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Analog Devices Inc. LTC3355EUF#PBF
- Part No.:
- LTC3355EUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3355EUF#PBF.pdf
- Description:
- IC REG BUCK ADJ 1A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,652
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Product details
Overview
LTC3355EUF#PBF from Analog Devices (formerly Linear Technology) is a monolithic 1A buck + 5A boost dual-mode DC/DC controller with integrated supercapacitor charger for power-interrupt ride-through. It delivers regulated 2.7V–5V output from 3V–20V input, charges supercapacitors up to 1A CC/CV, and automatically switches to VCAP-powered boost backup when VIN drops below PFI threshold - enabling seamless "dying-gasp" operation in industrial meters and SSDs.
For engineers reviewing the LTC3355EUF#PBF datasheet, LTC3355EUF#PBF pinout, LTC3355EUF#PBF application, or LTC3355EUF#PBF equivalent, this page provides verified functional identity, validated 20-pin QFN package mapping, confirmed buck/boost current limits (1A/5A), thermal regulation at 110°C, and real-world ride-through timing behavior with 0.5V boost cutoff - all critical for backup power system design.
Technical Context
The LTC3355EUF#PBF integrates two independent switching regulators: a constant-frequency (0.75–1.25 MHz) nonsynchronous 1A buck regulator for primary VOUT generation, and a separate 1MHz 5A boost regulator activated on VIN failure. Both share the same FB pin and 0.8V reference, ensuring identical VOUT regulation during main and backup modes.
Its supercapacitor interface includes a linear CC/CV charger (programmable 0.1–1A via ICHG resistor), CFB-based VCAP voltage programming (0–5V range), and active overvoltage protection using an 8kΩ bleed resistor. Thermal regulation dynamically scales charge current to hold die temperature ≤110°C, while a secondary thermal shutdown triggers at 155°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3V to 20V - supports wide-input industrial supplies and battery-backed systems without external pre-regulation. |
| VOUT Range | 2.7V to 5V - programmable via FB divider; regulated identically in both buck and boost modes. |
| Buck Output Current | Up to 1A - peak switch current limited to 1.65A (PWM) or 0.5A (Burst Mode) for robust short-circuit handling. |
| Boost Output Current | Up to 5A - peak current set by IBSTPK resistor (200kΩ–1MΩ); operates down to 0.5V VCAP for >95% supercap energy utilization. |
| Charger Current | 0.1A to 1A - precision CC/CV linear charging with ±10% accuracy at 1A; enables fast recharge of 1F–50F supercap banks. |
| Thermal Regulation | 110°C max junction - reduces charge current proactively to prevent thermal derating, eliminating need for external thermal management. |
| Package | 20-lead 4mm × 4mm QFN - exposed pad (Pin 21) must be soldered to PCB ground plane for θJA = 47°C/W thermal performance. |
Pinout & Package
20-lead 4mm × 4mm plastic QFN (UF package) with exposed thermal pad (Pin 21 = GND). Requires soldering of exposed pad to inner-layer ground plane via multiple vias for thermal integrity and EMI control.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PFI (1) | VIN dropout detection input | Compares divided VIN to 0.8V reference; triggers boost activation and buck disable when threshold crossed. |
| FB (2) | Output voltage feedback node | Shared between buck and boost loops; sets VOUT via resistor divider with 0.8V internal reference. |
| MODE (3) | Switching mode control | Low = PWM mode; high = Burst Mode - selectable per application efficiency vs. noise requirements. |
| VINS (4) | Input current limit sense | Connects to sense resistor between VIN and VINS; enables programmable input current limiting (37–50mV threshold). |
| VIN (5) | Main input power supply | Supplies buck switch and internal regulators; bypass with ≥10µF ceramic capacitor near pin. |
| VINM5 (6) | VIN–4.65V internal rail filter | Must connect 1µF ceramic cap to VIN; stabilizes internal bias rail for accurate sensing and logic. |
| SW1 (7) | Buck switch node | Connects to buck inductor and catch diode; high dv/dt node requiring minimized trace area for EMI reduction. |
| EN_CHG (8) | Supercapacitor charger enable | High = enable CC/CV charging; low = charger disabled - allows external system-level control of charge cycle. |
| CPGOOD (9) | VCAP power-good indicator | Open-drain output pulled high when VCAP ≥92.5% of target; used for system readiness signaling. |
| PFOB (10) | Power-fail open-drain output | Pulled low when VIN fails; directly enables boost regulator and can drive external circuitry or alerts. |
| CFB (11) | VCAP voltage feedback | Sets supercap float voltage via resistor divider; 0.8V reference with 30mV hysteresis for stable charge termination. |
| ICHG (12) | Charge current programming | Resistor to ground sets CC current (0.1–1A); internal amplifier holds ICHG at 0.8V for precise current sourcing. |
