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Analog Devices Inc. LT1308ACF
- Part No.:
- LT1308ACF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LT1308ACF.pdf
- Description:
- IC REG BST SEPIC ADJ 2A 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,192
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Product details
Overview
LT1308ACF 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 systems. It delivers up to 1A at 5V from 1V–10V input, features automatic Burst Mode™ operation at light loads (140μA no-load quiescent current), 300mV switch VCE(SAT) at 2A, and integrated low-battery detection with ±2% 200mV reference - used in digital cameras and handheld computers.
For engineers reviewing the LT1308ACF datasheet, LT1308ACF pinout, LT1308ACF application, or LT1308ACF equivalent, this page provides verified technical context, validated package mapping (14-lead TSSOP), confirmed pin functions, real-world efficiency curves, and two rigorously cross-checked alternative parts for design-in decisions.
Technical Context
The LT1308ACF implements current-mode PWM control with a 600kHz oscillator and internal ramp compensation to prevent subharmonic oscillation above 50% duty cycle. Its error amplifier drives the VC pin for external RC compensation, enabling stable regulation across wide input (1V–10V) and output (up to 34V) ranges.
Burst Mode™ operation (LT1308A variant only) disables all circuitry except the error amplifier and low-battery detector when FB rises above 1.22V under light load, reducing IQ to 140μA. The shutdown pin enables operation at ≥1V independent of VIN, and the 200mV LBI threshold is accurate to ±2% over temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 600kHz fixed - enables compact magnetics and EMI filtering with predictable spectral content. |
| Input Voltage Range | 1V to 10V - supports single Li-ion (2.7–4.2V), 2–4 NiCd/NiMH cells, and wide industrial supply rails. |
| Quiescent Current (No Load) | 140μA - minimizes battery drain during standby in portable devices with intermittent usage. |
| Feedback Reference Voltage | 1.22V ±1.6% - sets output via resistor divider (VOUT = 1.22V × (1 + R1/R2)) with high accuracy for stable regulation. |
| Switch VCE(SAT) | 290mV at 2A (25°C) - reduces conduction loss and improves efficiency at high output currents. |
| Low-Battery Threshold | 200mV ±2% - enables precise battery monitoring without external reference, compatible with standard resistive dividers. |
| Shutdown Current | 1μA max - ensures near-zero power draw when disabled, critical for long-term storage or emergency cutoff. |
Pinout & Package
LT1308ACF is housed in a 14-lead plastic TSSOP package (JEDEC MO-153, 5mm × 4.4mm × 1mm), rated for 0°C to 70°C operation. Thermal resistance θJA = 80°C/W with proper PCB copper thermal management.
| 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; trace area must be minimized to reduce noise coupling. |
| FB (Pin 2) | Feedback input | Monitors output via resistor divider; 1.22V reference enables precise VOUT setting; sensitive node requiring short, shielded routing. |
| SHDN (Pin 3) | Enable/disable control | Active-high logic input; ≥1V enables operation - no need to tie to VIN, simplifying system-level power sequencing. |
| GND (Pins 4–7) | Power and signal ground | Four dedicated GND pins must be connected together at the package; serve as primary heat path - connect to large copper pour. |
| SW (Pins 8–10) | Power switch output | Three paralleled SW pins handle high di/dt switching current; must be routed with minimal loop area to suppress EMI. |
| VIN (Pins 11–12) | Main power input | Dual VIN pins reduce IR drop and improve thermal performance; require local 47μF ceramic/tantalum bypass capacitor placed ≤5mm away. |
| LBI (Pin 13) | Low-battery detector input | Accepts voltage-divided battery sense signal; 200mV threshold with ±2% accuracy - float if unused. |
| LBO (Pin 14) | Low-battery open-collector output | Sinks 50μA; requires external pull-up (e.g., 220kΩ); asserts low when LBI < 200mV - directly interfaces with microcontroller GPIO. |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Burst Mode™ Operation | Reduces no-load IQ to 140μA by disabling non-essential circuitry while maintaining regulation - extends battery life in sleep-mode applications. |
| Integrated Low-Battery Detector | ±2% accurate 200mV reference with open-collector LBO output eliminates need for external supervisor IC in space-constrained designs. |
| High-Voltage Switch (36V Rating) | Supports output voltages up to 34V - enables LCD bias supplies, white LED drivers, and industrial sensor excitation without external FETs. |
| Start-Up into Heavy Loads | Delivers full switch current (≥3A peak) during startup - avoids brownout in systems with large output capacitance or active downstream loads. |
| Pin-for-Pin Upgrade from LT1308 | Direct replacement for legacy LT1308 designs - retains same footprint and functionality while improving efficiency, accuracy, and transient response. |
Applications
| Digital Cameras | GSM/CDMA Phones |
|---|---|
Use Scenario: Powering CCD/CMOS image sensors and flash LEDs from a single Li-ion cell (3.0–4.2V). IC Role / Device Role / Timing Role: Step-up converter generating stable 5V/3.3V rails and 12V flash voltage with fast transient response. Use Value: Burst Mode™ cuts standby current to 140μA, extending camera-on time between charges; 600kHz switching allows small 4.7μH inductors. |
Use Scenario: Supplying RF power amplifiers and baseband processors in dual-voltage mobile handsets. IC Role / Device Role / Timing Role: Generating regulated 2.8V/3.3V from declining battery voltage (3.6V → 2.8V) while maintaining GSM burst transmission integrity. Use Value: 300mV switch VCE(SAT) minimizes dropout and improves efficiency at high load currents (>500mA), preserving talk time. |
| LCD Bias Supplies | Battery Backup Supplies |
Use Scenario: Generating positive and negative bias voltages (e.g., +15V/–10V) for TFT-LCD panels in portable medical monitors. IC Role / Device Role / Timing Role: Primary boost stage in charge-pump or inverting converter topologies requiring tight output regulation and low ripple. Use Value: 1.22V feedback reference with ±1.6% tolerance ensures consistent contrast and grayscale fidelity across temperature and battery discharge. |
Use Scenario: Maintaining SRAM or real-time clock (RTC) power during main supply failure in industrial controllers. IC Role / Device Role / Timing Role: Always-on micropower converter drawing <1μA in shutdown and waking instantly upon backup battery insertion. Use Value: 1μA shutdown current prevents backup battery depletion over years; LBO output signals low-voltage condition to host MCU before cutoff. |
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 |
|---|---|---|---|
| LT1308BCF | Continuous switching at light loads (2.5mA IQ), no Burst Mode™ - higher no-load current but zero low-frequency output ripple. | Suitable for noise-sensitive analog circuits (e.g., ADC references) where Burst Mode™ ripple is unacceptable. | Select LT1308BCF when output voltage stability > efficiency at light load; same pinout and compensation network. |
| MAX771CPA+ | 500kHz switching, 1.25V feedback, 350mV switch RDS(on), no integrated low-battery detector - requires external supervision. | Used in legacy designs where MAX771 footprint compatibility is required; lacks LBI/LBO functionality. | Choose MAX771CPA+ only for drop-in replacement in existing MAX771 layouts; verify external low-battery circuit integration. |
Compared with LT1308ACF, LT1308BCF trades 140μA Burst Mode™ efficiency for ripple-free continuous operation, while MAX771CPA+ offers similar topology but omits the integrated 200mV detector - making LT1308ACF uniquely suited for battery-powered systems needing both ultra-low IQ and autonomous low-voltage monitoring.
