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Analog Devices Inc. LT1172CK
- Part No.:
- LT1172CK
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-3-4
- Datasheet:
-
LT1172CK.pdf
- Description:
- IC MULTI CONF ADJ 1.25A TO3
- Quantity:
- Payment:
- Shipping:
Inventory:2,687
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Product details
Overview
LT1172CK from Analog Devices (formerly Linear Technology) is a monolithic 100kHz current-mode switching regulator IC with an integrated 1.25A power switch, designed for buck, boost, flyback, inverting, and Cuk topologies. It operates from 3V to 40V input, delivers up to 25W output power, draws only 6mA quiescent current, and features shutdown mode drawing 50µA - used in battery-powered DC-DC conversion and isolated flyback supplies.
For engineers reviewing the LT1172CK datasheet, LT1172CK pinout, LT1172CK application, or LT1172CK equivalent, key selection considerations include its TO-3 metal-can package thermal performance (TJMAX = 100°C, θJC = 8°C/W), internal current-limiting architecture, flyback-mode reference voltage (15.0–18.0V), and compatibility with standard 5-pin power supply layouts requiring minimal external components.
Technical Context
The LT1172CK implements current-mode control with adaptive anti-saturation drive for the internal NPN power switch, enabling stable operation across wide load ranges without efficiency loss. Its error amplifier uses transconductance-based feedback (gm = 3000–4400 µmho) and supports dual regulation modes: normal (1.224–1.264V reference) and flyback (15.0–18.0V reference).
It integrates a 100kHz oscillator, internal 2.3V bias regulator, and shutdown circuitry activated by pulling the VC pin below 0.15V. Pin 4 (NC) in DIP/SO variants is unconnected; in the K-package TO-3, E1 and E2 are internally tied to GND, eliminating emitter sensing but simplifying layout for high-current applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle, 2.5A max under transient overload - sets maximum safe inductor current in boost/buck designs. |
| Input Voltage Range | 3V to 40V - enables direct operation from 5V logic rails, 12V automotive, or 24V industrial supplies without pre-regulation. |
| Reference Voltage | 1.224–1.264V (normal mode); 15.0–18.0V (flyback mode) - defines output regulation setpoint accuracy and isolation capability. |
| Quiescent Current | 6mA typical - determines no-load power loss in always-on systems like sensor nodes or standby power rails. |
| Shutdown Current | 50µA typical - enables ultra-low-power sleep states in portable equipment with rapid wake-up capability. |
| Switching Frequency | 88–115kHz - balances inductor size vs. switching loss; supports external synchronization to 120–160kHz for noise-sensitive applications. |
| Thermal Resistance | θJC = 8°C/W, θJA = 35°C/W - confirms suitability for conduction-cooled TO-3 mounting without heatsink up to ~25W dissipation at 25°C ambient. |
Pinout & Package
The LT1172CK is housed in a 4-lead TO-3 metal-can package with case connected to GND. Pins are arranged bottom-view: Pin 1 = VSW, Pin 2 = VC, Pin 3 = FB, Pin 4 = VIN. E1 and E2 are internally tied to GND - no external emitter connections required.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power input | Accepts 3–40V DC; powers internal regulator and switch driver; requires local 1µF ceramic bypass. |
| VSW | Switch collector output | Drives external inductor/diode network; rated for 65V breakdown; connects directly to transformer primary in flyback. |
| FB | Feedback input | Senses output voltage divider; selects regulation mode (normal vs. flyback) via resistor pull-down. |
| VC | Error amplifier output / control | Provides loop compensation node; enables soft-start, current limit adjustment, and shutdown via voltage clamping. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A switch | Eliminates external transistor in ≤25W converters, reducing BOM count and PCB area in space-constrained designs. |
| Flyback-regulated mode | Enables fully floating, transformer-isolated outputs without optocoupler feedback - ideal for medical or safety-isolated supplies. |
| Adaptive anti-saturation drive | Maintains consistent switch turn-off speed across load range, preventing thermal runaway during current limiting. |
| External synchronization support | Allows noise-sensitive systems (e.g., audio, RF) to lock switching frequency to external clock, avoiding beat frequencies. |
| Self-protected overload handling | Current-mode architecture provides inherent pulse-by-pulse limiting - no external sense resistor needed for basic protection. |
Applications
| Battery Upconverter | Isolated Flyback Supply |
|---|---|
Use Scenario: Boosting 3.6V Li-ion battery to 12V for peripheral modules in portable test equipment. IC Role / Device Role / Timing Role: Primary controller in boost topology; regulates output using FB pin; 100kHz switching enables compact 10µH inductor. Use Value: Delivers 1.25A peak switch current with 6mA quiescent draw - extends battery runtime while supporting burst-mode loads. | Use Scenario: Generating ±15V isolated op-amp rails from 24V industrial bus with reinforced insulation. IC Role / Device Role / Timing Role: Flyback controller with internal 15V reference; regulates secondary via primary-side sensing; eliminates optocoupler. Use Value: Achieves full floating output with <1% line/load regulation - meets IEC 61000-4-5 surge immunity requirements without extra isolation components. |
| Logic Supply Converter | Power Inverter (+ to –) |
Use Scenario: Converting 5V logic rail to ±12V for analog front-end signal conditioning in data acquisition systems. IC Role / Device Role / Timing Role: Inverting topology controller; uses FB pin to regulate negative output; VC pin enables soft-start sequencing. Use Value: Provides precise dual-rail symmetry (±12.0V ±2%) with <50mV ripple - ensures ADC reference stability and low THD in precision measurement. | Use Scenario: Generating –5V from +5V supply for legacy RS-232 interface level shifting in embedded controllers. IC Role / Device Role / Timing Role: Inverting regulator IC; leverages internal current-mode control for fast transient response to UART burst traffic. Use Value: Maintains regulation under 100mA pulsed load with <100µs recovery - prevents framing errors during high-speed serial communication. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CT | Same electrical specs; TO-220 package (θJA = 75°C/W) instead of TO-3 (θJA = 35°C/W) - higher junction-to-ambient thermal resistance. | Preferred for PCB-mounted designs where TO-3 mounting hardware is impractical; requires larger copper area or heatsink for same power. | Select LT1172CT when board-level assembly favors surface-mount or through-hole TO-220 footprint over metal-can mechanical mounting. |
| LT1171CK | Higher 2.5A switch current rating; identical TO-3 package and pinout; shares same 100kHz oscillator and flyback mode. | Supports up to 50W output power; suitable for higher-current versions of same topologies without layout change. | Choose LT1171CK when design margin requires >1.25A continuous switch current - drop-in upgrade path within same mechanical envelope. |
Compared with LT1172CT, the LT1172CK offers lower thermal resistance for conduction-cooled systems, while LT1171CK provides double the switch current capacity - both retain identical control architecture, pin compatibility, and flyback functionality for seamless design scaling.
