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Analog Devices Inc. LT1377IS8#PBF
- Part No.:
- LT1377IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1377IS8#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,300
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Product details
Overview
LT1377IS8#PBF from Analog Devices (formerly Linear Technology) is a monolithic 1MHz current-mode switching regulator IC in an 8-pin SOIC package, integrating a 1.5A power switch, oscillator, error amplifier, and protection circuitry. It operates in boost, buck, flyback, inverting, and Cuk topologies, supports ±2.7V to 25V input, regulates positive or negative outputs, and delivers up to 0.25A output current in boost configuration - used in laptop power supplies, CCFL backlight drivers, and multi-output flyback converters.
For engineers reviewing the LT1377IS8#PBF datasheet, LT1377IS8#PBF pinout, LT1377IS8#PBF application, or LT1377IS8#PBF equivalent, key selection considerations include its 1MHz switching frequency, ±2.49V/1.245V dual-reference architecture, 12µA shutdown current, 2.7V minimum input voltage, and industrial-grade –40°C to 125°C operating range.
Technical Context
The LT1377IS8#PBF employs peak-current-mode control with adaptive anti-saturation driver logic, enabling fast transient response and inherent pulse-by-pulse current limiting. Its error amplifier features nonlinear transconductance (700–2300 µmho) that increases tenfold above 40mV error to suppress startup/overload overshoot.
Oscillator frequency shifts 5:1 downward when FB voltage drops below 0.6V, reducing stress during overload; synchronization is supported at 1.2–1.6MHz. The VC pin serves triple duty - compensation node, soft-start control point, and current-limit adjustment interface - while NFB and FB pins enable independent regulation of negative and positive outputs using internal –2.49V and 1.245V references.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1.0 MHz typical (0.86–1.16 MHz over full temperature range); enables use of compact 4.7µH inductors and reduces EMI filter size. |
| Input Voltage Range | 2.7V to 25V; supports single-cell Li-ion, USB-powered, and wide-input industrial rails without external LDO pre-regulation. |
| Output Switch Current Limit | 1.5A typical (1.3–2.5A depending on duty cycle); sets maximum deliverable load current and defines inductor saturation margin. |
| Reference Voltages | +1.245V at FB pin (±0.015V tolerance); –2.490V at NFB pin (±0.05V); enables precise resistor-divider-based regulation of both polarities. |
| Quiescent Current | 4mA typical; minimizes no-load power loss in battery-backed or always-on systems. |
| Shutdown Supply Current | 12µA typical; allows deep sleep mode in portable equipment without external disconnect switches. |
| Operating Temperature | –40°C to +125°C junction; qualified for industrial and extended-temperature embedded applications. |
Pinout & Package
LT1377IS8#PBF is housed in an 8-lead plastic SOIC (S8) package with standard JEDEC MS-012AC footprint, 1.27mm pitch, and 120°C/W thermal resistance. Pin 6 (GND S) provides clean reference ground for feedback and error amplifier; Pin 7 (GND) carries high-switching-current return path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Error amplifier output / compensation node | Interface for RC frequency compensation; clamping controls soft-start and current limit; voltage range 0.8–2.3V determines duty cycle. |
| FB (Pin 2) | Positive output voltage sense input | Inverting input of main error amplifier referenced to 1.245V; also triggers oscillator frequency shift below 0.6V. |
| NFB (Pin 3) | Negative output voltage sense input | Connects to inverting input of dedicated negative-feedback amplifier; regulates at –2.49V with 100kΩ series source resistance. |
| S/S (Pin 4) | Shutdown and synchronization input | Logic-compatible input: low = shutdown (12µA IQ); AC-coupled square wave at 1.2–1.6MHz forces synchronized switching. |
| VIN (Pin 5) | Main power input | Bypass with ≥10µF capacitor; undervoltage lockout activates below 2.5V to prevent erratic operation. |
| GND S (Pin 6) | Clean reference ground | Ground reference for internal bandgap, error amplifiers, and feedback dividers; must be isolated from high-current GND paths. |
| GND (Pin 7) | Power switch emitter return | High-current return path for 1.5A switch; requires direct connection to low-impedance ground plane to minimize noise coupling. |
| VSW (Pin 8) | Power switch collector output | Drives external inductor/diode; high di/dt node requiring shortest possible trace routing to minimize EMI and voltage spikes. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables immediate line transient response, simplifies loop compensation across wide VIN/VOUT ranges, and provides inherent cycle-by-cycle current limiting. |
| Dual-reference regulation (±1.245V / –2.49V) | Allows single-IC regulation of both positive and negative outputs without external op-amps or level-shifters - critical for dual-rail analog supplies. |
| Nonlinear error amplifier transconductance | Transconductance jumps 10× when FB error exceeds 40mV, actively suppressing output overshoot during startup and load recovery. |
| Frequency-shifting overload protection | Oscillator slows 5:1 when FB < 0.6V, reducing switch stress and component heating during sustained overloads or short circuits. |
| Industrial temperature grade (–40°C to 125°C) | Qualified for deployment in automotive infotainment, industrial HMIs, and outdoor-connected devices without derating. |
Applications
| Laptop Computer Power Supply | CCFL Backlight Driver |
|---|---|
Use Scenario: Generating 12V/0.25A from 5V USB or single-cell Li-ion input in ultraportable notebooks. IC Role / Device Role / Timing Role: Primary DC-DC boost controller managing power conversion, feedback regulation, and soft-start sequencing. Use Value: Enables compact, high-efficiency power stage using only 4.7µH inductor and <0.5 in² board area - meeting strict space and thermal constraints. |
Use Scenario: Driving cold-cathode fluorescent lamps requiring regulated high-voltage AC (≈600V) from low-voltage DC bus. IC Role / Device Role / Timing Role: High-frequency current-mode controller in resonant flyback topology, regulating lamp current via primary-side sensing. Use Value: 1MHz operation allows smaller magnetics and tighter EMI control; shutdown pin enables instant lamp dimming/blanking. |
