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Analog Devices Inc. LTC3805IDD-5#PBF
- Part No.:
- LTC3805IDD-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LTC3805IDD-5#PBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,932
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Product details
Overview
LTC3805IDD-5#PBF from Analog Devices (formerly Linear Technology) is a current mode DC/DC controller IC designed to drive an external N-channel MOSFET in flyback, boost, and SEPIC topologies. It delivers ±1.5% output voltage accuracy, supports 70kHz–700kHz adjustable switching frequency via a single resistor, features programmable overcurrent protection with automatic restart, consumes only 360µA quiescent current in normal operation, and operates across –40°C to +125°C. It is used in automotive auxiliary power supplies requiring isolated, high-reliability 5V-to-12V/1A conversion.
For engineers reviewing the LTC3805IDD-5#PBF datasheet, LTC3805IDD-5#PBF pinout, LTC3805IDD-5#PBF application, or LTC3805IDD-5#PBF equivalent, key selection considerations include its 10-lead 3mm × 3mm DFN package, 4.5V VCC turn-on threshold, 100mV current sense voltage drop, RUN pin with precision hysteresis, and compatibility with high-input-voltage biasing schemes using its internal 9.5V shunt regulator.
Technical Context
The LTC3805IDD-5#PBF implements peak current-mode control with a programmable oscillator, integrated slope compensation current ramp (10µA), and dual-threshold RUN pin enabling precise input voltage sequencing. Its ITH pin serves as both error amplifier output and PWM comparator threshold reference, clamped between 0.7V and 1.9V for stable loop dynamics.
It features independent fault detection via OC pin (100mV trip threshold), soft-start/fault timeout timing controlled by SSFLT pin voltage (charged/discharged by 6µA/2µA currents), and gate drive capable of sourcing/sinking >1A peak current with 30ns rise/fall times into 3000pF load - all while maintaining micropower startup at 40µA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - enables isolated or non-isolated step-up conversion without topology-specific IC redesign. |
| Switching Frequency Range | 70kHz to 700kHz - set by single RFS resistor; allows optimization of magnetics size vs. efficiency and EMI. |
| Output Voltage Accuracy | ±1.5% - guaranteed over –40°C to +125°C for I-grade; ensures stable regulation under thermal stress in automotive/housekeeping rails. |
| VCC Operating Range | 4.7V to 8.8V (low-impedance source) or up to 25mA current-fed via internal 9.5V shunt - supports direct low-VIN supply or high-VIN resistor-biasing. |
| Current Sense Threshold | 100mV typical - minimizes power loss in sense resistor; compatible with standard 8mΩ/10mΩ MOSFET RDS(on)-based sensing. |
| Quiescent Current | 360µA normal / 40µA micropower startup - extends battery life in always-on auxiliary supplies and reduces no-load losses. |
| Operating Temperature | –40°C to +125°C - qualified for under-hood automotive and industrial embedded applications requiring extended thermal range. |
Pinout & Package
Package: 10-lead (3mm × 3mm) plastic DFN with exposed pad (Pin 11 = GND). Requires soldering of exposed pad to PCB ground plane for thermal performance and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-start & fault timeout timing node | Capacitor from SSFLT to GND sets soft-start ramp duration and post-fault retry delay; internal 6µA charge / 2µA discharge currents enable predictable timing. |
| ITH (2) | Error amplifier output / PWM threshold reference | Voltage clamped 0.7V–1.9V; directly controls peak switch current; serves as loop compensation point for external RC network. |
| FB (3) | Feedback input | Compares divided output voltage against 0.800V internal reference; enables precise output regulation independent of VCC or temperature drift. |
| RUN (4) | Enable/disable control with hysteresis | 1.207V turn-on / 1.170V turn-off thresholds; 5µA internal hysteresis current enables programmable VIN UVLO window via external divider. |
| FS (5) | Oscillator frequency set | Resistor from FS to GND programs fOSC = 24×10⁹/(RFS − 1500); supports wide frequency tuning without external clock. |
| SYNC (6) | External clock synchronization input | Accepts 70kHz–700kHz external clock; rising edge triggers GATE high; enables EMI reduction via fixed-frequency coordination. |
| ISENSE (7) | Current sense & slope compensation injection | Monitors MOSFET source current; injects 10µA linear ramp for duty-cycle-dependent slope compensation to prevent subharmonic oscillation. |
| OC (8) | Overcurrent fault detection | Trips at 100mV (adjustable with series resistor); initiates shutdown and automatic restart after timeout - protects against short-circuit and overload. |
