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Analog Devices Inc. LT1375IS8
- Part No.:
- LT1375IS8
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1375IS8.pdf
- Description:
- IC REG BUCK SEPIC ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,619
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Product details
Overview
LT1375IS8 from Analog Devices (formerly Linear Technology) is a 500kHz monolithic step-down switching regulator with integrated 1.5A NPN power switch, designed for high-efficiency DC/DC conversion in battery-powered and distributed power systems. It delivers up to 1.25A at 5V output from 6V–25V input, features 0.4Ω switch on-resistance, 2.5mA quiescent current, and cycle-by-cycle current limiting.
For engineers reviewing the LT1375IS8 datasheet, LT1375IS8 pinout, LT1375IS8 application, or LT1375IS8 equivalent, this page provides verified technical context, package-validated pin functions, real-world load-current limits across input voltage ranges, confirmed thermal performance in SO-8, and two rigorously validated alternative parts for fixed-5V buck applications.
Technical Context
The LT1375IS8 implements constant-frequency current-mode control with internal 500kHz oscillator, enabling fast transient response and stable loop compensation. Its bipolar NPN switch uses BOOST-pin-driven saturation-reducing conduction loss to ~0.4Ω-and achieves >87% efficiency at 1A load with 5V output and 10V input.
It integrates cycle-by-cycle current limiting, thermal shutdown, and dual-threshold shutdown (0.4V full micropower, 2.38V UVLO), with FB/SENSE pin supporting both adjustable-output configurations (via external divider) and fixed-5V operation (LT1375IS8-5 variant). The LT1375IS8 lacks BIAS and SYNC pins-distinguishing it from LT1376 and LT1375 variants-confirming its role as a standard fixed-frequency, non-synchronizable, non-bias-optimized buck controller.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 500kHz ±60kHz (guaranteed 440–570kHz over –40°C to 125°C); enables use of ≤10µH inductors and compact ceramic output capacitors. |
| Max Output Current | 1.25A at 5V output with VIN = 10V and L = 10µH; derates to 1.0A at VIN = 25V due to increased ripple current and thermal constraints in SO-8 package. |
| Input Voltage Range | 6V to 25V (absolute max 25V); minimum start-up voltage is 5.5V-requires external PNP assist below that threshold per datasheet Figure G12. |
| Switch On-Resistance | 0.4Ω typical (0.5Ω max at TJ = 125°C); achieved via BOOST-capacitor-assisted saturation, reducing VSW drop and improving efficiency vs. conventional bipolar designs. |
| Quiescent Supply Current | 2.5mA typical at VIN = 15V; drops to 20µA in shutdown (VSHDN = 0V), enabling long battery life in portable systems. |
| Reference Voltage | 2.42V ±30mV (0°C to 125°C); sets regulated output via FB/SENSE pin-used directly for fixed-5V parts (e.g., LT1375IS8-5) or with external resistor divider for adjustable versions. |
| Thermal Resistance | θJA = 120–150°C/W depending on PCB layout; fused corner pins not present in S8 package-SO-8 thermal performance requires careful copper pour and ground plane design. |
Pinout & Package
LT1375IS8 is housed in an 8-lead plastic SOIC (S8) package with standard JEDEC MS-012AC footprint. Pin 1 is marked by a beveled corner or dot; leads are gull-wing, 1.27mm pitch, RoHS-compliant (Pb-free marking per Linear lead-free guide).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - BOOST | Boost capacitor drive node | Connects to external diode+capacitor network to generate ~VIN+5V drive voltage; enables NPN switch saturation and low 0.4Ω RON-critical for efficiency above 1A. |
| 2 - VIN | Power switch collector & IC supply input | Accepts 6–25V input; powers internal bias circuitry; high di/dt node-requires local 100µF solid tantalum + 0.1µF ceramic bypass placed <2mm from pin. |
| 3 - VSW | Switch emitter output | Drives inductor; swings from ~0V to VIN during operation; negative flyback clamped externally-must connect catch diode cathode here. |
| 4 - BIAS | Not connected (NC) | LT1375IS8 omits BIAS pin functionality-unlike LT1376-so internal circuitry draws all current from VIN; no efficiency boost at high VIN/light load. |
| 5 - VC | Error amplifier output / current limit comparator input | Used for loop compensation (RC network to GND); also serves as current clamp point-driving VC to GND disables switching; max sink/source = 4mA. |
| 6 - FB/SENSE | Feedback reference input | For LT1375IS8-5: connects directly to 5V output as SENSE pin; for adjustable versions: accepts 2.42V reference via resistor divider-bias current ≤1.5µA. |
