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Analog Devices Inc. LT1959IR#PBF
- Part No.:
- LT1959IR#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LT1959IR#PBF.pdf
- Description:
- IC REG BUCK SEPIC ADJ 4.5A DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:306
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Product details
Overview
LT1959IR#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 minimum input down to 1.21V adjustable output and delivers up to 4.3A continuous load current at 5VIN/5VOUT, used in portable computers and battery-powered DC/DC conversion.
For engineers reviewing the LT1959IR#PBF datasheet, LT1959IR#PBF pinout, LT1959IR#PBF application, or LT1959IR#PBF equivalent, key selection criteria include verified 0.07Ω switch RDS(on) equivalent, cycle-by-cycle current limiting, shutdown current ≤75µA, synchronization capability up to 1MHz, and SO-8 package thermal performance with fused GND.
Technical Context
The LT1959IR#PBF implements constant-frequency current-mode control using an internal 500kHz oscillator, error amplifier (2000µMho transconductance), and peak-current comparator referenced to the VC pin. Its bipolar NPN switch is driven via BOOST pin voltage (≥VIN + 2.3V) to achieve saturation and low conduction loss.
Protection includes full cycle-by-cycle short-circuit limiting (4.5A typ), thermal shutdown (TJMAX = 150°C), undervoltage lockout (2.38V on SHDN), and dual-threshold shutdown (0.37V active, 0.45V start-up). Frequency foldback activates below 0.5V FB to limit dissipation during output shorts.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 4.5A typical at ≤50% duty cycle; enables 4.3A continuous output at 5VIN/5VOUT with 3.3µH inductor |
| Feedback Reference Voltage | 1.21V ±20mV over temperature; sets output via external resistor divider (e.g., R1=1.21kΩ, R2=2.49kΩ for 1.8V) |
| Switching Frequency | 500kHz ±40kHz; fixed frequency enables predictable EMI filtering and reduces external component size |
| Input Voltage Range | 4.0V to 16V min/max; supports single-cell Li-ion (4.2V) and 5V/12V rail inputs without pre-regulation |
| Shutdown Supply Current | 15µA typical, ≤75µA max; allows ultra-low-power standby in battery systems |
| BOOST Pin Min Voltage | 2.3V above VIN; ensures NPN switch saturation and <100mV VCE(sat) equivalent at full load |
| Thermal Resistance θJA | 30°C/W with 0.5 in² copper area; requires fused-GND SO-8 mounting for rated 4.5A operation |
Pinout & Package
The LT1959IR#PBF is packaged in an 8-lead plastic SO (SO-8) with fused GND tab, rated for 150°C junction temperature and 30°C/W thermal resistance when soldered to 0.5 in² copper area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Power switch collector & IC bias supply | Connects to input rail; high dI/dt node requiring local 100µF tantalum + 0.68µF ceramic bypass |
| BOOST | Switch driver boost voltage source | Must be ≥VIN + 2.3V; drives external capacitor/diode to saturate NPN switch and minimize conduction loss |
| GND | Reference ground & thermal tab | Fused GND pin tied directly to internal tab; must connect to large copper area for thermal and noise control |
| VSW | Power switch emitter | Drives inductor; swings negative during off-time; requires Schottky catch diode (e.g., MBRS330T3) |
| SYNC | Oscillator synchronization input | Logic-compatible (10–90% duty); extends frequency range from 580kHz to 1MHz; ground when unused |
| SHDN | Enable/shutdown control | 0.37V threshold disables switching; 0.45V restarts; 2.38V UVLO prevents operation until input stabilizes |
| VC | Error amplifier output & current limit setpoint | Compensation node (1–2V range); also accepts external clamp for current override or shutdown |
| FB | Output voltage feedback input | Senses 1.21V reference; enables foldback current limiting and frequency reduction below 0.5V during faults |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode control architecture | Enables fast transient response and stable loop compensation without external type-II/III networks |
| Integrated BOOST drive circuitry | Reduces switch VCE(sat) to ~100mV equivalent, improving efficiency to >89% at 4A vs. 75% in conventional bipolar designs |
| Cycle-by-cycle current limiting | Prevents switch destruction during output shorts by clamping peak current to 4.5A on every switching cycle |
| Frequency foldback protection | Reduces switching frequency 5:1 when FB < 0.5V, limiting power dissipation in IC, diode, and inductor during sustained faults |
| Dual-threshold shutdown | Separates UVLO (2.38V) from deep shutdown (0.37V), enabling precise input sequencing and micropower retention |
Applications
| Portable Computers | Battery-Powered Systems |
|---|---|
Use Scenario: Point-of-load regulation from 5V main rail to 3.3V/2.5V/1.8V core logic rails in laptops and tablets. IC Role / Device Role / Timing Role: Primary buck controller delivering up to 4.3A with 500kHz fixed frequency for compact filter design. Use Value: Enables use of 1.8µH inductors and small ceramic/tantalum output caps, reducing board area by >30% vs. lower-frequency alternatives. | Use Scenario: Step-down conversion in handheld medical devices and IoT sensors powered by single Li-ion cells (3.0–4.2V). IC Role / Device Role / Timing Role: High-efficiency buck regulator operating down to 4.0V input, supporting 1.21V–5V outputs with light-load quiescent current of 3.8mA. Use Value: Maintains >85% efficiency at 100mA load, extending battery life while delivering regulated 3.3V for MCU and RF subsystems. |
| Battery Chargers | Distributed Power |
