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Analog Devices Inc. LT1172CSW#PBF
- Part No.:
- LT1172CSW#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
LT1172CSW#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.25A 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,853
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Product details
Overview
LT1172CSW#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 60V input and delivering up to 25W in buck/boost/flyback topologies. It features 6mA quiescent current, shutdown mode drawing only 50µA, and internal 1.24V reference voltage - used in isolated flyback converters for LCD bias supplies and battery upconverters.
For engineers reviewing the LT1172CSW#PBF datasheet, LT1172CSW#PBF pinout, LT1172CSW#PBF application, or LT1172CSW#PBF equivalent, key selection criteria include verified 1.25A switch current limit at 100°C junction, 16-pin SO Wide package thermal resistance (θJA = 150°C/W), flyback reference voltage of 15.0–18.0V, and confirmed compatibility with external synchronization up to 160kHz.
Technical Context
The LT1172CSW#PBF implements current-mode control with adaptive anti-saturation drive, enabling stable operation across wide load ranges without efficiency loss. Its dual error amplifiers support both normal regulation (via FB pin at 1.24V) and isolated flyback mode (via FB pin pulled low to activate 15–18V flyback reference).
It integrates a 100kHz oscillator, 2.3V internal LDO, logic/driver circuitry, and protection functions including thermal limiting and pulse-by-pulse current limiting. The SW package exposes E1 and E2 emitter terminals separately, allowing configurable current limiting and reduced ground-path errors in high-precision designs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.25A at TJ ≥ 25°C (guaranteed minimum; enables 12V@1A boost or 5V@2A flyback with proper layout) |
| Input Voltage Range | 3V to 60V (supports wide-range industrial/battery inputs without external pre-regulation) |
| Quiescent Current | 6mA (enables high-efficiency light-load operation in always-on systems) |
| Shutdown Current | 50µA typical (reduces standby power in portable or energy-sensitive applications) |
| Reference Voltage | 1.24V ±20mV (tight tolerance enables accurate output voltage setting with standard resistor dividers) |
| Flyback Reference | 15.0–18.0V (allows direct regulation of transformer-coupled outputs without optocoupler feedback) |
| Switching Frequency | 85–115kHz (fixed internal oscillator; supports external sync up to 160kHz for EMI reduction) |
Pinout & Package
The LT1172CSW#PBF is housed in a 16-lead plastic SO wide (SW) package with exposed thermal pad (not electrically connected). Pin 1 is NC; pins 9–11 are NC; E1 and E2 are dedicated emitter terminals - E1 must be tied to GND, while E2 may be left open to halve current limit (at cost of doubled RDS(on)).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 13) | Main power input | Accepts 3–60V; powers internal LDO and switch driver; requires local 1µF ceramic bypass |
| VSW (Pin 12) | Switch collector output | Drives external inductor/diode; rated for 65V breakdown (non-HV grade); connects to primary winding in flyback |
| GND (Pin 3) | Power and signal ground | Common return for VIN, VC, FB, E1; tie E1 directly here; separate analog/digital grounding not required |
| VC (Pin 4) | Error amplifier output / control node | Sets current limit via voltage (1V = 0A, 2V = 2A); enables soft-start (capacitor), shutdown (<0.15V), and sync (pulsed to GND) |
| FB (Pin 5) | Feedback input | Compares output divider voltage to 1.24V (normal mode) or activates 15–18V flyback reference when pulled low |
| E1 (Pin 14) | Emitter 1 | Mandatory GND connection; internal emitter tie point; ensures correct current sensing path |
| E2 (Pin 15) | Emitter 2 | Optional connection; leaving open reduces max switch current to 0.625A and doubles on-resistance (1.0Ω) |
| NC (Pins 1, 2, 6–8, 9–11, 16) | No connect | Not bonded; no internal function; leave unconnected and un-routed |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.25A switch with 1.0Ω max RDS(on) | Eliminates external MOSFET in ≤25W DC/DC designs; reduces BOM count and layout complexity |
| Dual regulation modes (normal + flyback) | Enables isolated outputs without optocouplers or secondary-side controllers - critical for medical/safety-isolated supplies |
| Adaptive anti-saturation drive | Maintains high efficiency across 10:1 load range by dynamically adjusting gate drive to prevent transistor saturation |
| Separate E1/E2 emitter terminals | Removes ground-path voltage error in current sensing; allows precise current limit tuning via E2 disconnection |
| External synchronization (120–160kHz) | Permits EMI peak shifting and multi-regulator phase interleaving without modifying core design |
Applications
| Industrial Power Supply | LCD Bias Generation |
|---|---|
Use Scenario: Generating isolated ±15V rails from 24V DC bus in PLC I/O modules. IC Role / Device Role / Timing Role: Flyback controller regulating secondary windings via primary-side sensing; uses FB pin in flyback mode with 15–18V reference. Use Value: Eliminates optocoupler and TL431, reducing component count by 4 parts and improving long-term stability over temperature. | Use Scenario: Providing –10V to –26V contrast voltage for automotive TFT displays powered from 3–20V battery rail. IC Role / Device Role / Timing Role: Inverting converter with shutdown control; VC pin used for enable/disable sequencing. Use Value: Achieves <100µA total system standby current using 50µA shutdown mode and low IQ operation. |
| Battery Upconverter | Isolated Sensor Interface |
