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Analog Devices Inc. LT1578CS8#TRPBF
- Part No.:
- LT1578CS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1578CS8#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,605
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Product details
Overview
LT1578CS8#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 200kHz current-mode buck switching regulator with an integrated 1.5A NPN power switch, 0.2Ω on-resistance, 4V–15V input range, and adjustable 1.21V output voltage. It delivers up to 1.25A at 3.3V in portable computers and battery-powered systems.
For engineers reviewing the LT1578CS8#TRPBF datasheet, LT1578CS8#TRPBF pinout, LT1578CS8#TRPBF application, or LT1578CS8#TRPBF equivalent, key selection criteria include its cycle-by-cycle current limit, low 1.9mA quiescent current, fused-ground SO-8 thermal performance, 20µA shutdown current, and synchronization capability up to 400kHz.
Technical Context
The LT1578CS8#TRPBF implements constant-frequency current-mode control with internal slope compensation to prevent subharmonic oscillation across 8%–94% duty cycle range. Its error amplifier features 1000µMho transconductance and 400V/V gain, referenced to a precision 1.21V feedback threshold.
Switching is driven by a 200kHz oscillator with ±20kHz tolerance, line-regulated to 0.15%/V, and synchronizable via the dedicated SYNC pin. The BOOST pin enables saturation of the internal NPN switch using an external capacitor-diode network, reducing conduction loss and improving efficiency to >88% at 3.3V/1.25A.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.5A typical; sets maximum deliverable load current before foldback activation |
| Feedback Voltage | 1.21V ±1.25%; defines output regulation point when used with external resistor divider |
| Switch On Resistance | 0.2Ω typical; determines I²R conduction loss and thermal rise under full load |
| Quiescent Supply Current | 1.9mA typical; impacts no-load power budget in always-on battery systems |
| Shutdown Current | 20µA max; enables ultra-low-power sleep mode for extended battery life |
| Switching Frequency | 200kHz ±10%; balances EMI, inductor size, and efficiency across 4–15V input range |
| Input Voltage Range | 4V to 15V; supports single-cell Li-ion through 12V industrial rails without pre-regulation |
Pinout & Package
The LT1578CS8#TRPBF is housed in an 8-lead plastic SOIC package (SO-8) with fused ground pin for θJA = 80°C/W when mounted on a ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW (Pin 1) | Switch emitter node | Connects to inductor; carries full switching current and negative flyback voltage clamped by external diode |
| VIN (Pin 2) | Power switch collector & bias supply | Supplies internal circuitry; requires low-inductance bypassing near pin to suppress dI/dt spikes |
| BOOST (Pin 3) | Switch drive voltage booster | Accepts external capacitor-diode network to raise gate drive above VIN, enabling low VCE(sat) |
| GND (Pin 4) | Analog and power reference | Fused to internal tab; must connect directly to ground plane to minimize noise coupling and thermal resistance |
| VC (Pin 5) | Error amplifier output / current limit control | Provides loop compensation node; also serves as current clamp input for override or shutdown |
| FB/SENSE (Pin 6) | Output voltage sensing input | References 1.21V internal bandgap; drives frequency/current foldback below 0.7V during fault conditions |
| SHDN (Pin 7) | Enable/disable control | Two-threshold logic: 2.42V disables switching (UVLO), 0.4V forces micropower shutdown |
| SYNC (Pin 8) | External clock synchronization | Accepts 10–90% duty cycle signals up to 400kHz; grounded when unused |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode topology | Enables fast transient response and stable loop compensation without external type-II/III networks |
| Low-noise optimized design | Slowed switch transitions and revised pinout isolate high-dI/dt paths from sensitive analog circuitry |
| Integrated slope compensation | Nonlinear compensation maintains 1.5A peak switch current up to 80% duty cycle without subharmonics |
| Fused-ground SO-8 package | Reduces thermal resistance by >30% vs standard SO-8, extending ambient operating range to 125°C |
| Frequency foldback protection | Automatically reduces switching frequency 5:1 and current limit to <0.77A when FB < 0.7V during short-circuit |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Powering 3.3V logic rails in clamshell notebooks with dynamic CPU load changes. IC Role / Device Role / Timing Role: Primary step-down regulator delivering regulated 3.3V from 5–12V battery or adapter input. Use Value: 1.9mA quiescent current extends standby time; 20µA shutdown enables instant-on resume from hibernation. | Use Scenario: Supplying microcontroller, display, and sensor subsystems in handheld medical devices. IC Role / Device Role / Timing Role: Main DC-DC converter generating stable 3.3V rail from single Li-ion cell (4.2V) or two-cell pack (8.4V). Use Value: 0.2Ω switch RDS(on) minimizes dropout and heat generation in compact enclosures with limited airflow. |
| Battery Chargers | Distributed Power Systems |
Use Scenario: Providing isolated auxiliary 3.3V bias for charger controller ICs and status LEDs. IC Role / Device Role / Timing Role: Secondary buck regulator fed from main charging rail, independent of battery state. Use Value: Wide 4–15V input range accommodates variable bus voltages during CC/CV charge phases without reconfiguration. | Use Scenario: Local point-of-load conversion in telecom line cards with distributed 12V backplane. IC Role / Device Role / Timing Role: Compact, thermally robust POL regulator converting 12V backplane to 3.3V FPGA/core logic supply. Use Value: Fused-ground SO-8 package sustains 1.25A continuous output at 70°C ambient without derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3605EMS8E#TRPBF | 4MHz synchronous buck, 1.2A, 2.5–5.5V input, integrated MOSFETs, 25µA IQ | Higher frequency enables smaller magnetics but limited to low-input applications; no BOOST pin or NPN drive architecture | Select for space-constrained, low-voltage systems where 4–15V input range is not required |
| TPS54202DDCR | 2.5–17V input, 2A synchronous buck, 45µA IQ, integrated FETs, 500kHz–2.2MHz programmable frequency | Wider input range and higher current, but lacks fused-ground thermal enhancement and fixed 200kHz option | Select when higher output current or programmable frequency outweighs need for ultra-low-noise layout isolation |
Compared with LTC3605EMS8E#TRPBF and TPS54202DDCR, the LT1578CS8#TRPBF offers superior thermal performance in SO-8 via fused ground, deterministic 200kHz operation for EMI filtering, and BOOST-driven NPN architecture optimized for mid-range input voltages - making it preferred for noise-sensitive, thermally constrained 4–15V applications.
