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Analog Devices Inc. LT1245IS8#PBF
- Part No.:
- LT1245IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1245IS8#PBF.pdf
- Description:
- IC REG CTRLR BUCK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,981
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Product details
Overview
LT1245IS8#PBF from Analog Devices is an 8-pin, fixed-frequency, current-mode PWM controller IC optimized for off-line and DC/DC converters. It delivers 500 kHz switching capability, features a 1 A totem-pole output stage, 5 V ±1% trimmed bandgap reference, and active undervoltage lockout with 8.4 V start-up threshold and 0.4 V hysteresis - enabling reliable operation in industrial AC/DC power supplies.
For engineers reviewing the LT1245IS8#PBF datasheet, LT1245IS8#PBF pinout, LT1245IS8#PBF application, or LT1245IS8#PBF equivalent, key selection criteria include its 50 ns current sense delay, leading-edge blanking, oscillator frequency trim (±5% typical), 18 V output clamp, and compatibility with UC1845-based designs requiring extended temperature range support.
Technical Context
The LT1245IS8#PBF implements fixed-frequency current-mode control using an internal oscillator whose frequency and sink current (8.2 mA typ.) are both trimmed for tight tolerance. Its error amplifier provides 90 dB open-loop gain and 1 MHz unity-gain bandwidth, with feedback referenced to a stable 2.5 V internal node derived from the 5 V bandgap reference.
Current sensing employs a comparator with 100 ns blanking time (at VFB = 2.5 V), a 1 V internal clamp on the inverting input, and 70 dB PSRR. The output stage uses a high-current totem pole capable of ±1 A drive into capacitive loads, with 40 ns rise and 30 ns fall times (CL = 1 nF), and active low pull-down during UVLO.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | –40°C to 100°C - supports industrial-grade AC/DC converter deployment without derating. |
| Oscillator Frequency | Up to 1 MHz (500 kHz output) - enables compact magnetics and high-efficiency power stages. |
| Reference Voltage | 5.000 V ±1% (4.925–5.075 V) - ensures precise RT/CT timing and stable feedback divider biasing. |
| Start-Up Current | < 250 µA (170 µA typ.) - minimizes bleed resistor losses in offline flyback startup networks. |
| Output Drive | ±1 A peak - directly drives large gate capacitance MOSFETs without external buffers. |
| UVLO Threshold | 8.4 V start-up / 7.6 V minimum operating / 0.4 V hysteresis - prevents erratic latching during brownout conditions. |
| Current Sense Delay | 50 ns - enables accurate cycle-by-cycle current limiting at high switching frequencies. |
Pinout & Package
S8 package: 8-lead plastic SOIC, 1.27 mm pitch, JEDEC MS-012AC compliant, thermal resistance θJA = 150°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides loop compensation node; sources 0.5 mA / sinks 2 mA min; used to clamp current sense threshold. |
| 2 - FB | Inverting input of error amplifier | Internally biased to 2.5 V reference; accepts voltage feedback from output divider; sets blanking time. |
| 3 - ISENSE | Current sense comparator input | Accepts sensed voltage across Rs; trip point proportional to COMP output; includes 100 ns blanking. |
| 4 - RT/CT | Oscillator timing node | RC network sets frequency and deadtime; CT charges from VREF via RT; discharge current trimmed to 8.2 mA. |
| 5 - GND | Analog and power ground | Common return for all internal circuitry; requires dedicated low-impedance PCB trace to minimize noise coupling. |
| 6 - OUTPUT | Totem-pole driver output | Drives MOSFET gate; clamped to ≤18 V; actively pulled low (~1 V) during UVLO; ±1 A capable. |
| 7 - VCC | Positive supply input | Operates from 7.6 V to 25 V; powers internal bias circuits; bypass with ≥0.1 µF ceramic near pin. |
| 8 - VREF | 5 V bandgap reference output | Supplies RT charging current; powers internal logic; can source up to 20 mA; pulled low during UVLO. |
Key Features
| Feature | Design Value |
|---|---|
| Trimmed oscillator sink current | 8.2 mA ±0.3 mA - ensures consistent deadtime and maximum duty cycle across temperature and unit variance. |
| Active UVLO pull-down | VREF and OUTPUT pulled to ~1 V - eliminates need for external gate pull-down resistors and enables soft-start capacitor reset. |
| Leading-edge blanking | 100 ns fixed duration (VFB = 2.5 V) - suppresses transformer leakage spike false triggering without slowing current loop response. |
| High-speed output stage | 40 ns rise / 30 ns fall (CL = 1 nF) - preserves pulse fidelity at 500 kHz and reduces EMI from slow edges. |
| 18 V output clamp | Internal Zener-like clamp - protects MOSFET gate oxide from overvoltage during transients or layout parasitics. |
Applications
| Industrial AC/DC Power Supplies | Isolated DC/DC Converters |
|---|---|
Use Scenario: 90–240 VAC input, 12–24 VDC output, 30–100 W flyback or forward converter in factory automation equipment. IC Role / Device Role / Timing Role: Primary-side PWM controller generating gate drive signals synchronized to fixed-frequency current-mode modulation. Use Value: 500 kHz operation allows smaller transformers and output filters; –40°C to 100°C rating ensures reliability in uncooled enclosures. | Use Scenario: 48 V input telecom or server DC/DC brick delivering 3.3 V/5 V/12 V with tight regulation and fast transient response. IC Role / Device Role / Timing Role: Secondary-side synchronous rectification controller or primary-side current-mode modulator with slope compensation. Use Value: 1 A output drive eliminates external buffer; 50 ns current sense delay enables accurate peak current limiting under load steps. |
| Programmable LED Drivers | Industrial Motor Control Power Stages |