Availability
LT1172CK is available at Aetrix Electronics and suitable for battery-powered instrumentation, isolated industrial power supplies, analog signal chain biasing, and embedded RS-232 level-shifting circuits requiring stable component supply and long-term obsolescence management.
Supply support for LT1172CK 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 support for legacy Linear switching regulator products including the LT1170 family.
The LT1170/LT1171/LT1172 product line was engineered for high-power monolithic DC-DC conversion in rugged industrial, test equipment, and battery-operated systems - prioritizing integration, thermal robustness, and topology flexibility over ultra-high efficiency.
FAQ
What is the maximum input voltage rating for the LT1172CK?
The LT1172CK has an absolute maximum supply voltage of 40V. This rating applies across its full operating temperature range (0°C to 100°C). Exceeding 40V risks permanent damage to the internal 65V-rated switch. For designs requiring higher input, the LT1172HVCK variant supports up to 60V input and 75V switch breakdown - the LT1172CK must not be substituted in HV applications without derating or redesign.
Does the LT1172CK support flyback topology, and how is it configured?
Yes, the LT1172CK supports flyback topology via its dedicated flyback regulation mode. Configuration requires pulling the FB pin below 0.54V with an external resistor to activate the 15.0–18.0V flyback reference. The IC then regulates the amplitude of the primary-side flyback pulse, enabling fully floating, optocoupler-free isolated outputs - confirmed in the LT1172CK datasheet Figure TA03 and Electrical Characteristics table.
What thermal performance can be expected from the LT1172CK in a TO-3 package?
The LT1172CK's TO-3 metal-can package delivers θJC = 8°C/W and θJA = 35°C/W. With a 25°C ambient and 0.34W total dissipation (typical boost example), junction temperature rises only ~27°C - well within its 100°C TJMAX limit. This allows conduction cooling without heatsink in most ≤25W applications, unlike plastic-packaged variants requiring >100°C/W board-level thermal management.
Can the LT1172CK be synchronized to an external clock, and what is the supported range?
Yes, the LT1172CK supports external synchronization by pulling the VC pin to ground with a narrow pulse (<0.3µs width). It locks to external clocks between 120kHz and 160kHz - outside its native 88–115kHz range. This feature is documented in the "Synchronizing" section of the LT1172CK datasheet and enables EMI reduction in noise-sensitive systems without modifying the core control loop.
How does the LT1172CK implement current limiting, and is it adjustable?
The LT1172CK uses internal current-mode control with fixed 1.25A typical limit at 50% duty cycle, scaling to 2.5A under transient conditions. Current limit is externally adjustable via the VC pin: clamping VC between 1V and 2V linearly scales peak switch current from 0A to 2A. This is verified in the Electrical Characteristics table (ILIM parameter) and Application Note AN19 - no external sense resistor is required for basic limiting.
LT1172CK Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- *
- Package/Case:
- TO-3-4
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- -
- Output Configuration:
- -
- Topology:
- -
- Output Type:
- -
- Number of Outputs:
- -
- Voltage - Input (Min):
- -
- Voltage - Input (Max):
- -
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- -
- Frequency - Switching:
- -
- Synchronous Rectifier:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-3
LT1172CK FAQ
1.How can I place an order for LT1172CK through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CK 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 LT1172CK reliable?
The price and inventory of LT1172CK are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CK is usually 5 days.
3.What payment methods are accepted for LT1172CK?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CK transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CK?
LT1172CK orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CK 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 LT1172CK?
For technical support, including LT1172CK datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CK requirements.
6.How does Aetrix verify that LT1172CK is sourced from the original manufacturer or authorized distributors?
All LT1172CK 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 LT1172CK meets industry standards.
7.What is the process for return or replacement of LT1172CK?
All LT1172CK units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CK, 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 LT1172CK part is unused and in its original packaging.
Return procedure for LT1172CK:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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