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Analog Devices Inc. LT1172CQ#PBF
- Part No.:
- LT1172CQ#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LT1172CQ#PBF.pdf
- Description:
- IC REG BCK BST ADJ 1.25A DDPAK-5
- Quantity:
- Payment:
- Shipping:
Inventory:190
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Product details
Overview
LT1172CQ#PBF 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 supports shutdown mode drawing 50µA - enabling compact, efficient DC-DC conversion in space-constrained industrial power supplies.
For engineers reviewing the LT1172CQ#PBF datasheet, LT1172CQ#PBF pinout, LT1172CQ#PBF application, or LT1172CQ#PBF equivalent, key selection criteria include its 5-pin DD package thermal performance (θJA ≈ 25–45°C/W), flyback-regulated floating output capability, adaptive anti-saturation switch drive, and internal 1.24V reference with ±1% accuracy over temperature.
Technical Context
The LT1172CQ#PBF implements current-mode control with a fixed 100kHz oscillator, enabling fast line/load transient response and simplified loop compensation. Its error amplifier features transconductance of 3000–4400 µmho and clamps at 0.25V/1.8V, while the flyback amplifier provides dedicated regulation for isolated topologies with 15V reference and 4.5–9V reference variation.
It integrates a high-voltage 65V breakdown switch with 0.6Ω typical "on" resistance, uses adaptive anti-saturation drive to maintain efficiency across wide load ranges, and supports external synchronization (120–160kHz) via VC pin pulsing - all within a thermally optimized 5-lead DD package with tab-connected GND.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle; enables reliable 1A continuous output in boost/buck with margin for transient peaks |
| Input Voltage Range | 3V to 40V; supports wide-range industrial inputs including 5V, 12V, 24V rails and battery-backed systems |
| Quiescent Current | 6mA typical; minimizes no-load power loss in always-on applications like sensor nodes or standby supplies |
| Shutdown Current | 50µA typical; allows ultra-low-power sleep modes in portable or energy-harvesting designs |
| Reference Voltage | 1.24V ±1% over 0°C to 100°C; ensures stable feedback threshold for precise output voltage regulation |
| Switch Breakdown Voltage | 65V; permits safe operation with 40V max input and transient margin in automotive or industrial environments |
| Switch "On" Resistance | 0.6Ω max; limits conduction loss to ≤0.75W at 1.25A, critical for thermal management in DD package |
| Operating Frequency | 88–115kHz typical; balances EMI, inductor size, and efficiency for cost-sensitive medium-power converters |
Pinout & Package
The LT1172CQ#PBF is housed in a 5-lead DD (Dual Drain) plastic package with exposed tab electrically connected to GND, offering low thermal resistance (θJA ≈ 25–45°C/W depending on PCB copper area).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Power Input | Accepts 3V–40V unregulated input; connects directly to bulk capacitor and must be decoupled near the pin |
| VSW | Switch Output | Drives external inductor/diode; carries full switch current and high dv/dt - requires short, low-inductance routing |
| GND | Signal & Power Ground | Common return for control circuitry and switch emitter; tab connection enables direct heatsinking to PCB ground plane |
| FB | Feedback Input | Senses output voltage divider; dual-function pin enabling normal regulation (1.24V threshold) or flyback mode (15V threshold) |
| VC | Error Amplifier Output | Provides compensation node, soft-start control, current limit adjustment, and shutdown activation (≤0.15V) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A Switch | Eliminates external MOSFET in ≤25W designs, reducing BOM count and layout complexity for compact converters |
| Flyback-Regulated Mode | Enables fully floating, transformer-isolated outputs without optocoupler feedback - ideal for medical or safety-isolated supplies |
| Adaptive Anti-Saturation Drive | Maintains high efficiency across 10:1 load range by dynamically adjusting gate drive to prevent switch saturation losses |
| External Synchronization | Allows noise-sensitive systems to lock switching frequency to external clock (120–160kHz), easing EMI filtering design |
| Self-Protected Operation | Includes current limiting, thermal foldback, and shutdown - enables "bust-proof" use comparable to linear regulators |
| Wide Input Range (3V–40V) | Supports single IC across multiple input rails (e.g., 5V logic, 12V industrial, 24V PoE-powered systems) |
Applications
| Industrial Sensor Power Supply | Portable LCD Bias Generator |
|---|---|
Use Scenario: Generating stable ±12V from a 5V microcontroller rail to power analog front-end sensors in factory automation nodes. IC Role / Device Role / Timing Role: LT1172CQ#PBF operates in inverting topology to produce negative output, using internal 1.24V reference and current-mode control for tight regulation under varying sensor load. Use Value: Eliminates need for separate charge-pump IC or transformer-based supply, reducing solution size by 40% and improving PSRR vs. switched-capacitor alternatives. | Use Scenario: Providing adjustable –10V to –26V contrast voltage for monochrome LCD displays in handheld test equipment powered by 3–20V batteries. IC Role / Device Role / Timing Role: LT1172CQ#PBF functions as a boost-inverting converter with shutdown control, leveraging VC pin for enable/disable and FB pin for precision feedback scaling. Use Value: Achieves <±0.5% output stability over battery discharge curve and temperature, extending display readability life by 3× versus resistor-divider + LDO solutions. |
| Battery-Powered Upconverter | Isolated Flyback Power Module |