Use Scenario: Boosting single-cell Li-ion (3.0–4.2V) to 12V for RF transceiver bias in portable IoT nodes. IC Role / Device Role / Timing Role: Fixed-frequency boost controller; uses internal 100kHz oscillator and current-mode loop for fast line transient response. Use Value: Delivers [email protected] with >85% efficiency across full battery range without external compensation components. | Use Scenario: Powering isolated current-sense amplifiers in motor drive inverters where primary and secondary grounds must remain separated. IC Role / Device Role / Timing Role: Flyback regulator with fully floating output; E1/E2 configuration minimizes ground bounce in high-dv/dt environments. Use Value: Maintains <1% output regulation despite 1kV/µs common-mode transients due to transformer isolation and robust internal error amp. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CN8#PBF | 8-pin PDIP/SO package; no E2 terminal; θJA = 100–120°C/W; same electrical specs | Lacks emitter separation - unsuitable for precision current limiting or low-ground-error layouts | Select when board space permits DIP/SO and E2 functionality is unnecessary |
| LT1172CT#PBF | 5-pin TO-220 package; integrated heatsink tab; θJA = 75°C/W; identical electrical specs | Higher thermal performance but larger footprint; no E2 pin - fixed 1.25A limit | Select for higher-power (>15W continuous) or convection-cooled industrial designs |
Compared with LT1172CN8#PBF and LT1172CT#PBF, the LT1172CSW#PBF uniquely provides separate E1/E2 emitters in a surface-mount package, enabling configurable current limiting and improved ground integrity - essential for noise-sensitive isolated flyback and precision boost applications.
Availability
LT1172CSW#PBF is available at Aetrix Electronics and suitable for industrial power supplies, LCD bias generation, battery upconverters, and isolated sensor interfaces requiring stable component supply across extended temperature and lifecycle requirements.
Supply support for LT1172CSW#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 regulator products. Linear was renowned for high-performance analog and power management ICs with rigorous characterization.
The LT1172 series belongs to Linear's monolithic high-power switching regulator product line, designed specifically for rugged, low-component-count DC/DC conversion in industrial, automotive, and instrumentation applications where reliability and wide input range are critical.
FAQ
What is the maximum guaranteed switch current for LT1172CSW#PBF at 100°C junction temperature?
The LT1172CSW#PBF guarantees a minimum switch current limit of 1.25A when junction temperature is ≥25°C, and this value holds across its full commercial temperature range (0°C to 100°C). At TJ < 25°C, the limit increases to 1.00A for 80% duty cycle per datasheet Table on page 4. Derating is not required up to 100°C ambient in properly heatsinked SO wide layouts.
Can LT1172CSW#PBF be used in flyback topology without an optocoupler?
Yes, the LT1172CSW#PBF supports optocoupler-free flyback regulation via its dedicated flyback mode: pulling the FB pin below 0.54V activates a 15.0–18.0V internal reference that regulates the reflected flyback pulse amplitude. This enables fully floating, transformer-isolated outputs with tight regulation - confirmed in Typical Application TA03 and Block Diagram on page 8.
What is the purpose of the E2 pin on LT1172CSW#PBF, and how should it be used?
The E2 pin on LT1172CSW#PBF is the second emitter terminal of the internal power switch. It must be left unconnected to reduce the switch current limit from 1.25A to 0.625A and double the effective on-resistance to 1.0Ω - a deliberate trade-off for improved current-limit accuracy and reduced ground-path error in precision flyback designs. E1 must always be tied to GND.
Does LT1172CSW#PBF support external frequency synchronization?
Yes, the LT1172CSW#PBF supports external synchronization between 120kHz and 160kHz by pulsing the VC pin to ground with a narrow (<0.3µs) transistor-driven signal, as detailed in pages 10–11 of the datasheet. This capability allows EMI peak management and multi-phase coordination without altering the base 100kHz oscillator frequency.
What thermal considerations apply to LT1172CSW#PBF in the 16-pin SO wide package?
The LT1172CSW#PBF has θJA = 150°C/W in the SW package. At 25°C ambient and 0.34W total dissipation (e.g., 5V→[email protected] boost), junction rise is ~51°C - well within the 100°C max rating. For continuous >15W operation, copper pour under the thermal pad and 2oz PCB layers are recommended to maintain safe die temperatures.
LT1172CSW#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1172CSW#PBF FAQ
1.How can I place an order for LT1172CSW#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1172CSW#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 LT1172CSW#PBF reliable?
The price and inventory of LT1172CSW#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1172CSW#PBF is usually 5 days.
3.What payment methods are accepted for LT1172CSW#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1172CSW#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1172CSW#PBF?
LT1172CSW#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1172CSW#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 LT1172CSW#PBF?
For technical support, including LT1172CSW#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1172CSW#PBF requirements.
6.How does Aetrix verify that LT1172CSW#PBF is sourced from the original manufacturer or authorized distributors?
All LT1172CSW#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 LT1172CSW#PBF meets industry standards.
7.What is the process for return or replacement of LT1172CSW#PBF?
All LT1172CSW#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1172CSW#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 LT1172CSW#PBF part is unused and in its original packaging.
Return procedure for LT1172CSW#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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