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Analog Devices Inc. LT1377CS8#TRPBF
- Part No.:
- LT1377CS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1377CS8#TRPBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:729
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Product details
Overview
LT1377CS8#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 1MHz current-mode switching regulator IC in 8-pin SOIC package, integrating a 1.5A power switch, oscillator, error amplifier, and protection circuitry. It operates in boost, buck, flyback, forward, inverting, and Cuk configurations with 2.7V minimum input voltage, 4mA typical quiescent current, and ±10V transient tolerance on FB/NFB pins - used in laptop computer supplies and CCFL backlight drivers.
For engineers reviewing the LT1377CS8#TRPBF datasheet, LT1377CS8#TRPBF pinout, LT1377CS8#TRPBF application, or LT1377CS8#TRPBF equivalent, key selection considerations include its 1MHz switching frequency, dual positive/negative output regulation capability, 12µA shutdown current, internal 1.245V/–2.49V references, and compatibility with small 4.7µH inductors in space-constrained DC-DC designs.
Technical Context
The LT1377CS8#TRPBF uses current-mode control architecture where switch duty cycle is directly set by sensed switch current rather than output voltage feedback alone - enabling fast line transient response, simplified loop compensation, and inherent pulse-by-pulse overcurrent protection. Its adaptive anti-saturation driver minimizes switch saturation voltage and ensures rapid turn-off.
It features dual feedback paths: FB pin regulates positive outputs using a 1.245V reference, while NFB pin regulates negative outputs via a –2.49V reference with 100kΩ series source resistor. The VC pin serves as error amplifier output for compensation, soft-start, and current limit adjustment - supporting external RC networks and voltage clamping.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1MHz typical - enables use of compact 4.7µH inductors and reduces output filter size. |
| Integrated Switch Current Limit | 1.5A typical - defines maximum peak switch current in boost/flyback topologies. |
| Input Voltage Range | 2.7V to 25V - supports single-cell Li-ion up to 24V industrial rails without external LDO pre-regulation. |
| Quiescent Current | 4mA typical - maintains high light-load efficiency in battery-powered systems. |
| Shutdown Supply Current | 12µA typical - enables ultra-low-power standby mode for portable equipment. |
| Reference Voltages | +1.245V at FB, –2.49V at NFB - allows direct regulation of both polarities without external op-amps. |
| Feedback Pin Tolerance | ±10V transient rating - withstands inductive kickback during startup/fault conditions. |
Pinout & Package
LT1377CS8#TRPBF is housed in an 8-pin plastic SOIC (S8) package with standard JEDEC MS-012AC dimensions (4.9mm × 3.9mm × 1.75mm), thermal resistance θJA = 120°C/W, and rated operating junction temperature up to 125°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Error amplifier output / compensation node | Accepts RC network for loop stability; clamped externally for soft-start or current limit adjustment. |
| FB (Pin 2) | Positive output voltage sense input | Inverting input to error amp referenced to 1.245V; sets VOUT = 1.245V × (1 + R1/R2). |
| NFB (Pin 3) | Negative output voltage sense input | Connects to inverting input of negative feedback amp via 100kΩ resistor; regulates at –2.49V. |
| S/S (Pin 4) | Shutdown & synchronization input | Logic-level compatible; low = shutdown (12µA IQ); AC-coupled signal 1.2–1.6MHz synchronizes switching. |
| VIN (Pin 5) | Power input supply | Bypass with ≥10µF capacitor; triggers undervoltage lockout below 2.5V. |
| GND S (Pin 6) | Ground sense reference | "Clean" ground for internal reference, error amp, and NFB amp - isolate from high-current GND traces. |
| GND (Pin 7) | Power switch emitter return | High-current path for switch emitter - connect directly to ground plane to minimize noise coupling. |
| VSW (Pin 8) | Switch collector output | Drives external inductor/diode; requires short, low-inductance layout to suppress EMI and voltage spikes. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables immediate line transient response and eliminates need for slope compensation in most applications. |
| Nonlinear error amplifier transconductance | Doubles gm when FB exceeds VREF by 40mV - reduces output overshoot during startup and overload recovery. |
| Oscillator frequency shifting | Reduces switching frequency 5:1 when FB < 0.6V - protects components during overload by limiting minimum duty cycle. |
| Adaptive anti-saturation driver | Monitors switch saturation onset and adjusts drive current dynamically - minimizes VCE(sat) and improves efficiency. |
| External synchronization capability | Accepts 1.2–1.6MHz logic-level clock on S/S pin - enables noise-sensitive system-level timing coordination. |
Applications
| Laptop Computer Power Supply | CCFL Backlight Driver |
|---|---|
Use Scenario: Generating 12V–19V rail from 3.3V/5V system bus to power CPU core logic and display interface circuits. IC Role / Device Role / Timing Role: Primary DC-DC boost controller regulating stable output under dynamic load changes. Use Value: 1MHz operation allows 4.7µH inductor and <0.5 in² board area - critical for thin-profile clamshell designs. | Use Scenario: Driving cold cathode fluorescent lamp strings requiring 600–1000V AC with precise current regulation. IC Role / Device Role / Timing Role: High-frequency flyback controller with adjustable current limit and soft-start for lamp ignition control. Use Value: Nonlinear transconductance prevents lamp flash-on-startup; 12µA shutdown extends battery life during display off periods. |
| Inverting Power Supply | Multiple Output Flyback Supply |
