My Inquiry
My Account
Analog Devices Inc. LT1578CS8#PBF
- Part No.:
- LT1578CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1578CS8#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,460
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT1578CS8#PBF from Analog Devices (formerly Linear Technology) is a monolithic 200kHz current-mode step-down DC/DC switching regulator with an integrated 1.5A NPN power switch, 0.2Ω on-resistance, and adjustable 1.21V feedback reference. It operates from 4V to 15V input, delivers up to 1.25A at 3.3V output, and targets portable computers and battery-powered systems requiring high efficiency and low EMI.
For engineers reviewing the LT1578CS8#PBF datasheet, LT1578CS8#PBF pinout, LT1578CS8#PBF application, or LT1578CS8#PBF equivalent, key selection criteria include its fixed 200kHz switching frequency, cycle-by-cycle current limiting, 20µA shutdown current, SO-8 thermal-enhanced package with fused ground lead, and compatibility with small-value inductors (e.g., 15µH).
Technical Context
The LT1578CS8#PBF implements constant-frequency current-mode control using an internal 200kHz oscillator, error amplifier (1000µMho transconductance), and peak-current comparator referenced to the VC pin. Its BOOST pin enables saturation of the internal NPN switch via external capacitor-diode charge pump, reducing conduction loss and improving efficiency to >88% at 3.3V/1.25A.
It features dual shutdown thresholds (2.42V for UVLO, 0.4V for micropower shutdown), FB pin–driven frequency and current foldback below 0.7V, and SYNC pin synchronization up to 400kHz. The SO-8 package integrates a fused ground lead to achieve θJA = 80°C/W when mounted on a ground plane.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 200kHz typical; enables predictable EMI filtering and stable loop compensation without frequency foldback under normal load. |
| Max Output Current | 1.25A at 3.3V output with 15µH inductor; limited by 1.5A switch rating and duty-cycle–dependent current foldback. |
| Input Voltage Range | 4V to 15V; supports single-cell Li-ion (4.2V) through 12V industrial rails with margin for dropout and ripple. |
| Feedback Reference | 1.21V ±1.25%; sets output voltage via external resistor divider; enables outputs down to 1.21V with precision regulation. |
| Shutdown Current | 20µA max; reduces system standby power in battery-critical applications such as portable computing. |
| Switch On Resistance | 0.2Ω typical at 1.5A; minimizes conduction loss and thermal rise in SO-8 package, supporting 125°C junction operation. |
| Thermal Resistance | θJA = 80°C/W with fused ground pin connected to PCB ground plane; extends ambient operating range vs standard SO-8. |
Pinout & Package
LT1578CS8#PBF uses an 8-lead plastic SOIC (SO-8) package with fused ground lead thermally bonded to the die paddle for enhanced heat dissipation. Pin 4 (GND) serves as both signal reference and primary thermal path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW (Pin 1) | Switch emitter node | Connects to inductor; swings negative during off-time; clamped by external catch diode; must be routed with minimal trace inductance. |
| VIN (Pin 2) | Power switch collector & bias supply | Supplies internal circuitry; carries high dI/dt; requires local 100µF solid tantalum bypass capacitor adjacent to pin. |
| BOOST (Pin 3) | Charge-pump drive for switch saturation | Connected to VIN + boost capacitor/diode; enables 0.2Ω effective switch resistance and >88% efficiency at full load. |
| GND (Pin 4) | Signal reference & thermal ground | Fused to internal tab; must connect directly to large copper area; separates noise-sensitive control ground from high-current return paths. |
| VC (Pin 5) | Error amplifier output / current limit setpoint | Drives peak-current comparator; used for loop compensation (capacitor to GND); can be clamped to disable regulation. |
| FB/SENSE (Pin 6) | Output voltage sense / foldback trigger | 1.21V reference input; voltage <0.7V initiates frequency and current foldback for short-circuit protection. |
| SHDN (Pin 7) | Undervoltage lockout & micropower enable | 2.42V threshold enables UVLO; 0.4V threshold forces 20µA shutdown; supports accurate input rail sequencing. |
| SYNC (Pin 8) | External oscillator synchronization input | Logic-compatible; accepts 10–90% duty cycle signals up to 400kHz; disables foldback when active. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables fast transient response and inherent cycle-by-cycle overcurrent protection without external sensing resistors. |
| Integrated BOOST charge-pump circuitry | Reduces switch VCE(sat) to ~0.3V at 1.5A, achieving >88% efficiency at 3.3V/1.25A-30% lower loss than predecessor LT1507. |
| Two-threshold shutdown pin | 2.42V UVLO prevents startup until input stabilizes; 0.4V deep-sleep threshold cuts supply current to 20µA for extended battery life. |
| FB pin–activated protection | Automatically reduces switching frequency and peak current limit when output collapses below 50%, limiting fault power dissipation. |
| SO-8 fused-ground thermal design | Reduces θJA by ~30% vs standard SO-8, enabling 125°C junction operation with 1.25A load and minimal heatsinking. |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Core voltage regulation for embedded microcontrollers and I/O peripherals in clamshell notebooks. IC Role / Device Role / Timing Role: Primary 3.3V buck converter delivering regulated power to logic circuits with tight load-transient response. Use Value: 200kHz fixed frequency simplifies EMI filter design; 1.25A output supports burst-mode CPU loads; 20µA shutdown extends battery runtime between sessions. |
Use Scenario: Power management in handheld test equipment with dual Li-ion cells (8.4V max) and 3.3V digital subsystems. IC Role / Device Role / Timing Role: Main step-down regulator converting 8.4V battery to 3.3V system rail, interfacing with fuel gauge and USB interface ICs. Use Value: 4V–15V input range accommodates full battery discharge curve; low 1.9mA quiescent current preserves battery capacity during idle periods. |
| Battery Chargers | Distributed Power Systems |
