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Analog Devices Inc. LT1248IN#PBF
- Part No.:
- LT1248IN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- PFC (Power Factor Correction)
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1248IN#PBF.pdf
- Description:
- IC PFC CTR AV CURR 300KHZ 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,156
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Product details
Overview
LT1248IN#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency active power factor correction (PFC) controller IC designed for universal off-line preregulators up to 1500W. It implements high-frequency PWM current averaging without slope compensation, delivers 7.5V reference output, supports up to 300kHz switching, and integrates a 1.5A peak gate driver with 25ns rise/fall time. It is used in industrial and telecom AC/DC front-ends requiring high line-current fidelity.
For engineers reviewing the LT1248IN#PBF datasheet, LT1248IN#PBF pinout, LT1248IN#PBF application, or LT1248IN#PBF equivalent, key selection criteria include its 16-pin PDIP package, –40°C to 125°C operating range, 100°C/W thermal resistance, 16V VCC turn-on threshold, and integrated overvoltage protection with 1.05×VREF trip ratio.
Technical Context
The LT1248IN#PBF employs a current-mode control architecture centered on a high-gain (110dB DC), 3MHz unity-gain bandwidth current amplifier and a voltage error amplifier (100dB DC gain, 3MHz GBW) with clamped 13.5V output. Its multiplier uses a square-law gain function (IM = (IAC • IEA²)/(200µA)²) to reduce AC loop gain at light load, improving stability and reducing line-current distortion.
It features a programmable oscillator (RSET/CSET), soft-start via SS pin (12µA charging current), synchronization capability (EN/SYNC pin accepts >200ns pulses at 4.5–6.5V), and dual protection: instantaneous OVP (100ns propagation delay) and peak current limiting via PKLIM comparator with 400ns response.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Turn-On Threshold | 16.5V typical - ensures reliable startup only after auxiliary supply reaches stable operating voltage |
| Reference Voltage (VREF) | 7.50V ±12mV - precision internal reference used for OVP, RSET biasing, and amplifier biasing |
| Oscillator Frequency Range | 58–115kHz - set by RSET (10k–30k) and CSET (200pF–2200pF); enables design flexibility for EMI and magnetics optimization |
| GTDR Peak Output Current | 2A - drives MOSFET gates directly without external buffers, supporting fast switching of high-Ciss devices |
| Operating Temperature Range | –40°C to +125°C - qualified for industrial and telecom environments with full parameter guarantees |
| Supply Current (Active) | 12mA typical - low quiescent draw enables efficient operation across wide load range |
| EN/SYNC Shutdown Threshold | 2.6V rising - cleanly disables controller with minimal leakage, reducing system standby power |
Pinout & Package
LT1248IN#PBF is housed in a 16-lead plastic dual in-line package (PDIP, N package), 0.300" wide, with 100°C/W junction-to-ambient thermal resistance. Pin 1 is bottom-left corner when notch is up.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal reference ground | Common return for all internal circuits; must be low-inductance connection to minimize noise coupling into sensitive analog inputs |
| PKLIM (Pin 2) | Peak current limit comparator input | Threshold referenced to GND; sets secondary overcurrent protection level using resistor divider from VREF to sense resistor |
| CAOUT (Pin 3) | Current amplifier output | Drives PWM modulator; goes low to force zero duty cycle when current loop saturates or fault occurs |
| ISENSE (Pin 4) | Inverting input of current amplifier | Accepts voltage from current-sense resistor; clamped at –0.6V to prevent negative overdrive during transients |
| MOUT (Pin 5) | Multiplier high-impedance current output | Feeds CAOUT; high-Z node requires careful PCB layout to avoid noise injection; clamped at –0.6V/2V |
| IAC (Pin 6) | AC line voltage sensing current input | Bias at 2V minimizes dead zone; 32k series resistor enables simple RC filtering of switching noise |
| VAOUT (Pin 7) | Voltage error amplifier output | Clamped at 13.5V; drops below 2.5V to disable multiplier output, enabling no-load regulation via M1 amplifier |
| OVP (Pin 8) | Overvoltage comparator input | Trips at 1.05×VREF (≈7.875V); triggers fast shutdown to protect downstream components during load dump |
| VREF (Pin 9) | 7.5V precision reference output | Sources up to 5mA; powers internal circuitry and external resistive dividers for OVP and PKLIM thresholds |
| EN/SYNC (Pin 10) | Enable/shutdown and sync input | Below 2.6V → shutdown; pulses <5V with >200ns width → synchronize oscillator to external clock |