Use Scenario: Generating –5V or –12V bias rails for analog front-ends, op-amp supplies, or RS-232 level shifters. IC Role / Device Role / Timing Role: Inverting topology controller using NFB pin to regulate negative output directly. Use Value: Eliminates need for external inverting op-amp or charge pump - reduces component count and BOM cost. | Use Scenario: Simultaneously regulating +12V and –5V outputs from single 5V input in embedded instrumentation. IC Role / Device Role / Timing Role: Dual-feedback flyback controller monitoring both FB and NFB pins for cross-regulation. Use Value: Prevents unregulated overvoltage on lightly loaded output - ensures safety compliance without secondary sensing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1372CS8#TRPBF | 500kHz switching frequency; same pinout and feature set except lower fSW. | Better suited for higher output current at lower frequencies; requires larger 10µH inductor. | Select when efficiency at >0.35A load or EMI constraints favor 500kHz operation. |
| LT3573EDD#TRPBF | Higher integration: includes internal 1.5A switch, 2.5MHz fSW, and integrated soft-start; different pinout. | Requires PCB redesign; targets ultra-compact 2mm × 3mm layouts with minimal external components. | Choose for new designs prioritizing footprint reduction over legacy compatibility. |
Compared with LT1372CS8#TRPBF, the LT1377CS8#TRPBF delivers higher power density via 1MHz operation but trades off some peak current headroom; versus LT3573EDD#TRPBF, it offers pin compatibility with existing LT137x layouts but lacks integrated soft-start and higher-frequency EMI suppression.
Availability
LT1377CS8#TRPBF is available at Aetrix Electronics and suitable for laptop computer supplies, CCFL backlight drivers, inverting power supplies, and multiple-output flyback converters requiring stable component supply across industrial temperature ranges.
Supply support for LT1377CS8#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 engineering for legacy Linear parts including the LT1377 series.
The LT1377CS8#TRPBF belongs to Linear's high-efficiency monolithic switching regulator family, designed specifically for compact, multi-topology DC-DC conversion in portable and space-constrained industrial systems.
FAQ
What is the maximum recommended output current for LT1377CS8#TRPBF in boost configuration?
The LT1377CS8#TRPBF supports up to 0.25A output current in boost topology per manufacturer characterization data. This limit arises from the 1.5A switch current rating, duty cycle constraints, and thermal dissipation in the 8-pin SOIC package at 125°C junction temperature. Higher currents require careful thermal design and may necessitate derating based on ambient conditions and PCB copper area.
Can LT1377CS8#TRPBF regulate both positive and negative outputs simultaneously?
Yes, the LT1377CS8#TRPBF can regulate both polarities simultaneously using dual feedback: FB pin for positive output (referenced to +1.245V) and NFB pin for negative output (referenced to –2.49V). When both pins are active, the device prevents either output from exceeding its setpoint - ideal for dual-output flyback converters where cross-regulation is required without secondary-side controllers.
What is the purpose of the VC pin on LT1377CS8#TRPBF and how is it used in practice?
The VC pin on LT1377CS8#TRPBF is the error amplifier output and serves three functions: frequency compensation (via RC network to ground), soft-start (via capacitor-coupled clamp), and current limit adjustment (via external voltage clamp). During operation, VC voltage varies between ~1V (light load) and ~1.9V (heavy load); clamping it below 0.8V forces zero duty cycle and idle mode - a key technique for controlled current limiting.
Does LT1377CS8#TRPBF require an external diode in boost configuration, and what type is recommended?
Yes, LT1377CS8#TRPBF requires an external Schottky diode in boost configuration. The datasheet recommends MBRS120T3 (20V, 1A) or 1N5818 (30V, 1A) due to their low forward voltage (~0.42V at 1A) and fast recovery. Peak reverse voltage equals the output voltage, so diode VR must exceed VOUT; average forward current equals load current, making 1A rating sufficient for ≤0.25A output designs.
How does the LT1377CS8#TRPBF handle overload or short-circuit conditions?
The LT1377CS8#TRPBF employs pulse-by-pulse current limiting with blanking time (130–260ns) to protect the internal switch. Under sustained overload, oscillator frequency shifts 5:1 when FB drops below 0.6V - reducing minimum duty cycle and limiting average power. It lacks hiccup or latch-off modes; continuous short-circuit operation relies on thermal shutdown (150°C junction limit) and external current limiting in the power stage.
LT1377CS8#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, 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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1377CS8#TRPBF FAQ
1.How can I place an order for LT1377CS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1377CS8#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 LT1377CS8#TRPBF reliable?
The price and inventory of LT1377CS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1377CS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1377CS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1377CS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1377CS8#TRPBF?
LT1377CS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1377CS8#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 LT1377CS8#TRPBF?
For technical support, including LT1377CS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1377CS8#TRPBF requirements.
6.How does Aetrix verify that LT1377CS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1377CS8#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 LT1377CS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1377CS8#TRPBF?
All LT1377CS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1377CS8#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 LT1377CS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1377CS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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