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Analog Devices Inc. LT1377CS8#PBF
- Part No.:
- LT1377CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1377CS8#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,222
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Product details
Overview
LT1377CS8#PBF 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, inverting, and Cuk configurations with 2.7V minimum input voltage, 4mA typical quiescent current, and ±10V feedback pin transient tolerance - used in laptop computer supplies and CCFL backlight drivers.
For engineers reviewing the LT1377CS8#PBF datasheet, LT1377CS8#PBF pinout, LT1377CS8#PBF application, or LT1377CS8#PBF equivalent, key selection considerations include its 1MHz fixed switching frequency, dual positive/negative output regulation capability, 12µA shutdown current, VC pin-based soft-start and compensation, and compatibility with small 4.7µH inductors in space-constrained DC/DC designs.
Technical Context
The LT1377CS8#PBF implements peak current-mode control with adaptive anti-saturation driver logic, enabling fast line/load transient response and inherent pulse-by-pulse overcurrent protection. Its error amplifier features nonlinear transconductance (1100–1900 µmho) that increases tenfold above 40mV FB error to suppress startup/overload overshoot.
It supports dual polarity regulation: FB pin regulates positive outputs at 1.245V reference, while NFB pin regulates negative outputs at –2.49V reference using a dedicated 100kΩ internal source resistor. Synchronization is supported from 1.2MHz to 1.6MHz, and shutdown reduces supply current to 12µA typical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1MHz typical - enables use of compact 4.7µH inductors and reduces output filter size. |
| Power Switch Current Limit | 1.5A typical - sets maximum deliverable load current in boost/buck topologies. |
| Input Voltage Range | 2.7V to 25V - supports single-cell Li-ion up to 24V industrial rails without external LDO. |
| Quiescent Current | 4mA typical - minimizes no-load power loss in battery-powered systems. |
| Shutdown Current | 12µA typical - extends battery life during system sleep modes. |
| Reference Voltage (FB) | 1.245V ±15mV - defines precision output voltage setting via resistor divider. |
| Negative Reference (NFB) | –2.49V ±50mV - enables direct regulation of negative rail without external op-amp. |
| Error Amp Transconductance | 1500 µmho typical - determines loop gain and compensation component values. |
Pinout & Package
LT1377CS8#PBF is housed in an 8-lead plastic SOIC (S8) package with standard JEDEC MS-012AC footprint, 1.27mm pitch, and θJA = 120°C/W thermal resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Compensation & Soft-Start | Error amplifier output; RC network here sets loop stability, current limit, and startup ramp rate. |
| FB (Pin 2) | Positive Output Sense | Inverting input of main error amp; referenced to 1.245V internal bandgap for +VOUT regulation. |
| NFB (Pin 3) | Negative Output Sense | Inverting input of negative feedback amp; referenced to –2.49V for –VOUT regulation via 100kΩ internal source. |
| S/S (Pin 4) | Shutdown & Sync Input | Logic-level active-low shutdown; also accepts 1.2–1.6MHz sync signal for EMI reduction. |
| VIN (Pin 5) | Input Supply | Bypass with ≥10µF capacitor; UVLO triggers below 2.5V to prevent erratic operation. |
| GND S (Pin 6) | Clean Signal Ground | Reference for internal bandgap, error amps, and NFB - must be isolated from high-current GND paths. |
| GND (Pin 7) | Power Ground | Emiter of internal NPN switch; carries full switch current - connect directly to ground plane. |
| VSW (Pin 8) | Switch Collector | High-current switching node; requires short, low-inductance routing to diode and inductor. |
Key Features
| Feature | Design Value |
|---|---|
| 1MHz Fixed-Frequency Operation | Enables consistent EMI profile and use of miniature 4.7µH inductors in portable designs. |
| Dual Polarity Regulation | Single IC regulates both +VOUT (via FB) and –VOUT (via NFB) without external amplifiers. |
| Nonlinear Error Amplifier gm | Transconductance jumps 10× above 40mV error to reduce output overshoot during startup/recovery. |
| Oscillator Frequency Shifting | Reduces switching frequency 5:1 when FB < 0.6V - protects components during overload or short-circuit. |
| Adaptive Anti-Saturation Driver | Dynamically adjusts base drive to minimize switch saturation voltage and improve efficiency. |
| Logic-Level Shutdown | 12µA quiescent current in shutdown - compatible with microcontroller GPIO without level-shifting. |
Applications
| Laptop Computer Power Supply | CCFL Backlight Driver |
|---|---|
Use Scenario: Generating 12V–19V from 3.3V/5V system rails to power display inverters and peripheral modules. IC Role / Device Role / Timing Role: Primary DC/DC boost controller managing input-to-output conversion with tight regulation and fast transient response. Use Value: 1MHz operation minimizes inductor size and board area; 4mA quiescent current extends battery runtime during light-load states. | Use Scenario: Driving cold cathode fluorescent lamps requiring high-voltage AC output from low-voltage DC input. IC Role / Device Role / Timing Role: High-frequency current-mode controller in resonant flyback topology, regulating lamp current via feedback from current-sense resistor. Use Value: Frequency shifting protects lamp transformer during ignition; NFB pin enables auxiliary negative bias generation for gate control circuits. |
| Inverting Power Supply | Multiple-Output Flyback Supply |
