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Analog Devices Inc. LT3579IUFD-1#PBF
- Part No.:
- LT3579IUFD-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LT3579IUFD-1#PBF.pdf
- Description:
- IC REG BST CHARGE PUMP ADJ 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,762
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Product details
Overview
LT3579IUFD-1#PBF from Analog Devices is a dual-phase capable 6A, 42V monolithic boost/inverting DC/DC converter with integrated master/slave NPN switches (3.4A/2.6A), fault protection (output short, input overvoltage, overtemperature), and 200kHz–2.5MHz programmable switching frequency. It delivers 12V at 1.7A or –12V at 1.2A from 5V input and supports SEPIC/Flyback configurations in automotive ECU and TFT-LCD bias supplies.
For engineers reviewing the LT3579IUFD-1#PBF datasheet, LT3579IUFD-1#PBF pinout, LT3579IUFD-1#PBF application, or LT3579IUFD-1#PBF equivalent, this page provides verified pin functions, confirmed dual-phase timing behavior, validated fault response thresholds (750mV/1000mV FAULT pin), and real-world soft-start ramp characteristics (250kΩ internal charge path, 5.7–11.3µA SS current) critical for robust power-up sequencing and thermal-safe restart design.
Technical Context
The LT3579IUFD-1#PBF implements constant-frequency current-mode control with dual-phase capability enabled via CLKOUT phase inversion (180° out-of-phase, fixed 50% duty cycle), allowing interleaved operation with a second LT3579-1 to reduce input/output ripple and thermal stress. Its master/slave switch architecture supports combined 6A peak current with 0.78A/A current sharing ratio and 250mV typical VCE(SAT) at 5.5A.
Integrated fault management includes four independent FAULT1 triggers (SW1 overcurrent >3.4A, VIN OVLO >16.2V, SWx >42V, die temp >165°C) and external FAULT2 assertion, each initiating a controlled timeout sequence with SS pin charge/discharge cycling and GATE pin high-impedance transition to disable external PMOS disconnect switches.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Configuration | Dual NPN master/slave (3.4A/2.6A), combined 6A peak current limit - enables high-power boost/inverting topologies without external MOSFETs. |
| Input Voltage Range | 2.5V to 16V operating, 40V transient - supports wide automotive battery range and transient ride-through in ECU applications. |
| Switching Frequency | 200kHz to 2.5MHz (RT-programmable or external SYNC) - allows optimization of size vs. efficiency and EMI compliance in space-constrained designs. |
| Fault Detection Thresholds | FAULT pin low threshold: 750mV; high threshold: 1000mV - ensures noise-immune fault latching and clean recovery in noisy automotive environments. |
| Soft-Start Current | 5.7–11.3µA (charge/discharge) - defines precise ramp rate for external SS capacitor, enabling controlled inrush limiting during hot-plug events. |
| CLKOUT Duty Cycle | Fixed 50% (LT3579-1 variant) - guarantees deterministic phase relationship for dual-phase interleaving without external timing compensation. |
| Thermal Protection | Junction shutdown at 165°C (typical), TJMAX = 125°C - provides fail-safe thermal margin while maintaining continuous operation up to rated junction temperature. |
Pinout & Package
LT3579IUFD-1#PBF uses a 20-pin 4mm × 5mm plastic QFN package with exposed thermal pad (Pin 21, GND). The package features θJA = 34°C/W and θJC = 2.7°C/W, requiring soldering of the exposed pad to PCB ground for thermal integrity and EMI reduction.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB (Pin 1) | Positive/Negative Feedback Input | Accepts 1.215V reference for boost or 9mV for inverting configuration - sets output voltage via single resistor; bias current 83.3µA enables stable regulation across load/temperature. |
| VC (Pin 2) | Error Amplifier Output | Drives external compensation network (RC/CC) - determines loop stability and transient response for ±12V outputs with 1.7A/1.2A loads. |
| GATE (Pin 3) | PMOS Gate Drive Output | Pull-down current source (max 933µA) - controls external PMOS for output disconnect during fault; linear SS-voltage dependence enables soft turn-on. |
| FAULT (Pin 4) | Bidirectional Fault Indicator | Active-low open-collector output - pulls low internally on fault or accepts external low signal; requires 100kΩ pull-up for proper state detection. |
| VIN (Pin 5) | Main Input Supply | 2.5V–16V input rail with 40V absolute max - must be locally bypassed; internal UVLO disables chip below 2.3V (typical). |
| SW1 (Pins 6–10) | Master Switch Collector | Handles 3.4A min peak current - connects to inductor in boost/SEPIC; trace minimization required for EMI control. |
| GND (Pin 21 + Pins 8,9) | Power Ground | Exposes thermal pad (Pin 21) - must be soldered to PCB ground plane for thermal dissipation and noise immunity. |
| SW2 (Pins 11–15) | Slave Switch Collector | Handles 2.6A min peak current - tied to SW1 for 6A combined operation; shares same voltage rating (42V) and thermal path. |
| CLKOUT (Pin 16) | Synchronization Output | 50% duty cycle, 180° out-of-phase clock - synchronizes secondary converters in dual-phase systems; also serves as linear temperature monitor. |
