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Analog Devices Inc. LT1172IS8#TRPBF
- Part No.:
- LT1172IS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1172IS8#TRPBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.25A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,435
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Product details
Overview
LT1172IS8#TRPBF 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 60V input, delivers up to 25W output power in boost mode, draws only 6mA quiescent current, and features shutdown mode drawing 50µA - enabling use in battery-powered DC-DC conversion and isolated flyback supplies.
For engineers reviewing the LT1172IS8#TRPBF datasheet, LT1172IS8#TRPBF pinout, LT1172IS8#TRPBF application, or LT1172IS8#TRPBF equivalent, key selection criteria include its 1.25A internal switch rating, 8-pin SOIC (S8) package with separate emitter pins (E1/E2), –40°C to 100°C operating temperature range, and flyback-regulated floating output capability without optocoupler feedback.
Technical Context
The LT1172IS8#TRPBF implements current-mode control with adaptive anti-saturation drive for stable operation across wide load ranges. Its error amplifier provides transconductance of 3000–4400 µmho and reference voltage accuracy of ±1.2% (1.224V to 1.264V), enabling precise regulation in both normal (1.24V FB threshold) and flyback modes (15.0–18.0V FB reference).
It supports external synchronization (120–160kHz), features dual emitter terminals (E1 grounded, E2 optional for current limit scaling), and includes built-in protection: thermal shutdown, overcurrent limiting, and flyback blanking to suppress leakage spikes - all within a single 8-pin plastic SOIC package rated at θJA = 120–150°C/W depending on PCB layout.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A typical at 50% duty cycle; enables compact boost/flyback designs up to ~25W with minimal external components. |
| Input Voltage Range | 3V to 60V; supports wide-range industrial, automotive, and battery-input applications without pre-regulation. |
| Quiescent Current | 6mA; ensures high light-load efficiency in always-on systems like sensor nodes or standby power rails. |
| Shutdown Current | 50µA; allows ultra-low-power sleep states in portable equipment and IoT edge devices. |
| Reference Voltage | 1.244V ±1.2%; sets output voltage accuracy in standard configurations using resistor dividers on FB pin. |
| Flyback Reference | 15.0–18.0V; enables transformer-isolated outputs with primary-side sensing, eliminating optocouplers and TL431. |
| Switch Breakdown | 60V (S8 package); defines maximum safe VSW swing in boost/flyback topologies with margin for ringing. |
| Switch RDS(on) | 0.6Ω max; determines conduction loss and thermal rise under full load; doubles when E2 is left open. |
Pinout & Package
LT1172IS8#TRPBF is housed in an 8-lead plastic SOIC (S8) package with exposed pad thermal enhancement. Pin 4 (NC) must remain unconnected per datasheet; E1 and E2 are dedicated emitter terminals for precision current sensing and scalable current limiting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power ground reference | Primary return path for internal circuitry and switch emitter; connects to E1 internally in TO-220/TO-3 packages. |
| VC (Pin 2) | Error amplifier output / control node | Used for frequency compensation, soft-start (capacitor), current limit adjustment (voltage clamp), and shutdown (≤0.15V). |
| FB (Pin 3) | Feedback input | Senses output voltage divider; pulls low to enable flyback mode; clamped at 0.25V/2.3V for safety. |
| NC (Pin 4) | No connect | Not bonded; must be left floating - not tied to GND or any signal per datasheet warning. |
| E2 (Pin 5) | Secondary emitter terminal | Optional connection; leaving open halves switch current limit (to 0.625A) and doubles RDS(on) (to 1.2Ω). |
| VSW (Pin 6) | Switch collector output | Drives external inductor/diode; withstands 60V breakdown; requires snubber in flyback/boost for voltage spike suppression. |
| E1 (Pin 7) | Primary emitter terminal | Mandatory ground connection for switch emitter; separates power ground from signal ground to avoid sensing errors. |
| VIN (Pin 8) | Main supply input | Accepts 3–60V; powers internal 2.3V regulator; decoupling capacitor required near pin for stability. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control | Enables fast line/load transient response and inherent pulse-by-pulse overcurrent protection without external sense resistors. |
| Dual emitter outputs (E1/E2) | Allows precise ground-referenced current sensing and programmable 2:1 current limit reduction by disconnecting E2. |
| Flyback-regulated mode | Supports fully floating, optocoupler-free isolated outputs via primary-side flyback pulse amplitude regulation. |
| Adaptive anti-saturation drive | Minimizes switch turn-off delay and driver dissipation across load range, improving efficiency at light and heavy loads. |
| External synchronization | Accepts 120–160kHz sync pulses on VC pin for EMI reduction in multi-regulator systems or noise-sensitive applications. |
| Thermal shutdown | Protects die during overload or poor heatsinking; activates at ~125°C junction temperature (not tested, but functional). |
Applications
| Battery-Powered Boost Supply | Isolated Flyback Power Supply |
|---|---|
Use Scenario: Generating 12V from a 3.3V Li-ion cell for RF modules or sensors. IC Role / Device Role / Timing Role: Acts as primary-side controller in boost topology with integrated switch and current-mode PWM generator. Use Value: Eliminates need for external MOSFET and gate driver; 6mA quiescent current extends battery life in intermittent-use devices. | Use Scenario: Providing ±15V isolated rails for op-amps in medical instrumentation with no secondary-side feedback. IC Role / Device Role / Timing Role: Regulates output via flyback pulse amplitude sensing on primary side, using internal 15V reference and blanking circuitry. Use Value: Removes optocoupler and TL431, reducing BOM cost and board space while maintaining <±3% output regulation. |
| Inverting DC-DC Converter | Industrial Input Voltage Range Supply |