Use Scenario: Constant-voltage stage in multi-cell Li-ion charger modules, regulating 12V adapter input to 8.4V/12.6V charge rails. IC Role / Device Role / Timing Role: Secondary buck stage providing precise, ripple-free charging voltage with cycle-by-cycle current limiting for fault safety. Use Value: Foldback current limiting and thermal shutdown prevent thermal runaway during cell mismatch or short-circuit events. | Use Scenario: Intermediate bus converter in telecom equipment, stepping 12V backplane to 5V/3.3V for line cards and FPGA power domains. IC Role / Device Role / Timing Role: High-current (4.5A) buck regulator synchronized to system clock via SYNC pin to reduce conducted EMI. Use Value: Synchronization to 1MHz eliminates beat frequencies with other converters, simplifying EMI filter design and meeting EN55022 Class B limits. |
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 | External MOSFET driver; no integrated switch; 1.2V ref; supports 0.6V–24V output | Requires external high-side N-channel MOSFET; suited for >10A designs with custom thermal layout | Select when higher current (>6A), wider output range, or discrete FET optimization is required |
| TPS544B20RMLR | 4.5A integrated buck; 1.2V ref; 500kHz–2MHz programmable frequency; 2.95–16V input | Uses CMOS process; lower 2.95V min input; no BOOST pin; different compensation scheme | Select for lower VIN capability, digital interface support, or TI-design ecosystem compatibility |
Compared with LTC3850EFE#PBF and TPS544B20RMLR, the LT1959IR#PBF provides unique bipolar-BOOST architecture for superior saturation efficiency at high current, fixed 500kHz operation without programming overhead, and fused-GND SO-8 thermal performance optimized for 4.5A in space-constrained layouts.
Availability
LT1959IR#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 guaranteed traceable sourcing.
Supply support for LT1959IR#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 product lines with rigorous qualification and long-term support.
The LT1959IR#PBF belongs to Linear's monolithic current-mode buck regulator family, designed specifically for high-efficiency, high-current DC/DC conversion in space- and thermal-constrained portable and industrial systems.
FAQ
What is the minimum input voltage specification for the LT1959IR#PBF?
The LT1959IR#PBF has a guaranteed minimum input voltage of 4.0V over temperature, defined as the point where internal bias lines remain regulated to maintain stable reference voltage and oscillator frequency. Actual operational minimum depends on output voltage and load current - e.g., 4.3V is required for 3.3V output at full load per Typical Performance Characteristics graphs.
How does the BOOST pin function in the LT1959IR#PBF and what external components are required?
The BOOST pin on the LT1959IR#PBF supplies elevated gate drive to the internal NPN switch, enabling saturation and reducing effective on-resistance to 0.07Ω. It requires an external flying capacitor (e.g., 100nF ceramic) and Schottky diode (e.g., 1N914) connected between VIN and BOOST to generate a voltage ≥VIN + 2.3V during switch on-time.
Does the LT1959IR#PBF support synchronization, and what is its valid sync frequency range?
Yes, the LT1959IR#PBF supports external synchronization via the SYNC pin (SO-8 only). The valid synchronizing range extends from the nominal 580kHz up to 1MHz, with logic-level compatibility (10–90% duty cycle). When not used, the SYNC pin must be grounded to prevent noise coupling and erratic operation.
What thermal considerations apply to the LT1959IR#PBF in SO-8 package?
The LT1959IR#PBF in SO-8 uses a fused-GND tab that must be soldered to ≥0.5 in² copper area to achieve the specified θJA of 30°C/W. Without this, θJA degrades to 80°C/W, limiting continuous current to ~2.5A. Thermal shutdown triggers at 150°C junction temperature, and GND plane routing must minimize impedance to avoid load regulation errors.
How does the LT1959IR#PBF implement short-circuit protection beyond cycle-by-cycle current limiting?
In addition to cycle-by-cycle current limiting (4.5A peak), the LT1959IR#PBF employs frequency foldback - reducing switching frequency 5:1 when FB voltage drops below 0.5V - and dual-threshold shutdown (2.38V UVLO and 0.37V deep shutdown). These features collectively limit power dissipation in the IC, external diode, and inductor during sustained output shorts.
LT1959IR#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- 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:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DDPAK-7
LT1959IR#PBF FAQ
1.How can I place an order for LT1959IR#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1959IR#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 LT1959IR#PBF reliable?
The price and inventory of LT1959IR#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1959IR#PBF is usually 5 days.
3.What payment methods are accepted for LT1959IR#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1959IR#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1959IR#PBF?
LT1959IR#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1959IR#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 LT1959IR#PBF?
For technical support, including LT1959IR#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1959IR#PBF requirements.
6.How does Aetrix verify that LT1959IR#PBF is sourced from the original manufacturer or authorized distributors?
All LT1959IR#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 LT1959IR#PBF meets industry standards.
7.What is the process for return or replacement of LT1959IR#PBF?
All LT1959IR#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1959IR#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 LT1959IR#PBF part is unused and in its original packaging.
Return procedure for LT1959IR#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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