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Analog Devices Inc. LT1959IS8#TRPBF
- Part No.:
- LT1959IS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1959IS8#TRPBF.pdf
- Description:
- IC REG BUCK SEPIC ADJ 4.5A 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,364
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Product details
Overview
LT1959IS8#TRPBF from Analog Devices (formerly Linear Technology) is a 500kHz monolithic step-down switching regulator with integrated 4.5A NPN power switch, current-mode control, and 1.21V feedback reference. It operates from 4V input down to 1.21V output, features cycle-by-cycle current limiting, 0.07Ω switch on-resistance, and shutdown current of 15µA. Designed for portable computers and battery-powered systems requiring compact, high-efficiency DC/DC conversion.
For engineers reviewing the LT1959IS8#TRPBF datasheet, LT1959IS8#TRPBF pinout, LT1959IS8#TRPBF application, or LT1959IS8#TRPBF equivalent, key selection criteria include minimum input voltage (4.0V), output adjustability via FB divider, BOOST pin voltage requirements (≥2.3V), synchronization capability (580kHz–1MHz), and thermal derating in SO-8 package with fused ground.
Technical Context
The LT1959IS8#TRPBF 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 uses BOOST-pin-driven saturation to achieve low conduction loss (0.07Ω typical), enabling >89% efficiency at full load.
Protection architecture includes dual-threshold shutdown (0.37V start-up / 2.38V lockout), full cycle-by-cycle short-circuit limiting, thermal shutdown (TJ = 150°C), and frequency/current foldback triggered below 0.7V on FB pin-ensuring safe operation during output shorts without external intervention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 500 kHz nominal; enables use of small 1.8 µH inductors and reduces filter size vs. lower-frequency buck regulators. |
| Feedback Reference Voltage | 1.21 V ±2%; sets output voltage via external resistor divider (e.g., 5V output requires R1/R2 = 3.13). |
| Max Switch Current | 4.5 A at ≤50% duty cycle; decreases nonlinearly to 3.7 A at 80% duty cycle due to internal slope compensation. |
| Switch On Resistance | 0.07 Ω typical; achieved via BOOST-pin-assisted saturation, reducing conduction loss vs. standard bipolar designs. |
| Shutdown Supply Current | 15 µA typical; enables ultra-low-power standby in battery systems without external disconnect circuitry. |
| Min Input Voltage | 4.0 V guaranteed; supports single-cell Li-ion (3.0–4.2V) with margin when boosted by system rail or auxiliary supply. |
| BOOST Pin Min Voltage | 2.3 V required across boost capacitor; ensures full saturation of internal NPN switch and maintains low RCE(sat). |
Pinout & Package
LT1959IS8#TRPBF is housed in an 8-lead plastic SO (SO-8) package with fused ground pin (Pin 3 connected to internal tab). Thermal resistance θJA = 30°C/W with 0.5 in² copper area over ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Input power collector | Supplies internal bias circuitry and powers NPN switch collector; requires low-inductance path to bypass cap and catch diode. |
| BOOST (Pin 2) | Switch drive voltage booster | Must be ≥2.3V above VIN to saturate internal NPN; connects to external boost capacitor/diode network. |
| GND (Pin 3) | Power and signal reference | Fused ground tied to internal tab; must connect to large copper area for thermal management and low-impedance return path. |
| VSW (Pin 4) | Switch emitter | Drives inductor; swings from near VIN (on) to –0.8V (off); requires external catch diode clamping. |
| SYNC (Pin 5) | Oscillator synchronization input | Logic-compatible (10–90% duty cycle); extends frequency range from 580kHz to 1MHz; grounded if unused. |
| SHDN (Pin 6) | Enable/shutdown control | Two thresholds: 0.37V (start-up), 2.38V (UVLO lockout); drives regulator into micropower mode below 0.37V. |
| VC (Pin 7) | Error amp output / current limit setpoint | Sets peak switch current; used for loop compensation; clamped at 0.9V (low) and 2.1V (high). |
| FB (Pin 8) | Output voltage sense input | Compares divided output to 1.21V reference; triggers frequency/current foldback below 0.7V during overload. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control | Enables fast transient response and inherent loop stability without external compensation components beyond standard RC network on VC pin. |
| BOOST-assisted saturation | Reduces effective switch resistance to 0.07Ω, improving efficiency by >14% vs. conventional bipolar buck regulators at 4.5A load. |
| Frequency and current foldback | Automatically lowers switching frequency (5:1) and peak current limit when FB < 0.7V, limiting power dissipation during output shorts. |
| Dual-threshold shutdown | Separate 0.37V (enable) and 2.38V (UVLO) thresholds allow precise input voltage sequencing and brown-out protection. |
| All-surface-mount design | Supports compact PCB layouts with standard 1.8 µH inductor, solid tantalum output capacitor (e.g., AVX TPS 100µF/10V), and Schottky catch diode. |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Point-of-load conversion from 5V main rail to 3.3V or 1.8V core logic in ultrabooks and tablets. IC Role / Device Role / Timing Role: Primary buck regulator delivering up to 4A continuous output with tight regulation and fast load-step response. Use Value: Enables compact, thermally efficient power delivery meeting Intel IMVP-6/7 spec margins while supporting dynamic voltage scaling. | Use Scenario: Power management in handheld medical devices and IoT sensors operating from single Li-ion cell (3.0–4.2V). IC Role / Device Role / Timing Role: Step-down converter generating stable 1.21V–3.3V outputs with ultra-low shutdown current (15µA) for extended battery life. Use Value: Eliminates need for external enable FET or LDO pre-regulator, reducing BOM count and board space in space-constrained designs. |
| Battery Chargers | Distributed Power |