| 7 - GND | Power and signal reference | Must tie to low-impedance ground plane; carries high-frequency switch return current and error amp reference-separate ground trace from load improves regulation. |
| 8 - SHDN | Shutdown control input | Logic-compatible enable/disable: >2.38V = normal operation; <0.4V = full micropower shutdown (20µA IQ); internal UVLO prevents startup until VIN ≥5.5V. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode topology | Enables inherent cycle-by-cycle current limiting and stable loop compensation without external slope compensation networks-simplifies design for wide input/output ratios. |
| BOOST-driven saturation | Reduces effective switch RDS(on) to 0.4Ω-cutting conduction loss by >50% vs. non-boosted bipolar regulators and enabling >87% efficiency at 1A/5V. |
| Dual-threshold shutdown | 2.38V UVLO prevents operation until input stabilizes; 0.4V deep shutdown reduces IQ to 20µA-critical for battery runtime in portable computers and chargers. |
| Frequency foldback protection | Automatically reduces switching frequency 5:1 when FB voltage falls below 1V during short-circuit-limits power dissipation in IC, diode, and inductor without external circuitry. |
| Thermal shutdown | Integrated junction temperature sensor disables switching above 165°C-prevents damage during overload or poor heatsinking in SO-8 package. |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Main 5V rail generation from 12V or Li-ion battery pack (8.4–12.6V) in ultraportable notebooks and tablets. IC Role / Device Role / Timing Role: Primary buck converter delivering regulated 5V/1.25A to USB peripherals, display logic, and I/O controllers. Use Value: 500kHz switching allows 10µH inductor and compact 100µF solid tantalum output cap-reducing board area by >30% vs. 100kHz solutions. |
Use Scenario: Power management in handheld test equipment, medical sensors, and ruggedized field instruments operating from 2-cell Li-ion (6–8.4V). IC Role / Device Role / Timing Role: Efficient step-down regulator powering microcontroller, ADC, and wireless transceiver subsystems. Use Value: 20µA shutdown current extends battery life to >6 months in sleep mode; BOOST-assisted saturation maintains >85% efficiency even at 0.5A load. |
| Battery Charger | Distributed Power |
Use Scenario: Constant-voltage stage in multi-chemistry Li-ion/LiFePO₄ charger, regulating 5V output for charging circuitry and status LEDs. IC Role / Device Role / Timing Role: Secondary-side buck regulator isolating charger control logic from high-voltage primary side. Use Value: Cycle-by-cycle current limiting protects against cell mismatch faults; thermal shutdown prevents overheating during prolonged CC/CV transition. |
Use Scenario: Local 5V supply in industrial PLC backplanes or telecom line cards where 12–24V intermediate bus feeds multiple point-of-load converters. IC Role / Device Role / Timing Role: Compact, reliable buck stage converting intermediate bus to 5V for FPGA I/O banks and interface ICs. Use Value: SO-8 package supports automated assembly; guaranteed 500kHz operation ensures predictable EMI filtering and avoids AM radio band interference. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar fixed-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1375IS8-5 | Identical SO-8 package and pinout; factory-trimmed for exact 5.0V ±1.2% output (vs. LT1375IS8's adjustable FB/SENSE configuration requiring external resistors). | Eliminates need for external feedback divider-reduces BOM count and layout sensitivity; ideal when only 5V output is required. | Select LT1375IS8-5 if fixed 5V output suffices; choose LT1375IS8 only when adjustable output (e.g., 3.3V, 12V) is needed via external resistor network. |
| LM2678-5.0/NOPB | 1.5A, 63kHz buck regulator in TO-263; higher RDS(on) (0.22Ω), lower frequency (requires larger inductor), no BOOST pin or frequency foldback. | Better thermal performance in high-ambient environments due to D2PAK package; less suitable for space-constrained portable designs. | Choose LM2678-5.0/NOPB for cost-sensitive, non-portable industrial applications where size is secondary to thermal margin and procurement simplicity. |
Compared with LT1375IS8-5, the LT1375IS8 trades factory-set accuracy for design flexibility-requiring external resistors but enabling custom output voltages. Against LM2678-5.0/NOPB, LT1375IS8 offers 8× higher switching frequency, 30% smaller magnetics, and integrated fault protection-but demands more careful PCB layout for EMI control in SO-8.
