My Inquiry
My Account
Analog Devices Inc. LT1578IS8#PBF
- Part No.:
- LT1578IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1578IS8#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:200
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT1578IS8#PBF from Analog Devices (formerly Linear Technology) is a 200kHz monolithic current-mode buck switching regulator with integrated 1.5A NPN power switch, optimized for noise-sensitive applications. It operates from 4V to 15V input, delivers adjustable output down to 1.21V (or fixed 2.5V in -2.5 variant), and achieves >88% efficiency at 3.3V/1.25A using small inductors. Used in portable computers and battery-powered systems requiring low EMI and stable regulation.
For engineers reviewing the LT1578IS8#PBF datasheet, LT1578IS8#PBF pinout, LT1578IS8#PBF application, or LT1578IS8#PBF equivalent, key selection factors include its 0.2Ω typical switch on-resistance, 1.9mA quiescent current, 20µA shutdown current, cycle-by-cycle current limiting, and SO-8 fused-ground thermal package - all critical for compact, thermally constrained DC/DC designs.
Technical Context
The LT1578IS8#PBF implements constant-frequency current-mode control with internal 200kHz oscillator, slope-compensated peak-current sensing, and dual-loop feedback (error amplifier + current comparator). Its BOOST pin enables saturation of the internal NPN switch via external capacitor/diode, reducing conduction loss and improving efficiency over conventional bipolar regulators.
Pinout isolation separates high-dI/dt switching nodes (VSW, VIN, BOOST) from low-noise analog circuitry (FB/SENSE, VC, SHDN), while the fused ground lead in the SO-8 package reduces θJA to 80°C/W. Frequency foldback below 0.7V FB voltage and synchronized operation up to 400kHz support robust short-circuit protection and system-level clock alignment.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Rating | 1.5A max at ≤50% duty cycle; derates nonlinearly to 1.3A at 80% DC - defines maximum continuous load capability under typical operating conditions. |
| Input Voltage Range | 4V to 15V - supports wide-range industrial and battery-derived supplies without external pre-regulation. |
| Feedback Reference Voltage | 1.21V ±1.25% - sets output voltage via external resistor divider; enables outputs as low as 1.21V with precision regulation. |
| Quiescent Supply Current | 1.9mA typical - minimizes no-load power draw in always-on systems like battery backup circuits. |
| Shutdown Current | 20µA max - ensures ultra-low standby consumption during system sleep modes. |
| Switch On Resistance | 0.2Ω typical at 1.5A - directly determines conduction loss and thermal rise under full load. |
| Switching Frequency | 200kHz nominal (180–220kHz range) - balances efficiency, inductor size, and EMI profile for mid-power buck conversion. |
Pinout & Package
LT1578IS8#PBF uses an 8-lead plastic SOIC (SO-8) package with fused ground pin connected to internal tab for enhanced thermal dissipation (θJA = 80°C/W when mounted on ground plane).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW (Pin 1) | Switch emitter node | Connects to inductor; driven to VIN during on-time; clamped negative by catch diode during off-time - high dI/dt path requiring short layout. |
| VIN (Pin 2) | Power switch collector & IC supply | Supplies internal bias and drives NPN switch; high dI/dt node - requires local bypass capacitor and proximity to GND. |
| BOOST (Pin 3) | Switch drive voltage booster | Accepts external boost capacitor/diode to raise gate drive above VIN, enabling low VCE(sat) (~0.2Ω equivalent) and >88% efficiency. |
| GND (Pin 4) | Analog & power reference | Reference for FB/VC/SHDN; fused to internal tab - must connect to large copper area for thermal and EMI control. |
| VC (Pin 5) | Error amplifier output / current limit setpoint | Controls peak switch current; used for compensation; 1V–2V swing across load range - sensitive analog node. |
| FB/SENSE (Pin 6) | Output voltage sense / foldback trigger | 1.21V reference input (adjustable version); drops below 0.7V to initiate frequency/current foldback during overload. |
| SHDN (Pin 7) | Undervoltage lockout & micropower enable | 2.42V threshold enables UVLO; 0.4V threshold forces full shutdown - dual-threshold logic for sequenced power control. |
| SYNC (Pin 8) | External oscillator synchronization | Accepts 10–90% duty cycle signal up to 400kHz - enables deterministic EMI reduction and multi-regulator phase alignment. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode topology | Enables fast transient response and inherent loop stability without external compensation components beyond standard RC network on VC pin. |
| Reduced EMI generation | Slowed switch transition times and isolated high-frequency routing (via dedicated VSW/VIN/BOOST pins) lower radiated emissions in compact layouts. |
| Fused-ground SO-8 package | Thermal resistance reduced to 80°C/W - extends ambient operating range to –40°C to 125°C junction temperature. |
| Frequency foldback | Switching frequency drops ~5:1 when FB < 0.7V - limits power dissipation in IC and external components during short-circuit faults. |
| Low thermal resistance design | Internal fused ground lead and optimized die attach allow sustained 1.5A operation without external heatsink in PCB-mounted applications. |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Core voltage regulation for low-power microcontrollers and peripherals in clamshell notebooks with limited board space and thermal budget. IC Role / Device Role / Timing Role: Primary 3.3V/1.25A buck converter supplying CPU I/O and memory interface rails. Use Value: 0.2Ω switch RDS(on) and 1.9mA quiescent current extend battery runtime; SO-8 fused ground maintains safe junction temperature during burst loads. | Use Scenario: Power management in handheld test equipment requiring stable 2.5V analog reference and low-noise digital supply. IC Role / Device Role / Timing Role: Adjustable-output buck regulator generating precision 2.5V rail from single Li-ion cell (4.2V max) with tight load regulation. Use Value: 1.21V reference tolerance (±1.25%) and low 20µA shutdown current preserve battery charge during idle periods. |
| Battery Chargers | Distributed Power Systems |
