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Analog Devices Inc. LT1245IN8#PBF
- Part No.:
- LT1245IN8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1245IN8#PBF.pdf
- Description:
- IC REG CTRLR BUCK 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:160
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Product details
Overview
LT1245IN8#PBF from Analog Devices is an 8-pin PDIP-packaged, fixed-frequency current-mode PWM controller optimized for off-line and DC/DC converters. It features <250µA start-up current, 50ns current sense delay, 500kHz max output switching frequency (1MHz oscillator), 1A totem-pole output, and active pull-down during undervoltage lockout - enabling robust gate driving in high-reliability AC/DC power supplies.
For engineers reviewing the LT1245IN8#PBF datasheet, LT1245IN8#PBF pinout, LT1245IN8#PBF application, or LT1245IN8#PBF equivalent, key selection criteria include its –40°C to 125°C industrial temperature range, UC1845-compatible pinout, 8.4V start-up threshold with 0.4V hysteresis, 50% maximum duty cycle, and integrated leading-edge blanking for noise-immune current sensing in flyback and forward converters.
Technical Context
The LT1245IN8#PBF implements a fixed-frequency current-mode control architecture where the oscillator (RT/CT pin) sets both switching frequency and deadtime via trimmed 8.2mA sink current and precision RC timing. Its error amplifier delivers 90dB DC gain and 1MHz unity-gain bandwidth, with internal 2.5V reference tied to FB pin and 5V bandgap VREF output.
Current sensing uses a clamped comparator with 100ns blanking (voltage-dependent), 0.9–1.1V input threshold, and cycle-by-cycle peak current limiting. The 1A totem-pole output drives MOSFET gates directly, with 18V high-level clamp and active low-state pull-down (<1V) during UVLO - eliminating external gate discharge resistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | –40°C to 125°C - supports industrial-grade power supply designs without derating. |
| Start-Up Threshold | 8.4V ±0.6V - enables reliable turn-on after bulk capacitor charging in universal-input AC/DC converters. |
| Max Duty Cycle | 50% - limits conduction time for stable operation in discontinuous conduction mode (DCM) flyback topologies. |
| Oscillator Freq | Up to 1MHz - allows 500kHz output switching for compact magnetics and reduced EMI in high-density SMPS. |
| Output Drive | ±1A peak - directly drives large-gate-charge MOSFETs without external buffers, reducing BOM count. |
| VREF Output | 5.000V ±75mV - powers RT resistor and provides stable bias for external circuitry with <0.1mV/°C drift. |
| Current Sense Delay | 50ns - ensures fast overcurrent response while maintaining stability under transient load steps. |
Pinout & Package
N8 package: 8-lead plastic dual in-line package (PDIP), 0.3" width, through-hole mounting, θJA = 130°C/W, TJMAX = 100°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides loop compensation node; sources 0.5mA / sinks 2mA; used to clamp current sense threshold below 1V. |
| 2 - FB | Inverting input of error amp | Internally referenced to 2.5V; accepts feedback voltage divider for output regulation; blanking time varies with FB voltage. |
| 3 - ISENSE | Current sense comparator input | Receives MOSFET source current via sense resistor; trip point proportional to COMP voltage; includes 100ns blanking window. |
| 4 - RT/CT | Oscillator timing node | Connects external RT (to VREF) and CT (to GND); sets frequency and deadtime via trimmed 8.2mA sink current. |
| 5 - GND | Analog/digital ground reference | Common return for all internal circuits; requires dedicated low-impedance PCB trace connected to star ground point. |
| 6 - OUTPUT | Totem-pole gate driver output | Drives MOSFET gate directly; ±1A drive strength; clamped to 18V; actively pulled low (<1V) during UVLO. |
| 7 - VCC | Positive supply input | Accepts 7.6–25V; powers internal circuitry; quiescent current <10mA; includes undervoltage lockout with hysteresis. |
| 8 - VREF | 5V bandgap reference output | Stable 5.000V ±75mV source; supplies RT current and internal bias; capable of sourcing up to 20mA. |
Key Features
| Feature | Design Value |
|---|---|
| Low start-up current | <250µA enables efficient high-voltage start-up using high-value bleed resistors in offline converters. |