Use Scenario: Converting 24V industrial bus to –12V for analog front-end biasing. IC Role / Device Role / Timing Role: Configured in inverting topology with single inductor; uses internal 1.25A switch and current-mode loop for stability. Use Value: Achieves regulated negative output without split-rail input; supports wide VIN (3–60V) to tolerate brownouts and surges. | Use Scenario: Powering PLC I/O modules from unregulated 12–48V field wiring. IC Role / Device Role / Timing Role: Functions as buck regulator with adjustable output; leverages 60V switch rating and 100kHz fixed frequency for predictable EMI filtering. Use Value: Withstands 48V transients and maintains regulation down to 3V, enabling direct connection to harsh industrial power buses. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CS8#TRPBF | Same silicon, 0°C to 100°C temp grade; lacks extended –40°C low-temp qualification. | Not suitable for automotive cold-cranking or outdoor industrial deployments below 0°C. | Select LT1172IS8#TRPBF when operation below 0°C is required; otherwise CS8 offers identical performance at lower cost. |
| LM2577-ADJ | 5A switch, 52kHz fixed frequency, no flyback mode, no dual emitter pins, wider VIN (3.5–40V). | Lacks primary-side isolated regulation and fine current limit scaling; requires external current sense for overcurrent protection. | Choose LM2577-ADJ for higher-current non-isolated applications where flyback capability and emitter flexibility are unnecessary. |
Compared with LT1172CS8#TRPBF and LM2577-ADJ, the LT1172IS8#TRPBF uniquely combines –40°C operation, flyback-regulated isolation, and dual-emitter current scaling - making it optimal for ruggedized isolated DC-DC and low-temperature embedded power.
Availability
LT1172IS8#TRPBF is available at Aetrix Electronics and suitable for battery-powered converters, isolated flyback supplies, industrial input-range regulators, and inverting DC-DC applications requiring stable component supply across extended temperature conditions.
Supply support for LT1172IS8#TRPBF 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, datasheets, and application notes for legacy Linear parts including the LT117x family.
The LT117x series was designed as monolithic high-power switching regulators targeting cost-sensitive, space-constrained applications needing robust, self-protected DC-DC conversion without external power switches.
FAQ
What is the maximum output power achievable with the LT1172IS8#TRPBF in boost configuration?
The LT1172IS8#TRPBF supports up to ~25W in boost mode at typical conditions (e.g., 5V input to 12V output at 2A), limited by its 1.25A switch current and 60V VSW rating. Derating is required above 60°C ambient due to θJA = 120–150°C/W in SOIC; actual power depends on layout, inductor DCR, and thermal management. The LT1172IS8#TRPBF datasheet specifies "divide vertical power scale by four for LT1172" relative to LT1170's 100W capability.
Can the LT1172IS8#TRPBF be used in flyback topology without an optocoupler?
Yes. The LT1172IS8#TRPBF supports flyback-regulated mode where the feedback pin (FB) senses the reflected flyback pulse amplitude directly on the primary side. When FB is pulled below 0.54V, the IC switches to flyback mode and regulates using its internal 15.0–18.0V reference - eliminating need for optocoupler, TL431, or secondary-side sensing. This is explicitly documented in the LT1172IS8#TRPBF datasheet's "Operation" section.
What is the purpose of the NC pin (Pin 4) on the LT1172IS8#TRPBF?
Pin 4 on the LT1172IS8#TRPBF is designated NC (No Connect) and must remain unconnected - it is not bonded internally and may become active in future revisions. Connecting it to GND, VIN, or any signal violates the datasheet requirement and risks unpredictable behavior. This applies specifically to the S8 (SOIC) and N8 (PDIP) packages of the LT1172IS8#TRPBF, as confirmed in the Pin Configuration diagram.
How does disconnecting E2 affect the LT1172IS8#TRPBF's performance?
Leaving E2 unconnected on the LT1172IS8#TRPBF reduces the switch current limit by 2:1 (to ~0.625A) and doubles the effective RDS(on) (to ~1.2Ω), increasing conduction loss. However, it also halves I²R dissipation during current-limit events and improves current-sense accuracy by isolating the emitter path. This trade-off is intentional and documented for applications requiring tighter overload control - a unique feature of the LT1172IS8#TRPBF's 8-pin package.
Does the LT1172IS8#TRPBF support external clock synchronization?
Yes. The LT1172IS8#TRPBF can be synchronized to an external clock in the 120–160kHz range by pulling the VC pin to ground with a narrow (<0.3µs) pulse via an external transistor. This capability is specified in the "LT1170/LT1171/LT1172 Synchronizing" section of the datasheet and enables EMI reduction in multi-rail systems - a verified function of the LT1172IS8#TRPBF, not inferred.
LT1172IS8#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- -40°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1172IS8#TRPBF FAQ
1.How can I place an order for LT1172IS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172IS8#TRPBF 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 LT1172IS8#TRPBF reliable?
The price and inventory of LT1172IS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172IS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1172IS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172IS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172IS8#TRPBF?
LT1172IS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172IS8#TRPBF 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 LT1172IS8#TRPBF?
For technical support, including LT1172IS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172IS8#TRPBF requirements.
6.How does Aetrix verify that LT1172IS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1172IS8#TRPBF 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 LT1172IS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1172IS8#TRPBF?
All LT1172IS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172IS8#TRPBF, 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 LT1172IS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1172IS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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