| VSENSE (Pin 11) | Inverting input of voltage error amplifier | Summing node tied to VREF via diode; senses regulated output voltage through feedback divider |
| RSET (Pin 12) | Oscillator timing and max current setting | Sets CSET charging current and maximum multiplier output IM(MAX) = 3.75V/RSET; primary line-current limit control |
| SS (Pin 13) | Soft-start control | 12µA current source charges external capacitor; below 7.5V, it becomes reference for voltage amplifier to ramp VOUT smoothly |
| CSET (Pin 14) | Oscillator timing capacitor connection | With RSET, determines frequency: f = 1.5/(RSET × CSET); ramp amplitude is fixed at 5V peak-to-peak |
| VCC (Pin 15) | Supply voltage input | Operates from 11.5V to 18V; requires local 0.1µF ceramic + ≥56µF low-ESR electrolytic bypass for gate-driver current spikes |
| GTDR (Pin 16) | High-current MOSFET gate driver output | 1.5A peak, 25ns edge speed; clamped at 15V but may overshoot with capacitive loads; requires ≥5Ω series gate resistor |
Key Features
| Feature | Design Value |
|---|---|
| Fixed-frequency current-mode PFC | Eliminates need for slope compensation while maintaining stability in both CCM and DCM operation |
| Square-law multiplier gain | Reduces AC loop gain at light load, minimizing line-current THD and improving system robustness |
| Integrated 1.5A gate driver | Directly drives power MOSFETs without external drivers, reducing BOM count and layout complexity |
| Programmable oscillator (RSET/CSET) | Enables precise tuning of switching frequency and maximum line current limit in one shared component |
| Two-level overcurrent protection | RSET sets primary current limit; PKLIM provides fast secondary shutdown to prevent catastrophic failure |
| Line-switching noise rejection | Internal 32k resistor at IAC pin allows simple RC filter, preventing instability from high-impedance line noise injection |
Applications
| Industrial AC/DC Front-Ends | Telecom Rectifier Modules |
|---|---|
Use Scenario: 300–1500W universal-input (90–270VAC) offline power supplies feeding isolated DC/DC converters in factory automation systems. IC Role / Device Role / Timing Role: Primary PFC controller regulating boost stage to achieve >0.99 power factor and low THD across full load range. Use Value: Enables compliance with IEC 61000-3-2 Class A/D harmonic limits while supporting wide ambient temperature operation (–40°C to +125°C). | Use Scenario: 48V telecom rectifier shelves accepting 100–240VAC input, delivering tightly regulated –48V DC with high efficiency and reliability. IC Role / Device Role / Timing Role: Active PFC controller managing boost converter pre-regulation before downstream buck or forward stages. Use Value: Delivers stable 382V bus under varying line conditions, with OVP and PKLIM protecting against load dump and short-circuit events. |
| Medical Power Systems | Server PSU Pre-Regulators |
Use Scenario: UL/IEC 60601-1 compliant AC/DC power supplies for diagnostic imaging equipment requiring low EMI and high reliability. IC Role / Device Role / Timing Role: Core PFC controller ensuring clean input current waveform and stable intermediate bus voltage. Use Value: Supports medical-grade safety isolation by eliminating need for mechanical line switches and enabling consistent performance across global mains voltages. | Use Scenario: High-density 80 PLUS Titanium server PSUs where space-constrained designs demand high integration and thermal resilience. IC Role / Device Role / Timing Role: High-efficiency PFC controller operating up to 300kHz to shrink magnetic size while maintaining >98% efficiency at 50% load. Use Value: Reduces boost inductor volume by ~30% vs. 65kHz designs, while 100°C/W θJA enables convection-cooled layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar power factor correction applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1249CS8#TRPBF | 8-pin SOIC package; simplified pinout; lower max frequency (200kHz); no SS pin or M1 amplifier | Targeted at cost-sensitive, lower-power (<500W) designs where board space is critical and soft-start is handled externally | Choose LT1249 for compact, low-part-count PFC where full LT1248IN#PBF feature set is unnecessary |
| UCC28070PW | Texas Instruments' average-current-mode PFC controller; 16-pin TSSOP; supports interleaved operation; higher integration (no external multiplier) | Designed for high-efficiency, multi-phase PFC in enterprise PSUs; includes built-in zero-current detection and digital soft-start | Choose UCC28070 for designs needing interleaving support, tighter THD control, or TI ecosystem compatibility |
Compared with LT1249CS8#TRPBF and UCC28070PW, the LT1248IN#PBF offers superior thermal performance in PDIP packaging, full analog control transparency for custom loop shaping, and dedicated M1 amplifier for no-load regulation-making it preferred for ruggedized, high-reliability industrial and telecom applications.