| Leading-edge blanking | 100ns (at VFB = 2.5V) eliminates false triggering from transformer leakage spikes without slowing current loop response. |
| Trimmed oscillator | Initial frequency accuracy ±5% and sink current trimmed to 8.2mA typ - minimizes unit-to-unit variation in timing and deadtime. |
| Active UVLO pull-down | Internal Darlington transistors pull both OUTPUT and VREF low during undervoltage lockout - removes need for external gate discharge resistors. |
| High-current output stage | ±1A peak drive capability with 40ns rise / 30ns fall times into 1nF load - supports fast-switching GaN and SiC MOSFETs. |
Applications
| AC/DC Flyback Converter | Isolated DC/DC Forward Converter |
|---|---|
Use Scenario: Universal-input (90–264VAC) 30W adapter powering IoT edge devices with tight no-load power requirements. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode feedback, slope compensation, and soft-start via COMP pin. Use Value: <250µA start-up current reduces standby losses; 50ns current sense delay enables precise overcurrent protection at light loads. | Use Scenario: 48V input telecom power module delivering 12V/5A to baseband processing boards with strict EMI limits. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller synchronizing gate drive to transformer reset timing via RT/CT network. Use Value: 1A output drive eliminates external buffer; 18V output clamp protects MOSFET gate oxide; 50% max duty cycle prevents core saturation. |
| Industrial Motor Drive Power Supply | Medical Equipment Auxiliary PSU |
Use Scenario: DIN-rail mounted 24V/2A auxiliary supply for PLC I/O modules operating in harsh factory environments. IC Role / Device Role / Timing Role: Off-line controller managing wide-input-range (85–305VAC) conversion with reinforced isolation and thermal derating. Use Value: –40°C to 125°C rating ensures reliability across ambient extremes; active UVLO pull-down prevents latch-up during brownouts. | Use Scenario: Patient-connected diagnostic device requiring <100µA no-load consumption and certified 2×MOPP isolation. IC Role / Device Role / Timing Role: Secondary-side regulated controller with isolated feedback via optocoupler to FB pin, leveraging internal 2.5V reference. Use Value: Tight 5V reference tolerance (±1.5%) ensures accurate output regulation; low 7mA operating current extends battery backup runtime. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC1845N8 | Same pinout, but higher 500µA start-up current, no leading-edge blanking, ±0.5A output drive, 100°C max junction temp. | Limited to commercial-temp applications; lacks noise immunity for high-dV/dt flyback designs; requires external gate pull-down. | Select UC1845N8 only for cost-sensitive, non-industrial designs where layout noise is minimal and thermal margin is ample. |
| UCC3805N | 8-pin SOIC, 100°C max temp, 12V VREF, no internal 5V reference, 0.5A output, no blanking, 1.5V current sense threshold. | Requires external 5V LDO for bias; less suitable for direct replacement due to different reference architecture and sensing threshold. | Choose UCC3805N when redesigning for surface-mount assembly and lower-cost BOM, accepting added external components. |
Compared with UC1845N8 and UCC3805N, the LT1245IN8#PBF delivers superior noise immunity via blanking, tighter reference and oscillator specs, wider temperature range, and higher drive strength - making it optimal for ruggedized, high-reliability power supplies where layout constraints prevent perfect noise isolation.
Availability
LT1245IN8#PBF is available at Aetrix Electronics and suitable for AC/DC flyback converters, isolated DC/DC forward supplies, and industrial motor drive auxiliary power systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1245IN8#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 (now part of Analog Devices, Inc. following merger with Linear Technology) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving industrial, automotive, communications, and healthcare markets.
The LT1241 series - including LT1245IN8#PBF - was designed specifically for high-efficiency, high-reliability current-mode switch-mode power supplies, emphasizing low start-up current, fast current sensing, and robust gate drive in demanding off-line and DC/DC applications.
