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Analog Devices Inc. LT1959CR#PBF
- Part No.:
- LT1959CR#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LT1959CR#PBF.pdf
- Description:
- IC REG BUCK SEPIC ADJ 4.5A DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:2,222
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Product details
Overview
LT1959CR#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 output and delivers up to 4.3A continuous load current at 5VIN/3.3VOUT with 1.8µH inductor. Used in portable computers and battery-powered systems requiring high efficiency at light-to-full load.
For engineers reviewing the LT1959CR#PBF datasheet, LT1959CR#PBF pinout, LT1959CR#PBF application, or LT1959CR#PBF equivalent, key selection criteria include its 0.07Ω typical switch on-resistance, cycle-by-cycle current limiting, shutdown current of 15µA, synchronization capability up to 1MHz, and thermal shutdown with fused-lead SO-8 package compatibility.
Technical Context
The LT1959CR#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-equivalent to a 0.07Ω FET-enabling >89% efficiency at full load.
It features dual shutdown thresholds (0.4V for micropower shutdown, 2.38V for UVLO lockout), frequency foldback below 0.5V FB voltage, and current limit foldback below 0.8V FB voltage-both active during short-circuit conditions to limit power dissipation in IC, diode, and inductor without external circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 4.5A typical at ≤50% duty cycle; enables 4.3A max output at 5VIN/3.3VOUT with 10µH inductor |
| Feedback Reference Voltage | 1.21V ±20mV over temperature; sets output voltage via external resistor divider |
| Switch On Resistance | 0.07Ω typical at 4.5A; achieved via BOOST-driven saturation, reducing VCE(sat) to FET-equivalent level |
| Shutdown Supply Current | 15µA typical; reduces system standby power in battery applications |
| Switching Frequency | 500kHz nominal (460–540kHz); enables compact 1.8µH inductors and low-profile ceramic/tantalum output capacitors |
| Minimum Input Voltage | 4.0V guaranteed; supports operation from single-cell Li-ion (fully charged) or 5V rail with dropout margin |
| Operating Junction Temp | 0°C to 125°C; validated for industrial portable equipment with θJA = 30°C/W on 0.5 in² copper |
Pinout & Package
LT1959CR#PBF is supplied in a 7-lead plastic DD package with fused ground pin and thermal tab, and is also compatible with standard 8-lead SO-8 (LT1959CS8). The DD package provides lower thermal resistance (θJA = 30°C/W vs. 80°C/W for SO-8) when mounted to large copper areas.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB | Feedback input | Senses 1.21V reference; triggers frequency/current foldback below 0.5V/0.8V; disables sync below 0.7V |
| BOOST | Switch drive boost supply | Accepts ≥VIN+2.3V to saturate NPN switch; reduces conduction loss to 0.07Ω equivalent |
| VIN | Input power collector | Supplies internal bias and powers NPN collector; requires low-inductance bypass near pin |
| GND | Power and signal reference | Fused ground pin tied to thermal tab; must connect directly to ground plane to minimize EMI and load regulation error |
| VSW | Switch emitter output | Drives inductor; swings from VIN to –0.8V clamped; requires catch diode with fast recovery |
| SHDN | Shutdown control | 0.4V threshold forces micropower mode (15µA); 2.38V threshold enables UVLO lockout |
| VC | Error amp output / current limit setpoint | Controls peak switch current; used for compensation; clampable to 0V for forced shutdown |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode topology | Enables fast transient response and stable loop compensation without external type-II/III networks |
| BOOST-assisted saturation | Reduces switch conduction loss by >50% vs. conventional bipolar designs, enabling >89% efficiency at 4A |
| Integrated cycle-by-cycle current limiting | Protects switch and external components during overload without external sense resistor or protection IC |
| Frequency and current foldback | Automatically reduces switching frequency to ~100kHz and limits peak current to <3A during output short |
| Synchronization capability | Accepts external logic-level signal (10–90% duty) to scale frequency from 580kHz to 1MHz for EMI reduction |
Applications
| Portable Computing Power | Battery-Powered Systems |
|---|---|
Use Scenario: Step-down conversion from 5V main rail to 3.3V or 2.5V core logic in laptops and tablets. IC Role / Device Role / Timing Role: Primary DC/DC buck regulator delivering regulated output with fast load-step response. Use Value: 500kHz switching enables use of 1.8µH inductors and low-ESR tantalum output caps, minimizing board area and height. |
Use Scenario: Power management in handheld test instruments, medical monitors, and IoT edge nodes. IC Role / Device Role / Timing Role: High-efficiency point-of-load regulator operating from Li-ion (3.0–4.2V) or alkaline stacks. Use Value: 4V minimum input and 15µA shutdown current extend battery runtime; fused-DD package improves thermal performance in sealed enclosures. |
| 5V to 1.8V Conversion | Distributed Power Architecture |
Use Scenario: Generating 1.8V supply for FPGA I/O banks or DDR memory interfaces from 5V backplane. IC Role / Device Role / Timing Role: Fixed-frequency current-mode buck converter with precise 1.21V reference for tight output tolerance. Use Value: 0.07Ω switch RDS(on)-equivalent and BOOST drive maintain >87% efficiency at 3A, reducing thermal load on PCB. |
Use Scenario: Local regulation at remote subsystems in telecom or industrial control racks. IC Role / Device Role / Timing Role: Standalone buck controller supporting synchronization to system clock to avoid beat frequencies. Use Value: SYNC pin allows alignment of switching edges across multiple LT1959CR#PBF units, simplifying EMI filtering design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3850EMSE#PBF | Higher 600kHz default frequency; MOSFET drivers (external FETs); no integrated switch | Supports higher output currents (>10A) with external power stage; requires more BOM components | Select when scalable power delivery or >5A output is required; not drop-in for LT1959CR#PBF footprint |
| LM2678SD-ADJ/NOPB | Fixed 260kHz frequency; 5A switch; 1.22V reference; no BOOST or sync pins | Lacks frequency foldback, sync, and BOOST-assisted efficiency; simpler layout but lower peak efficiency | Choose for cost-sensitive, non-synchronized 5V→3.3V/2.5V applications where 500kHz EMI is not critical |
Compared with LTC3850EMSE#PBF and LM2678SD-ADJ/NOPB, the LT1959CR#PBF uniquely combines integrated 4.5A NPN switch, BOOST-driven saturation, and dual-foldback protection in a thermally optimized DD package-making it optimal for space-constrained, high-efficiency 1–4A buck designs where simplicity and reliability are prioritized over scalability or ultra-low cost.
