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Analog Devices Inc. LT1172IN8#PBF
- Part No.:
- LT1172IN8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1172IN8#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 1.25A 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:336
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Product details
Overview
LT1172IN8#PBF from Analog Devices (formerly Linear Technology) is a monolithic 100kHz current-mode switching regulator IC with an integrated 1.25A power switch, operating from 3V to 60V input and delivering up to 25W in buck/boost/flyback topologies. It features 6mA quiescent current, shutdown mode drawing 50µA, and internal 1.24V reference voltage - used in isolated flyback converters for LCD bias supplies and battery-powered DC-DC conversion.
For engineers reviewing the LT1172IN8#PBF datasheet, LT1172IN8#PBF pinout, LT1172IN8#PBF application, or LT1172IN8#PBF equivalent, key selection criteria include its –40°C to 100°C industrial temperature range, 8-pin PDIP/SO package with separate emitter pins (E1/E2), flyback-regulated floating output capability, and adaptive anti-saturation switch drive for wide load-current efficiency retention.
Technical Context
The LT1172IN8#PBF implements current-mode control: the internal oscillator initiates each switching cycle, and the power switch turns off when sensed current reaches a level set by the VC pin voltage. This architecture delivers fast line transient response and simplifies loop compensation across varying input and load conditions.
It supports multiple topologies via external component configuration - including flyback with fully floating outputs regulated via feedback pin threshold detection (0.45V typical), buck-boost with inverting polarity, and boost with external catch diode. The dual-emitter (E1/E2) package enables optional 2:1 current limit reduction by disconnecting E2, at the cost of doubled RDS(on).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A (guaranteed at TJ ≥ 25°C, 50% duty cycle); enables compact 25W flyback designs without external MOSFETs |
| Input Voltage Range | 3V to 60V; supports wide-range industrial/battery inputs including 12V, 24V, and 48V systems |
| Quiescent Current | 6mA; ensures low standby loss in always-on applications like remote sensors |
| Shutdown Current | 50µA typical; allows ultra-low-power sleep modes in portable equipment |
| Reference Voltage | 1.24V ±20mV; provides stable feedback threshold for precise output regulation |
| Switching Frequency | 100kHz nominal; balances EMI, inductor size, and efficiency for mid-power SMPS |
| Operating Temp | –40°C to 100°C; qualified for industrial environments without derating |
Pinout & Package
N8 package: 8-pin plastic DIP (PDIP) with lead-free finish, JEDEC MS-001 standard footprint. Thermal resistance θJA = 130°C/W (plastic), requiring minimal heatsinking below 0.35W dissipation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (GND) | Power Ground Reference | Common return for internal regulators and error amplifier; must be low-impedance connection |
| 2 (VC) | Error Amplifier Output / Control Input | Controls switch current limit, enables soft-start (capacitor), and triggers shutdown (<0.15V) |
| 3 (FB) | Feedback Input | Senses output voltage; pulled low (≤0.45V) to enter flyback regulation mode |
| 4 (NC) | No Connect | Not internally bonded; must remain unconnected per datasheet warning |
| 5 (E2) | Secondary Emitter Terminal | Optional disconnection reduces max switch current to 0.625A and doubles RDS(on) |
| 6 (VSW) | Switch Collector Output | Drives external inductor/diode; rated for 65V breakdown (LT1172, non-HV grade) |
| 7 (E1) | Primary Emitter Terminal | Mandatory ground connection for switch emitter; ties to GND pin internally in TO-220/TO-3 |
| 8 (VIN) | Input Supply Voltage | Accepts 3V–60V; powers internal 2.3V regulator and logic; bypass capacitor required |
Key Features
| Feature | Design Value |
|---|---|
| Flyback-regulated floating outputs | Enables transformer-isolated multi-rail supplies (e.g., ±15V op-amp rails) without optocouplers or secondary-side sensing |
| Adaptive anti-saturation switch drive | Maintains high efficiency across 10:1 load current range by dynamically adjusting gate drive to prevent BJT saturation |
| Separate emitter terminals (E1/E2) | Allows user-selectable 1.25A/0.625A current limit without changing PCB layout or components |
| External synchronization support | Accepts 120–160kHz sync pulses on VC pin to eliminate beat frequencies in multi-regulator systems |
| Self-protected overload operation | Includes current limiting, thermal foldback, and safe shutdown - no external protection circuitry needed |
Applications
| Logic Supply Generation | Battery Upconverter |
|---|---|
Use Scenario: Generating 5V at 10A from a 3.3V or 5V system rail in embedded controllers. IC Role / Device Role / Timing Role: Primary switching controller implementing synchronous boost topology with external MOSFET and Schottky diode. Use Value: Eliminates need for discrete PWM controller + gate driver; achieves >90% efficiency at full load with only 6mA quiescent draw. | Use Scenario: Boosting single-cell Li-ion (3.0–4.2V) to 5V/12V for USB peripherals or instrumentation. IC Role / Device Role / Timing Role: Monolithic flyback controller regulating isolated output via primary-side sensing, avoiding optocoupler complexity. Use Value: Enables compact, low-cost isolated supply with <±2% output accuracy over battery discharge curve and temperature. |
| Op Amp Dual-Rail Supply | Industrial Sensor Bias |