Use Scenario: Auxiliary supply generation in multi-cell Li-ion charger ICs requiring isolated 5V or 3.3V rails for communication and monitoring circuits. IC Role / Device Role / Timing Role: Secondary buck regulator powered from charger's high-side switch node or auxiliary winding. Use Value: Provides regulated output independent of main charging path, ensuring reliable USB-C PD negotiation and fuel-gauge accuracy. | Use Scenario: Local DC/DC conversion in industrial PLC I/O modules where 12V or 24V backplane supplies must be stepped down to 5V/3.3V for microcontrollers and analog front-ends. IC Role / Device Role / Timing Role: High-current, robust buck converter with thermal shutdown and short-circuit protection for harsh environments. Use Value: Delivers 4.5A peak current with built-in fault handling, reducing need for external current-limiting or thermal monitoring circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3850EMSE#PBF | External MOSFET driver; no integrated switch; supports up to 60V input; requires external gate drivers and power FETs. | Used in higher-input-voltage (>16V) or higher-output-current (>4.5A) applications where thermal management favors discrete switches. | Select LTC3850EMSE#PBF only when input exceeds 16V or when paralleling multiple phases is required; not drop-in compatible. |
| TPS544B20RHLT | 4.5A integrated buck with 2.95–16V input; 0.6V reference; D-CAP2 control; no BOOST pin; smaller 3mm × 3mm QFN package. | Preferred for space-constrained designs needing faster transient response and simpler layout (no BOOST capacitor/diode required). | Choose TPS544B20RHLT for new designs targeting miniaturization and reduced component count; requires redesign of compensation and layout. |
Compared with LTC3850EMSE#PBF and TPS544B20RHLT, the LT1959IS8#TRPBF offers unique BOOST-pin-assisted bipolar saturation for high efficiency at 4–16V inputs, but requires careful attention to BOOST capacitor sizing and thermal pad grounding-making it optimal for cost-sensitive, medium-power applications where SO-8 footprint is acceptable.
Availability
LT1959IS8#TRPBF 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 LT1959IS8#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 acquired Linear Technology in 2017 and maintains its legacy of high-performance analog and power management ICs with rigorous reliability testing and automotive-grade qualification paths.
The LT1959IS8#TRPBF belongs to Linear's monolithic buck regulator product line, engineered for high-current, low-voltage point-of-load conversion in portable and battery-operated equipment where efficiency, thermal performance, and integration are critical.
FAQ
What is the minimum input voltage required for stable operation of the LT1959IS8#TRPBF?
The LT1959IS8#TRPBF guarantees stable operation down to 4.0V input voltage across its full temperature range. Below this threshold, internal bias lines may lose regulation, causing oscillator frequency drift or reference voltage inaccuracy. Actual minimum operational input depends on output voltage and load current-e.g., a 1.21V output at 4A requires ≥4.3V input per typical performance curves. Always verify under worst-case conditions including line and load transients.
How does the BOOST pin function in the LT1959IS8#TRPBF, and what happens if it is improperly biased?
The BOOST pin in the LT1959IS8#TRPBF supplies elevated drive voltage to the base of the internal NPN power switch, enabling saturation and achieving 0.07Ω on-resistance. It must be held ≥2.3V above VIN via external capacitor and diode. If BOOST voltage falls below specification, switch saturation degrades, increasing conduction loss and junction temperature-potentially triggering thermal shutdown or reducing efficiency by >10% at full load.
Can the LT1959IS8#TRPBF synchronize to an external clock, and what is its valid sync frequency range?
Yes, the LT1959IS8#TRPBF supports external synchronization via the SYNC pin (Pin 5), which accepts logic-level signals with 10–90% duty cycle. Its synchronizing range extends from the natural oscillator frequency (440–560kHz) up to 1MHz. When synchronized, internal frequency locks to the external source-enabling EMI reduction through fixed-frequency operation or noise spreading across multiple converters in a system.
What protection features are built into the LT1959IS8#TRPBF, and how do they activate during fault conditions?
The LT1959IS8#TRPBF integrates cycle-by-cycle current limiting, thermal shutdown (150°C), dual-threshold shutdown (0.37V enable / 2.38V UVLO), and FB-triggered frequency/current foldback. During output short, FB voltage drops below 0.7V, reducing switching frequency ~5:1 and lowering peak current limit from 4.5A to <3A-limiting power dissipation in both IC and external components without latching off.
Is the LT1959IS8#TRPBF pin-compatible with other members of the LT1959 family, such as the LT1959CS8?
Yes, the LT1959IS8#TRPBF shares identical pinout, package (SO-8), and electrical characteristics with the LT1959CS8, differing only in temperature grade: LT1959IS8#TRPBF is rated for –40°C to 125°C junction, while LT1959CS8 is rated for 0°C to 125°C. Both use the same marking "1959I" on top of the SO-8 package and require identical external components and layout.
LT1959IS8#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, 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:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1959IS8#TRPBF FAQ
1.How can I place an order for LT1959IS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1959IS8#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 LT1959IS8#TRPBF reliable?
The price and inventory of LT1959IS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1959IS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1959IS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1959IS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1959IS8#TRPBF?
LT1959IS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1959IS8#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 LT1959IS8#TRPBF?
For technical support, including LT1959IS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1959IS8#TRPBF requirements.
6.How does Aetrix verify that LT1959IS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1959IS8#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 LT1959IS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1959IS8#TRPBF?
All LT1959IS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1959IS8#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 LT1959IS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1959IS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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