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Analog Devices Inc. LTC3805EDD-5#PBF
- Part No.:
- LTC3805EDD-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LTC3805EDD-5#PBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,702
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Product details
Overview
LTC3805EDD-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, and operates from 4.7V–8.8V VCC or high-VIN bias via internal 9.5V shunt regulator - enabling use in automotive auxiliary power supplies.
For engineers reviewing the LTC3805EDD-5#PBF datasheet, LTC3805EDD-5#PBF pinout, LTC3805EDD-5#PBF application, or LTC3805EDD-5#PBF equivalent, key selection considerations include its 10-lead 3mm × 3mm DFN package, 100mV current sense threshold, micropower 40µA startup current, RUN pin with precision undervoltage lockout (1.207V turn-on), and synchronous capability for noise-sensitive systems.
Technical Context
The LTC3805EDD-5#PBF implements peak current-mode control using an internal error amplifier (333µA/V transconductance), programmable slope compensation (10µA ramp injected at ISENSE), and dual-threshold RUN pin logic with 35mV built-in hysteresis plus user-adjustable hysteresis via 5µA sourcing. Its oscillator uses a resistor-to-frequency transfer function (fOSC = 24×10⁹/(RFS − 1500)) and supports external synchronization via the SYNC pin.
Protection architecture integrates independent overcurrent detection (OC pin, 100mV threshold), fault timeout (4.5ms internal, extendable via SSFLT capacitor), and soft-start (1.8ms internal, programmable via SSFLT). The ITH pin serves as both loop compensation node and current comparator threshold input, clamped between 0.7V and 1.9V during regulation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VFB Reference | 0.800V ±1.5% - sets output voltage via external resistor divider; enables precise regulation across load and line variations. |
| fOSC Range | 70kHz to 700kHz - set by single RFS resistor; allows optimization of size vs. efficiency and EMI performance. |
| IQ (Normal) | 360µA - low quiescent current enables high light-load efficiency in battery-backed or standby systems. |
| IQ (Startup) | 40µA - micropower start-up mode extends hold-up time in capacitor-fed bias schemes. |
| VCC Clamp | 9.5V (1mA), 9.5V (25mA) - internal shunt regulator permits direct high-VIN biasing without external LDO. |
| VTURNON | 4.5V - VCC undervoltage lockout ensures gate driver operates only above minimum functional supply. |
| VRUNON | 1.207V - precision RUN pin threshold enables accurate input-voltage sequencing and brownout protection. |
| VISENSE Threshold | 100mV - low-sense-voltage operation reduces power loss in current-sense resistor and improves efficiency. |
Pinout & Package
Package: 10-lead (3mm × 3mm) plastic DFN with exposed pad (Pin 11 = GND). Thermal performance requires soldering exposed pad to PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-start & fault timeout timing node | Capacitor to GND programs soft-start ramp and post-fault restart delay; internal 6µA charge / 2µA discharge currents. |
| ITH (2) | Error amplifier output / current comparator threshold | Clamped 0.7V–1.9V; connects to RC compensation network; directly sets peak switch current limit. |
| FB (3) | Feedback input | Compares divided output voltage against 0.800V reference; closed-loop regulation point for output voltage accuracy. |
| RUN (4) | Enable/disable control with hysteresis | 1.207V turn-on / 1.170V turn-off thresholds; 5µA sourced current enables user-programmable VIN hysteresis. |
| FS (5) | Oscillator frequency set | Resistor to GND sets fOSC from 70kHz–700kHz; supports external clock sync via SYNC pin. |
| SYNC (6) | External clock input | Rising-edge triggered; overrides internal oscillator to synchronize switching and reduce EMI in multi-rail systems. |
| ISENSE (7) | Current sense & slope compensation injection | Monitors MOSFET source current; injects 10µA linear ramp for slope compensation in continuous conduction mode. |
| OC (8) | Dedicated overcurrent fault input | Independent 100mV threshold detects overload/short-circuit; triggers shutdown and automatic restart after timeout. |
| VCC (9) | Supply input with internal shunt regulator | Accepts 4.7V–8.8V low-impedance supply or high-VIN via series resistor; clamped to ~9.5V internally. |
