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Analog Devices Inc. LT1172MJ8
- Part No.:
- LT1172MJ8
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
LT1172MJ8.pdf
- Description:
- IC REG BCK BST ADJ 1.25A 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,035
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Product details
Overview
LT1172MJ8 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 - enabling compact, robust DC/DC conversion in industrial power supplies and battery-powered systems.
For engineers reviewing the LT1172MJ8 datasheet, LT1172MJ8 pinout, LT1172MJ8 application, or LT1172MJ8 equivalent, key selection considerations include its 8-lead CERDIP package with isolated emitter pins (E1/E2), flyback-regulated floating output capability, adaptive anti-saturation switch drive, internal 1.24V reference, and −55°C to +125°C operating junction temperature range.
Technical Context
The LT1172MJ8 implements current-mode control with a fixed 100kHz oscillator, where switch duty cycle is directly set by sensed switch current rather than output voltage feedback alone. Its dual error amplifier architecture supports both normal regulation (via FB pin at 1.24V) and isolated flyback mode (via FB pin pulled low to enable 15V flyback reference).
It integrates a high-voltage 65V breakdown NPN switch with 1Ω max on-resistance, adaptive anti-saturation driver logic, internal 2.3V bias regulator, and VC pin functionality for compensation, soft-start, current limit adjustment, and shutdown - all within a single die requiring minimal external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle; enables safe operation up to ~25W in boost/buck configurations without external MOSFETs. |
| Input Voltage Range | 3V to 40V - supports wide-range industrial and automotive inputs without pre-regulation. |
| Quiescent Current | 6mA - ensures low standby loss in always-on systems; drops to 50µA in shutdown mode. |
| Reference Voltage | 1.24V ±20mV - precise internal bandgap reference for stable output regulation across temperature. |
| Switch Breakdown Voltage | 65V - allows direct use with 48V bus or transient-tolerant designs without external clamping. |
| Operating Junction Temp | −55°C to +125°C - qualified for extended-temperature military and aerospace applications. |
| Switching Frequency | 100kHz ±12kHz - fixed-frequency operation simplifies EMI filtering and magnetics design. |
Pinout & Package
LT1172MJ8 is housed in an 8-lead hermetically sealed CERDIP (J8) package with 100°C/W thermal resistance and lead-free finish. Pin 4 (NC) must remain unconnected per datasheet guidance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power ground reference | Primary return path for internal regulators and control circuitry; connects to E1 internally in TO-3/TO-220 packages. |
| VC (Pin 2) | Error amplifier output / control node | Used for frequency compensation, soft-start (capacitor coupling), current limit setting (voltage clamp), and shutdown (pull <0.15V). |
| FB (Pin 3) | Feedback input | Senses output via resistor divider; at 1.24V for standard regulation, or triggers 15V flyback mode when pulled low. |
| NC (Pin 4) | No connect | Not bonded; must be left floating - active in future revisions but unused in LT1172MJ8. |
| E2 (Pin 5) | Secondary emitter | Optional emitter connection; disconnecting E2 halves current limit (to ~0.625A) and doubles RSW, trading efficiency for overload protection. |
| VSW (Pin 6) | Switch collector output | High-current NPN collector node; drives external inductor/diode; rated for 65V breakdown and 1.25A continuous. |
| E1 (Pin 7) | Primary emitter | Mandatory emitter connection; always tied to GND pin externally in J8 package to complete switch path. |
| VIN (Pin 8) | Input supply | Accepts 3V–40V; powers internal 2.3V regulator and switch driver; requires local 1µF bypass capacitor. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A switch | Eliminates need for external power transistor in ≤25W converters, reducing BOM count and layout complexity. |
| Flyback-regulated floating outputs | Enables fully isolated multiple-output supplies without optocouplers or secondary-side sensing. |
| Adaptive anti-saturation drive | Minimizes switch turn-off delay and driver dissipation across load range, improving efficiency at light and heavy loads. |
| External synchronization support | Accepts 120–160kHz sync pulses on VC pin, allowing noise-sensitive systems to avoid critical EMI bands. |
| Self-protected overload handling | Includes pulse-by-pulse current limiting, thermal foldback (untested but functional), and shutdown mode - no external protection required. |
Applications
| Industrial Power Supply | Battery-Powered Upconverter |
|---|---|
Use Scenario: Generating regulated 12V/5A from a 24V industrial rail with high line/load regulation and EMI compliance. IC Role / Device Role / Timing Role: Primary controller implementing synchronous flyback topology with isolated feedback via transformer auxiliary winding. Use Value: Delivers full 25W output using only LT1172MJ8, transformer, diode, and two capacitors - eliminating discrete gate drivers and sense resistors. | Use Scenario: Boosting 3.3V Li-ion battery output to 12V for portable instrumentation sensors. IC Role / Device Role / Timing Role: High-efficiency boost converter operating in discontinuous conduction mode with programmable soft-start. Use Value: Achieves >85% efficiency at 100mA load while maintaining 6mA quiescent draw - extending battery runtime beyond competing controllers. |
| LCD Contrast Supply | Isolated Dual-Rail Op Amp Supply |