Availability
LT1959CR#PBF is available at Aetrix Electronics and suitable for portable computing power, battery-powered instrumentation, 5V-to-1.8V conversion, and distributed power architecture requiring stable component supply, long-lifecycle support, and traceable sourcing.
Supply support for LT1959CR#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 technical and manufacturing continuity for legacy Linear power products including the LT1959 family.
The LT1959 belongs to Linear's monolithic current-mode buck regulator product line, designed specifically for high-efficiency, low-noise, and thermally robust DC/DC conversion in portable and industrial applications where integrated power switches and advanced protection features are essential.
FAQ
What is the maximum continuous output current achievable with the LT1959CR#PBF?
The LT1959CR#PBF supports up to 4.3A continuous output current under typical conditions: 5V input, 3.3V output, 10µH inductor, and 25°C ambient. This is constrained by its 4.5A switch current limit at ≤50% duty cycle and reduced peak current at higher duty cycles due to internal slope compensation. At 5VIN/1.8VOUT, maximum output drops to ~3.7A due to increased duty cycle and ripple current effects.
How does the BOOST pin improve efficiency in the LT1959CR#PBF?
The BOOST pin on the LT1959CR#PBF supplies a voltage ≥VIN+2.3V to the base drive of the internal NPN switch, forcing deep saturation and reducing effective on-resistance to 0.07Ω. This cuts conduction losses significantly versus standard bipolar designs-raising efficiency from ~75% to >89% at full load-and eliminates need for external gate drivers or MOSFETs.
Can the LT1959CR#PBF be synchronized to an external clock, and what is its sync range?
Yes-the LT1959CR#PBF supports external synchronization via its SYNC pin (SO-8 only; not present on DD package). It accepts logic-level signals (10–90% duty) and locks to frequencies from 580kHz up to 1MHz. This feature allows EMI reduction through frequency alignment across multiple regulators or avoidance of sensitive bands in system-level noise analysis.
What protection features are built into the LT1959CR#PBF?
The LT1959CR#PBF integrates full-cycle-by-cycle current limiting, thermal shutdown, undervoltage lockout (2.38V SHDN threshold), micropower shutdown (0.4V SHDN threshold), frequency foldback (<0.5V FB), and current limit foldback (<0.8V FB). These operate autonomously without external components, protecting both the IC and external inductor/diode during startup, overload, or short-circuit events.
Is the LT1959CR#PBF pin-compatible with other Linear buck regulators like the LT1506?
The LT1959CR#PBF is functionally identical to the LT1506 but optimized for lower output voltages (1.21V vs. 2.42V minimum) and improved efficiency. While both share the same 7-pin DD and 8-pin SO-8 footprints and pinouts, the LT1959CR#PBF requires tighter BOOST capacitor placement and benefits from updated compensation due to its higher transconductance error amplifier (2000 µMho vs. 1000 µMho).
LT1959CR#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DDPAK-7
LT1959CR#PBF FAQ
1.How can I place an order for LT1959CR#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1959CR#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 LT1959CR#PBF reliable?
The price and inventory of LT1959CR#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1959CR#PBF is usually 5 days.
3.What payment methods are accepted for LT1959CR#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1959CR#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1959CR#PBF?
LT1959CR#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1959CR#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 LT1959CR#PBF?
For technical support, including LT1959CR#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1959CR#PBF requirements.
6.How does Aetrix verify that LT1959CR#PBF is sourced from the original manufacturer or authorized distributors?
All LT1959CR#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 LT1959CR#PBF meets industry standards.
7.What is the process for return or replacement of LT1959CR#PBF?
All LT1959CR#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1959CR#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 LT1959CR#PBF part is unused and in its original packaging.
Return procedure for LT1959CR#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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