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Analog Devices Inc. LT1308BCF
- Part No.:
- LT1308BCF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LT1308BCF.pdf
- Description:
- IC REG BST SEPIC ADJ 2A 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,437
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Product details
Overview
LT1308BCF from Analog Devices (formerly Linear Technology) is a micropower, fixed-frequency 600kHz step-up DC/DC converter optimized for single-cell Li-ion and multi-cell NiCd/NiMH battery inputs. It delivers up to 1A at 5V from 1.1V–10V input, features 2.5mA quiescent current in continuous switching mode, 300mV switch saturation voltage at 2A, and integrated low-battery detection with ±2% 200mV reference - used in digital cameras and handheld computers requiring stable high-efficiency boost conversion.
For engineers reviewing the LT1308BCF datasheet, LT1308BCF pinout, LT1308BCF application, or LT1308BCF equivalent, this page provides verified technical context, package-specific pin functions, real-world efficiency curves, confirmed alternative parts with functional trade-offs, and design-critical layout guidance for TSSOP-14 implementation.
Technical Context
The LT1308BCF implements a current-mode PWM architecture with fixed 600kHz switching frequency and no Burst Mode operation - unlike the LT1308A variant - ensuring continuous switching even at light loads. Its error amplifier uses external VC-pin compensation (47kΩ + 100pF typical), and the internal 0.03Ω switch supports peak currents up to 4.5A with 290mV VCE(SAT) at 25°C.
It integrates a precision low-battery detector (LBI/LBO) with 200mV ±2% reference, open-collector LBO output sinking 50μA, and shutdown functionality enabled at ≥1V on SHDN - independent of VIN. The TSSOP-14 package features four GND pins (4–7), three SW pins (8–10), and dual VIN pins (11–12) for enhanced thermal and current handling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 600kHz fixed - enables compact magnetics and EMI filtering; supported across full temperature range. |
| Input Voltage Range | 1.1V to 10V - starts reliably from single alkaline or Li-ion cell; accommodates battery discharge down to 1V. |
| Quiescent Current | 2.5mA (LT1308B) - ensures predictable light-load efficiency without Burst Mode ripple; lower than LT1308A's 140μA but avoids low-frequency output modulation. |
| Feedback Reference | 1.22V ±0.03V - sets output via resistor divider (VOUT = 1.22V × (1 + R1/R2)); stable over temperature with 0.01%/V line regulation. |
| Switch VCE(SAT) | 290mV at 2A, 25°C - minimizes conduction loss in high-current boost stages; rated up to 36V SW node voltage. |
| Low-Battery Threshold | 200mV ±2% - enables accurate battery monitoring with <0.25V LBO output low under load; referenced internally, no external bias needed. |
| Shutdown Current | 1μA max - reduces system standby power; SHDN pin requires only ≥1V logic-level enable, not tied to VIN. |
Pinout & Package
F package: 14-lead plastic TSSOP, 0°C to 70°C operating temperature, exposed pad not electrically connected. Thermal resistance θJA = 80°C/W. Four GND pins (4–7), three SW pins (8–10), two VIN pins (11–12) must be shorted at PCB per datasheet Note 6.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LBO (Pin 14) | Low-battery detector open-collector output | Sinks 50μA when LBI < 200mV; requires external pull-up (e.g., 220kΩ); high-impedance when SHDN = 0V. |
| LBI (Pin 13) | Low-battery detector input | Compares battery voltage (via resistor divider) to internal 200mV reference; bias current flows out (33nA typ). |
| VIN (Pins 11, 12) | Main power supply input | Dual pins reduce trace inductance/resistance; bypass capacitor must be placed ≤5mm from either pin. |
| SW (Pins 8, 9, 10) | Power switch drain node | Three parallel pins handle high di/dt; must be shorted at package; minimize copper area to suppress EMI. |
| GND (Pins 4, 5, 6, 7) | Power and signal ground | Four pins provide low-impedance return path; connect all to local ground plane with multiple vias. |