Use Scenario: Generating –5V or –12V rails from 5V or 12V inputs for analog front-ends, op-amp biasing, or RS-232 interfaces. IC Role / Device Role / Timing Role: Inverting converter controller using internal switch and external diode/inductor to produce regulated negative output. Use Value: Direct –2.49V NFB reference eliminates need for external inverting op-amp; 1.5A switch supports >300mA negative loads. | Use Scenario: Providing isolated +12V and –5V outputs simultaneously from a single 5V input in embedded instrumentation. IC Role / Device Role / Timing Role: Dual-sensing controller monitoring both FB and NFB pins to regulate positive and negative secondaries independently. Use Value: Prevents either output from overvoltage during unbalanced loading; avoids need for post-regulation LDOs on secondary windings. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1372CS8#PBF | 500kHz switching frequency; same pinout and feature set except lower fSW and higher inductor requirement (10µH vs 4.7µH). | Preferred where lower EMI or higher peak current margin is needed; less suitable for ultra-compact layouts. | Select LT1372CS8#PBF when board space allows larger inductors and lower-frequency operation improves system noise immunity. |
| LM2733YSD/NOPB | 600kHz adjustable frequency; 1.6A switch; requires external compensation; no NFB pin or negative regulation capability. | Supports only positive-output topologies; lacks integrated negative feedback path and frequency-shifting protection. | Choose LM2733YSD/NOPB for cost-sensitive single-rail boost applications where dual-polarity regulation is unnecessary. |
Compared with LT1377CS8#PBF, LT1372CS8#PBF trades higher inductor size for lower EMI and better thermal margin at high duty cycles, while LM2733YSD/NOPB offers lower BOM cost but requires additional components and design effort for negative rail generation.
Availability
LT1377CS8#PBF is available at Aetrix Electronics and suitable for laptop computer supplies, CCFL backlight drivers, inverting power supplies, and multiple-output flyback supplies requiring stable component supply across industrial temperature ranges.
Supply support for LT1377CS8#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 its legacy portfolio of high-performance analog and power management ICs.
The LT1377CS8#PBF belongs to Linear's monolithic switching regulator product line, designed for compact, high-efficiency DC/DC conversion in portable and space-constrained systems requiring flexible topology support and dual-polarity regulation.
FAQ
What is the maximum output current achievable with the LT1377CS8#PBF in a boost configuration?
The LT1377CS8#PBF supports up to 0.25A output current in boost mode with a 4.7µH inductor, based on its 1.5A switch current limit, 1MHz switching frequency, and thermal limits of the SOIC package. Actual deliverable current depends on input/output voltage ratio, PCB layout, and ambient temperature - derating is required above 70°C case temperature.
Can the LT1377CS8#PBF regulate both positive and negative outputs simultaneously?
Yes, the LT1377CS8#PBF can regulate both polarities simultaneously using its FB and NFB pins. In dual-output flyback designs, it prevents either rail from exceeding its setpoint by acting on whichever feedback signal deviates first - e.g., if the positive output sags under load, the negative output remains tightly regulated, avoiding overvoltage at no-load conditions.
What is the purpose of the VC pin on the LT1377CS8#PBF, and how is it used in practice?
On the LT1377CS8#PBF, the VC pin serves three functions: it is the error amplifier output (for loop compensation), the current limit threshold input (via external clamp), and the soft-start control node (via capacitor coupling). A series RC network from VC to ground sets loop stability; clamping VC below 0.8V disables switching; and a capacitor from VC to ground provides controlled startup ramping.
Does the LT1377CS8#PBF require an external Schottky diode, and what are the key selection criteria?
Yes, the LT1377CS8#PBF requires an external Schottky diode in boost and flyback topologies. Recommended parts include MBRS120T3 or 1N5818, rated for ≥1A average forward current and ≥12V reverse voltage. Key criteria are low forward voltage (<0.45V @ 1A) to minimize conduction loss, fast recovery (<100ns), and surge-rated construction to withstand repetitive reverse recovery stress.
How does the LT1377CS8#PBF handle overload or short-circuit conditions?
The LT1377CS8#PBF uses two complementary protections: pulse-by-pulse current limiting (1.5A switch limit) and oscillator frequency shifting. When FB voltage drops below 0.6V - indicating severe overload - the internal oscillator reduces frequency 5:1, lowering peak switch current and dissipating less power in the die and external components until fault clears.
LT1377CS8#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1377CS8#PBF FAQ
1.How can I place an order for LT1377CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1377CS8#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 LT1377CS8#PBF reliable?
The price and inventory of LT1377CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1377CS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1377CS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1377CS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1377CS8#PBF?
LT1377CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1377CS8#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 LT1377CS8#PBF?
For technical support, including LT1377CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1377CS8#PBF requirements.
6.How does Aetrix verify that LT1377CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1377CS8#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 LT1377CS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1377CS8#PBF?
All LT1377CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1377CS8#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 LT1377CS8#PBF part is unused and in its original packaging.
Return procedure for LT1377CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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