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Analog Devices Inc. LT3579IUFD#PBF
- Part No.:
- LT3579IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LT3579IUFD#PBF.pdf
- Description:
- IC REG BST CHARGE PUMP ADJ 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:607
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Product details
Overview
LT3579IUFD#PBF from Analog Devices is a 6A, 42V dual-switch PWM DC/DC converter in a 20-pin 4mm × 5mm QFN package, configured for boost, inverting, SEPIC, or flyback topologies. It delivers 12V at 1.7A or –12V at 1.2A from 5V input, with integrated fault protection against output short circuits, input/output overvoltage (up to 40V transient), and overtemperature (165°C trip). It serves as a local power supply IC in high-reliability embedded systems.
For engineers reviewing the LT3579IUFD#PBF datasheet, LT3579IUFD#PBF pinout, LT3579IUFD#PBF application, or LT3579IUFD#PBF equivalent, key selection criteria include its 2.5V–16V input range, 200kHz–2.5MHz programmable switching frequency, master/slave switch current sharing (3.4A/2.6A), and fault-activated GATE-driven PMOS disconnect capability.
Technical Context
The LT3579IUFD#PBF implements constant-frequency current-mode control with internal 1.215V positive and 9mV negative feedback references, enabling precise regulation in both boost and inverting configurations. Its dual NPN switches-SW1 (3.4A min) and SW2 (2.6A min)-are designed for combined 6A peak current handling when tied together, with 250mV typical VCE(SAT) at 5.5A.
It features synchronized operation via SYNC pin (1.3V high threshold), buffered CLKOUT output (2.1V high, 200mV low, 42% duty cycle), and fault detection logic that triggers shutdown on SW overcurrent, VIN >16.2V, SW voltage >42V, or die temperature >165°C. Soft-start is controlled by external capacitor on SS pin with 250kΩ internal ramp source.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 16V operating; supports 40V transient - enables robust operation in automotive and industrial 12V rail environments. |
| Switch Current Limit | SW1: 3.4A min; SW2: 2.6A min; combined: 6A min - allows high-power local bias generation without external current sensing. |
| Switch VCE(SAT) | 250mV typical at 5.5A (SW1+SW2 tied) - reduces conduction loss and thermal stress in high-current boost/inverting supplies. |
| Switching Frequency | 200kHz to 2.5MHz, set by RT resistor or external SYNC - permits EMI optimization and compact magnetics in space-constrained designs. |
| Feedback Reference | Positive FB: 1.215V ±15mV; Negative FB: 9mV ±6mV - enables accurate output regulation across boost (VOUT > VIN) and inverting (VOUT < 0) topologies. |
| Fault Protection | Detects output short, VIN OVLO (16.2V min), SW overvoltage (42V min), and overtemperature (165°C typ) - autonomously disables switches and asserts FAULT pin low. |
| Quiescent Current | 2.4mA typical (active); 1µA max (shutdown) - supports low-power standby modes in battery-backed or always-on systems. |
Pinout & Package
LT3579IUFD#PBF is housed in a 20-lead, 4mm × 5mm plastic QFN package with exposed thermal pad (Pin 21 = GND). The package supports θJA = 34°C/W and θJC = 2.7°C/W, requiring soldered GND pad for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB (Pin 1) | Positive/Negative Feedback Input | Accepts regulated voltage divider from VOUT; sets output via 1.215V (boost) or 9mV (inverting) reference - determines regulation accuracy and loop stability. |
| VC (Pin 2) | Error Amplifier Output | Drives external compensation network (R-C-RC) - directly controls PWM comparator threshold to maintain output regulation. |
| GATE (Pin 3) | PMOS Gate Drive Output | Sinks up to 933µA (linear with SS voltage); drives external PMOS for output disconnect during fault - enables hot-swap-safe power path isolation. |
| FAULT (Pin 4) | Bidirectional Fault Indicator | Active-low open-collector; pulled low internally on fault or externally to trigger shutdown - provides system-level fault signaling and latchable protection. |
| VIN (Pin 5) | Main Input Supply | 2.5V–16V input with 40V transient rating; requires local ceramic bypass - powers internal circuitry and high-side switch drivers. |
| SW1 (Pins 6–10) | Master NPN Switch Collector | Handles ≥3.4A peak current; connects to inductor/transformer primary - forms main power path in boost/flyback/SEPIC topologies. |
| GND (Pin 21, Exposed Pad) | Power & Signal Ground | Thermal and electrical reference plane; must be soldered to PCB ground - critical for EMI control, thermal dissipation, and stable regulation. |
| SW2 (Pins 11–15) | Slave NPN Switch Collector | Handles ≥2.6A peak current; ties to SW1 for 6A combined current - enables higher output power without external paralleling. |
