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Analog Devices Inc. LT1172MJ8#PBF
- Part No.:
- LT1172MJ8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
LT1172MJ8#PBF.pdf
- Description:
- IC REG BCK BST ADJ 1.25A 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,185
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Product details
Overview
LT1172MJ8#PBF from Analog Devices (formerly Linear Technology) is a monolithic 1.25A high-efficiency current-mode switching regulator IC in an 8-lead CERDIP package, operating from 3V to 40V input, delivering up to 25W in buck/boost/flyback topologies with 100kHz fixed-frequency switching, 6mA quiescent current, and internal switch saturation voltage of 0.6Ω (max). It enables isolated flyback regulation via dedicated FB pin mode for industrial power supplies.
For engineers reviewing the LT1172MJ8#PBF datasheet, LT1172MJ8#PBF pinout, LT1172MJ8#PBF application, or LT1172MJ8#PBF equivalent, key selection criteria include its –55°C to 125°C extended temperature grade, CERDIP hermetic packaging for high-reliability environments, flyback reference voltage of 15.0V (min), and shutdown current of 100µA - critical for aerospace, military, and downhole instrumentation designs.
Technical Context
The LT1172MJ8#PBF implements current-mode control with adaptive anti-saturation drive for wide load-current efficiency stability, using a 100kHz oscillator and internal 1.244V bandgap reference. Its dual error amplifier architecture supports both normal regulation (via FB pin at 1.244V) and isolated flyback mode (FB pulled low, regulating 15.0V ±1.3V flyback pulse amplitude).
Pin 4 (NC) is unconnected per datasheet; E1 and E2 emitter terminals are exposed for ground-path optimization and 2:1 current-limit scaling. Thermal design requires θJA = 100°C/W derating due to CERDIP package limitations, with junction temperature limited to 125°C under continuous operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle; enables 25W output in buck mode with 20V input. |
| Input Voltage Range | 3V to 40V; supports wide-range industrial inputs including 12V/24V/36V rails without external regulators. |
| Quiescent Current | 6mA; ensures low standby loss in battery-backed systems. |
| Flyback Reference Voltage | 15.0V min; sets isolated output voltage via transformer turns ratio without optocoupler feedback. |
| Shutdown Supply Current | 100µA max; allows ultra-low-power sleep states in portable instrumentation. |
| Switch "On" Resistance | 0.6Ω max; determines conduction loss and thermal rise at full load. |
| Operating Temperature | –55°C to 125°C; qualified for extended-temperature military and automotive under-hood applications. |
Pinout & Package
LT1172MJ8#PBF uses an 8-lead CERDIP (J8) package with hermetic ceramic sealing and θJA = 100°C/W. Pin 4 is NC (no connection); E1 must be tied to GND, while E2 enables current-limit scaling when left open.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal reference ground | Primary return path for switch current and error amplifier; tie directly to low-impedance ground plane. |
| VC (Pin 2) | Error amplifier output / control voltage | Set point for current limit; clamp at 1V–2V to adjust peak switch current; pull ≤0.15V for shutdown. |
| FB (Pin 3) | Feedback input / mode select | 1.244V reference for standard regulation; pulled low to enable 15V flyback mode for isolated outputs. |
| NC (Pin 4) | No connection | Unbonded; must remain floating - no external circuitry permitted per datasheet. |
| E2 (Pin 5) | Secondary emitter terminal | Optional connection; leaving open halves current limit (to 0.625A) but doubles RDS(on), increasing conduction loss. |
| VSW (Pin 6) | Switch collector output | Drives external inductor/diode; withstands 65V max; connects to primary winding in flyback topologies. |
| E1 (Pin 7) | Primary emitter terminal | Mandatory GND connection; provides low-impedance emitter return to minimize ground bounce errors. |
| VIN (Pin 8) | Main supply input | Accepts 3V–40V; powers internal 2.3V regulator and logic; bypass with ≥1µF ceramic near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables immediate line transient response and simplifies loop compensation across 3:1 input ranges. |
| Dual error amplifier with flyback mode | Eliminates optocouplers in isolated DC/DC converters by regulating flyback pulse amplitude directly. |
| Adaptive anti-saturation drive | Maintains >85% efficiency from 10% to full load by dynamically adjusting base drive to prevent transistor saturation. |
| Externally scalable current limit | Pin-selectable 1.25A/0.625A limits via E2 connection state, enabling single-BOM flexibility for varying power tiers. |
| Hermetic CERDIP packaging | Guarantees long-term reliability in high-humidity, high-vibration, or radiation-prone environments (e.g., avionics). |
Applications
| Industrial Power Supply | Aerospace Avionics |
|---|---|
Use Scenario: Generating regulated ±15V op-amp supplies from 28V aircraft bus with strict EMI and thermal constraints. IC Role / Device Role / Timing Role: Primary controller in flyback topology; regulates isolated secondary windings using FB pin's 15V reference mode. Use Value: Eliminates optocoupler and TL431, reducing BOM count by 3 parts and improving long-term drift stability over temperature. | Use Scenario: LCD contrast voltage generation (–10V to –26V) in cockpit displays requiring operation from –55°C to +125°C. IC Role / Device Role / Timing Role: Inverting boost regulator with shutdown control; VC pin used for soft-start and fault-induced shutdown. Use Value: CERDIP package ensures zero moisture ingress and stable performance across extreme thermal cycling. |
| Downhole Oilfield Instrumentation | Military Portable Radios |
