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Analog Devices Inc. LT1959CS8#PBF
- Part No.:
- LT1959CS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1959CS8#PBF.pdf
- Description:
- IC REG BUCK SEPIC ADJ 4.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:707
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Product details
Overview
LT1959CS8#PBF from Analog Devices (formerly Linear Technology) is a monolithic 500kHz current-mode buck switching regulator with integrated 4.5A NPN power switch, 1.21V feedback reference, and BOOST pin for switch saturation. It operates from 4V to 16V input and delivers adjustable output down to 1.21V, optimized for portable computers and battery-powered systems requiring high efficiency at light-to-full load.
For engineers reviewing the LT1959CS8#PBF datasheet, LT1959CS8#PBF pinout, LT1959CS8#PBF application, or LT1959CS8#PBF equivalent, key selection criteria include verified 0.07Ω switch RDS(on), cycle-by-cycle current limiting, shutdown current of 15µA, synchronization capability up to 1MHz, and SO-8 package thermal performance with fused GND.
Technical Context
The LT1959CS8#PBF implements constant-frequency current-mode control using an internal 500kHz oscillator, error amplifier (2000 µMho transconductance), and peak-current comparator referenced to the VC pin. Its bipolar NPN switch is driven via BOOST voltage to achieve low conduction loss (0.07Ω typical), enabling >89% efficiency at 5V→3.3V conversion.
Protection architecture includes dual-threshold shutdown (0.37V start-up / 2.38V UVLO lockout), full cycle-by-cycle short-circuit limiting, thermal shutdown, and frequency/current foldback triggered below 0.7V FB voltage-ensuring safe operation under output short conditions without external circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Rating | 4.5A max at ≤50% duty cycle; derates nonlinearly to 3.7A at 80% DC-limits max continuous output current in buck topology |
| Feedback Reference Voltage | 1.21V ±20mV over temp-sets output voltage via external resistor divider; enables 1.21V–15V adjustable range |
| Switch On Resistance | 0.07Ω typical at 4.5A-reduces conduction loss and improves efficiency vs. standard bipolar designs |
| Shutdown Supply Current | 15µA typical-enables ultra-low-power standby in battery systems without external disconnect |
| Switching Frequency | 500kHz ±40kHz-allows compact 1.8µH inductor; synchronizable from 580kHz to 1MHz via SYNC pin |
| Minimum Input Voltage | 4.0V guaranteed-supports single-cell Li-ion (3.0–4.2V) with margin when boosted by system rail |
| BOOST Pin Voltage Requirement | ≥2.3V above VIN-ensures NPN switch saturation; requires external boost capacitor/diode network |
Pinout & Package
LT1959CS8#PBF is housed in an 8-lead plastic SOIC (SO-8) package with fused GND pin thermally connected to the internal tab. The package supports θJA = 30°C/W when soldered to ≥0.5 in² copper area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply and NPN collector | Supplies internal bias circuitry; carries high dI/dt switching current-requires local bypass cap and catch diode |
| BOOST | Switch drive voltage booster | Accepts voltage ≥VIN + 2.3V to saturate internal NPN; reduces VCE(sat) to ~0.32V at 4.5A |
| GND | Power and signal reference | Fused GND pin tied to internal tab-must connect to large copper pour for thermal/EMI control |
| VSW | NPN emitter switch node | Drives inductor; swings negative during off-time-requires external catch diode clamped to −0.8V |
| SYNC | Oscillator synchronization input | Logic-compatible input (10–90% duty); enables external clock sync up to 1MHz-ground if unused |
| SHDN | Enable/disable control | Dual-threshold: 0.37V (start) / 2.38V (UVLO lockout); pulls supply current to 15µA in shutdown |
| VC | Error amp output / current limit setpoint | 1–2V range sets peak switch current; usable for loop compensation, current clamp, or override |
| FB | Output voltage feedback | Senses 1.21V reference; enables foldback protection: <0.7V disables sync, <0.5V reduces frequency 5:1 |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables fast transient response and stable loop compensation without external slope compensation |
| Integrated BOOST drive circuitry | Allows NPN switch saturation with external capacitor/diode-achieves FET-like 0.07Ω Ron |
| Cycle-by-cycle current limiting | Prevents switch damage during overload/short-circuit; combined with foldback for thermal safety |
| Two-level shutdown threshold | 0.37V enables soft-start; 2.38V provides precise undervoltage lockout-eliminates brown-out oscillation |
| Frequency and current foldback | Reduces switching frequency 5:1 and lowers current limit when FB < 0.5V-limits power dissipation during shorts |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Core voltage regulation for embedded microcontrollers and FPGAs in clamshell notebooks. IC Role / Device Role / Timing Role: Primary buck converter delivering 1.8V/2.5V/3.3V from 5V or single-cell Li-ion input. Use Value: 500kHz switching enables use of 1.8µH inductors-reducing board area by >40% vs. 100kHz designs. | Use Scenario: Power management in handheld test equipment with variable battery voltage (3.0–4.2V). IC Role / Device Role / Timing Role: Step-down regulator maintaining stable 3.3V rail across battery discharge curve. Use Value: 4V minimum input and 15µA shutdown current extend runtime in sleep mode by >3× vs. legacy regulators. |
| Battery Chargers | Distributed Power |