Use Scenario: Constant-voltage stage in multi-cell Li-ion charger where input varies from 9V (adapter) to 15V (unregulated wall transformer). IC Role / Device Role / Timing Role: Intermediate 5V buck stage feeding linear post-regulator for precise CC/CV charging control. Use Value: 4V–15V input range accommodates unregulated inputs; cycle-by-cycle current limit protects against inrush into depleted batteries. | Use Scenario: Point-of-load conversion in industrial PLC backplanes where multiple 3.3V rails are derived from a shared 12V intermediate bus. IC Role / Device Role / Timing Role: Synchronized buck regulator operating at 300kHz (via SYNC pin) to align switching edges and reduce conducted EMI on shared bus. Use Value: External synchronization up to 400kHz enables deterministic noise spectrum placement and simplifies EMI filter design across multiple converters. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3605EDE#PBF | Higher integration: includes internal MOSFETs, soft-start, and power-good; 3MHz switching; smaller 12-lead DFN package. | Targets space-constrained, high-density designs needing faster transient response and tighter output tolerance (±1% vs ±1.25%). | Select LTC3605EDE#PBF when footprint, efficiency at light load, and feature count outweigh cost and thermal requirements of LT1578IS8#PBF. |
| TPS54202DRCT | Integrated FETs, 4.5–17V input, 2A output, 500kHz–2.2MHz programmable frequency; no BOOST pin required. | Suited for higher-current, wider-input applications where external boost capacitor complexity is undesirable. | Choose TPS54202DRCT for simplified BOM and higher output current, but verify thermal performance - SO-8 fused ground gives LT1578IS8#PBF advantage in sustained 1.5A operation. |
Compared with LTC3605EDE#PBF and TPS54202DRCT, the LT1578IS8#PBF offers superior thermal performance in SO-8 due to fused ground, lower quiescent current (1.9mA vs ≥25µA active, but higher shutdown), and proven noise-reduction architecture - making it preferred for thermally constrained, noise-sensitive 1.5A buck applications.
Availability
LT1578IS8#PBF 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 guaranteed traceable sourcing.
Supply support for LT1578IS8#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 product support, documentation, and manufacturing continuity for legacy Linear parts including the LT1578 series.
The LT1578 product line was designed specifically for medium-power, noise-sensitive buck conversion in portable and battery-operated equipment - emphasizing low EMI, thermal robustness in SO-8, and reliable operation across wide input ranges.
FAQ
What is the maximum output current capability of the LT1578IS8#PBF at 3.3V output with 12V input?
The LT1578IS8#PBF delivers up to 1.25A at 3.3V/12V input in continuous conduction mode using a 15µH inductor. This is determined by its 1.5A switch current limit at ≤50% duty cycle (DC = 3.3/12 ≈ 27.5%), minus half the inductor ripple current. Derating applies at higher duty cycles or with smaller inductors - consult the "Maximum Output Current" graphs in the LT1578IS8#PBF datasheet for exact values per L and VIN.
Does the LT1578IS8#PBF require an external boost capacitor, and why?
Yes, the LT1578IS8#PBF requires an external boost capacitor (and catch diode) connected between BOOST and VIN pins. This generates a voltage higher than VIN to fully saturate the internal NPN power switch, reducing its effective on-resistance to ~0.2Ω and enabling >88% efficiency - a key differentiator from conventional bipolar buck regulators.
How does the LT1578IS8#PBF handle short-circuit conditions?
The LT1578IS8#PBF employs dual-foldback protection: when FB voltage drops below 0.7V, it reduces switching frequency ~5:1 and lowers peak switch current limit from 1.5A to <0.77A. This coordinated action limits power dissipation in both the IC and external components during sustained short-circuit events, preventing thermal runaway.
What is the purpose of the fused ground pin in the LT1578IS8#PBF SO-8 package?
The fused ground pin in the LT1578IS8#PBF SO-8 package provides a low-impedance thermal path from the die to the PCB ground plane, reducing junction-to-ambient thermal resistance to 80°C/W. This allows the device to sustain 1.5A output current at ambient temperatures up to 85°C without additional heatsinking - critical for compact, sealed enclosures.
Can the LT1578IS8#PBF be synchronized to an external clock, and what is its sync range?
Yes, the LT1578IS8#PBF can be synchronized to an external clock via the SYNC pin (Pin 8). It accepts logic-level signals with 10–90% duty cycle and supports synchronization from 250kHz to 400kHz - extending beyond its native 200kHz frequency to enable EMI reduction and multi-regulator phase alignment in complex power systems.
LT1578IS8#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-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:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1578IS8#PBF FAQ
1.How can I place an order for LT1578IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1578IS8#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 LT1578IS8#PBF reliable?
The price and inventory of LT1578IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1578IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1578IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1578IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1578IS8#PBF?
LT1578IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1578IS8#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 LT1578IS8#PBF?
For technical support, including LT1578IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1578IS8#PBF requirements.
6.How does Aetrix verify that LT1578IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1578IS8#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 LT1578IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1578IS8#PBF?
All LT1578IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1578IS8#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 LT1578IS8#PBF part is unused and in its original packaging.
Return procedure for LT1578IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1578IS8#PBF Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