| GATE (10) | N-channel MOSFET gate driver output | Push-pull driver capable of sourcing/sinking sufficient current for typical 1A gate charge; 30ns rise/fall times. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable frequency with single resistor | Enables precise EMI shaping and inductor size optimization without changing IC or layout. |
| Separate OC pin with automatic restart | Provides robust short-circuit protection independent of main current sensing path, eliminating latch-up risk. |
| Adjustable RUN pin hysteresis | Allows precise input-voltage sequencing control using only two resistors - no external comparators required. |
| Internal 9.5V VCC shunt regulator | Permits direct high-input-voltage biasing (e.g., 24V automotive rail) without external regulators or Zeners. |
| 100mV current sense threshold | Reduces power loss and thermal stress in sense resistor, improving efficiency in high-current boost/SEPIC designs. |
| Synchronous clock input (SYNC) | Enables deterministic switching alignment across multiple converters, critical for PoE and telecom power systems. |
Applications
| Automotive Auxiliary Power | Telecom Housekeeping Supply |
|---|---|
|
Use Scenario: Generating isolated 5V/12V bias rails from 12V/24V vehicle battery for infotainment, ADAS sensors, and CAN transceivers. IC Role / Device Role / Timing Role: Current-mode flyback controller regulating output voltage while rejecting wide input transients (load dump, cold crank). Use Value: ±1.5% VFB accuracy and 40µA micropower startup ensure stable microcontroller operation during engine cranking. |
Use Scenario: Providing 3.3V/5V auxiliary power to FPGA configuration, PHY management, and monitoring circuits in 48V telecom rectifiers. IC Role / Device Role / Timing Role: Boost controller delivering regulated output from partially discharged backup batteries or intermediate bus rails. Use Value: 70kHz–700kHz frequency adjustability allows EMI compliance in dense telecom chassis without filter redesign. |
| Isolated Industrial Sensors | Power over Ethernet (PoE) PD Bias |
|
Use Scenario: Generating galvanically isolated 3.3V supply for analog front-ends in hazardous-area pressure/temperature transmitters. IC Role / Device Role / Timing Role: SEPIC controller enabling output voltage > input (e.g., 24V out from 12V input) with inherent input-output isolation. Use Value: Dual-threshold RUN pin and programmable hysteresis support safe power-up sequencing in SIL2-certified sensor modules. |
Use Scenario: Deriving 5V/12V bias for PoE-powered device (PD) controllers and interface ICs from IEEE 802.3af/at PSE output. IC Role / Device Role / Timing Role: Flyback controller operating across wide input range (37–57V) with tight regulation under dynamic load steps. Use Value: 100mV ISENSE threshold minimizes sense resistor dissipation in space-constrained PD modules. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode flyback/boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3751EMSE#PBF | Higher VCC rating (100V), integrated high-side gate driver, no SYNC pin, fixed 100mV OCP threshold. | Targeted at high-input-voltage flyback (e.g., AC/DC offline), lacks programmable frequency and soft-start flexibility. | Select when input exceeds 40V or high-side drive is needed; avoid if SYNC or fine frequency tuning is required. |
| UCC28086DR | VFB = 2.5V, higher IQ (1.5mA), no internal VCC shunt, requires external bias, fixed 1MHz max fOSC. | Designed for cost-sensitive industrial SMPS; lacks micropower startup, RUN hysteresis, and OC pin independence. | Select for high-volume, non-battery-backed applications where 2.5V feedback simplifies divider design. |
Compared with LT3751EMSE#PBF and UCC28086DR, the LTC3805EDD-5#PBF offers superior startup efficiency (40µA), flexible biasing (9.5V shunt), and dedicated fault handling (separate OC pin), making it optimal for low-power, wide-input-range isolated DC/DC where reliability and design simplicity are prioritized over ultra-high input voltage tolerance.
Availability
LTC3805EDD-5#PBF is available at Aetrix Electronics and suitable for automotive auxiliary power supplies, telecom housekeeping rails, isolated industrial sensor interfaces, and Power over Ethernet (PoE) powered device biasing requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LTC3805EDD-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 full technical and manufacturing continuity for all Linear power products, including rigorous qualification and long-term supply commitment.