Use Scenario: Constant-voltage stage in multi-cell Li-ion charger with system load sharing. IC Role / Device Role / Timing Role: Secondary buck stage regulating charge voltage (e.g., 8.4V→5.0V) for USB-PD compliance. Use Value: Synchronization capability allows alignment with primary AC/DC controller-reducing EMI peaks. | Use Scenario: Point-of-load conversion in industrial IoT gateways with 12V/24V backplane. IC Role / Device Role / Timing Role: Local 5V→3.3V conversion for Ethernet PHY and MCU subsystems. Use Value: SO-8 fused-GND package delivers 30°C/W thermal resistance-enabling 4.5A continuous operation without heatsink. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3866EFE#PBF | External MOSFET driver; no integrated switch; supports 4–36V input; 0.6V ref | Requires external high-side N-channel MOSFET; better suited for >10A or >24V input designs | Select when higher output current or wider input range is required; not drop-in compatible |
| TPS54331DR | 3.5A integrated MOSFET; 0.8V ref; 570kHz fixed freq; no BOOST pin; smaller SO-8 | Lacks BOOST-driven saturation-higher RDS(on) (0.14Ω) limits efficiency at high current | Choose for cost-sensitive, lower-current (<3A) applications where 89% efficiency is acceptable |
Compared with LTC3866EFE#PBF and TPS54331DR, the LT1959CS8#PBF uniquely combines integrated 4.5A bipolar switch, BOOST-assisted saturation, and dual-threshold shutdown-making it optimal for space-constrained, high-efficiency 4–16V input systems needing robust short-circuit protection without external components.
Availability
LT1959CS8#PBF is available at Aetrix Electronics and suitable for portable computers, battery-powered systems, and distributed power applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT1959CS8#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 high-performance analog and power management portfolio.
The LT1959CS8#PBF belongs to Linear's monolithic buck regulator product line, designed specifically for high-efficiency, low-voltage DC/DC conversion in portable and battery-critical applications.
FAQ
What is the maximum output current achievable with the LT1959CS8#PBF in a 5V-to-3.3V application?
The LT1959CS8#PBF delivers up to 4.3A continuous output in a 5V-to-3.3V configuration with 10µH inductor and 500kHz switching. This is constrained by the 4.5A switch rating and duty-cycle-dependent current derating-peak switch current reaches 4.3A at 62.5% duty cycle (3.3V/5V), confirmed in Typical Performance Characteristics Figure G13.
Does the LT1959CS8#PBF require an external boost capacitor, and what happens if it is omitted?
Yes, the LT1959CS8#PBF requires an external boost capacitor (and diode) connected between VIN and BOOST pins. Without it, the internal NPN switch cannot saturate-resulting in ~1.5V VCE(sat), excessive power loss (>2W at 4.5A), and efficiency dropping below 75%. The BOOST pin must be held ≥2.3V above VIN to guarantee 0.07Ω on-resistance.
How does the LT1959CS8#PBF handle output short-circuit conditions?
The LT1959CS8#PBF uses dual-stage protection: (1) cycle-by-cycle current limiting trips at 4.5A (typical), and (2) when FB voltage drops below 0.5V, it activates frequency foldback (5:1 reduction) and current foldback (to <3A). This combination limits power dissipation in both the IC and external components during sustained shorts-verified in Figure G10 and Applications Information Section.
Can the LT1959CS8#PBF synchronize to an external clock, and what is its valid sync frequency range?
Yes, the LT1959CS8#PBF supports external synchronization via the SYNC pin (SO-8 only). It accepts logic-level signals (10–90% duty cycle) and locks to frequencies from 580kHz to 1MHz-extending beyond its native 500kHz. This feature reduces EMI by aligning switching edges with system clocks, as documented in Electrical Characteristics Table and Pin Functions section.
What is the thermal performance of the LT1959CS8#PBF in SO-8 package, and how is it achieved?
The LT1959CS8#PBF achieves θJA = 30°C/W in SO-8 when mounted on ≥0.5 in² copper area connected to the fused GND pin. This is enabled by direct thermal coupling of the GND pin to the internal power tab-confirmed in Package/Order Information diagram and Thermal Characteristics notes. Without adequate copper, θJA degrades to >40°C/W, risking thermal shutdown above 3A continuous load.
LT1959CS8#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, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.3V
- Voltage - Input (Max):
- 15V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 12.9V
- Current - Output:
- 4.5A (Switch)
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1959CS8#PBF FAQ
1.How can I place an order for LT1959CS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1959CS8#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 LT1959CS8#PBF reliable?
The price and inventory of LT1959CS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1959CS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1959CS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1959CS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1959CS8#PBF?
LT1959CS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1959CS8#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 LT1959CS8#PBF?
For technical support, including LT1959CS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1959CS8#PBF requirements.
6.How does Aetrix verify that LT1959CS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1959CS8#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 LT1959CS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1959CS8#PBF?
All LT1959CS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1959CS8#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 LT1959CS8#PBF part is unused and in its original packaging.
Return procedure for LT1959CS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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