capacitance without foldback. |
| VCE(SAT) @ 2A | 290mV at 25°C; minimizes conduction loss and thermal rise in high-current boost stages. |
| Quiescent Current | 2.5mA during switching; balances efficiency vs. output ripple stability for portable systems requiring consistent regulation. |
| Shutdown Current | 1μA maximum; preserves battery life during system sleep modes with no external discharge path required. |
Pinout & Package
LT1308BCF#PBF is housed in a 14-lead plastic TSSOP package (JEDEC MO-153AC) with exposed pad for thermal enhancement. θJA = 80°C/W when properly soldered to ≥1in² copper area. Four GND pins (4–7), three SW pins (8–10), and two VIN pins (11–12) must be shorted together at the package per datasheet Note 6.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Compensation node for error amplifier | Connects external RC network (e.g., 47kΩ + 100pF) to set loop stability; critical for ceramic capacitor designs. |
| FB (Pin 2) | Feedback input referenced to 1.22V | Sets output voltage via R1/R2 divider: VOUT = 1.22V × (1 + R1/R2); low 27nA bias current minimizes divider error. |
| SHDN (Pin 3) | Enable control with 1V threshold | Active-high logic interface; no need to tie to VIN-simplifies power sequencing and reduces BOM count. |
| GND (Pins 4–7) | Power and signal ground return | All four pins must connect to same low-impedance ground plane; PCB copper acts as heatsink to manage 2A switching losses. |
| SW (Pins 8–10) | Internal NPN switch collector | High-dI/dt node; requires minimized trace area and direct connection to inductor/diode to reduce EMI and voltage spikes. |
| VIN (Pins 11–12) | Main supply input (1V–10V) | Requires local 47μF tantalum + 100pF ceramic bypass; dual pins reduce IR drop and improve transient response. |
| LBI (Pin 13) | Low-battery detector input | Accepts divided battery voltage; trips at 200mV ±2%; bias current flows *out*-affects divider design. |
| LBO (Pin 14) | Open-collector low-battery output | Sinks 50μA; requires external pull-up (e.g., 220kΩ) to signal host processor when battery falls below threshold. |
Key Features
| Feature | Design Value |
|---|---|
| Continuous light-load operation | Eliminates Burst Mode ripple (unlike LT1308A), enabling stable output for noise-sensitive analog circuits and RF modules. |
| 36V switch voltage rating | Supports >30V outputs (e.g., LCD bias, white LED strings) using standard 40V Schottky diodes like MBRS140. |
| Integrated low-battery detector | ±2% accuracy over temperature enables reliable end-of-life battery signaling without external comparators or references. |
| Start-up into heavy loads | Charges output capacitor directly from VIN-no bootstrapping required-ensuring reliable power-up under full load (e.g., 5Ω). |
| TSSOP-14 thermal performance | θJA = 80°C/W (vs. 190°C/W for SO-8) allows sustained 1A output in space-constrained handheld designs. |
Applications
| GSM/CDMA Handsets | Digital Cameras |
|---|---|
Use Scenario: Powering RF power amplifiers and baseband processors from single Li-ion cell. IC Role / Device Role / Timing Role: Step-up converter generating stable 5V rail for PA bias and digital core logic. Use Value: 2.5mA quiescent current extends talk time; 36V switch rating accommodates future 12V PA architectures. | Use Scenario: Supplying CCD/CMOS sensor bias and flash LED drivers in compact camera modules. IC Role / Device Role / Timing Role: High-efficiency boost regulator delivering 12V from 3.3V system rail for image sensor analog front-end. Use Value: Continuous switching prevents low-frequency ripple that would corrupt image data acquisition timing. |
| LCD Bias Supplies | Battery Backup Systems |
Use Scenario: Generating positive and negative bias voltages (e.g., +15V/–10V) for TFT-LCD panels in industrial HMIs. IC Role / Device Role / Timing Role: Primary boost stage in charge-pump or inverting topology providing regulated high-voltage rails. Use Value: 600kHz switching enables small 4.7μH inductors and low-ESR ceramic capacitors, reducing board area by >30% vs. 100kHz solutions. | Use Scenario: Maintaining SRAM or real-time clock power during main supply failure in medical or industrial equipment. IC Role / Device Role / Timing Role: Micropower DC/DC converter sustaining 3.3V backup rail from coin cell or supercapacitor. Use Value: 1μA shutdown current preserves energy for >10 years; ±2% LBI threshold ensures precise brown-out detection before data loss. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-up DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1308BCS8#PBF | Same electrical specs, but in 8-lead SO package (θJA = 190°C/W); lower current capability due to thermal limits. | Preferred for cost-sensitive, low-power (<500mA) designs where PCB area is less constrained than thermal budget. | Select LT1308BCF#PBF when output current exceeds 600mA or ambient temperature exceeds 50°C. |
| MAX771CPA+ | 500kHz fixed frequency, 1.5A switch limit, 28V max switch voltage; no integrated low-battery detector. | Suitable for legacy designs requiring pin-compatible upgrade from MAX771; lacks LBI/LBO functionality. | Choose MAX771CPA+ only if existing layout uses 8-pin DIP and low-battery monitoring is handled externally. |
Compared with LT1308BCS8#PBF, the LT1308BCF#PBF delivers 65% lower thermal resistance for sustained 1A operation, while the MAX771CPA+ trades integrated battery monitoring for broader vendor support-but requires external components to match LT1308B's feature set.