Availability
LT1308ACF is available at Aetrix Electronics and suitable for digital cameras, GSM/CDMA phones, and LCD bias supplies requiring stable component supply, long-lifecycle support, and guaranteed commercial-grade (0°C to 70°C) performance.
Supply support for LT1308ACF 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 precision analog and power management portfolio. Linear Technology pioneered high-performance DC/DC converters with industry-leading efficiency and integration.
The LT1308A/LT1308B family was designed specifically for battery-powered portable electronics requiring micropower operation, wide input range, and integrated system monitoring - with LT1308ACF targeting space-constrained TSSOP applications.
FAQ
What is the maximum output voltage achievable with the LT1308ACF?
The LT1308ACF switch is rated for 36V, enabling regulated output voltages up to 34V when used in boost configuration. This capability supports applications such as LCD bias generation and white LED drivers. Output voltage is set by the FB resistor divider (VOUT = 1.22V × (1 + R1/R2)), and stability must be verified with appropriate compensation on the VC pin for each output voltage and load condition. The LT1308ACF datasheet confirms 34V operation in typical application circuits.
Does the LT1308ACF support SEPIC topology?
Yes, the LT1308ACF supports SEPIC (Single-Ended Primary Inductance Converter) topology, enabling regulated outputs that can be higher or lower than the input voltage - ideal for applications with wide input ranges like multi-cell battery packs. Figure 8 in the LT1308A/LT1308B datasheet explicitly shows a 3V–10V input to 5V/500mA SEPIC design using the LT1308B, and the LT1308ACF shares identical control architecture, pinout, and electrical specifications with the LT1308BCF variant.
How does the LT1308ACF's Burst Mode™ differ from standard pulse-skipping?
The LT1308ACF's Burst Mode™ operation fully disables the oscillator, driver, and power switch while retaining error amplifier and low-battery detector bias - reducing no-load IQ to 140μA. Unlike generic pulse-skipping, it uses a hysteretic comparator (A1) with built-in hysteresis to gate entire switching cycles, producing regulated output with controlled low-frequency ripple. This is distinct from continuous-mode skipping (e.g., LT1308B), which maintains clocked operation and avoids ripple but draws 2.5mA.
Can the LT1308ACF start up into a precharged output capacitor?
Yes, the LT1308ACF can start up into heavy loads and precharged output capacitors - unlike bootstrapped converters. Its internal bias is derived from VIN, not VOUT, allowing immediate switch activation even when VOUT is already charged. Figure 13 in the datasheet demonstrates successful start-up from 1.5V input into a 20Ω load (250mA steady-state), with inductor current peaking at 3.5A during capacitor charging - confirming robust start-up capability for systems with hold-up capacitors or hot-swap requirements.
What is the recommended PCB layout practice for the LT1308ACF's SW pins?
For the LT1308ACF's three paralleled SW pins (Pins 8–10), minimize trace length and loop area by connecting them together directly at the package using short, wide copper pours - not vias or daisy-chained traces. Place the catch diode and inductor adjacent to these pins, and avoid routing other signals beneath or near the SW node. Figure 7 in the datasheet specifies this layout for the TSSOP package, and violating it causes EMI, instability, or reduced efficiency due to parasitic inductance in high-di/dt paths.
LT1308ACF 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
LT1308ACF FAQ
1.How can I place an order for LT1308ACF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1308ACF 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 LT1308ACF reliable?
The price and inventory of LT1308ACF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1308ACF is usually 5 days.
3.What payment methods are accepted for LT1308ACF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1308ACF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1308ACF?
LT1308ACF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1308ACF 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 LT1308ACF?
For technical support, including LT1308ACF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1308ACF requirements.
6.How does Aetrix verify that LT1308ACF is sourced from the original manufacturer or authorized distributors?
All LT1308ACF 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 LT1308ACF meets industry standards.
7.What is the process for return or replacement of LT1308ACF?
All LT1308ACF units undergo pre-shipment inspection (PSI). If there is an issue with LT1308ACF, 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 LT1308ACF part is unused and in its original packaging.
Return procedure for LT1308ACF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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