Availability
LT1248IN#PBF is available at Aetrix Electronics and suitable for industrial AC/DC front-ends, telecom rectifier modules, and medical power systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LT1248IN#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 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT1248 family.
The LT1248IN#PBF belongs to Linear's high-performance analog power management portfolio, engineered specifically for universal-input active PFC preregulators demanding precision, stability, and ruggedness in harsh operating environments.
FAQ
What is the operating temperature range for the LT1248IN#PBF?
The LT1248IN#PBF is rated for operation from –40°C to +125°C, with full electrical specifications guaranteed across this extended industrial temperature range. Its N-package (PDIP) has a thermal resistance of 100°C/W junction-to-ambient, making it suitable for convection-cooled or moderately forced-air applications without derating up to 125°C junction temperature.
How does the LT1248IN#PBF implement soft-start, and what external component is required?
The LT1248IN#PBF implements soft-start via the SS pin (Pin 13), which sources a constant 12µA current. An external capacitor connected from SS to GND ramps the voltage from 0V to 8V; below 7.5V, this voltage serves as the reference for the voltage amplifier, gradually increasing the output voltage. A typical 0.01µF capacitor yields ~625ms ramp time, preventing inrush current and transformer saturation during startup.
Can the LT1248IN#PBF be synchronized to an external clock, and what are the timing requirements?
Yes, the LT1248IN#PBF supports synchronization via the EN/SYNC pin (Pin 10). Pulses must fall below 5V (threshold 4.5–6.5V) with minimum width of 200ns and repetition rate up to 1.6× the natural oscillator frequency. The internal one-shot timer ensures reliable reset; pulses must not drop below 3V to avoid unintended shutdown, and the pin retains dual functionality for enable/disable control.
What is the purpose of the M1 amplifier in the LT1248IN#PBF, and when does it activate?
The M1 amplifier in the LT1248IN#PBF activates when VAOUT (Pin 7) falls to 2.2V, typically under no-load or very light-load conditions. It injects up to 7µA into the ISENSE node to cancel current amplifier offset voltage, preventing uncontrolled VOUT rise due to amplifier VOS. This ensures stable regulation even at zero output power, a critical capability for systems with highly variable loads.
How is the maximum line current set in the LT1248IN#PBF, and what is the formula?
The maximum line current in the LT1248IN#PBF is primarily set by RSET (Pin 12) using the formula IM(MAX) = 3.75V / RSET, where IM(MAX) is the maximum multiplier output current. This current flows through RREF (e.g., 4kΩ) to generate a reference for the current amplifier. For a 0.2Ω sense resistor RS, line current limit ≈ (IM(MAX) × RREF) / RS - e.g., RSET = 15kΩ gives IM(MAX) = 250µA and ~5A line limit.
LT1248IN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Mode:
- Average Current
- Frequency - Switching:
- 300kHz
- Current - Startup:
- 250 µA
- Voltage - Supply:
- 15.5V ~ 27V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
LT1248IN#PBF FAQ
1.How can I place an order for LT1248IN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1248IN#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 LT1248IN#PBF reliable?
The price and inventory of LT1248IN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1248IN#PBF is usually 5 days.
3.What payment methods are accepted for LT1248IN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1248IN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1248IN#PBF?
LT1248IN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1248IN#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 LT1248IN#PBF?
For technical support, including LT1248IN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1248IN#PBF requirements.
6.How does Aetrix verify that LT1248IN#PBF is sourced from the original manufacturer or authorized distributors?
All LT1248IN#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 LT1248IN#PBF meets industry standards.
7.What is the process for return or replacement of LT1248IN#PBF?
All LT1248IN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1248IN#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 LT1248IN#PBF part is unused and in its original packaging.
Return procedure for LT1248IN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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