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Analog Devices Inc. LT1172CJ8
- Part No.:
- LT1172CJ8
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
LT1172CJ8.pdf
- Description:
- IC MULTI CONF ADJ 1.25A 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,629
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Product details
Overview
LT1172CJ8 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 in boost mode, draws only 6mA quiescent current, and features shutdown mode drawing 50µA - enabling compact, efficient DC-DC conversion in industrial power supplies and battery-powered systems.
For engineers reviewing the LT1172CJ8 datasheet, LT1172CJ8 pinout, LT1172CJ8 application, or LT1172CJ8 equivalent, key selection criteria include its 1.25A internal switch rating, 8-pin CERDIP package with separate emitter pins (E1/E2), flyback-regulated floating output capability, adaptive anti-saturation drive, and compatibility with standard 5V logic-level control signals.
Technical Context
The LT1172CJ8 implements current-mode control with a fixed 100kHz oscillator, where switch duty cycle is directly determined by sensed switch current rather than output voltage feedback alone. Its dual error amplifier architecture supports both normal regulation (1.24V reference at FB pin) and isolated flyback mode (15.0V flyback reference), with dedicated VC pin for compensation, soft-start, current limit adjustment, and shutdown.
It integrates a high-voltage 65V breakdown switch, adaptive anti-saturation driver, internal 2.3V bias regulator, and thermal protection. The J8 package exposes both emitters (E1 and E2) - E1 must be connected to GND, while E2 can be left open to halve current limit (to 0.625A) at the cost of doubled RDS(on), enabling design flexibility for overload management without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle; enables direct replacement of discrete switch + controller in low-to-mid power converters |
| Input Voltage Range | 3V to 40V; supports wide-range industrial inputs and unregulated battery rails without pre-regulation |
| Switching Frequency | 100kHz fixed; balances efficiency, magnetics size, and EMI performance in cost-sensitive designs |
| Quiescent Current | 6mA; minimizes no-load power loss in always-on systems such as remote sensors or backup supplies |
| Shutdown Current | 50µA; allows ultra-low-power standby in portable equipment with logic-controlled enable |
| Reference Voltage | 1.24V ±20mV at FB pin; provides stable feedback threshold for precise output voltage setting via resistor divider |
| Flyback Reference | 15.0V ±1.3V; enables transformer-isolated regulation without optocoupler or secondary-side sensing |
Pinout & Package
LT1172CJ8 is housed in an 8-lead ceramic dual in-line package (CERDIP, J8), rated for 0°C to 100°C operation, with θJA = 100°C/W. The package exposes both emitter terminals (E1 and E2) separately from GND to minimize ground path errors and support configurable current limiting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (GND) | Power Ground Reference | Primary return path for internal circuitry; E1 must be tied to this pin |
| 2 (VC) | Error Amplifier Output / Control Node | Provides compensation node, soft-start ramp, current limit control, and shutdown activation (≤0.15V) |
| 3 (FB) | Feedback Input | Accepts 1.24V reference for standard regulation or <0.54V to enter flyback mode with 15V reference |
| 4 (NC) | No Connect | Not internally bonded; must remain unconnected per datasheet - future revision may assign function |
| 5 (E2) | Secondary Emitter Terminal | Optional connection; leaving open halves current limit (to 0.625A) and doubles switch RON |
| 6 (VSW) | Switch Collector Output | High-voltage (65V max) switched node driving external inductor/diode/transformer |
| 7 (E1) | Primary Emitter Terminal | Mandatory GND connection; carries full switch current when E2 is used |
| 8 (VIN) | Input Supply Voltage | Accepts 3V–40V; powers internal regulator and switch driver; bypass capacitor required |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A, 65V switch | Eliminates external MOSFET and gate driver, reducing BOM count and layout complexity in ≤25W converters |
| Separate emitter pins (E1/E2) | Enables user-selectable current limit scaling (1.25A or 0.625A) without changing PCB layout or external parts |
| Flyback-regulated floating outputs | Supports fully isolated multi-output supplies using transformer coupling - no optocoupler or secondary-side IC needed |
| Adaptive anti-saturation drive | Maintains high efficiency across 10:1 load range by dynamically adjusting base drive to prevent transistor saturation |
| External synchronization (120–160kHz) | Allows noise-sensitive systems to lock switching frequency to external clock, avoiding beat frequencies or EMI peaks |
Applications
| Battery Upconverter | Isolated Flyback Power Supply |
|---|---|
Use Scenario: Boosting single-cell Li-ion (3.0–4.2V) or alkaline (1.5–3.0V) battery voltage to 5V or 12V for microcontroller peripherals. IC Role / Device Role / Timing Role: Primary switching regulator controlling inductor current and diode conduction timing to generate regulated output from variable low-voltage source. Use Value: Enables >85% efficiency at 1.25A peak switch current, extending runtime versus linear regulators; shutdown mode reduces quiescent draw to 50µA during sleep. | Use Scenario: Generating isolated ±15V op-amp rails or 5V logic supply from 24V industrial bus, with no galvanic connection between input and output. IC Role / Device Role / Timing Role: Flyback controller regulating primary-side reflected voltage pulse amplitude to maintain stable secondary output without optocoupler feedback loop. Use Value: Achieves fully floating outputs up to transformer breakdown rating; eliminates secondary-side sensing components and simplifies safety certification. |
| Logic Supply Converter | Inverting DC-DC Converter |