Use Scenario: Converting 5V logic supply to ±15V for precision op amps in data acquisition front-ends. IC Role / Device Role / Timing Role: Inverting buck-boost controller driving center-tapped transformer to generate symmetrical floating rails. Use Value: Delivers fully floating ±15V outputs referenced to signal ground - critical for noise-sensitive analog circuits. | Use Scenario: Providing –10V to –26V bias for LCD contrast control in factory HMIs operating from 3–20V battery or bus supply. IC Role / Device Role / Timing Role: Inverting boost converter with shutdown control, configured per Typical Application TA04. Use Value: Supports wide input range and programmable shutdown, enabling long battery life in unattended field devices. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CN8#PBF | Same silicon, 0°C to 100°C temp grade; lacks extended low-temp operation | Not suitable for cold-environment deployments (e.g., outdoor telecom, automotive under-hood) | Select LT1172IN8#PBF when ambient operation down to –40°C is required |
| LT1172IS8#PBF | Identical specs and temp range; surface-mount SO-8 package instead of PDIP | Requires rework of through-hole PCB; better thermal performance in dense layouts | Choose LT1172IS8#PBF for automated assembly or space-constrained designs |
Compared with LT1172CN8#PBF, the LT1172IN8#PBF adds guaranteed –40°C startup and operation - essential for industrial automation. Versus LT1172IS8#PBF, it offers through-hole mechanical robustness and simplified prototyping, though with higher θJA.
Availability
LT1172IN8#PBF is available at Aetrix Electronics and suitable for industrial sensor bias, LCD contrast supplies, battery upconverters, and isolated op amp rails requiring stable component supply across extended temperature ranges.
Supply support for LT1172IN8#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.
The LT117x family was designed as rugged, easy-to-use monolithic switching regulators targeting industrial, automotive, and medical power systems where reliability, wide input range, and topology flexibility are critical.
FAQ
What is the maximum output power achievable with the LT1172IN8#PBF in flyback configuration?
The LT1172IN8#PBF delivers up to 25W in flyback mode using its 1.25A switch and 65V breakdown rating. Actual output power depends on transformer design, input voltage, and duty cycle - with peak power limited by thermal dissipation in the N8 package (130°C/W). For sustained 25W operation, board-level copper area and airflow must be optimized per AN19 thermal guidelines.
Can the LT1172IN8#PBF be used in boost topology with an external MOSFET?
No - the LT1172IN8#PBF integrates a bipolar power transistor and is not a controller-only IC. It is designed for use with external diodes and inductors in boost, buck, or flyback configurations, but cannot drive an external MOSFET gate. Its VSW pin connects directly to the collector of the internal switch; substituting an external FET would require redesigning the entire power stage and is not supported.
How does the LT1172IN8#PBF achieve flyback regulation without an optocoupler?
The LT1172IN8#PBF uses primary-side sensing: when the FB pin voltage drops ≤0.45V, it switches to flyback mode and regulates the amplitude of the reflected flyback pulse relative to VIN. This eliminates the need for optocouplers or secondary-side references, reducing cost and improving reliability while maintaining ±2% output accuracy across line and load.
What is the purpose of the NC pin (Pin 4) on the LT1172IN8#PBF?
Pin 4 on the LT1172IN8#PBF is designated NC (No Connect) and must remain unconnected. It is not bonded internally and may become active in future revisions. Connecting it risks unpredictable behavior or damage. The datasheet explicitly warns against routing traces or placing components on this pin - it serves solely as a placeholder for potential future functionality.
Does the LT1172IN8#PBF support external frequency synchronization?
Yes - the LT1172IN8#PBF can be synchronized to an external clock between 120kHz and 160kHz by applying narrow (<0.3µs) pulses to the VC pin via an NPN transistor or logic gate. This feature suppresses beat frequencies in multi-regulator systems and improves EMI compliance, but requires careful pulse-width control to avoid offset voltage shifts in the error amplifier.
LT1172IN8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- 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:
- -40°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LT1172IN8#PBF FAQ
1.How can I place an order for LT1172IN8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172IN8#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 LT1172IN8#PBF reliable?
The price and inventory of LT1172IN8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172IN8#PBF is usually 5 days.
3.What payment methods are accepted for LT1172IN8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172IN8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172IN8#PBF?
LT1172IN8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172IN8#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 LT1172IN8#PBF?
For technical support, including LT1172IN8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172IN8#PBF requirements.
6.How does Aetrix verify that LT1172IN8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172IN8#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 LT1172IN8#PBF meets industry standards.
7.What is the process for return or replacement of LT1172IN8#PBF?
All LT1172IN8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172IN8#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 LT1172IN8#PBF part is unused and in its original packaging.
Return procedure for LT1172IN8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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