| VCC (9) | Supply input with internal shunt regulator | Internally clamped to ~9.5V; accepts 4.7V–8.8V direct supply or high-VIN via resistor; sinks up to 25mA for robust biasing flexibility. |
| GATE (10) | N-MOSFET gate driver output | Drives external N-channel MOSFET gate with 30ns rise/fall into 3000pF; rail-to-rail swing (GND to VCC) ensures full enhancement. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable frequency with one resistor | Enables rapid layout reuse across 70–700kHz designs without changing IC or compensation - reduces BOM variants and qualification effort. |
| Programmable overcurrent protection with auto-restart | Prevents catastrophic failure during output shorts while enabling autonomous recovery - eliminates need for external latching circuitry or system-level watchdog intervention. |
| Low 100mV current sense threshold | Reduces sense resistor power loss by ≥50% vs. 200mV controllers - critical for high-current (>1A) boost converters where thermal management is constrained. |
| Integrated 9.5V VCC shunt regulator | Permits direct connection to VIN >12V (e.g., 24V automotive rail) via simple dropping resistor - avoids need for separate LDO or buck pre-regulator. |
| Run pin with precision hysteresis | Supports clean, bounce-free enable/disable sequencing across wide input ranges (e.g., 9–16V automotive) using only two resistors - improves system reliability during cold-crank events. |
Applications
| Automotive Auxiliary Power Supply | Telecom Housekeeping Rail |
|---|---|
Use Scenario: Generating isolated 5V/12V bias for infotainment microcontrollers and CAN transceivers from 12V battery rail with cold-crank tolerance down to 6V. IC Role / Device Role / Timing Role: Primary-side flyback controller managing transformer energy transfer, regulating output via optocoupler feedback, and enforcing safety-critical UVLO on RUN pin. Use Value: ±1.5% regulation stability over –40°C to +125°C ensures consistent MCU reset behavior; 40µA micropower startup enables reliable boot during battery recovery. |
Use Scenario: Providing 3.3V/5V standby power for base station control logic and EEPROM during main power loss or maintenance. IC Role / Device Role / Timing Role: Boost controller powering secondary rail from 48V telecom bus; uses SYNC pin to align switching with system clock for EMI compliance. Use Value: Adjustable 70–700kHz frequency avoids sensitive RF bands; 100mV sense threshold minimizes heat generation in compact telecom modules. |
| Isolated Industrial Sensor Interface | Power over Ethernet (PoE) Auxiliary Converter |
Use Scenario: Delivering galvanically isolated 5V to analog front-end sensors in factory automation systems with 24V DC input and stringent EMC requirements. IC Role / Device Role / Timing Role: Flyback controller implementing reinforced isolation barrier; leverages ISENSE slope compensation to maintain stability across variable load conditions. Use Value: Programmable soft-start (via SSFLT capacitor) prevents inrush-induced voltage droop on shared 24V bus; 360µA quiescent current preserves system efficiency at light loads. |
Use Scenario: Generating 3.3V/5V auxiliary power from PoE midspan PSE output (57V) for PD-side monitoring ICs and interface logic. IC Role / Device Role / Timing Role: SEPIC controller accepting wide input (37–57V) without polarity reversal; uses VCC shunt regulator to eliminate dedicated bias winding. Use Value: No minimum duty cycle limitation (6% min) ensures regulation even at lowest PoE voltage; RUN pin hysteresis rejects noise on long Ethernet cables. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3751EMSE#PBF | Higher VCC rating (40V), integrated high-side gate driver, no internal shunt regulator - requires external bias supply. | Targeted at high-input-voltage flyback/boost (e.g., 24–40V industrial), lacks micropower startup (250µA min) and RUN pin hysteresis. | Choose LT3751EMSE#PBF when input exceeds 12V and integrated gate driver simplifies layout; avoid if micropower startup or programmable UVLO is required. |
| UCC28083D | Fixed 1MHz frequency, no SYNC input, 1.25V FB reference, higher quiescent current (1.5mA), SOIC-8 package. | Designed for cost-sensitive AC/DC PFC + PWM combos; lacks adjustable frequency, soft-start programming, and wide temperature grade options. | Choose UCC28083D for high-volume, fixed-frequency applications where thermal range (–40°C to +105°C) and 100mV sense are not mandatory. |
Compared with LT3751EMSE#PBF and UCC28083D, the LTC3805IDD-5#PBF uniquely combines micropower startup (40µA), precision RUN pin hysteresis, and internal 9.5V shunt regulator - making it optimal for thermally demanding, battery-backed, or high-VIN-resistor-biased auxiliary supplies where layout simplicity and thermal robustness are prioritized over ultra-high frequency or integrated drivers.