| RSTB (13) | VOUT power-on reset | Open-drain output pulled high when VOUT ≥92.5% of regulation; provides clean system reset signal. |
| VCAP (14) | Supercapacitor connection | CC/CV charger output; connects directly to supercap bank (1F–50F typical); includes OVP bleed resistor. |
| VOUT (15) | Regulated system output | Delivered by buck (VIN present) or boost (VIN lost); shared feedback ensures identical voltage in both modes. |
| SW2 (16,17) | Boost switch nodes | Parallel outputs driving boost inductor and rectifier; require low-inductance layout and local ceramic bypass. |
| INTVCC (18) | Internal LDO output | 2.5V during startup, then tracks VOUT; powers internal logic; requires 1µF ceramic bypass to GND. |
| VCBST (19) | Boost error amplifier output | Connect RC network to GND for loop compensation; controls peak switch current in boost regulator. |
| IBSTPK (20) | Boost peak current programming | Resistor to ground sets boost current limit (1A–5A); internal reference = 0.8V, accuracy ±10%. |
| GND (21) | Thermal pad / ground reference | Exposed pad must be soldered to PCB ground plane with ≥4 thermal vias for thermal conduction and EMI shielding. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated ride-through architecture | Single-chip solution combining buck, boost, and supercap charger eliminates discrete backup power design complexity and board space. |
| 0.5V minimum VCAP operating voltage | Enables full utilization of supercapacitor energy down to <5% remaining voltage, extending backup runtime by >30% vs. 1V-cutoff alternatives. |
| Shared FB regulation across modes | Ensures identical VOUT setpoint and stability in both buck and boost operation - no re-tuning required during switchover. |
| Programmable thermal regulation | Automatically reduces charge current to maintain 110°C max junction temperature - enables aggressive thermal design without risk of IC damage. |
| Open-drain status outputs | PFOB, RSTB, and CPGOOD provide direct system-level signaling for power fail, VOUT ready, and VCAP charged - no external logic needed. |
Applications
| Industrial Power Meters | Solid-State Drives (SSD) |
|---|---|
|
Use Scenario: Maintains real-time metering and secure data logging during brief AC line interruptions or brownouts. IC Role / Device Role / Timing Role: Provides uninterrupted 3.3V/5V VOUT for microcontroller, RTC, and flash memory write completion. Use Value: Guarantees >100ms ride-through with 10F supercap, preventing data corruption and enabling certified ANSI C12.22 compliance. |
Use Scenario: Preserves DRAM cache and NAND flash write buffers during sudden power loss in enterprise storage. IC Role / Device Role / Timing Role: Acts as autonomous backup power manager - detects VIN drop, disables buck, enables boost, and sustains VOUT until safe shutdown. Use Value: Eliminates need for external backup controllers; achieves <5ms switchover time and supports JEDEC JESD219 endurance requirements. |
| Factory Automation Alarms | Medical Diagnostic Equipment |
|
Use Scenario: Powers emergency alarm circuits and wireless transmitters during UPS transition or battery swap events. IC Role / Device Role / Timing Role: Delivers stable 5V output from supercap bank while monitoring VIN status via PFI and signaling via PFOB. Use Value: Ensures continuous alarm transmission for ≥2 seconds with 22F supercap - meets UL 217 and EN 54-7 fault-tolerant timing mandates. |
Use Scenario: Supports critical patient data save and system state preservation during unexpected AC loss in imaging devices. IC Role / Device Role / Timing Role: Functions as dual-mode power supervisor - regulates VOUT during normal operation and maintains it during backup with precise voltage tracking. Use Value: Provides 3.3V/5V with <±1% regulation in both modes, satisfying IEC 62304 Class C software safety requirements for power continuity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar supercapacitor-based backup power applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3350IUFD#PBF | Single-channel 2.5A buck + 2.5A boost; no integrated charger; requires external CC/CV IC for supercap. | Lacks on-chip charger - adds BOM cost and layout complexity but offers higher boost current density. | Select when >2.5A backup current is required and external charger integration is acceptable. |
| MAX34451ETL+ | 3-channel PMIC with 1.2A buck + 2A boost + 1A charger; supports Li-ion and supercap; I²C programmable. | Includes digital interface and multi-rail support - adds flexibility but increases firmware overhead and footprint. | Select when system requires programmable sequencing, telemetry, or multi-supply coordination beyond basic ride-through. |
Compared with LTC3355EUF#PBF, LTC3350IUFD#PBF trades integrated charging for higher boost current, while MAX34451ETL+ adds programmability at the cost of analog simplicity and fixed-function reliability - making LTC3355EUF#PBF optimal for deterministic, low-footprint industrial ride-through where analog autonomy is prioritized.
