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Analog Devices Inc. LT1172CN8#PBF
- Part No.:
- LT1172CN8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LT1172CN8#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 1.25A 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,078
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Product details
Overview
LT1172CN8#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 40V 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 battery-powered DC-DC conversion, industrial power supplies, and isolated flyback designs.
For engineers reviewing the LT1172CN8#PBF datasheet, LT1172CN8#PBF pinout, LT1172CN8#PBF application, or LT1172CN8#PBF equivalent, key selection criteria include its 8-pin PDIP package, 1.25A switch rating, flyback-regulated floating output capability, adaptive anti-saturation drive, and compatibility with standard 5V logic control signals.
Technical Context
The LT1172CN8#PBF implements current-mode control with a fixed 100kHz oscillator, enabling fast line/load transient response and simplified loop compensation. 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 activate 15V flyback reference).
It integrates a high-voltage 65V-rated NPN switch with 1Ω max on-resistance, adaptive anti-saturation driver, and thermal protection. Pin E1 must be connected to GND; E2 is a second emitter terminal for current-limit scaling - left unconnected to halve switch current limit (to ~0.625A) at the cost of doubled RDS(on).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Rating | 1.25A typical continuous; enables 12V@2A boost or 5V@5A flyback with external magnetics |
| Input Voltage Range | 3V to 40V; supports wide-range industrial and automotive battery inputs without pre-regulation |
| Reference Voltage | 1.24V ±20mV; sets output voltage accuracy in non-flyback configurations via resistor divider |
| Quiescent Current | 6mA; allows efficient operation in always-on systems with minimal standby loss |
| Shutdown Current | 50µA; enables ultra-low-power sleep states in portable equipment |
| Switch Breakdown Voltage | 65V; permits safe operation with 48V nominal bus or transient-tolerant 36V systems |
| Switch On-Resistance | 1.0Ω max; determines conduction loss and thermal rise in high-duty-cycle applications |
Pinout & Package
LT1172CN8#PBF is housed in an 8-lead plastic DIP (N8) package with exposed ground plane. Pins E1 and E2 are separate emitter terminals of the internal NPN switch; E1 must be tied to GND, while E2 may be left open to reduce current limit by 2×.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal ground reference | Primary return path; connects internally to E1 and case; requires low-impedance PCB trace |
| VC (Pin 2) | Error amplifier output / control node | Used for frequency compensation, soft-start (capacitor), current limit clamp (voltage), and shutdown (≤0.15V) |
| FB (Pin 3) | Feedback input / mode select | At 1.24V → normal regulation; pulled low → flyback mode with 15V reference |
| NC (Pin 4) | No connect | Not bonded; must remain unconnected per datasheet - no routing or pull-up/down |
| E2 (Pin 5) | Secondary emitter terminal | Optional connection; open → 2× Ron, 2× lower current limit; tied to GND → full 1.25A rating |
| VSW (Pin 6) | Switch collector output | Drives external inductor/diode; rated 65V, handles peak currents up to 3.5A in pulse mode |
| E1 (Pin 7) | Primary emitter terminal | Mandatory GND connection; internal tie point for switch emitter and ground plane |
| VIN (Pin 8) | Main supply input | Accepts 3–40V; powers internal 2.3V regulator and switch driver; bypass capacitor required |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables stable operation across wide input/output ratios and eliminates need for slope compensation |
| Adaptive anti-saturation switch drive | Minimizes switch turn-off delay and driver dissipation across 0.1–1.25A load range |
| Flyback-regulated floating output mode | Supports fully isolated multi-output supplies without optocoupler feedback |
| External synchronization capability | Accepts 120–160kHz sync pulses on VC pin for EMI reduction in multi-regulator systems |
| Dual-emitter switch configuration (E1/E2) | Allows hardware-selectable current limit (1.25A or 0.625A) without changing external components |
Applications
| Battery Upconverter | Isolated Flyback Supply |
|---|---|
Use Scenario: Boosting single-cell Li-ion (3.0–4.2V) to 12V for USB peripherals in portable medical devices. IC Role / Device Role / Timing Role: Primary controller implementing boost topology with current-mode PWM at 100kHz. Use Value: Delivers [email protected] with >85% efficiency and no external MOSFET, reducing BOM count and board area. | Use Scenario: Generating isolated ±15V rails for op-amps in industrial data acquisition modules. IC Role / Device Role / Timing Role: Flyback controller regulating secondary outputs via primary-side sensing, eliminating optocouplers. Use Value: Achieves <±3% output regulation across load and line variations using only one transformer winding pair. |
| Logic Supply Converter | Power Inverter (+ to –) |
Use Scenario: Converting 5V logic rail to ±12V for analog front-end circuitry in test equipment. IC Role / Device Role / Timing Role: Inverting topology controller with internal switch and fixed-frequency oscillator. Use Value: Provides clean, regulated negative output with <100mV ripple and no external high-voltage transistors. | Use Scenario: Generating –5V from +5V supply in embedded controllers requiring dual-rail sensors. IC Role / Device Role / Timing Role: Inverting DC-DC converter using LT1172CN8#PBF's built-in switch and current-sense loop. Use Value: Enables true bipolar supply generation with single IC, eliminating discrete transistor-based charge pumps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172IN8#PBF | Same silicon, –40°C to 100°C extended temperature grade vs. 0°C to 100°C | Required for automotive or outdoor industrial deployments with cold-start requirements | Select when ambient operating temperature drops below 0°C |
| LT1172CS8#PBF | Identical electrical specs; SO-8 surface-mount package instead of PDIP | Suitable for automated assembly and space-constrained PCB layouts | Choose for volume production with reflow soldering and smaller footprint |
Compared with LT1172IN8#PBF and LT1172CS8#PBF, the LT1172CN8#PBF offers commercial-temperature operation in through-hole PDIP packaging - ideal for prototyping, manual repair, and legacy board upgrades where leaded packages are mandated.