Use Scenario: Stepping up 3.7V Li-ion battery voltage to regulated 12V for powering small solenoids or RF modules in wireless IoT edge devices. IC Role / Device Role / Timing Role: LT1172CQ#PBF runs in boost configuration with 100kHz fixed frequency, using internal switch and adaptive anti-sat drive to sustain >85% efficiency down to 0.1A load. Use Value: Delivers 12V/0.5A from single-cell battery with <15mm² PCB area, enabling coin-cell-sized form factors impossible with discrete controller + MOSFET solutions. | Use Scenario: Building a 5V/1A isolated auxiliary supply for PLC I/O modules requiring reinforced insulation between field-side and controller-side circuits. IC Role / Device Role / Timing Role: LT1172CQ#PBF operates in flyback-regulated mode, using FB pin to sense reflected primary voltage and regulate secondary output without optocoupler or secondary-side sensing. Use Value: Reduces bill-of-materials by eliminating optocoupler, TL431, and secondary bias winding - cutting total isolation BOM cost by 35% while maintaining <±3% cross-regulation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2574HVS-12/NOPB | Fixed 12V output, 52kHz switching, 0.5A switch, SOIC-8 package | Limited to non-isolated buck only; no flyback or inverting support | Select when fixed-output, lower-cost, lower-power (≤6W) buck conversion suffices and board space allows SOIC-8 |
| TPS54202DRCT | 2A synchronous buck, 4.5–28V input, 500kHz, 3mm × 3mm WSON-10 | No isolation capability; requires external FETs for boost/flyback; higher frequency increases EMI risk | Choose for higher-efficiency, higher-density buck-only designs where synchronous rectification justifies added complexity |
Compared with LM2574HVS-12/NOPB and TPS54202DRCT, the LT1172CQ#PBF offers unique multi-topology flexibility and flyback isolation in a thermally robust DD package - making it optimal for space-constrained, multi-rail, or safety-isolated designs where fixed-output or synchronous-only alternatives fall short.
Availability
LT1172CQ#PBF is available at Aetrix Electronics and suitable for industrial sensor power supplies, portable LCD bias generators, battery-powered upconverters, and isolated flyback power modules requiring stable component supply across extended production lifecycles.
Supply support for LT1172CQ#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 support for legacy Linear power products, including long-term manufacturing, documentation, and technical resources.
The LT1172CQ#PBF belongs to the LT117x family of monolithic high-power switching regulators, designed specifically for rugged, multi-topology DC-DC conversion in industrial, instrumentation, and embedded systems where reliability and design simplicity are critical.
FAQ
What is the maximum continuous output power achievable with the LT1172CQ#PBF in boost configuration?
The LT1172CQ#PBF can deliver up to 25W continuous output power in boost topology under typical conditions (e.g., 5V input to 12V output at 1A), constrained by its 1.25A switch current limit, 0.6Ω "on" resistance, and thermal limits of the 5-lead DD package. Derating is required above 60°C ambient or with poor PCB copper area.
Does the LT1172CQ#PBF support flyback topology with true galvanic isolation?
Yes, the LT1172CQ#PBF supports flyback-regulated mode via its FB pin, enabling fully floating outputs with transformer isolation. When FB is pulled below 0.54V, it activates the flyback amplifier with 15V reference, allowing regulation of reflected primary voltage - eliminating need for optocoupler or secondary-side feedback components in the LT1172CQ#PBF design.
What is the purpose of the VC pin on the LT1172CQ#PBF, and how is it used for shutdown?
On the LT1172CQ#PBF, the VC pin serves four functions: error amplifier output (for compensation), current limit adjustment, soft-start control, and shutdown activation. Pulling VC below 0.15V places the LT1172CQ#PBF into shutdown mode, reducing supply current to 50µA - a feature confirmed in the Electrical Characteristics table and used in low-power standby applications.
Can the LT1172CQ#PBF be synchronized to an external clock, and what is the supported frequency range?
Yes, the LT1172CQ#PBF supports external synchronization via the VC pin. A narrow pulse (<0.3µs) pulling VC to ground synchronizes the internal 100kHz oscillator to an external clock in the 120kHz–160kHz range, as documented in the "LT1170/LT1171/LT1172 Synchronizing" section - useful for EMI reduction in noise-sensitive systems.
What thermal considerations apply to the LT1172CQ#PBF in its 5-lead DD package?
The LT1172CQ#PBF's 5-lead DD package has θJA ranging from ~25°C/W (with 2.8 sq. in. 1oz copper) to ~45°C/W (with minimal copper), requiring careful PCB layout. Total power dissipation includes 6mA quiescent current plus I²R losses in the 0.6Ω switch; die temperature must stay ≤100°C. Thermal derating is essential above 55°C ambient unless additional copper or airflow is provided.
LT1172CQ#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, Cuk, Flyback, Forward Converter
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.244V
- Voltage - Output (Max):
- 65V (Switch)
- Current - Output:
- 1.25A (Switch)
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DDPAK-5
LT1172CQ#PBF FAQ
1.How can I place an order for LT1172CQ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CQ#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 LT1172CQ#PBF reliable?
The price and inventory of LT1172CQ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CQ#PBF is usually 5 days.
3.What payment methods are accepted for LT1172CQ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CQ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CQ#PBF?
LT1172CQ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CQ#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 LT1172CQ#PBF?
For technical support, including LT1172CQ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CQ#PBF requirements.
6.How does Aetrix verify that LT1172CQ#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172CQ#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 LT1172CQ#PBF meets industry standards.
7.What is the process for return or replacement of LT1172CQ#PBF?
All LT1172CQ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CQ#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 LT1172CQ#PBF part is unused and in its original packaging.
Return procedure for LT1172CQ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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