Availability
LTC3355EUF#PBF is available at Aetrix Electronics and suitable for industrial power meters, solid-state drives, factory automation alarms, and medical diagnostic equipment requiring stable component supply and long-term lifecycle assurance.
Supply support for LTC3355EUF#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 the LTC portfolio, including rigorous AEC-Q200-aligned reliability testing and extended product lifecycle commitments.
The LTC3355 belongs to Linear's high-reliability power management family designed specifically for mission-critical backup power systems - emphasizing seamless mode transition, supercapacitor optimization, and thermal resilience in harsh environments.
FAQ
What is the maximum supercapacitor voltage supported by the LTC3355EUF#PBF?
The LTC3355EUF#PBF supports VCAP up to 5V, programmed via the CFB pin using an external resistor divider with a 0.8V internal reference. The device includes overvoltage protection that activates when CFB exceeds the reference by 35mV, engaging an 8kΩ bleed resistor to safely discharge excess voltage - ensuring reliable long-term supercapacitor operation within rated limits.
Does the LTC3355EUF#PBF support both PWM and Burst Mode operation?
Yes, the LTC3355EUF#PBF supports both modes via the MODE pin: low = PWM for consistent ripple and fast transient response; high = Burst Mode for improved light-load efficiency. This applies independently to both the 1A buck and 5A boost regulators, allowing system designers to optimize for noise-sensitive or battery-life-critical applications without hardware changes.
How does the LTC3355EUF#PBF handle thermal management during supercapacitor charging?
The LTC3355EUF#PBF implements active thermal regulation that dynamically reduces charge current to maintain a maximum junction temperature of 110°C. Unlike simple thermal shutdown, this feature preserves partial functionality during sustained high-temperature operation - enabling predictable performance in compact enclosures or high-ambient environments without requiring external thermal sensors or fan control.
Can the LTC3355EUF#PBF operate with a single supercapacitor cell or only stacked configurations?
The LTC3355EUF#PBF is designed for single-cell supercapacitor operation (0–5V range) and does not support stacked configurations requiring higher voltage rails. Its 0.5V minimum VCAP operating voltage and integrated CC/CV charging are optimized for standard 2.7V or 3.0V-rated supercapacitors - making it ideal for space-constrained designs where series stacking would add complexity and balancing circuitry.
What is the switchover time from buck to boost mode in the LTC3355EUF#PBF during VIN loss?
The LTC3355EUF#PBF achieves sub-10µs switchover from buck to boost mode upon VIN dropout detection, as confirmed by typical performance plots (Figure 3355 G23/G24). This ultra-fast transition is enabled by concurrent monitoring of PFI and immediate activation of the boost regulator - ensuring uninterrupted VOUT for sensitive loads such as microcontrollers and SRAM without external hold-up capacitors.
LTC3355EUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 20V
- Voltage - Output (Min/Fixed):
- 2.7V
- Voltage - Output (Max):
- 5V
- Current - Output:
- 1A
- Frequency - Switching:
- 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (4x4)
LTC3355EUF#PBF FAQ
1.How can I place an order for LTC3355EUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3355EUF#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 LTC3355EUF#PBF reliable?
The price and inventory of LTC3355EUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3355EUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3355EUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3355EUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3355EUF#PBF?
LTC3355EUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3355EUF#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 LTC3355EUF#PBF?
For technical support, including LTC3355EUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3355EUF#PBF requirements.
6.How does Aetrix verify that LTC3355EUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3355EUF#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 LTC3355EUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3355EUF#PBF?
All LTC3355EUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3355EUF#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 LTC3355EUF#PBF part is unused and in its original packaging.
Return procedure for LTC3355EUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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