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Analog Devices Inc. LT1959IR#TRPBF
- Part No.:
- LT1959IR#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LT1959IR#TRPBF.pdf
- Description:
- IC REG BUCK SEPIC ADJ 4.5A DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:2,881
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Product details
Overview
LT1959IR#TRPBF 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 down to 4V input and regulates output voltages as low as 1.21V, delivering high efficiency in portable computers and battery-powered systems using surface-mount inductors as small as 1.8µH.
For engineers reviewing the LT1959IR#TRPBF datasheet, LT1959IR#TRPBF pinout, LT1959IR#TRPBF application, or LT1959IR#TRPBF equivalent, key selection considerations include its fused-lead SO-8 package, cycle-by-cycle current limiting, shutdown current of 15µA, synchronization capability up to 1MHz, and thermal shutdown with full-cycle short-circuit protection.
Technical Context
The LT1959IR#TRPBF implements constant-frequency current-mode control with 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 0.07Ω on-resistance and >89% efficiency at 5V-to-3.3V conversion.
It features dual-threshold shutdown (0.37V start-up / 2.38V UVLO lockout), frequency foldback below 0.5V FB voltage, and current limit foldback below 0.8V FB voltage-enabling robust short-circuit protection without external circuitry. The IC supports continuous or discontinuous conduction mode and includes slope compensation to prevent subharmonic oscillation at duty cycles above 50%.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 500 kHz typical; enables compact 1.8µH inductor use and reduces EMI filtering burden. |
| Feedback Reference Voltage | 1.21 V ±2%; sets regulated output via external resistor divider with <0.1% error at R2 ≤ 2.5kΩ. |
| Integrated Switch Current Limit | 4.5 A at ≤50% duty cycle; derates nonlinearly to 3.7 A at 80% DC due to internal slope compensation. |
| Input Voltage Range | 4.0 V to 16 V minimum; supports single-cell Li-ion (4.2V) and 5V/12V rail inputs. |
| Shutdown Supply Current | 15 µA typical; reduces system standby power in battery applications. |
| Switch On-Resistance | 0.07 Ω typical at 4.5A; achieved via BOOST-pin-assisted saturation, minimizing conduction loss. |
| Thermal Shutdown Threshold | Junction temperature ≥150°C; protects die during overload or poor PCB thermal design. |
Pinout & Package
The LT1959IR#TRPBF is housed in a 7-lead plastic DD package with fused ground lead and exposed tab for thermal dissipation (θJA = 80°C/W). Pin 1 is FB; pin 2 is BOOST; pin 3 is VIN; pin 4 is GND (fused); pin 5 is VSW; pin 6 is SHDN; pin 7 is VC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB | Feedback input | Senses output voltage divider; also triggers frequency foldback (<0.5V) and current limit foldback (<0.8V). |
| BOOST | Switch drive boost supply | Accepts capacitor-diode charge pump to raise drive voltage above VIN, enabling NPN saturation and low RON. |
| VIN | Input power collector | Supplies internal bias and powers NPN switch collector; requires local 100µF tantalum + ceramic bypass. |
| GND | Reference and power return | Fused ground pin connected to internal tab; must tie to large copper area for thermal and EMI control. |
| VSW | Switch emitter | Drives inductor; swings negative during off-time-requires external catch diode clamped to −0.8V max. |
| SHDN | Shutdown control | Logic-compatible input: <0.37V enables operation; >2.38V disables switching (UVLO); open = enabled. |
| VC | Error amplifier output / current limit setpoint | Compensation node; also serves as current clamp point (0.9V threshold) and override interface. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables fast transient response and stable loop compensation across wide load and input ranges. |
| BOOST-pin-assisted saturation | Reduces switch VCE(sat) to ~0.32V at 4.5A, improving efficiency over conventional bipolar designs by >14%. |
| Programmable frequency synchronization | Accepts external logic-level signal (10–90% duty) to shift frequency from 580kHz to 1MHz, easing EMI compliance. |
| Dual-threshold shutdown | Separate 0.37V (start-up) and 2.38V (UVLO) thresholds enable precise input voltage sequencing and brownout protection. |
| Integrated short-circuit protection | Full cycle-by-cycle current limiting plus thermal shutdown prevents damage during sustained overload or output short. |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Step-down conversion from 5V main rail to 3.3V, 2.5V, or 1.8V core logic supplies in laptops and tablets. IC Role / Device Role / Timing Role: Primary buck regulator providing tightly regulated, low-noise power to CPU I/O, memory interfaces, and peripheral controllers. Use Value: High 500kHz switching frequency allows use of 1.8µH inductors, reducing board area and component height while maintaining >89% efficiency at 4A load. |
Use Scenario: Power management in handheld medical devices, barcode scanners, and wireless sensors operating from single Li-ion cells. IC Role / Device Role / Timing Role: Main DC-DC converter enabling operation down to 4.0V input, supporting full functionality until battery reaches end-of-discharge. Use Value: 15µA shutdown current extends battery life in sleep modes; foldback protection prevents thermal runaway during accidental shorts. |
| Battery Chargers | Distributed Power |
Use Scenario: Constant-voltage stage in multi-cell Li-ion charger circuits where precise 1.21V reference enables accurate termination voltage setting. IC Role / Device Role / Timing Role: Regulated output stage delivering stable voltage to charging IC or microcontroller ADC reference. Use Value: 1.21V feedback reference with ±2% tolerance ensures ±25mV accuracy in 4.2V cell termination, critical for cycle life and safety. |