| CLKOUT (Pin 16) | Buffered Oscillator Output | 2.1V/200mV CMOS signal at fOSC; duty cycle varies with junction temperature - synchronizes secondary regulators and enables on-chip thermal monitoring. |
| SHDN (Pin 17) | Shutdown Control Input | 1.33V turn-on threshold with 30mV hysteresis; accepts slow-rising signals - allows sequenced power-up and configurable UVLO using resistor divider from VIN. |
| RT (Pin 18) | Frequency Setting Input | Connects to ground via resistor (34kΩ–432kΩ) to set fOSC from 200kHz–2.5MHz - defines switching speed and magnetic component size. |
| SYNC (Pin 20) | External Clock Input | Accepts 0.4V/1.3V logic levels; overrides RT setting - enables deterministic EMI reduction and multi-phase coordination with other converters. |
| SS (Pin 19) | Soft-Start Timing Node | Charged by 250kΩ internal source to 2.1V; controls GATE current ramp and switch enable timing - prevents inrush current and ensures controlled startup. |
Key Features
| Feature | Design Value |
|---|---|
| 6A Combined Switch Capability | SW1 (3.4A) + SW2 (2.6A) tied for single-stage high-current conversion - eliminates need for external MOSFETs in [email protected] or –[email protected] bias supplies. |
| Output Short Circuit Protection | Sample-mode current sensing triggers FAULT within one cycle if FB falls outside regulation window - protects downstream loads without external current sense resistors. |
| User-Configurable Undervoltage Lockout | SHDN pin accepts resistor divider from VIN to set custom turn-on threshold (e.g., 8V or 10V) - enables brown-out immunity and power sequencing in multi-rail systems. |
| Integrated Frequency Foldback | Reduces fOSC to 1/6 normal when FB is between 350mV–900mV - improves controllability during startup and light-load conditions. |
| CLKOUT Synchronization & Temp Monitoring | CLKOUT pin provides phase-aligned clock for other regulators and linear junction temperature readout via duty cycle - simplifies multi-converter timing and thermal management. |
Applications
| Vacuum Fluorescent Display (VFD) Bias Supply | TFT-LCD Panel Bias Supply |
|---|---|
Use Scenario: Generating +30V and –30V rails from 5V or 12V for VFD segment/grid drive. IC Role / Device Role / Timing Role: Dual-output inverting/boost controller with independent feedback paths and fault-isolated GATE drive. Use Value: Delivers regulated high-voltage bias with automatic shutdown on filament short, eliminating risk of display damage during hot-plug events. | Use Scenario: Providing AVDD (+15V), VGH (+25V), and VGL (–10V) for TFT gate driver ICs. IC Role / Device Role / Timing Role: Multi-topology DC/DC controller supporting boost, inverting, and charge-pump-augmented configurations. Use Value: Achieves tight regulation across three outputs using single IC with shared power switches - reduces BOM count and PCB area vs. discrete solutions. |
| Automotive Engine Control Unit (ECU) Local Supply | Industrial Programmable Logic Controller (PLC) I/O Module |
Use Scenario: Deriving isolated 5V or 3.3V auxiliary rails from noisy 12V vehicle battery with load dump tolerance. IC Role / Device Role / Timing Role: Fault-protected buck-derived (via inverting) or boost regulator with 40V transient immunity and thermal shutdown. Use Value: Maintains operation during cold-crank (2.5V) and load-dump (40V) transients while protecting against sensor short circuits. | Use Scenario: Powering analog front-end circuitry (ADCs, op-amps) requiring low-noise ±15V rails in harsh factory environments. IC Role / Device Role / Timing Role: High-reliability inverting converter with output disconnect via GATE-driven PMOS during overcurrent events. Use Value: Prevents cascading failure when field wiring shorts, enabling safe field maintenance without system power-down. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3891EFE#PBF | Single-channel synchronous buck controller; no integrated switches; supports up to 60V input; requires external MOSFETs. | Used where higher efficiency (>95%) and adjustable frequency (50kHz–900kHz) are prioritized over integration and fault autonomy. | Select LTC3891EFE#PBF when designing for >3A continuous loads with external FET optimization and lower quiescent current (25µA). |
| LT8330EFE#PBF | Single-switch 60V boost converter with 2.5A switch; no slave switch or output short protection; fixed 1.2V FB reference only. | Applicable for simpler boost-only designs without inverting capability or autonomous fault response. | Choose LT8330EFE#PBF for cost-sensitive, single-output boost applications where fault protection is handled externally. |
Compared with LTC3891EFE#PBF and LT8330EFE#PBF, the LT3579IUFD#PBF uniquely integrates dual 42V switches, output short circuit detection with automatic PMOS disconnect, and dual-mode feedback for boost/inverting topologies - making it optimal for compact, self-protecting bias supplies where board space and reliability are critical.