Availability
LT1308BCF#PBF is available at Aetrix Electronics and suitable for GSM/CDMA handsets, digital cameras, LCD bias supplies, and battery backup systems requiring stable component supply with guaranteed long-term availability and full industrial temperature compliance.
Supply support for LT1308BCF#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 ICs, serving precision instrumentation, communications, and industrial markets.
The LT1308B belongs to Linear's micropower DC/DC converter product line, engineered specifically for battery-powered portable electronics demanding high efficiency across wide load ranges and robust start-up into heavy capacitive loads.
FAQ
What is the maximum output voltage achievable with the LT1308BCF#PBF?
The LT1308BCF#PBF supports output voltages up to 34V, limited by its 36V-rated internal switch. This is achieved using an external resistor divider on the FB pin, where VOUT = 1.22V × (1 + R1/R2). For example, a 309kΩ/R2 = 100kΩ divider yields 5V; scaling R1 to 2.4MΩ achieves 30V. Always verify switch voltage stress (VSW = VOUT + VF(DIODE)) remains <36V.
Does the LT1308BCF#PBF require an external compensation network?
Yes, the LT1308BCF#PBF requires an external RC network (e.g., 47kΩ + 100pF) between VC and GND to stabilize the error amplifier loop. This is essential for maintaining phase margin-especially when using low-ESR ceramic output capacitors, which lack the inherent ESR zero provided by tantalum types. Omitting compensation risks oscillation or poor transient response.
How does the LT1308BCF#PBF differ from the LT1308ACF#PBF?
The LT1308BCF#PBF operates in continuous switching mode at all loads, with 2.5mA quiescent current, while the LT1308ACF#PBF enters Burst Mode™ below ~100mA load, reducing IQ to 140μA but introducing low-frequency output ripple. Both share identical pinout, package, and absolute maximum ratings-making them drop-in replacements where ripple tolerance permits.
Can the LT1308BCF#PBF start up into a fully loaded output capacitor?
Yes, the LT1308BCF#PBF can start up into heavy loads-including fully discharged 220μF tantalum output capacitors-without external soft-start circuitry. Its internal current limit (2A min) and direct VIN-derived bias allow inrush currents up to 3.5A (per Figure 13), enabling reliable power-up in systems like handheld computers where output capacitance exceeds 100μF.
What is the recommended inductor for the LT1308BCF#PBF in a 5V/1A boost application?
For 5V/1A output from a 3.6V Li-ion input, Murata LQH6C4R7 (4.7μH, 2.5A saturation current, DCR <35mΩ) is the recommended inductor. It meets both requirements: handling 2A steady-state and >3A transients without >50% inductance drop, while minimizing copper loss. Lower DCR improves efficiency; values between 2μH–10μH are acceptable, but 4.7μH optimizes size vs. ripple trade-off for this load point.
LT1308BCF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Boost, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1V
- Voltage - Input (Max):
- 10V
- Voltage - Output (Min/Fixed):
- 1.22V
- Voltage - Output (Max):
- 34V
- Current - Output:
- 2A (Switch)
- Frequency - Switching:
- 600kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-TSSOP
LT1308BCF#PBF FAQ
1.How can I place an order for LT1308BCF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1308BCF#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 LT1308BCF#PBF reliable?
The price and inventory of LT1308BCF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1308BCF#PBF is usually 5 days.
3.What payment methods are accepted for LT1308BCF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1308BCF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1308BCF#PBF?
LT1308BCF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1308BCF#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 LT1308BCF#PBF?
For technical support, including LT1308BCF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1308BCF#PBF requirements.
6.How does Aetrix verify that LT1308BCF#PBF is sourced from the original manufacturer or authorized distributors?
All LT1308BCF#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 LT1308BCF#PBF meets industry standards.
7.What is the process for return or replacement of LT1308BCF#PBF?
All LT1308BCF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1308BCF#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 LT1308BCF#PBF part is unused and in its original packaging.
Return procedure for LT1308BCF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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