Use Scenario: Local point-of-load regulation in telecom line cards or industrial PLCs converting 12V/24V backplane rails to 5V, 3.3V, or 2.5V subsystem supplies. IC Role / Device Role / Timing Role: High-current buck controller handling up to 4.5A peak switch current with minimal external components. Use Value: Integrated 4.5A switch and fused SO-8 package eliminate discrete MOSFET layout complexity and reduce BOM count by 3–5 parts per channel. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3850EFE#PBF | 4-phase synchronous buck controller (no integrated switch); 850kHz max frequency; requires external MOSFETs. | Targets higher-current (>10A), multi-phase applications with tighter ripple and thermal distribution requirements. | Select LTC3850EFE#PBF when scalability, phase interleaving, or synchronous rectification efficiency gains outweigh added component count and layout complexity. |
| LM2678SD-ADJ/NOPB | 5A step-down regulator with 63V input rating; fixed 260kHz frequency; no BOOST pin or sync capability. | Suited for industrial 24V/48V input systems requiring ruggedness over compact size or low-VOUT capability. | Select LM2678SD-ADJ/NOPB when input voltage exceeds 16V or when simplified design with no frequency foldback or BOOST circuitry is preferred. |
Compared with LTC3850EFE#PBF and LM2678SD-ADJ/NOPB, the LT1959IR#TRPBF uniquely combines integrated 4.5A NPN switch, BOOST-assisted saturation for low-loss operation at 1.21V output, and dual-threshold shutdown-making it optimal for space-constrained, battery-sensitive 4–16V input systems requiring <1.5V outputs.
Availability
LT1959IR#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 for production programs.
Supply support for LT1959IR#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 LT1959IR#TRPBF belongs to Linear's monolithic buck regulator product line, designed specifically for high-efficiency, low-output-voltage DC-DC conversion in space- and power-constrained portable and battery-operated equipment.
FAQ
What is the minimum input voltage required for stable operation of the LT1959IR#TRPBF?
The LT1959IR#TRPBF guarantees stable regulation down to 4.0V input across its full temperature range. This minimum is defined by internal bias line regulation-not direct measurement-and assumes sufficient BOOST voltage (≥2.3V above VIN) and proper external component selection. At lower VIN, output regulation may degrade before the absolute 4.0V limit is reached, especially under heavy load or high ambient temperature.
How does the BOOST pin function in the LT1959IR#TRPBF, and what external components are required?
The BOOST pin on the LT1959IR#TRPBF provides elevated gate drive to saturate the internal NPN switch, reducing conduction loss. It requires an external flying capacitor (e.g., 10nF ceramic) and Schottky diode (e.g., MBRS330T3) connected between VIN and BOOST. During switch turn-on, the capacitor charges to VIN; during turn-off, it lifts BOOST to ~VIN + 5V, enabling low 0.07Ω on-resistance and >89% efficiency.
Can the LT1959IR#TRPBF be synchronized to an external clock, and what is its synchronization range?
Yes, the LT1959IR#TRPBF supports external synchronization via the SYNC pin (available only in the SO-8 variant, not the DD package of LT1959IR#TRPBF). When used, it accepts logic-level signals (10–90% duty cycle) to shift the internal oscillator from its nominal 500kHz up to 1MHz. For the LT1959IR#TRPBF in DD package, synchronization is not supported-the SYNC pin is absent.
What protection features are built into the LT1959IR#TRPBF?
The LT1959IR#TRPBF integrates cycle-by-cycle current limiting, full-cycle short-circuit protection, thermal shutdown at 150°C junction temperature, and dual-threshold shutdown (0.37V start-up / 2.38V UVLO). It also features frequency foldback below 0.5V FB voltage and current limit foldback below 0.8V FB voltage-automatically reducing power dissipation during output shorts without external components.
What is the recommended output capacitor type and ESR range for the LT1959IR#TRPBF?
For the LT1959IR#TRPBF, solid tantalum capacitors (e.g., AVX TPS series) are recommended with ESR between 0.05Ω and 0.2Ω. A typical choice is 100µF/10V D-case TPS rated ≤0.1Ω ESR. Ceramic capacitors may be used but require reduced compensation pole frequency (by ~10×) due to lack of ESR-induced loop zero; their low ESL can cause instability if compensation is unchanged.
LT1959IR#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- 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:
- DDPAK-7
LT1959IR#TRPBF FAQ
1.How can I place an order for LT1959IR#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1959IR#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 LT1959IR#TRPBF reliable?
The price and inventory of LT1959IR#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1959IR#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1959IR#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1959IR#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1959IR#TRPBF?
LT1959IR#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1959IR#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 LT1959IR#TRPBF?
For technical support, including LT1959IR#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1959IR#TRPBF requirements.
6.How does Aetrix verify that LT1959IR#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1959IR#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 LT1959IR#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1959IR#TRPBF?
All LT1959IR#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1959IR#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 LT1959IR#TRPBF part is unused and in its original packaging.
Return procedure for LT1959IR#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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