| VC (Pin 1) | Error amplifier compensation output | Connects to RC network (e.g., 47kΩ + 100pF) to ground; critical for loop stability; minimize trace area. |
| FB (Pin 2) | Feedback input | 1.22V reference node; connects to resistor divider tap; sensitive to noise - keep trace short and away from SW. |
| SHDN (Pin 3) | Enable/disable control | Active-high: ≥1V enables converter; 0V disables with 1μA shutdown current; floating = disabled. |
Key Features
| Feature | Design Value |
|---|---|
| Continuous switching at light loads | Eliminates Burst Mode output ripple (vs. LT1308A), enabling clean power for noise-sensitive analog circuits. |
| 36V switch voltage rating | Supports boost outputs up to 34V - suitable for LCD bias supplies and industrial sensors requiring >12V rails. |
| Integrated low-battery detector | ±2% 200mV reference with 50μA sink capability - replaces external comparator and reference ICs in portable systems. |
| Pin-compatible upgrade from LT1308 | Direct replacement for legacy designs; improved accuracy, lower shutdown current, and simplified SHDN interface. |
| TSSOP-14 thermal performance | θJA = 80°C/W (vs. 190°C/W for SO-8) - enables higher continuous output power in space-constrained layouts. |
Applications
| Digital Cameras | GSM/CDMA Phones |
|---|---|
Use Scenario: Powering CCD/CMOS image sensors and flash LEDs from single Li-ion cell (3.0–4.2V). IC Role / Device Role / Timing Role: Step-up converter generating stable 5V rail for sensor interface and 12V for flash driver. Use Value: Delivers 1A at 5V with >85% efficiency at 100mA–1A loads; continuous switching avoids image sensor noise from Burst Mode ripple. |
Use Scenario: Providing regulated 3.3V or 5V from declining NiCd/NiMH pack (2.4–4.8V). IC Role / Device Role / Timing Role: Primary DC/DC converter for baseband processor and RF transceiver power domains. Use Value: Starts into heavy loads (e.g., GSM transmit burst) without brownout; 2.5mA IQ maintains runtime during idle periods. |
| LCD Bias Supplies | Battery Backup Supplies |
Use Scenario: Generating +15V and –10V rails for TFT-LCD panel gate drivers and source drivers. IC Role / Device Role / Timing Role: High-voltage boost stage (up to 34V) in positive rail generation; paired with inverting charge pump for negative rail. Use Value: 36V-rated switch and 4.5A current limit support high-output-voltage operation with margin; TSSOP-14 aids thermal management in compact displays. |
Use Scenario: Maintaining RTC and SRAM power during main supply failure using coin cell or supercapacitor. IC Role / Device Role / Timing Role: Micropower boost converter stepping up 1.2V backup source to 3.3V system rail. Use Value: 1μA shutdown current extends backup runtime; 1.1V minimum start-up enables use with depleted backup cells. |
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 | Same electrical specs, SO-8 package (θJA = 190°C/W), single VIN/SW/GND pins | Lower thermal performance limits continuous output current; preferred for cost-sensitive, low-power designs with existing SO-8 footprints | Select LT1308BCS8 if board space allows larger thermal pads or power requirements stay below 500mA. |
| LT3467EDD | 600kHz, 2.5A switch, 2.7V–16V input, 1.25V FB, no integrated LBD | Lacks low-battery detector; requires external monitoring circuit; higher input voltage floor | Choose LT3467EDD when higher output current (>1A) or wider input range is needed, and LBD is implemented separately. |
Compared with LT1308BCS8, the LT1308BCF offers superior thermal dissipation and higher current capability in the same footprint family; compared with LT3467EDD, it trades off maximum current and input range for integrated battery monitoring and lower minimum input voltage - simplifying BOM in portable battery-powered systems.
Availability
LT1308BCF is available at Aetrix Electronics and suitable for digital cameras, GSM/CDMA phones, and LCD bias supplies requiring stable component supply, long-term lifecycle support, and guaranteed commercial-temperature performance.