| SHDN (Pin 17) | Shutdown Control | High-impedance input with 1.33V turn-on threshold - enables configurable UVLO using resistor divider; 30mV hysteresis prevents false triggering. |
| RT (Pin 18) | Frequency Set Resistor | Connects to ground to set fSW - 432kΩ yields 200kHz, 34kΩ yields 2.5MHz; no floating allowed. |
| SYNC (Pin 20) | External Clock Input | Accepts 0.4V–1.3V logic levels - overrides RT setting; drives internal oscillator when >1.3V high, reverts to free-running when <0.4V. |
| SS (Pin 19) | Soft-Start Capacitor Node | Charged by 250kΩ internal resistor - ramps to 1.8V then 2.1V; initiates timeout sequence during fault with controlled discharge to 50mV. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-phase synchronization | CLKOUT provides 180° out-of-phase, fixed 50% duty cycle signal - enables deterministic interleaving with second LT3579-1 to halve input ripple current and reduce thermal stress. |
| Integrated fault protection | Four autonomous FAULT1 triggers (SW overcurrent, VIN OVLO, SW overvoltage, overtemperature) plus external FAULT2 - eliminates need for discrete monitoring circuits in safety-critical automotive power rails. |
| Configurable undervoltage lockout | SHDN pin accepts resistor divider from VIN - allows user-defined turn-on voltage (e.g., 9V for automotive cold-crank immunity) without external comparators. |
| Output short-circuit recovery | SS pin executes timed charge/discharge cycle (1.8V → 2.1V → 50mV) after fault - enforces minimum off-time for thermal recovery and prevents latch-up during sustained shorts. |
| Low-loss switching | 250mV typical VCE(SAT) at 5.5A combined current - reduces conduction loss by >30% vs. discrete NPN solutions, improving efficiency in [email protected] boost applications. |
Applications
| Automotive Engine Control Unit (ECU) Power | TFT-LCD Bias Supplies |
|---|---|
Use Scenario: Generating stable 12V/–12V rails from 12V battery in engine bay with cold-crank (5.5V) and load-dump (40V) transients. IC Role / Device Role / Timing Role: Dual-phase boost/inverting controller managing master/slave switches and synchronizing auxiliary regulators via CLKOUT. Use Value: 40V transient tolerance and 165°C thermal shutdown protect against under-hood thermal runaway; dual-phase reduces input capacitor RMS current by 30%. |
Use Scenario: Providing high-voltage positive/negative bias for TFT panel gate drivers requiring precise ±15V at 100mA with fast transient response. IC Role / Device Role / Timing Role: Inverting converter with adjustable soft-start and fault-limited current delivery to prevent display damage during startup faults. Use Value: 9mV negative FB reference enables accurate low-voltage inverting regulation; GATE-driven PMOS disconnect isolates panel during FAULT events. |
| Vacuum Fluorescent Display (VFD) Bias Supplies | Industrial Local Power Supply |
Use Scenario: Generating 30V–60V anode supply and –10V cathode bias from 5V/12V system rail in point-of-sale terminals with strict EMI limits. IC Role / Device Role / Timing Role: Flyback-configured controller using SW1/SW2 for high-voltage isolation and RT-programmed 1.2MHz switching to shrink magnetics. Use Value: 42V switch rating supports 60V output with margin; 2.5MHz max frequency enables <10mm² solution size for compact displays. |
Use Scenario: Local 12V/–12V generation for FPGA I/O banks or analog front-ends in industrial PLCs where board space and thermal management are constrained. IC Role / Device Role / Timing Role: SEPIC converter with dual-phase interleaving to minimize input ripple and meet EN55022 Class B conducted EMI limits. Use Value: Combined 6A current capability supports multiple downstream rails; exposed QFN pad achieves 2.7°C/W θJC for direct heatsink attachment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost/inverting DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EUF#PBF | 4-switch synchronous buck-boost controller (no integrated switches); supports 4–36V input, up to 60V output; requires external MOSFETs and gate drivers. | Used where higher efficiency (>95%) and wider output range (±60V) are needed; lacks integrated fault protection and dual-phase sync. | Select LTC3789EUF#PBF when designing for >3A continuous output with synchronous rectification and external FET optimization. |
| LT8330EFE#PBF | Single-switch 6A boost converter (no inverting/SEPIC support); 3–40V input, 5–400V output; includes integrated 150V switch and spread-spectrum EMI reduction. | Preferred for high-voltage boost-only applications (e.g., LED drivers); lacks slave switch, dual-phase capability, and negative output support. | Choose LT8330EFE#PBF for cost-sensitive 400V boost designs where inverting topology and fault-triggered PMOS disconnect are not required. |
Compared with LTC3789EUF#PBF and LT8330EFE#PBF, the LT3579IUFD-1#PBF uniquely integrates dual NPN switches with 6A combined current, native inverting/SEPIC capability, and bidirectional FAULT signaling - making it the only option among the three that delivers fault-isolated ±12V outputs from a single IC in automotive-grade QFN packaging.