Availability
LT3579IUFD#PBF is available at Aetrix Electronics and suitable for vacuum fluorescent display (VFD) bias supplies, TFT-LCD panel power, and automotive engine control unit (ECU) local power requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT3579IUFD#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, communications, and automotive markets.
The LT3579IUFD#PBF belongs to Analog Devices' Power by Linear™ family of monolithic DC/DC converters, engineered specifically for high-reliability local power generation in space- and thermal-constrained applications with stringent fault tolerance requirements.
FAQ
What is the maximum input voltage the LT3579IUFD#PBF can withstand?
The LT3579IUFD#PBF has an absolute maximum VIN rating of 40V for transient conditions, with guaranteed operation from 2.5V to 16V. Its internal input overvoltage lockout activates at 16.2V (minimum), disabling switching to protect downstream components. This makes the LT3579IUFD#PBF suitable for automotive 12V systems subject to load dump events.
Does the LT3579IUFD#PBF support inverting converter topology?
Yes, the LT3579IUFD#PBF natively supports inverting topology using its dual-switch architecture and negative feedback reference of 9mV. When configured as an inverter, the FB pin senses |VOUT| + 9mV, enabling stable regulation of negative outputs such as –12V at 1.2A from a 5V input - a capability confirmed in the device's typical application circuits and electrical characteristics table.
How does the LT3579IUFD#PBF provide output short circuit protection?
The LT3579IUFD#PBF implements output short circuit protection via Sample Mode: when FB falls outside regulation (e.g., <45mV for inverting mode), the IC forces both SW1 and SW2 on each cycle to sample inductor current. If sampled current exceeds 3.4A (SW1) or 6A (combined), FAULT pin pulls low, GATE goes high-impedance to turn off external PMOS, and CLKOUT disables - all within one switching cycle. This behavior is documented in the State Diagram and Operation–FAULT section.
Can the LT3579IUFD#PBF synchronize to an external clock?
Yes, the LT3579IUFD#PBF accepts external synchronization via the SYNC pin, which operates with TTL-compatible thresholds (low <0.4V, high >1.3V). When driven, it overrides the RT-set oscillator frequency and aligns switching edges. The CLKOUT pin then mirrors this synchronized frequency, enabling deterministic EMI reduction and multi-phase coordination - a feature explicitly specified in the Electrical Characteristics table under SYNC parameters.
What package type and thermal performance does the LT3579IUFD#PBF use?
The LT3579IUFD#PBF uses a 20-lead, 4mm × 5mm plastic QFN package with exposed thermal pad (Pin 21 = GND). Its thermal resistance is θJA = 34°C/W and θJC = 2.7°C/W, requiring the exposed pad to be soldered to a PCB ground plane for optimal heat dissipation. This package enables higher power density than the TSSOP variant while maintaining compatibility with standard reflow profiles.
LT3579IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Boost, Charge Pump, Cuk, Flyback, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 1.215V
- Voltage - Output (Max):
- 42V (Switch)
- Current - Output:
- 6A (Switch)
- Frequency - Switching:
- 200kHz ~ 2.5MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (4x5)
LT3579IUFD#PBF FAQ
1.How can I place an order for LT3579IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3579IUFD#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 LT3579IUFD#PBF reliable?
The price and inventory of LT3579IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3579IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT3579IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3579IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3579IUFD#PBF?
LT3579IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3579IUFD#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 LT3579IUFD#PBF?
For technical support, including LT3579IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3579IUFD#PBF requirements.
6.How does Aetrix verify that LT3579IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3579IUFD#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 LT3579IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT3579IUFD#PBF?
All LT3579IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3579IUFD#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 LT3579IUFD#PBF part is unused and in its original packaging.
Return procedure for LT3579IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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