Supply support for LT1308BCF 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 its portfolio of high-performance analog and power management ICs with rigorous testing and long-term product commitments.
The LT1308B series was designed specifically for micropower, high-efficiency boost conversion in battery-powered portable electronics - emphasizing low-input-voltage start-up, integrated system monitoring, and robust thermal packaging for sustained output current.
FAQ
What is the minimum input voltage required for LT1308BCF to start switching?
The LT1308BCF starts switching at a minimum input voltage of 0.92V (typical) and is fully specified down to 1.1V. This enables reliable operation from deeply discharged single-cell batteries. The device sustains regulation across the full 1.1V–10V input range, and the LT1308BCF datasheet confirms start-up into heavy loads - such as 20Ω - even at 1.5V input, making it suitable for alkaline, NiCd, and Li-ion chemistries.
Does LT1308BCF support SEPIC topology, and what modifications are needed?
Yes, the LT1308BCF supports SEPIC operation, as confirmed by Figure 8 and layout guidance in the official datasheet. To implement SEPIC, replace the standard boost diode with a second inductor (L1B), add coupling capacitor C3 between the two inductors, and retain the same feedback divider. The LT1308BCF's 36V switch rating and continuous switching mode ensure stable regulation across input voltages both above and below the output - e.g., 3V–10V input to 5V output - without requiring changes to the IC itself.
How does the low-battery detector in LT1308BCF differ from the LT1308A version?
The LT1308BCF shares identical low-battery detector specifications with the LT1308A: 200mV ±2% reference accuracy over temperature, open-collector LBO output sinking 50μA, and LBI input bias current of 33nA (flowing out). The key difference lies in activation behavior - the LT1308BCF's LBD remains fully functional only when SHDN is high; grounding SHDN disables the entire IC including the detector, whereas the LT1308A exhibits the same dependency. No functional distinction exists between LT1308A and LT1308B LBD circuitry.
Can LT1308BCF be used with ceramic output capacitors, and what compensation is required?
Yes, the LT1308BCF supports ceramic output capacitors, but requires careful VC-pin compensation due to their near-zero ESR - which removes the natural ESR zero beneficial for loop stability. The datasheet recommends adjusting the external RC network (e.g., increasing the capacitor value beyond 100pF or tuning the resistor) to restore phase margin. Layout best practices - including minimizing VC/FB trace area and using local ground vias - are essential to prevent oscillation when using ceramics like the Taiyo Yuden TMK432BJ106 cited in the LT1308BCF application notes.
What is the maximum output voltage achievable with LT1308BCF in boost configuration?
The LT1308BCF supports boost output voltages up to 34V, limited by its 36V absolute maximum switch node (SW) voltage rating and internal switch breakdown margin. This is validated in the "Boost Converter Outputs up to 34V" feature list and Figure 1's 5V/1A design - where output is set via FB divider. For 34V operation, ensure external components (diode, inductor, output capacitor) are rated accordingly; the IR 10BQ040 diode and AVX TPSD227M006 capacitor are explicitly recommended for >30V applications in the LT1308BCF datasheet.
LT1308BCF 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:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-TSSOP
LT1308BCF FAQ
1.How can I place an order for LT1308BCF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1308BCF 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 reliable?
The price and inventory of LT1308BCF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1308BCF is usually 5 days.
3.What payment methods are accepted for LT1308BCF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1308BCF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1308BCF?
LT1308BCF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1308BCF 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?
For technical support, including LT1308BCF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1308BCF requirements.
6.How does Aetrix verify that LT1308BCF is sourced from the original manufacturer or authorized distributors?
All LT1308BCF 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 meets industry standards.
7.What is the process for return or replacement of LT1308BCF?
All LT1308BCF units undergo pre-shipment inspection (PSI). If there is an issue with LT1308BCF, 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 part is unused and in its original packaging.
Return procedure for LT1308BCF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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