Use Scenario: Auxiliary 3.3V supply for charger controller ICs and status LEDs in multi-bay Li-ion chargers. IC Role / Device Role / Timing Role: Secondary regulator deriving clean 3.3V from main 12V charging bus, isolated from high-current charging paths. Use Value: SO-8 fused ground minimizes thermal coupling to charger MOSFETs; FB foldback protects against output shorts during connector insertion. |
Use Scenario: Local point-of-load conversion in industrial PLC backplanes where 12V or 24V distributed rails feed 3.3V FPGA I/O banks. IC Role / Device Role / Timing Role: Compact, thermally robust buck stage replacing discrete switcher designs to reduce board area and BOM count. Use Value: Synchronizable to system clock (up to 400kHz) eliminates beat frequencies; 0.2Ω switch resistance maintains >85% efficiency even at 75°C ambient. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3605EMS8E#PBF | 4MHz synchronous buck, 3A output, 2.5V–5.5V input; no external diode required; higher efficiency at light loads due to Burst Mode™. | Targets space-constrained, high-efficiency apps (e.g., medical wearables); not pin-compatible; requires different layout and compensation. | Select LTC3605 if >90% efficiency at 10mA load is critical and board area permits smaller inductor; avoid if 200kHz EMI profile or legacy SO-8 footprint is required. |
| TPS5430DDAR | 3.5A, 500kHz adjustable-frequency buck; 5.5V–36V input; integrated high-side FET; 1.221V reference; no BOOST pin. | Suited for wide-input industrial supplies (e.g., 24V bus); lacks FB foldback and fused-ground thermal enhancement. | Choose TPS5430 for higher current or wider input range; use LT1578CS8#PBF when low-noise 200kHz operation, proven EMI performance, or SO-8 thermal reliability are prioritized. |
Compared with LTC3605EMS8E#PBF and TPS5430DDAR, the LT1578CS8#PBF offers superior thermal performance in SO-8 via fused ground, deterministic 200kHz EMI signature, and integrated foldback protection-making it preferred for cost-sensitive, thermally constrained, or noise-sensitive 3.3V/1.25A applications where pin compatibility and legacy design reuse matter.
Availability
LT1578CS8#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 consistent parametric performance across production batches.
Supply support for LT1578CS8#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, datasheets, and application engineering for the LT® family of high-performance analog ICs.
The LT1578CS8#PBF belongs to Linear's legacy monolithic switching regulator product line, designed specifically for noise-sensitive, thermally demanding DC/DC conversion in portable and industrial equipment where fixed-frequency predictability and robust fault handling are essential.
FAQ
What is the maximum output current achievable with the LT1578CS8#PBF at 3.3V output?
The LT1578CS8#PBF delivers up to 1.25A at 3.3V output when using a 15µH inductor and 5V input, as confirmed in the Typical Application circuit (Figure TA01). This value decreases with higher input voltage due to increased inductor ripple current and duty-cycle–dependent switch current foldback, reaching ~0.94A at VIN = 15V per the Maximum Output Load Current calculation in the Applications Information section.
Does the LT1578CS8#PBF require an external catch diode, and what type is recommended?
Yes, the LT1578CS8#PBF requires an external Schottky catch diode (e.g., 1N5818) connected from VSW to GND. The diode must handle ≥1.25A average current and ≥2.5A peak reverse voltage, with low forward voltage (<0.5V) to minimize conduction loss. Fast recovery is unnecessary-the device's 200kHz frequency allows standard Schottky types.
How does the BOOST pin function in the LT1578CS8#PBF, and what external components are needed?
The BOOST pin on the LT1578CS8#PBF provides a voltage higher than VIN to saturate the internal NPN switch, reducing its effective on-resistance to 0.2Ω. It requires an external capacitor (typically 10nF) and Schottky diode (e.g., 1N5818) connected from VIN to BOOST. During switch-on, the diode charges the capacitor; during switch-off, the charged capacitor drives the base of the NPN switch, enabling low-loss conduction.
Can the LT1578CS8#PBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT1578CS8#PBF supports external synchronization via the SYNC pin (Pin 8). It accepts logic-level signals with 10–90% duty cycle across a 250kHz to 400kHz range. When synchronized, the internal oscillator locks to the external signal, eliminating beat frequencies in multi-regulator systems. If unused, SYNC must be grounded to prevent noise coupling.
What thermal considerations apply to the LT1578CS8#PBF's SO-8 package?
The LT1578CS8#PBF's SO-8 package features a fused ground lead directly bonded to the die paddle, reducing θJA to 80°C/W when soldered to a minimum 1-inch² copper area. To maintain 125°C junction temperature at 1.25A, the PCB must provide adequate copper pour on the GND pad and avoid thermal isolation. No external heatsink is required under these conditions.
LT1578CS8#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1578CS8#PBF FAQ
1.How can I place an order for LT1578CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1578CS8#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 LT1578CS8#PBF reliable?
The price and inventory of LT1578CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1578CS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1578CS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1578CS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1578CS8#PBF?
LT1578CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1578CS8#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 LT1578CS8#PBF?
For technical support, including LT1578CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1578CS8#PBF requirements.
6.How does Aetrix verify that LT1578CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1578CS8#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 LT1578CS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1578CS8#PBF?
All LT1578CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1578CS8#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 LT1578CS8#PBF part is unused and in its original packaging.
Return procedure for LT1578CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1578CS8#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…