| Multiple Output Flyback Supply | Inverting Power Supply |
Use Scenario: Providing isolated +12V and –12V rails simultaneously from 5V input in test instrumentation or data acquisition systems. IC Role / Device Role / Timing Role: Dual-feedback controller using both FB and NFB pins to regulate two independent outputs with cross-regulation stability. Use Value: Eliminates need for secondary-side optocouplers or post-regulators - reducing BOM cost and improving reliability. |
Use Scenario: Generating –5V rail from +5V supply for op-amp biasing or RS-232 interface circuitry. IC Role / Device Role / Timing Role: Inverting topology controller with NFB pin directly sensing negative output voltage. Use Value: Achieves precise –5.0V regulation (±1%) using only two resistors and no external components - simplifying design and layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1372IS8#PBF | 500kHz switching frequency; 0.29A max boost output; same pinout and dual-reference architecture. | Better suited for lower-noise, higher-current applications where 1MHz EMI is problematic. | Select when lower switching frequency improves EMI compliance or allows larger inductors for higher output current. |
| LM2733YMF/NOPB | Fixed 1.6MHz frequency; 0.6A switch; no NFB pin or negative output capability; requires external compensation. | Limited to single-positive-output boost; lacks integrated negative regulation or frequency shifting. | Choose only for simple, cost-sensitive single-rail boost where dual polarity and advanced protection are unnecessary. |
Compared with LT1372IS8#PBF, the LT1377IS8#PBF offers higher frequency and lower output current but identical feature set and pin compatibility; versus LM2733YMF/NOPB, it provides superior flexibility for bipolar supplies and robust overload handling at the cost of slightly higher complexity.
Availability
LT1377IS8#PBF is available at Aetrix Electronics and suitable for laptop computer supplies, CCFL backlight drivers, multiple-output flyback supplies, and inverting power supplies requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for LT1377IS8#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 technical and manufacturing continuity for legacy Linear products including the LT1377 series.
The LT1377IS8#PBF belongs to Linear's high-frequency monolithic switching regulator product line, designed specifically for space-constrained, multi-topology DC-DC conversion in portable and industrial systems requiring dual-polarity regulation and robust fault handling.
FAQ
What is the maximum output current achievable with the LT1377IS8#PBF in boost configuration?
The LT1377IS8#PBF supports up to 0.25A output current in boost topology under typical conditions (VIN = 5V, VOUT = 12V), limited by its 1.5A internal switch current rating, thermal dissipation in the SOIC package, and inductor saturation characteristics. Higher currents require careful thermal design and may necessitate external current limiting or parallel configurations.
Can the LT1377IS8#PBF regulate both positive and negative outputs simultaneously?
Yes - the LT1377IS8#PBF can regulate both polarities simultaneously using its dedicated FB and NFB pins. When both pins are connected to separate resistor dividers, the IC prevents either output from exceeding its setpoint, enabling stable dual-output flyback or forward converters without secondary-side regulation.
What is the purpose of the NFB pin on the LT1377IS8#PBF?
The NFB pin on the LT1377IS8#PBF provides a dedicated –2.49V reference input for negative output voltage sensing. It connects internally to a separate amplifier with 100kΩ series resistance, allowing precise regulation of negative rails (e.g., –5V, –12V) without external components - a key differentiator from standard boost controllers.
Does the LT1377IS8#PBF support external synchronization, and what is the valid frequency range?
Yes - the S/S pin on the LT1377IS8#PBF supports external synchronization with a guaranteed range of 1.2MHz to 1.6MHz. This allows noise-sensitive systems to lock switching to a master clock, reducing beat frequencies and easing EMI filtering. Synchronization must begin only after FB voltage exceeds 0.7V to avoid startup instability.
How does the LT1377IS8#PBF handle overload or short-circuit conditions?
The LT1377IS8#PBF uses two coordinated protections: (1) pulse-by-pulse current limiting caps switch current at ~1.5A, and (2) if FB voltage falls below 0.6V, the oscillator shifts to 1/5 frequency (200kHz), reducing power dissipation and component stress. These features enable safe operation during sustained overloads without latch-off or thermal shutdown.
LT1377IS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm 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, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.245V
- Voltage - Output (Max):
- 35V (Switch)
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1377IS8#PBF FAQ
1.How can I place an order for LT1377IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1377IS8#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 LT1377IS8#PBF reliable?
The price and inventory of LT1377IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1377IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1377IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1377IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1377IS8#PBF?
LT1377IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1377IS8#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 LT1377IS8#PBF?
For technical support, including LT1377IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1377IS8#PBF requirements.
6.How does Aetrix verify that LT1377IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1377IS8#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 LT1377IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1377IS8#PBF?
All LT1377IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1377IS8#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 LT1377IS8#PBF part is unused and in its original packaging.
Return procedure for LT1377IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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