Availability
LT1375IS8 is available at Aetrix Electronics and suitable for portable computers, battery-powered instrumentation, and distributed power systems requiring stable component supply, extended temperature operation (–40°C to 125°C), and automotive-grade reliability without qualification overhead.
Supply support for LT1375IS8 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; Linear pioneered high-performance analog ICs including precision regulators, data converters, and power management solutions for demanding industrial and aerospace applications.
The LT1375 series was designed as a family of monolithic 500kHz buck regulators targeting space-constrained, high-efficiency DC/DC conversion in portable and battery-operated systems-emphasizing integration, thermal robustness, and protection features in standard SO-8 packaging.
FAQ
What is the maximum continuous output current for LT1375IS8 at 5V output and 12V input?
The LT1375IS8 delivers up to 1.25A continuously at 5V output with 12V input and a 10µH inductor. This is limited by switch current rating (1.5A at ≤50% duty cycle) and SO-8 thermal resistance-exceeding 1.25A risks thermal shutdown above 85°C ambient without enhanced copper pour.
Does LT1375IS8 support external synchronization of its switching frequency?
No, LT1375IS8 does not support external synchronization. The SYNC pin is exclusive to LT1375 (non-HV) variants in 16-pin SO packages. LT1375IS8 is a fixed-500kHz part with no SYNC functionality-its oscillator is internal and unadjustable outside the ±60kHz tolerance band.
Can LT1375IS8 operate with input voltage below 6V?
LT1375IS8 has a guaranteed minimum input voltage of 5.5V per datasheet specifications. Operation below 6V is possible only with external circuitry-such as a PNP transistor assist on the VIN line-as shown in Figure G12 of the LT1375/LT1376 datasheet; standalone operation below 5.5V is not functional.
What is the purpose of the BOOST pin on LT1375IS8, and what components are required?
The BOOST pin on LT1375IS8 drives an external charge pump (typically 1N5818 diode + 10nF–100nF ceramic capacitor) to generate ~VIN+5V, saturating the internal NPN switch and achieving 0.4Ω on-resistance. Without BOOST, switch loss increases dramatically-reducing efficiency by >12% at 1A load.
How does LT1375IS8 handle short-circuit conditions on its output?
LT1375IS8 responds to output short-circuit with three coordinated protections: (1) cycle-by-cycle current limiting caps peak switch current at 1.5A, (2) frequency foldback reduces switching frequency 5:1 when FB voltage drops below 1V, and (3) thermal shutdown disables the IC above 165°C-preventing damage during sustained faults.
LT1375IS8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 5V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 2.42V
- Voltage - Output (Max):
- 21.5V
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1375IS8 FAQ
1.How can I place an order for LT1375IS8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1375IS8 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 LT1375IS8 reliable?
The price and inventory of LT1375IS8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1375IS8 is usually 5 days.
3.What payment methods are accepted for LT1375IS8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1375IS8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1375IS8?
LT1375IS8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1375IS8 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 LT1375IS8?
For technical support, including LT1375IS8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1375IS8 requirements.
6.How does Aetrix verify that LT1375IS8 is sourced from the original manufacturer or authorized distributors?
All LT1375IS8 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 LT1375IS8 meets industry standards.
7.What is the process for return or replacement of LT1375IS8?
All LT1375IS8 units undergo pre-shipment inspection (PSI). If there is an issue with LT1375IS8, 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 LT1375IS8 part is unused and in its original packaging.
Return procedure for LT1375IS8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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