My Inquiry
My Account
Analog Devices Inc. LT1172CT#PBF
- Part No.:
- LT1172CT#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-220-5
- Datasheet:
-
LT1172CT#PBF.pdf
- Description:
- IC REG BCK BST ADJ 1.25A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:233
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT1172CT#PBF from Analog Devices (formerly Linear Technology) is a monolithic 1.25A high-efficiency current-mode switching regulator IC in a 5-lead plastic TO-220 package. It operates from 3V to 40V input, delivers up to 25W output power in buck/boost/flyback topologies, integrates a 1.25A/65V internal switch, and features 100kHz fixed-frequency operation with 6mA quiescent current - used in isolated flyback converters for industrial power supplies.
For engineers reviewing the LT1172CT#PBF datasheet, LT1172CT#PBF pinout, LT1172CT#PBF application, or LT1172CT#PBF equivalent, key selection criteria include verified 1.25A switch current limit at 25°C, 65V switch breakdown voltage, flyback reference voltage of 15.0–18.0V, shutdown threshold of 50–300mV, and thermal resistance θJA = 75°C/W - all confirmed for the CT package variant.
Technical Context
The LT1172CT#PBF implements current-mode control with adaptive anti-saturation drive, enabling stable regulation across wide load ranges without efficiency loss. Its dual error amplifier architecture supports both standard (1.24V feedback) and flyback modes (15–18V reference), with separate VC pin control for soft-start, current limiting, and shutdown.
It uses a 100kHz oscillator and integrates all functions - oscillator, PWM comparator, driver, protection, and 2.3V internal regulator - eliminating external timing components. The TO-220 package ties E1 and E2 internally to GND, simplifying layout versus miniDIP variants where emitter pins are exposed.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A at TJ ≥ 25°C (guaranteed minimum for overload protection) |
| Switch Breakdown Voltage | 65V (supports ≤40V input in standard grade; enables flyback designs up to 55V with HV variant) |
| Reference Voltage | 1.224–1.274V (tight 4% tolerance at FB pin; sets output voltage via resistor divider) |
| Quiescent Current | 6mA (enables high efficiency at light loads; critical for battery-powered boost converters) |
| Shutdown Current | 100–250µA (reduces system standby power; triggered by VC ≤ 0.15V) |
| Switching Frequency | 88–115kHz (fixed internal oscillator; allows predictable EMI filtering and inductor sizing) |
| Flyback Reference | 15.0–18.0V (enables transformer-coupled isolated outputs without optocoupler feedback) |
Pinout & Package
LT1172CT#PBF is housed in a 5-lead plastic TO-220 package with tab connected to GND. E1 and E2 terminals are internally tied to GND - no external emitter connections required. Thermal resistance θJA = 75°C/W enables operation up to 100°C ambient without heatsink under typical loads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input Supply | Accepts 3V–40V DC; powers internal regulator and switch driver |
| VSW | Switch Output | Drives external inductor/diode; connects to drain of integrated NPN switch |
| GND | Power & Signal Ground | Common return for VIN, VSW, FB, VC; tab is electrically connected |
| FB | Feedback Input | Senses output voltage divider; selects normal (1.24V) or flyback (15–18V) mode |
| VC | Error Amplifier Output | Controls duty cycle, current limit, soft-start, and shutdown via external clamp |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A/65V switch | Eliminates external MOSFET in ≤25W designs; reduces BOM count and layout complexity |
| Flyback-regulated mode | Enables fully floating, isolated outputs without optocouplers or secondary-side sensing |
| Adaptive anti-saturation drive | Maintains high efficiency across 10:1 load range by dynamically adjusting base drive |
| External shutdown via VC pin | Reduces supply current to ≤250µA; supports low-power sleep states in portable systems |
| Self-protected against overloads | Current-mode architecture provides pulse-by-pulse limiting; prevents thermal runaway |
Applications
| Industrial Power Supply | Battery-Powered Boost Converter |
|---|---|
Use Scenario: 24V AC/DC input converted to isolated ±15V for PLC I/O modules. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating secondary output via primary-side sensing. Use Value: Eliminates optocoupler and TL431, reducing component count by 3 and improving long-term reliability. | Use Scenario: 3.7V Li-ion battery boosted to 12V for portable instrumentation. IC Role / Device Role / Timing Role: High-efficiency boost converter with 100kHz fixed frequency for compact LC filter design. Use Value: 6mA quiescent current extends battery life; 1.25A switch supports 1A output at >85% efficiency. |
| LCD Contrast Voltage Generator | Isolated Sensor Interface |
Use Scenario: Generating –10V to –26V negative bias for LCD segment drivers in handheld medical devices. IC Role / Device Role / Timing Role: Inverting topology regulator using single inductor and diode. Use Value: Flyback mode enables precise negative output without additional charge pumps or transformers. | Use Scenario: Providing isolated 5V supply for current-sense amplifiers in motor drive inverters. IC Role / Device Role / Timing Role: Primary-side regulated flyback controller with transformer-isolated feedback. Use Value: 65V switch rating supports 48V bus input; floating output withstands >1kV isolation test. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172HVCT#PBF | 60V switch breakdown (vs. 65V), 40V max input (vs. 40V), same 1.25A current limit | Supports higher input transients in automotive 24V systems; identical pinout and footprint | Select when operating near 40V input with surge margin requirement |
| LM2574N-12 | Fixed 12V output, 0.5A switch, 52V max input, no flyback mode, 55kHz switching | Lower cost for non-isolated fixed-output applications; requires external feedback for adjustability | Choose only for simple 12V step-down where isolation and adjustability are unnecessary |
Compared with LT1172HVCT#PBF, the LT1172CT#PBF offers higher switch breakdown (65V vs. 60V) for improved flyback safety margin, while LM2574N-12 lacks flyback capability and adjustable output - making LT1172CT#PBF uniquely suited for isolated, multi-topology, and programmable-output designs.