Availability
LT3579IUFD-1#PBF is available at Aetrix Electronics and suitable for automotive ECU power, TFT-LCD bias supplies, and industrial local power supply designs requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term lifecycle continuity.
Supply support for LT3579IUFD-1#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, and automotive markets since 1965.
The LT3579IUFD-1#PBF belongs to Analog Devices' Power by Linear™ family of monolithic DC/DC converters, designed specifically for high-reliability local power generation in harsh environments where fault resilience, thermal robustness, and multi-topology flexibility are mandatory.
FAQ
What distinguishes LT3579IUFD-1#PBF from the standard LT3579IUFD#PBF?
The LT3579IUFD-1#PBF includes dual-phase capability via its CLKOUT pin, which outputs a 180° out-of-phase, fixed 50% duty cycle signal synchronized to the internal oscillator. This enables interleaved operation with a second LT3579-1 device to reduce input/output ripple and thermal stress. The standard LT3579IUFD#PBF has a variable CLKOUT duty cycle (~42%) and lacks guaranteed phase inversion, making it unsuitable for deterministic dual-phase designs. Both share identical pinout, package, and fault protection features.
How does the FAULT pin behavior differ between LT3579IUFD-1#PBF and other boost controllers?
The FAULT pin on LT3579IUFD-1#PBF is bidirectional and actively pulled low internally during any FAULT1 event (SW overcurrent, VIN OVLO, SW overvoltage, overtemperature) or when externally driven below 750mV (FAULT2). Unlike open-drain-only controllers, it can both assert and detect faults, enabling system-level coordination. Upon fault detection, LT3579IUFD-1#PBF disables switches, forces GATE to high impedance, and initiates SS pin timeout cycling - all verified in the official datasheet Rev. B timing diagrams.
Can LT3579IUFD-1#PBF operate in inverting configuration with negative feedback?
Yes, LT3579IUFD-1#PBF supports inverting configuration using its dual feedback reference: the FB pin accepts either 1.215V for boost/SEPIC or 9mV for inverting topologies. When configured as an inverter, the feedback resistor is calculated as RFB = (|VOUT| + 9mV)/83.3µA, enabling precise negative output regulation (e.g., –12V at 1.2A from 5V input). This dual-reference architecture is explicitly documented in the Pin Functions section of the datasheet.
What is the maximum achievable switching frequency for LT3579IUFD-1#PBF?
The LT3579IUFD-1#PBF supports a maximum switching frequency of 2.5MHz when the RT pin is connected to ground via a 34kΩ resistor, as specified in the Electrical Characteristics table (Rev. B, page 3). This high-frequency operation allows use of smaller inductors and capacitors, reducing solution size. Operation above 2.5MHz is not supported - the datasheet confirms 200kHz–2.5MHz as the valid free-running range, with no characterization beyond 2.5MHz.
Does LT3579IUFD-1#PBF require external components for soft-start, and how is it controlled?
Yes, LT3579IUFD-1#PBF requires an external capacitor on the SS pin to set soft-start duration. The internal 250kΩ resistor charges this capacitor, with soft-start current specified as 5.7–11.3µA. The SS voltage ramps from 0V to 1.8V (enabling CLKOUT) then to ~2.1V (full operation). During fault, SS discharges to 50mV before recharging - all timing behavior is defined by the SS capacitor value and verified in the Typical Performance Characteristics plots (G05).
LT3579IUFD-1#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-1#PBF FAQ
1.How can I place an order for LT3579IUFD-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3579IUFD-1#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-1#PBF reliable?
The price and inventory of LT3579IUFD-1#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-1#PBF is usually 5 days.
3.What payment methods are accepted for LT3579IUFD-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3579IUFD-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3579IUFD-1#PBF?
LT3579IUFD-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3579IUFD-1#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-1#PBF?
For technical support, including LT3579IUFD-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3579IUFD-1#PBF requirements.
6.How does Aetrix verify that LT3579IUFD-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3579IUFD-1#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-1#PBF meets industry standards.
7.What is the process for return or replacement of LT3579IUFD-1#PBF?
All LT3579IUFD-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3579IUFD-1#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-1#PBF part is unused and in its original packaging.
Return procedure for LT3579IUFD-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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