Use Scenario: Converting 5V system rail to ±12V for analog front-end signal conditioning in data acquisition modules. IC Role / Device Role / Timing Role: Boost converter operating in continuous conduction mode, with VC pin used for soft-start to limit inrush current. Use Value: Delivers up to 12V@1A from 5V input using minimal external parts; 100kHz frequency allows small, low-cost magnetics. | Use Scenario: Generating negative voltage (e.g., –5V) from positive 5V or 12V supply for sensor biasing or level-shifting circuits. IC Role / Device Role / Timing Role: Inverting topology controller managing polarity-reversal energy transfer through coupled inductor or transformer. Use Value: Provides clean, regulated negative output without requiring dual-input supplies; uses same IC footprint and control logic as boost configuration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CN8#TRPBF | Same electrical specs, but in plastic DIP (N8) instead of ceramic DIP (J8); higher θJA (130°C/W vs 100°C/W). | Suitable for cost-sensitive, non-military applications where extended temperature range (–40°C to 100°C) and moisture resistance are not required. | Select LT1172CN8#TRPBF only if ceramic packaging is unnecessary and thermal margin permits higher junction rise. |
| LT1172CS8#TRPBF | Same specs in SO-8 surface-mount package; requires PCB rework for through-hole-to-SMT transition. | Preferred for automated assembly and space-constrained layouts; lacks exposed emitters (E1/E2), eliminating configurable current limit. | Choose LT1172CS8#TRPBF when board area and manufacturing efficiency outweigh need for E2-based current scaling. |
Compared with LT1172CN8#TRPBF and LT1172CS8#TRPBF, the LT1172CJ8 offers superior thermal performance (100°C/W) and unique emitter configurability - critical for ruggedized designs needing adjustable overload protection without layout changes.
Availability
LT1172CJ8 is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered instrumentation, isolated sensor interfaces, and embedded DC-DC conversion requiring stable component supply across extended lifecycle programs.
Supply support for LT1172CJ8 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 long-term supply for legacy Linear parts including the LT1172 series.
The LT1172 belongs to Linear's monolithic high-power switching regulator family, engineered to replace discrete switch + controller combinations in cost- and space-constrained applications while delivering robust fault protection and topology flexibility.
FAQ
What is the maximum input voltage rating for the LT1172CJ8?
The LT1172CJ8 has an absolute maximum supply voltage of 40V, as specified in the Absolute Maximum Ratings table. Operation above this voltage risks permanent damage. For flyback configurations with transformer isolation, the switch breakdown voltage remains 65V - meaning reflected voltages must stay within that limit regardless of input rail.
Can the LT1172CJ8 be used in flyback topology without an optocoupler?
Yes, the LT1172CJ8 supports flyback-regulated mode using its internal 15.0V flyback reference. When the FB pin is pulled below 0.54V, the IC switches to regulating the amplitude of the primary-side flyback pulse - enabling stable isolated outputs without secondary-side feedback components like optocouplers or TL431s.
What is the purpose of Pin 4 (NC) on the LT1172CJ8?
Pin 4 on the LT1172CJ8 is designated NC (No Connect) and must remain unconnected in all designs. The datasheet explicitly states it is not internally bonded and warns against routing or terminating this pin - future revisions may assign functionality, so leaving it floating avoids potential compatibility issues.
How does the E2 pin affect current limiting in the LT1172CJ8?
Leaving E2 unconnected on the LT1172CJ8 disables half the internal switch emitter area, reducing the guaranteed current limit from 1.25A to 0.625A while doubling the effective switch "on" resistance. This provides a simple hardware method to lower peak stress during overload conditions without modifying compensation or feedback networks.
Is the LT1172CJ8 RoHS-compliant and lead-free?
Yes, the LT1172CJ8#TRPBF ordering part number indicates lead-free finish and RoHS compliance. The "PBF" suffix denotes lead-free packaging, and "TRPBF" confirms tape-and-reel delivery with Pb-free termination - consistent with Analog Devices' standard environmental compliance for legacy Linear products.
LT1172CJ8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- *
- Package/Case:
- 8-CDIP (0.300", 7.62mm)
- 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:
- 8-CERDIP
LT1172CJ8 FAQ
1.How can I place an order for LT1172CJ8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CJ8 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 LT1172CJ8 reliable?
The price and inventory of LT1172CJ8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CJ8 is usually 5 days.
3.What payment methods are accepted for LT1172CJ8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CJ8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CJ8?
LT1172CJ8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CJ8 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 LT1172CJ8?
For technical support, including LT1172CJ8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CJ8 requirements.
6.How does Aetrix verify that LT1172CJ8 is sourced from the original manufacturer or authorized distributors?
All LT1172CJ8 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 LT1172CJ8 meets industry standards.
7.What is the process for return or replacement of LT1172CJ8?
All LT1172CJ8 units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CJ8, 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 LT1172CJ8 part is unused and in its original packaging.
Return procedure for LT1172CJ8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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