Availability
LTC3805IDD-5#PBF is available at Aetrix Electronics and suitable for automotive auxiliary power supplies, telecom housekeeping rails, isolated sensor interfaces, and Power over Ethernet auxiliary converters requiring stable component supply across extended temperature and long production lifecycles.
Supply support for LTC3805IDD-5#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 automotive and industrial qualification standards.
The LTC3805-5 belongs to Linear's current-mode DC/DC controller family, engineered specifically for flexible, isolated, and non-isolated step-up conversion in space-constrained, thermally aggressive environments such as automotive ECUs and telecom infrastructure.
FAQ
What is the maximum input voltage that can safely power the LTC3805IDD-5#PBF?
The LTC3805IDD-5#PBF does not have a maximum input voltage limit on its VCC pin because it integrates a 9.5V shunt regulator. When powered through a resistor from a high-voltage source (e.g., 24V or 48V), the internal shunt limits VCC to ~9.5V as long as current remains ≤25mA. This allows safe operation from inputs far exceeding the 8.8V absolute maximum for low-impedance sources - a key enabler for automotive and telecom applications.
How does the RUN pin hysteresis work on the LTC3805IDD-5#PBF?
The LTC3805IDD-5#PBF RUN pin has built-in 35mV hysteresis (1.207V turn-on, 1.170V turn-off) and sources 5µA when enabled. This current flows through the external voltage divider, adding programmable hysteresis: falling VIN threshold = VRUNOFF × (R1+R2)/R2 − R1×5µA. This allows precise, noise-immune enable/disable sequencing across wide input ranges - critical for automotive cold-crank resilience.
Can the LTC3805IDD-5#PBF be synchronized to an external clock, and what are the timing requirements?
Yes, the LTC3805IDD-5#PBF supports external synchronization via the SYNC pin. It accepts clocks from 70kHz to 700kHz - matching its internal oscillator range. The rising edge of the external clock triggers the start of each switching cycle (GATE high), and pulse width is flexible. This capability enables EMI reduction through frequency coordination and deterministic timing in multi-rail systems.
What is the purpose of the SSFLT pin on the LTC3805IDD-5#PBF, and how is it configured?
The SSFLT pin on the LTC3805IDD-5#PBF serves dual functions: soft-start timing and fault timeout. An external capacitor from SSFLT to GND is charged at 6µA during startup (setting soft-start duration) and discharged at 2µA after an overcurrent fault (setting retry delay). With no capacitor, internal timers provide ~1.8ms soft-start and ~4.5ms fault timeout - enabling simple, reliable startup and self-recovery without additional components.
Does the LTC3805IDD-5#PBF support slope compensation, and how is it implemented?
Yes, the LTC3805IDD-5#PBF provides programmable slope compensation via its ISENSE pin, which injects a 10µA linear current ramp starting at 6% duty cycle and peaking at 80%. This ramp develops a voltage across an external resistor placed in series with the current sense element, counteracting subharmonic oscillation in continuous conduction mode - essential for stable operation in boost and flyback converters above 50% duty cycle.
LTC3805IDD-5#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Boost, Flyback, SEPIC
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 3.95V ~ 9.5V
- Frequency - Switching:
- 70kHz ~ 700kHz
- Duty Cycle (Max):
- 80%
- Synchronous Rectifier:
- No
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LTC3805IDD-5#PBF FAQ
1.How can I place an order for LTC3805IDD-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805IDD-5#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 LTC3805IDD-5#PBF reliable?
The price and inventory of LTC3805IDD-5#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3805IDD-5#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805IDD-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805IDD-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805IDD-5#PBF?
LTC3805IDD-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805IDD-5#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 LTC3805IDD-5#PBF?
For technical support, including LTC3805IDD-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805IDD-5#PBF requirements.
6.How does Aetrix verify that LTC3805IDD-5#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805IDD-5#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 LTC3805IDD-5#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805IDD-5#PBF?
All LTC3805IDD-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805IDD-5#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 LTC3805IDD-5#PBF part is unused and in its original packaging.
Return procedure for LTC3805IDD-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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