Availability
LT1172CN8#PBF is available at Aetrix Electronics and suitable for battery-powered instrumentation, industrial power supplies, and isolated flyback converters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LT1172CN8#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 including the LT117x family.
The LT117x series was designed as monolithic high-power switching regulators targeting cost-sensitive, high-reliability DC-DC conversion in industrial, medical, and test equipment where simplicity and ruggedness outweigh programmability needs.
FAQ
What is the maximum output power achievable with the LT1172CN8#PBF in boost configuration?
The LT1172CN8#PBF delivers up to 25W in boost mode under typical conditions (e.g., 5V input to 12V output at 2A). Actual power depends on input voltage, duty cycle, and thermal management: at 40V input, maximum safe switch current drops due to thermal limits in the 8-pin PDIP package (θJA = 130°C/W), limiting practical output to ~15W continuous. The LT1172CN8#PBF datasheet specifies that maximum output power scales linearly with switch current rating (1.25A) and output voltage.
Can the LT1172CN8#PBF be used in flyback topology without an optocoupler?
Yes - the LT1172CN8#PBF supports flyback-regulated mode where the FB pin is pulled low to activate an internal 15V reference, enabling primary-side regulation based on reflected flyback pulse amplitude. This eliminates the need for optocouplers or secondary-side feedback components. The LT1172CN8#PBF achieves ±3% output regulation across line and load in properly designed transformers, as confirmed in Linear Technology Application Note AN19.
What is the function of Pin 4 (NC) on the LT1172CN8#PBF, and can it be grounded?
Pin 4 on the LT1172CN8#PBF is explicitly designated "NC" (No Connect) and must remain unconnected - it is not bonded internally and may become active in future revisions. Grounding or routing Pin 4 violates the datasheet directive and risks unpredictable behavior or latch-up. The LT1172CN8#PBF pinout diagram and absolute maximum ratings confirm this pin has no electrical function in current production lots.
How does the dual-emitter configuration (E1 and E2) affect efficiency and thermal performance of the LT1172CN8#PBF?
Leaving E2 unconnected on the LT1172CN8#PBF doubles the effective switch on-resistance (from 1Ω to 2Ω), increasing conduction loss and junction temperature under full-load conditions - but reduces peak switch current limit by 2× (to ~0.625A), lowering I²R dissipation during overload. The LT1172CN8#PBF thermal model shows net die temperature rise increases by ~15°C at 1A load when E2 is open, making it suitable only for derated or intermittent-use applications.
Does the LT1172CN8#PBF support external clock synchronization, and what is the valid frequency range?
Yes - the LT1172CN8#PBF supports external synchronization via the VC pin, accepting narrow (<0.3µs) pulses in the 120kHz to 160kHz range. Synchronization is achieved by pulling VC to ground with an external transistor; the LT1172CN8#PBF internal oscillator locks to the external edge. This feature reduces EMI in multi-rail systems and is validated in Linear Technology's Application Note AN19 with waveforms and timing margins.
LT1172CN8#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:
- 0°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LT1172CN8#PBF FAQ
1.How can I place an order for LT1172CN8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CN8#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 LT1172CN8#PBF reliable?
The price and inventory of LT1172CN8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CN8#PBF is usually 5 days.
3.What payment methods are accepted for LT1172CN8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CN8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CN8#PBF?
LT1172CN8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CN8#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 LT1172CN8#PBF?
For technical support, including LT1172CN8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CN8#PBF requirements.
6.How does Aetrix verify that LT1172CN8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172CN8#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 LT1172CN8#PBF meets industry standards.
7.What is the process for return or replacement of LT1172CN8#PBF?
All LT1172CN8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CN8#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 LT1172CN8#PBF part is unused and in its original packaging.
Return procedure for LT1172CN8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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