Availability
LT1578CS8#TRPBF is available at Aetrix Electronics and suitable for portable computers, battery-powered systems, and distributed power systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT1578CS8#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, Inc. (acquired Linear Technology in 2017) designs high-performance analog, mixed-signal, and power management ICs for precision, reliability, and signal integrity.
The LT1578CS8#TRPBF belongs to Linear's legacy monolithic buck regulator family, engineered specifically for noise-sensitive, thermally demanding applications in portable and industrial equipment where low EMI and robust fault protection are critical.
FAQ
What is the minimum input voltage required for LT1578CS8#TRPBF to regulate a 3.3V output?
The LT1578CS8#TRPBF guarantees regulation down to 4.0V minimum input voltage across temperature. At 3.3V output, typical startup occurs at ~4.2V with 15µH inductor and 5V input per characterization data. Below 4.0V, internal bias rails collapse and regulation is not assured - verify minimum VIN vs load using Figure 14 (Minimum Input Voltage to Start with 3.3V Output) in the official datasheet for LT1578CS8#TRPBF.
Can LT1578CS8#TRPBF be synchronized to an external clock, and what is its sync range?
Yes, the LT1578CS8#TRPBF supports external synchronization via its SYNC pin (Pin 8), accepting logic-level signals with 10–90% duty cycle across a 250kHz–400kHz range. This allows precise EMI reduction by aligning switching edges with system clocks or avoiding sensitive frequency bands. When unused, SYNC must be tied to GND to prevent noise coupling into the oscillator.
How does the BOOST pin function in LT1578CS8#TRPBF, and what external components are required?
The BOOST pin (Pin 3) in LT1578CS8#TRPBF supplies elevated drive voltage to the internal NPN switch base, enabling saturation and minimizing VCE(sat). It requires an external bootstrap capacitor (typically 10nF–100nF ceramic) and Schottky diode (e.g., 1N5817) connected between VIN and BOOST. During switch-off, the diode charges the capacitor; during switch-on, the capacitor provides >VIN drive to reduce conduction loss - a key enabler of the 0.2Ω effective on-resistance.
What protection features does LT1578CS8#TRPBF implement during output short-circuit conditions?
The LT1578CS8#TRPBF employs dual foldback protection: when FB pin voltage drops below 0.7V, it reduces switching frequency ~5:1 (to ~40kHz) and lowers peak switch current limit from 1.5A to <0.77A. This coordinated action limits power dissipation in both the IC and external diode/inductor during sustained shorts. The feature is automatic, transparent under normal operation, and disabled only if FB is externally clamped above 0.7V - which is not recommended without careful thermal analysis.
Is LT1578CS8#TRPBF pin-compatible with other members of the LT1578 family, such as LT1578IS8 or LT1578CS8-2.5?
Yes, all LT1578 variants including LT1578CS8#TRPBF, LT1578IS8, and LT1578CS8-2.5 share identical SO-8 pinout and footprint. Differences lie in temperature grade (C-grade: 0°C–125°C vs I-grade: –40°C–125°C) and internal feedback configuration (adjustable 1.21V vs fixed 2.5V). No PCB changes are needed when substituting within the same package variant, though resistor divider values must be adjusted for the adjustable version.
LT1578CS8#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-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 15V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 14.1V
- Current - Output:
- 1.5A
- Frequency - Switching:
- 200kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1578CS8#TRPBF FAQ
1.How can I place an order for LT1578CS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1578CS8#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 LT1578CS8#TRPBF reliable?
The price and inventory of LT1578CS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1578CS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1578CS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1578CS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1578CS8#TRPBF?
LT1578CS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1578CS8#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 LT1578CS8#TRPBF?
For technical support, including LT1578CS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1578CS8#TRPBF requirements.
6.How does Aetrix verify that LT1578CS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1578CS8#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 LT1578CS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1578CS8#TRPBF?
All LT1578CS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1578CS8#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 LT1578CS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1578CS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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