FAQ
What is the start-up threshold voltage for LT1245IN8#PBF, and how does it differ from LT1242?
The LT1245IN8#PBF has a start-up threshold of 8.4V with 0.4V hysteresis, enabling earlier turn-on than LT1242 (16V threshold). This lower threshold reduces stress on the start-up resistor and improves efficiency in universal-input AC/DC designs. The LT1245IN8#PBF's 8.4V specification is confirmed in the Electrical Characteristics table under "Undervoltage Lockout" and applies across its full –40°C to 125°C operating range.
Does LT1245IN8#PBF support 500kHz switching, and what oscillator configuration achieves this?
Yes, LT1245IN8#PBF supports 500kHz output switching (1MHz oscillator frequency) using appropriate RT/CT values - e.g., RT = 13.0kΩ and CT = 500pF yields 248kHz typical oscillator frequency, so scaling down CT further (e.g., 220pF) with same RT reaches ~500kHz. The datasheet confirms operation "to 500kHz" and shows oscillator frequencies up to 1MHz in Typical Performance Characteristics. This capability is intrinsic to the LT1245IN8#PBF's trimmed 8.2mA oscillator sink current and low-delay architecture.
How does the leading-edge blanking function in LT1245IN8#PBF improve system reliability?
The LT1245IN8#PBF implements voltage-dependent leading-edge blanking (100ns at VFB = 2.5V) that disables the current sense comparator immediately after switch turn-on, preventing false triggering from transformer leakage spikes and diode reverse recovery noise. This eliminates the need for RC filters at ISENSE, preserving current-loop bandwidth and reducing short-circuit peak currents. The feature is documented in Applications Information section "Blanking" and verified in TPC24 waveform plots - a key reliability advantage of LT1245IN8#PBF over legacy UC1845.
Can LT1245IN8#PBF drive a 10nF MOSFET gate directly, and what are the timing implications?
Yes, LT1245IN8#PBF can drive a 10nF gate directly: its ±1A output drive and 40ns/30ns rise/fall times (measured into 1nF) scale predictably - rise time ≈ 400ns into 10nF (linear approximation). However, gate ringing may occur without proper layout; the datasheet recommends a Schottky clamp diode from OUTPUT to GND if negative excursions exceed 0.7V. This capability is specified in Absolute Maximum Ratings and confirmed in TPC22/TPC23 waveforms - a core design value of LT1245IN8#PBF.
What is the maximum allowable VCC voltage for LT1245IN8#PBF, and what protection exists above this limit?
The absolute maximum VCC voltage for LT1245IN8#PBF is 25V, per Absolute Maximum Ratings. Exceeding this risks permanent damage. No internal overvoltage protection is provided - external clamping (e.g., Zener diode) is required if VCC transients exceed 25V. This rating is consistent across all LT1241-series variants and is validated in stress testing per Note 1 of the datasheet. Designers must ensure bulk capacitor ripple and surge margins stay within this limit for reliable LT1245IN8#PBF operation.
LT1245IN8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 8.2V ~ 25V
- Frequency - Switching:
- 500kHz
- Duty Cycle (Max):
- 48%
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Frequency Control
- Operating Temperature:
- -40°C ~ 100°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LT1245IN8#PBF FAQ
1.How can I place an order for LT1245IN8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1245IN8#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 LT1245IN8#PBF reliable?
The price and inventory of LT1245IN8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1245IN8#PBF is usually 5 days.
3.What payment methods are accepted for LT1245IN8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1245IN8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1245IN8#PBF?
LT1245IN8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1245IN8#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 LT1245IN8#PBF?
For technical support, including LT1245IN8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1245IN8#PBF requirements.
6.How does Aetrix verify that LT1245IN8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1245IN8#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 LT1245IN8#PBF meets industry standards.
7.What is the process for return or replacement of LT1245IN8#PBF?
All LT1245IN8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1245IN8#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 LT1245IN8#PBF part is unused and in its original packaging.
Return procedure for LT1245IN8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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