Use Scenario: Constant-current LED string driver for high-bay lighting or signage, operating from 24–48 VDC input with analog/digital dimming. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller regulating LED current via sense resistor feedback and PWM dimming interface. Use Value: Trimmed oscillator and 1% reference ensure stable dimming linearity; 18 V output clamp protects MOSFETs driving high-Vf LED strings. | Use Scenario: Low-power BLDC or stepper motor driver with integrated gate driver, powered from 12–24 VDC bus in CNC or robotics systems. IC Role / Device Role / Timing Role: Gate driver controller providing timed PWM outputs for half-bridge or full-bridge configurations with current foldback protection. Use Value: Leading-edge blanking prevents false overcurrent shutdown during MOSFET switching transitions; active UVLO ensures safe startup under varying bus conditions. |
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 |
|---|---|---|---|
| UC1845N | Same pinout, but higher start-up current (1 mA), no oscillator trim, no leading-edge blanking, 0°C to 70°C only. | Limited to commercial-temp consumer power supplies; lacks industrial robustness and noise immunity. | Choose UC1845N only if cost is critical and ambient temperature stays below 70°C with clean input rails. |
| UCC38C45D | Pin-compatible SOIC-8, 1 A output, 500 kHz max, but 5 V reference not trimmed (±2%), no active UVLO pull-down, 0°C to 70°C. | Requires external pull-down resistors; less stable timing due to untrimmed oscillator; unsuitable for wide-temp industrial use. | Select UCC38C45D only for legacy redesigns where footprint reuse is mandatory and temperature range is constrained. |
Compared with UC1845N and UCC38C45D, the LT1245IS8#PBF offers tighter reference and oscillator tolerances, built-in blanking, active UVLO pull-down, and extended temperature range - making it the preferred choice for new industrial power designs demanding reliability and noise immunity.
Availability
LT1245IS8#PBF is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, isolated DC/DC converters, and programmable LED drivers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1245IS8#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 digital signal processing semiconductors.
The LT124x series was designed specifically for rugged, high-frequency current-mode switching power supplies - emphasizing low start-up current, noise-immune current sensing, and robust gate drive for industrial and telecom power applications.
FAQ
What is the operating temperature range of the LT1245IS8#PBF?
The LT1245IS8#PBF is rated for –40°C to 100°C junction temperature, matching the "I" grade designation in its part number. This extended range supports deployment in industrial environments without forced cooling, unlike commercial-grade alternatives such as UC1845N (0°C to 70°C). The S8 package's θJA of 150°C/W must be considered in thermal design.
How does the LT1245IS8#PBF differ from the LT1242IS8#PBF in terms of UVLO behavior?
The LT1245IS8#PBF has an 8.4 V start-up threshold and 7.6 V minimum operating voltage with 0.4 V hysteresis, while the LT1242IS8#PBF uses a 15 V start-up threshold and 9.0 V minimum with 5.5 V hysteresis. This makes the LT1245IS8#PBF suitable for lower-input-voltage DC/DC applications, whereas LT1242IS8#PBF targets higher-voltage offline designs.
Can the LT1245IS8#PBF drive a 2000 pF MOSFET gate directly?
Yes - the LT1245IS8#PBF's ±1 A totem-pole output is specified for capacitive loads up to 2000 pF per cycle, with 40 ns rise and 30 ns fall times measured at 1 nF. Driving larger gates may require verifying slew rate and power dissipation, but typical 600–1200 V MOSFETs (e.g., MPT2N60) are fully supported per the TA06 reference design.
What is the purpose of the blanking function on the ISENSE pin of the LT1245IS8#PBF?
The blanking function disables the current sense comparator for 100 ns after each OUTPUT turn-on edge, preventing false triggering from leading-edge spikes caused by transformer leakage inductance or diode reverse recovery. This eliminates the need for RC filtering at ISENSE, preserving current-loop speed and reducing short-circuit peak current in fault conditions.
Does the LT1245IS8#PBF support external clock synchronization?
No - the LT1245IS8#PBF uses a self-contained, trimmed RC oscillator and does not provide an external sync input pin. Unlike some later controllers (e.g., LT3748), synchronization requires replacing the RT/CT network with a current-source-driven sawtooth generator, which is not recommended. For sync capability, consider the LT3748 or UC3846 family instead.
LT1245IS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1245IS8#PBF FAQ
1.How can I place an order for LT1245IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1245IS8#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 LT1245IS8#PBF reliable?
The price and inventory of LT1245IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1245IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1245IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1245IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1245IS8#PBF?
LT1245IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1245IS8#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 LT1245IS8#PBF?
For technical support, including LT1245IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1245IS8#PBF requirements.
6.How does Aetrix verify that LT1245IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1245IS8#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 LT1245IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1245IS8#PBF?
All LT1245IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1245IS8#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 LT1245IS8#PBF part is unused and in its original packaging.
Return procedure for LT1245IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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