The LTC3805EDD-5#PBF belongs to Linear's high-precision current-mode controller family, engineered specifically for isolated and non-isolated DC/DC converters where accuracy, low quiescent current, and robust fault management are critical in automotive, telecom, and industrial environments.
FAQ
What is the maximum input voltage that can be applied to the VCC pin of the LTC3805EDD-5#PBF?
The LTC3805EDD-5#PBF VCC pin accepts up to 8.8V from a low-impedance source. When powered from higher voltages (e.g., 24V), a series resistor must be used - the internal 9.5V shunt regulator limits VCC to ~9.5V while sinking up to 25mA. Exceeding 25mA risks regulator thermal failure, so resistor value must ensure current stays within this limit across min/max input conditions. The LTC3805EDD-5#PBF datasheet specifies absolute maximum VCC as 8.8V for low-impedance sources and does not permit direct connection above that without current limiting.
Can the LTC3805EDD-5#PBF be synchronized to an external clock, and what are the electrical requirements for the SYNC pin?
Yes, the LTC3805EDD-5#PBF supports external synchronization via the SYNC pin (Pin 6). The SYNC signal must have a rising edge that triggers the start of each switching cycle, with amplitude ≥2.9V and compatible with TTL/CMOS logic levels. The acceptable SYNC frequency range matches the internal oscillator range: 70kHz to 700kHz. Pulse width is flexible, but duty cycle should avoid violating the minimum off-time required for proper current sensing blanking. This capability is confirmed in the LTC3805EDD-5#PBF Electrical Characteristics table and Typical Application schematics.
How does the RUN pin hysteresis work on the LTC3805EDD-5#PBF, and how is it programmed?
The LTC3805EDD-5#PBF RUN pin has built-in 35mV hysteresis (1.207V turn-on, 1.170V turn-off) and adds user-programmable hysteresis via a 5µA current source active during operation. When enabled, this current flows through the upper resistor (R1) of the VIN-to-RUN divider, lowering the effective turn-off threshold. The falling VIN threshold is calculated as VIN(RUN,FALLING) = VRUNOFF × (R1+R2)/R2 − R1×5µA. This allows precise brownout recovery points without external components. The LTC3805EDD-5#PBF Applications Information section provides the full derivation and example calculations.
What is the purpose of the separate OC pin on the LTC3805EDD-5#PBF, and how does it differ from ISENSE-based overcurrent protection?
The OC pin on the LTC3805EDD-5#PBF provides independent overcurrent detection with a dedicated 100mV threshold, separate from the main ISENSE path used for current-mode regulation. While ISENSE controls peak current during normal operation (clamped at ~100mV when ITH reaches 1.9V), the OC pin triggers immediate shutdown if sensed current exceeds its threshold - preventing damage during hard shorts or overload before duty cycle reduction becomes ineffective. This dual-path protection is explicitly documented in the LTC3805EDD-5#PBF Operation section and block diagram, ensuring robust fault coverage beyond standard current-mode limits.
Does the LTC3805EDD-5#PBF support slope compensation, and how is it implemented?
Yes, the LTC3805EDD-5#PBF supports adjustable slope compensation via a 10µA peak current ramp injected from the ISENSE pin (Pin 7). This linear ramp begins at 6% duty cycle and peaks at 80%, developing a voltage across an external resistor placed in series with the current sense element. The ramp compensates for subharmonic oscillation in continuous conduction mode (CCM) flyback/boost designs. Implementation details, including resistor calculation and timing alignment, are provided in the LTC3805EDD-5#PBF Applications Information section and confirmed in the Pin Functions description.
LTC3805EDD-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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LTC3805EDD-5#PBF FAQ
1.How can I place an order for LTC3805EDD-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805EDD-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 LTC3805EDD-5#PBF reliable?
The price and inventory of LTC3805EDD-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 LTC3805EDD-5#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805EDD-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805EDD-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805EDD-5#PBF?
LTC3805EDD-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805EDD-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 LTC3805EDD-5#PBF?
For technical support, including LTC3805EDD-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805EDD-5#PBF requirements.
6.How does Aetrix verify that LTC3805EDD-5#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805EDD-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 LTC3805EDD-5#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805EDD-5#PBF?
All LTC3805EDD-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805EDD-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 LTC3805EDD-5#PBF part is unused and in its original packaging.
Return procedure for LTC3805EDD-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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