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Analog Devices Inc. LT1308ACF#TR
- Part No.:
- LT1308ACF#TR
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LT1308ACF#TR.pdf
- Description:
- IC REG BST SEPIC ADJ 2A 14TSSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT1308ACF#TR 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, consumes only 140μA quiescent current at no load, and integrates a ±2% accurate 200mV low-battery detector. It is used in digital cameras and handheld computers requiring high-efficiency boost conversion with minimal standby power.
For engineers reviewing the LT1308ACF#TR datasheet, LT1308ACF#TR pinout, LT1308ACF#TR application, or LT1308ACF#TR equivalent, this page provides verified technical context, package-specific pin functions, real-world efficiency curves, confirmed alternative parts with functional differences, and design-critical layout guidance for TSSOP-14 implementation.
Technical Context
The LT1308ACF#TR employs current-mode PWM control with a fixed 600kHz oscillator and internal ramp compensation to prevent subharmonic oscillation above 50% duty cycle. Its error amplifier uses external VC-pin compensation (typically 47kΩ + 100pF), and its Burst Mode™ operation-enabled only in the LT1308A variant-dynamically disables switching circuitry below ~400mA load to maintain >75% efficiency at 1mA output current.
It integrates a precision 200mV reference (±2% over temperature) for the LBI/LBO low-battery detection path, an improved 36V-rated switch with 300mV VCE(SAT) at 2A, and a shutdown pin that enables the device at ≥1V (independent of VIN). The TSSOP-14 package features four GND pins, three SW pins, and two VIN pins-all internally connected per datasheet Note 6.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 600kHz fixed-enables compact magnetics and filtering; supports <5mm input capacitor placement per layout guidelines. |
| Input Voltage Range | 1V to 10V-supports direct regulation from single Li-ion (2.7–4.2V), alkaline (1.5V × 2), or NiCd (1.2V × 4) stacks. |
| No-Load Quiescent Current | 140μA-achieved via Burst Mode™ shutdown of non-essential blocks; critical for battery runtime in standby. |
| Feedback Reference Voltage | 1.22V ±1.6%-sets output via external resistor divider; enables precise 3.3V, 5V, or 12V outputs with standard 1% resistors. |
| Switch Current Limit | 2A minimum-guarantees start-up into heavy loads (e.g., 20Ω at 1.5V input yields 3.5A peak inductor current). |
| Low-Battery Threshold Accuracy | ±2% at 200mV-reduces false low-battery triggers in portable devices; specified over full 0°C to 70°C commercial range. |
| Shutdown Current | ≤1μA-ensures zero-load battery drain during system sleep; SHDN pin floats to disable by default. |
Pinout & Package
LT1308ACF#TR is housed in a 14-lead plastic TSSOP package (JEDEC MO-153, 5.0mm × 6.4mm × 1.2mm), rated for 0°C to 70°C operation. Thermal resistance θJA = 80°C/W with proper PCB copper heatsinking across all four GND pins.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Compensation node for error amplifier | Connect series RC (e.g., 47kΩ + 100pF) to ground; controls loop stability and transient response. |
| FB (Pin 2) | Inverting input of feedback error amplifier | 1.22V reference point; output voltage set by R1/R2 divider: VOUT = 1.22V × (1 + R1/R2). |
| SHDN (Pin 3) | Enable/disable control input | ≥1V enables converter; 0V or floating disables it; draws ≤5μA at 6V-compatible with logic-level GPIO. |
| GND (Pins 4–7) | Power and signal ground return | All four pins must be tied together at package and connected to local ground plane; primary thermal path. |
| SW (Pins 8–10) | Internal NPN switch collector | Three parallel pins reduce trace inductance and EMI; connect directly to inductor/diode node with minimal copper area. |
| VIN (Pins 11–12) | Main power supply input | Two parallel pins lower impedance; requires local 47μF tantalum capacitor placed <5mm away per layout rules. |
| LBI (Pin 13) | Low-battery detector input | Accepts voltage divider from battery; trips LBO when input falls below 200mV ±2%; bias current flows out (33nA typical). |
| LBO (Pin 14) | Open-collector low-battery output | Sinks 50μA max; requires external pull-up (e.g., 220kΩ to VIN); asserts low when LBI < 200mV. |
Key Features
| Feature | Design Value |
|---|---|
| Burst Mode™ Operation | Reduces no-load IQ to 140μA by disabling oscillator, driver, and ramp generator-extending battery life in intermittent-use devices. |
| 36V Switch Rating | Enables 34V maximum output (e.g., 12V SEPIC or 24V boost) without external clamp; eliminates need for higher-voltage MOSFETs. |
| Multi-Pin Parallel Routing | Three SW and two VIN pins in TSSOP-14 lower effective trace inductance and thermal resistance-critical for 2A continuous switching. |
| Independent SHDN Logic Interface | Enables converter using any ≥1V source (e.g., microcontroller I/O); removes dependency on VIN rail-simplifies power sequencing. |
| ±2% Low-Battery Threshold | Minimizes premature shutdown in battery-powered systems; tighter than LT1308's ±5% spec-improves usable battery capacity. |
Applications
| Digital Cameras | GSM/CDMA Phones |
|---|---|
Use Scenario: Powering CCD/CMOS image sensors and LCD backlights from a single Li-ion cell (3.0–4.2V). IC Role / Device Role / Timing Role: Step-up converter generating stable 5V/1A or 12V/500mA rails; Burst Mode™ maintains >80% efficiency at 10mA display standby current. Use Value: Enables 10+ hour video recording runtime by minimizing quiescent loss; 600kHz switching allows use of 4.7μH shielded inductors under 3mm height. | Use Scenario: Supplying RF power amplifiers and baseband processors during transmit bursts in 2G/3G handsets. IC Role / Device Role / Timing Role: High-current boost regulator delivering 3.3V/800mA from declining 3.2–3.6V battery; starts reliably into 5Ω load per Figure 14. Use Value: Eliminates bootstrapping failure during deep discharge; 2A switch current limit ensures PA turn-on without brownout. |
| LCD Bias Supplies | Battery Backup Supplies |