Availability
LT1172CT#PBF is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered boost converters, LCD contrast generators, and isolated sensor interfaces requiring stable component supply and long-lifecycle support.
Supply support for LT1172CT#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 support for legacy Linear switching regulators. The company specializes in high-performance analog, mixed-signal, and power management ICs.
The LT1170/LT1171/LT1172 product line was designed for rugged, high-power DC/DC conversion in industrial, telecom, and embedded systems - emphasizing integration, topology flexibility, and self-protection without external components.
FAQ
What is the maximum input voltage rating for LT1172CT#PBF?
The LT1172CT#PBF has an absolute maximum supply voltage of 40V. Operation above this level risks permanent damage. Its switch breakdown voltage is rated at 65V, but the 40V limit applies to continuous VIN operation per Absolute Maximum Ratings. For transient-tolerant designs, the LT1172HVCT#PBF variant supports 60V input.
Does LT1172CT#PBF support flyback topology with isolated outputs?
Yes, the LT1172CT#PBF supports flyback-regulated mode by pulling the FB pin below 0.54V, activating its internal flyback error amplifier with 15.0–18.0V reference. This enables fully floating, transformer-isolated outputs without optocouplers - a core feature confirmed in the datasheet's Block Diagram and Typical Applications sections.
What is the thermal resistance θJA for LT1172CT#PBF?
The LT1172CT#PBF has a junction-to-ambient thermal resistance (θJA) of 75°C/W, measured on a standard PCB with 1 oz. copper. This value is specified in the Pin Configuration section for the T-package (TO-220) and enables operation up to 100°C ambient temperature at full load without a heatsink in most layouts.
Can LT1172CT#PBF be synchronized to an external clock?
No, the LT1172CT#PBF does not support external synchronization. Synchronization capability (120–160kHz) is explicitly documented only for the LT1170 and LT1171 variants. The LT1172 datasheet omits sync circuitry description and shows no sync-related pins or timing diagrams - confirming it is limited to its internal 100kHz oscillator.
What is the guaranteed switch current limit for LT1172CT#PBF at 85°C ambient?
At junction temperature ≥25°C (which includes 85°C ambient under typical thermal conditions), the LT1172CT#PBF guarantees a minimum switch current limit of 1.25A. This is specified in the Electrical Characteristics table under "ILIM (LT1172)" with condition "Duty Cycle = 50%, TJ ≥ 25°C" - a tested and production-validated parameter.
LT1172CT#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-220-5
- 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:
- TO-220-5
LT1172CT#PBF FAQ
1.How can I place an order for LT1172CT#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CT#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 LT1172CT#PBF reliable?
The price and inventory of LT1172CT#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CT#PBF is usually 5 days.
3.What payment methods are accepted for LT1172CT#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CT#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CT#PBF?
LT1172CT#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CT#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 LT1172CT#PBF?
For technical support, including LT1172CT#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CT#PBF requirements.
6.How does Aetrix verify that LT1172CT#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172CT#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 LT1172CT#PBF meets industry standards.
7.What is the process for return or replacement of LT1172CT#PBF?
All LT1172CT#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CT#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 LT1172CT#PBF part is unused and in its original packaging.
Return procedure for LT1172CT#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1172CT#PBF Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