Use Scenario: Converting 12V battery to 5V/3A for downhole telemetry modules exposed to 150°C ambient (with heatsink). IC Role / Device Role / Timing Role: Buck regulator with external MOSFET sync capability; E1/E2 pins used to calibrate current sense for sensor biasing. Use Value: Extended temperature rating avoids derating penalties; 6mA quiescent current extends battery life during idle logging cycles. | Use Scenario: 5V-to-12V boost converter powering RF power amplifiers in handheld radios with burst transmission duty cycles. IC Role / Device Role / Timing Role: High-efficiency boost controller; VC pin clamped for programmable peak current limiting during transmit peaks. Use Value: Internal 1.25A switch eliminates external FET, reducing board area by 35% versus discrete solutions. |
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 die, plastic DIP package; θJA = 130°C/W; 0°C to 100°C temp range. | Lacks hermetic seal and extended temperature capability; unsuitable for military/aerospace. | Select only for commercial-grade cost-sensitive designs where CERDIP reliability is unnecessary. |
| LT1172CT#PBF | TO-220 package; θJA = 75°C/W; same 0°C to 100°C range; higher thermal mass. | Better thermal performance than J8 but larger footprint; no E2 scaling option. | Choose when >1.25A continuous current or >50°C/W thermal resistance is required in non-hermetic environments. |
Compared with LT1172CN8#PBF and LT1172CT#PBF, the LT1172MJ8#PBF uniquely delivers extended temperature operation and hermetic reliability in a compact 8-pin format - essential where environmental robustness outweighs cost or thermal margin requirements.
Availability
LT1172MJ8#PBF is available at Aetrix Electronics and suitable for industrial power supplies, aerospace avionics, and downhole instrumentation requiring stable component supply across extended temperature and high-reliability environments.
Supply support for LT1172MJ8#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 LT1172 family was designed as a monolithic high-power switching regulator IC targeting ruggedized, wide-input industrial and military power conversion where discrete solutions lacked integration, reliability, or thermal performance.
FAQ
What is the maximum input voltage rating for LT1172MJ8#PBF?
The LT1172MJ8#PBF has an absolute maximum supply voltage of 40V, as specified in the Absolute Maximum Ratings table. Operation above this voltage risks permanent damage. The device is rated for continuous operation from 3V to 40V, making it suitable for 24V industrial buses and 28V aircraft systems with appropriate input filtering and transient protection.
Does LT1172MJ8#PBF support flyback topology with isolated outputs?
Yes, the LT1172MJ8#PBF supports flyback topology via its dedicated flyback mode: pulling the FB pin below 0.45V switches the internal error amplifier to regulate a 15.0V ±1.3V flyback pulse amplitude. This enables fully floating, optocoupler-free isolated outputs - confirmed in the Electrical Characteristics table (VFB = 15.0V min) and Typical Application TA03.
What is the purpose of Pin 4 (NC) on LT1172MJ8#PBF?
Pin 4 on the LT1172MJ8#PBF is designated NC (No Connection) and must remain unconnected. The datasheet explicitly states: "Do not connect Pin 4 of the LT1172 DIP or SO to external circuitry. This pin may be active in future revisions." Connecting it risks undefined behavior or latch-up, as it is unbonded and unused in the LT1172MJ8#PBF silicon.
How does the E1/E2 emitter configuration affect LT1172MJ8#PBF performance?
The LT1172MJ8#PBF exposes both E1 (mandatory GND tie) and E2 (optional) emitter terminals. Leaving E2 open reduces switch current limit by 2:1 (to 0.625A) but doubles RDS(on) to ~1.2Ω, increasing conduction loss. This trade-off allows single-BOM current scaling - verified in the "Extra Pins" section (page 9) and Thermal Considerations.
Is LT1172MJ8#PBF RoHS compliant and lead-free?
Yes, LT1172MJ8#PBF is lead-free and RoHS compliant, as indicated by the "#PBF" suffix per Linear Technology's marking convention (documented in Order Information, page 3). The part uses matte tin lead finish and meets JEDEC J-STD-609 Category 1 requirements for lead-free soldering profiles.
LT1172MJ8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-CDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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:
- -55°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-CERDIP
LT1172MJ8#PBF FAQ
1.How can I place an order for LT1172MJ8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172MJ8#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 LT1172MJ8#PBF reliable?
The price and inventory of LT1172MJ8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172MJ8#PBF is usually 5 days.
3.What payment methods are accepted for LT1172MJ8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172MJ8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172MJ8#PBF?
LT1172MJ8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172MJ8#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 LT1172MJ8#PBF?
For technical support, including LT1172MJ8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172MJ8#PBF requirements.
6.How does Aetrix verify that LT1172MJ8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172MJ8#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 LT1172MJ8#PBF meets industry standards.
7.What is the process for return or replacement of LT1172MJ8#PBF?
All LT1172MJ8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172MJ8#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 LT1172MJ8#PBF part is unused and in its original packaging.
Return procedure for LT1172MJ8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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