Use Scenario: Generating ±10V or +20V bias for TFT-LCD gate drivers and source drivers in portable displays. IC Role / Device Role / Timing Role: Configured in SEPIC topology (Figure 8) to regulate 5V output from 3–10V input; uses dual inductors and ceramic output caps. Use Value: Achieves <100mVpp ripple with 10μF X5R ceramics due to low 300mV VCE(SAT) and controlled ESR zero via VC compensation. | Use Scenario: Maintaining SRAM or real-time clock voltage during main power loss in industrial controllers. IC Role / Device Role / Timing Role: Always-on boost converter powered from backup coin cell (1.5–3.0V); LBO pin signals battery depletion to host MCU. Use Value: ±2% LBI threshold prevents false RTC reset; 1μA shutdown current extends 2032 coin cell life to >5 years. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1308BCF#TR | Continuous switching at light loads (no Burst Mode™); 2.5mA quiescent current vs. 140μA; same pinout and package. | Preferred where low-frequency output ripple is unacceptable (e.g., audio codec supplies); sacrifices battery runtime for ripple performance. | Select LT1308BCF#TR only if system requires constant-frequency operation and can tolerate 18× higher no-load current. |
| MAX761CSA+ | 520kHz switching; 100μA IQ; 30V switch rating; SO-8 only; no integrated low-battery detector. | Lacks LBI/LBO functionality; requires external supervisor IC for battery monitoring; smaller footprint but lower max output voltage. | Choose MAX761CSA+ when board space is constrained and low-battery detection is handled elsewhere in system. |
Compared with LT1308BCF#TR and MAX761CSA+, the LT1308ACF#TR uniquely balances ultra-low quiescent current, integrated precision battery monitoring, and TSSOP-14 thermal performance-making it optimal for space-constrained, battery-critical applications like handheld medical devices.
Availability
LT1308ACF#TR 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 LT1308ACF#TR 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 product support, datasheets, and application engineering for legacy Linear parts including the LT1308 family.
The LT1308A/B series was designed specifically for micropower, high-current boost conversion in portable battery-powered equipment-emphasizing start-up reliability, light-load efficiency, and integrated system supervision.
FAQ
What is the maximum output voltage achievable with the LT1308ACF#TR?
The LT1308ACF#TR switch is rated for 36V, enabling regulated output voltages up to 34V in boost configuration. This is confirmed in the Absolute Maximum Ratings table and supported by application circuits in Figures 1 and 8. Output voltage is set by the FB divider ratio; for example, a 309kΩ/47kΩ divider yields 12V. Always verify diode and capacitor voltage ratings exceed the intended VOUT + margin.
Does the LT1308ACF#TR require an external compensation network?
Yes, the LT1308ACF#TR requires an external RC network from VC (Pin 1) to ground for loop stability. Typical values are 47kΩ and 100pF, as shown in Figure 1 and detailed in the PIN FUNCTIONS section. Omitting this network causes instability, oscillation, or poor transient response-especially with low-ESR ceramic output capacitors.
Can the LT1308ACF#TR start up into a precharged output capacitor?
Yes, the LT1308ACF#TR can start up into heavy loads, including precharged output capacitors. Figure 13 shows successful start-up into a 20Ω load (250mA steady-state) from 1.5V input, with peak inductor current reaching 3.5A. This capability stems from its internal current-mode architecture and independent bias generation-not bootstrapped from VOUT.
How does the low-battery detector on the LT1308ACF#TR interface with a microcontroller?
The LT1308ACF#TR low-battery detector uses open-collector LBO (Pin 14) and referenced LBI (Pin 13) inputs. Connect LBI to a resistor divider from the battery, and tie LBO to a microcontroller GPIO with a pull-up (e.g., 100kΩ to VIN). When LBI drops below 200mV ±2%, LBO pulls low-triggering an interrupt. The LT1308ACF#TR datasheet Figure 10 shows exact component values for trip-point setting.
Is the LT1308ACF#TR pin-compatible with the older LT1308?
Yes, the LT1308ACF#TR is pin-for-pin upgrade compatible with the LT1308 in the same TSSOP-14 package, as explicitly stated in the FEATURES section. However, key improvements-including lower quiescent current (140μA vs. 250μA), tighter low-battery accuracy (±2% vs. ±5%), and higher switch voltage rating (36V vs. 25V)-require verifying system-level timing and protection margins after replacement.
LT1308ACF#TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- 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#TR FAQ
1.How can I place an order for LT1308ACF#TR through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1308ACF#TR 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#TR reliable?
The price and inventory of LT1308ACF#TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1308ACF#TR is usually 5 days.
3.What payment methods are accepted for LT1308ACF#TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1308ACF#TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1308ACF#TR?
LT1308ACF#TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1308ACF#TR 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#TR?
For technical support, including LT1308ACF#TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1308ACF#TR requirements.
6.How does Aetrix verify that LT1308ACF#TR is sourced from the original manufacturer or authorized distributors?
All LT1308ACF#TR 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#TR meets industry standards.
7.What is the process for return or replacement of LT1308ACF#TR?
All LT1308ACF#TR units undergo pre-shipment inspection (PSI). If there is an issue with LT1308ACF#TR, 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#TR part is unused and in its original packaging.
Return procedure for LT1308ACF#TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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