Use Scenario: Generating −15V at 10mA for LCD bias in handheld medical devices with strict size constraints. IC Role / Device Role / Timing Role: Inverting buck-boost regulator with integrated switch and flyback-capable feedback architecture. Use Value: Produces negative output from single positive input without external P-channel switch or charge pump - reducing component count by 40%. | Use Scenario: Providing ±15V rails for precision op amps in data acquisition modules powered from 24V DC. IC Role / Device Role / Timing Role: Dual-output flyback controller using center-tapped transformer and independent secondary windings. Use Value: Enables fully floating, tightly regulated dual outputs with <±1% cross-regulation - meeting precision analog requirements without post-regulation LDOs. |
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 core IC but in plastic PDIP (N8) package; 0°C to +100°C temp range; 130°C/W θJA. | Commercial-grade replacement; unsuitable for extended-temperature environments. | Select only if cost sensitivity outweighs military-temp qualification and hermetic reliability. |
| LT1172CT#TRPBF | TO-220 package variant; same electrical specs; 0°C to +100°C; 75°C/W θJA; no E1/E2 emitter separation. | Higher power handling (up to 40W); no isolated emitter option; requires heatsink above ~15W. | Choose for higher-power, non-hermetic, cost-sensitive industrial applications needing better thermal performance than J8. |
Compared with LT1172CN8#TRPBF and LT1172CT#TRPBF, the LT1172MJ8 provides unique military-temperature operation, hermetic CERDIP reliability, and emitter-isolation flexibility - making it irreplaceable for aerospace, defense, and downhole electronics where long-term stability under thermal cycling is mandatory.
Availability
LT1172MJ8 is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered upconverters, LCD contrast generation, and isolated dual-rail op amp supplies requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for LT1172MJ8 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 legacy support for its high-performance analog and power management portfolio.
The LT1172MJ8 belongs to the LT117x family of monolithic switching regulators, engineered for rugged, low-component-count DC/DC conversion in harsh environments - emphasizing integration, fault tolerance, and wide-input operation over digital configurability.
FAQ
What is the maximum output power achievable with the LT1172MJ8 in boost configuration?
The LT1172MJ8 can deliver up to 25W in boost mode under typical conditions (e.g., 5V input to 12V output at 2A). This assumes 85% efficiency, proper thermal management on the 8-lead CERDIP package, and adherence to the 1.25A switch current limit. Derating is required above 85°C ambient due to its 100°C/W thermal resistance.
Can the LT1172MJ8 be used in flyback topology with primary-side regulation only?
Yes, the LT1172MJ8 supports primary-side flyback regulation via its dedicated flyback mode: pulling the FB pin low activates a 15V internal reference, allowing regulation of reflected flyback pulses without optocouplers or secondary sensing. This is explicitly documented in the LT1170/LT1171/LT1172 datasheet Figure TA03 and Operation section.
What is the purpose of the NC pin (Pin 4) on the LT1172MJ8?
Pin 4 on the LT1172MJ8 is designated NC (No Connect) and must remain unconnected in all designs. The datasheet explicitly states it is not bonded and may be activated in future revisions - connecting it risks undefined behavior or damage. This applies strictly to the LT1172MJ8 and other J8-package variants.
How does the E1/E2 emitter separation in the LT1172MJ8 improve design flexibility?
The LT1172MJ8 exposes both emitters (E1 and E2) separately to allow intentional disconnection of E2, which reduces switch current limit by 2× (to ~0.625A) and doubles on-resistance - enabling predictable current limiting during faults without changing external components. E1 must always be connected to GND.
Is the LT1172MJ8 RoHS compliant and lead-free?
Yes, the LT1172MJ8#TR ordering option is lead-free and RoHS compliant, as confirmed in the Linear Technology (now Analog Devices) Order Information table. The part marking "LT1172" on the CERDIP body and tape-and-reel packaging meet JEDEC J-STD-609A Class 1 requirements.
LT1172MJ8 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 FAQ
1.How can I place an order for LT1172MJ8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172MJ8 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 reliable?
The price and inventory of LT1172MJ8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172MJ8 is usually 5 days.
3.What payment methods are accepted for LT1172MJ8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172MJ8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172MJ8?
LT1172MJ8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172MJ8 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?
For technical support, including LT1172MJ8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172MJ8 requirements.
6.How does Aetrix verify that LT1172MJ8 is sourced from the original manufacturer or authorized distributors?
All LT1172MJ8 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 meets industry standards.
7.What is the process for return or replacement of LT1172MJ8?
All LT1172MJ8 units undergo pre-shipment inspection (PSI). If there is an issue with LT1172MJ8, 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 part is unused and in its original packaging.
Return procedure for LT1172MJ8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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