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Analog Devices Inc. LTC3805HMSE-5#PBF
- Part No.:
- LTC3805HMSE-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3805HMSE-5#PBF.pdf
- Description:
- IC REG CTRLR MULT TOP 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:164
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Product details
Overview
LTC3805HMSE-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 across –40°C to 150°C junction temperature. It enables high-voltage input automotive auxiliary power supplies.
For engineers reviewing the LTC3805HMSE-5#PBF datasheet, LTC3805HMSE-5#PBF pinout, LTC3805HMSE-5#PBF application, or LTC3805HMSE-5#PBF equivalent, this page provides verified pin functions, thermal-grade-specific electrical limits, slope compensation implementation details, soft-start/fault timeout timing control, and real-world converter design constraints for flyback/boost/SEPIC configurations.
Technical Context
The LTC3805HMSE-5#PBF implements peak current-mode control using an internal error amplifier with transconductance of 333 µA/V, ITH clamping between 0.7V and 1.9V, and a 10µA programmable slope compensation ramp injected at ISENSE. Its oscillator uses a single external resistor (RFS) to set frequency from 70kHz to 700kHz, and supports synchronization via the SYNC pin with 2.9V minimum amplitude.
It integrates dual shutdown mechanisms: VCC undervoltage lockout (4.3V–4.7V turn-on, 3.75V–4.15V turn-off) and a precision RUN pin with 1.122V–1.292V threshold and user-programmable hysteresis. Overcurrent detection occurs at OC pin with 85mV–115mV trip range, while ISENSE senses peak current with only 100mV drop across the sense resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no internal power switch; requires external N-MOSFET. |
| Output Voltage Accuracy | ±1.5% over –40°C to 150°C (H-grade), enabling stable regulation in under-hood automotive environments. |
| Switching Frequency Range | 70kHz to 700kHz, set by one resistor on FS pin - allows EMI optimization and magnetics size trade-offs. |
| Quiescent Current | 360µA normal operation; 40µA micropower startup - extends battery life in always-on auxiliary supplies. |
| VCC Operating Range | 4.7V to 8.8V low-impedance supply, or high-VIN via internal 9.5V shunt regulator - simplifies bias design from 12V/24V/48V rails. |
| Current Sense Threshold | 100mV typical drop at ISENSE - minimizes conduction loss in high-current sense resistors. |
| Overcurrent Trip Range | 85mV to 115mV at OC pin - adjustable with external resistor for precise fault margin setting. |
| Soft-Start Control | Programmable via capacitor on SSFLT pin - also defines fault timeout duration before auto-restart. |
Pinout & Package
Package: 10-lead plastic MSOP (MSE) with exposed pad (Pin 11 = GND). Thermal resistance θJA = 45°C/W. Exposed pad must be soldered to PCB ground for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-start & fault timeout timing node | Capacitor to GND sets both startup ramp time and post-fault holdoff duration; internal 6µA charge / 2µA discharge currents. |
| ITH (2) | Error amplifier output / compensation point | Voltage clamped 0.7V–1.9V; controls peak current comparator threshold; connects to RC network for loop stability. |
| FB (3) | Feedback input | Compares divided output voltage against 0.800V reference (H-grade); ±1.5% accuracy enables tight regulation. |
| RUN (4) | Enable/disable control with hysteresis | 1.207V turn-on / 1.170V turn-off threshold; 5µA hysteresis current enables programmable VIN UVLO window. |
| FS (5) | Oscillator frequency set | Resistor to GND sets fOSC = 24×10⁹/(RFS − 1500); supports 70–700kHz range without trimming. |
| SYNC (6) | External clock synchronization input | Accepts 2.9V+ rising-edge trigger; aligns GATE edge to external source - critical for multi-rail noise reduction. |
| ISENSE (7) | Current sensing & slope compensation injection | Monitors MOSFET source current; injects 10µA linear ramp for duty-cycle-dependent slope compensation. |
| OC (8) | Dedicated overcurrent fault input | Independent of ISENSE path; trips at 85–115mV - enables robust short-circuit protection without compromising regulation. |
| VCC (9) | Supply input with internal shunt regulator | Internally clamped to ~9.5V; accepts 4.7–8.8V direct or high-VIN via series resistor - eliminates need for LDO. |
| GATE (10) | N-MOSFET gate driver output | Push-pull driver swings GND to VCC; 30ns rise/fall into 3000pF - supports fast-switching GaN or SiC FETs. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable slope compensation | 10µA programmable ramp injected at ISENSE pin - prevents subharmonic oscillation in >50% duty-cycle boost/flyback designs. |
| Two-stage shutdown control | Independent VCC UVLO (4.5V) and RUN pin (1.207V) with hysteresis - ensures clean start/stop sequencing in noisy automotive environments. |
| Auto-restart fault protection | OC-triggered shutdown followed by fixed 4.5ms internal timeout or user-defined SSFLT capacitor timeout - prevents latch-up during sustained overload. |
| Micropower startup mode | 40µA quiescent current when VRUN < VRUNON or VCC < VTURNON – 100mV - preserves battery charge during cold-cranking events. |
| High-temp rated H-grade operation | Guaranteed performance from –40°C to 150°C junction - qualified for engine compartment auxiliary power and PoE midspans. |
| Synchronizable oscillator | SYNC pin accepts external clock up to 700kHz - enables deterministic EMI spreading and multi-phase interleaving. |
Applications
| Automotive Auxiliary Power Supply | Telecom Housekeeping Converter |
|---|---|
|
Use Scenario: 12V/24V battery-fed isolated 5V/3.3V rail for infotainment microcontrollers and CAN transceivers in engine bay. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via optocoupler feedback; manages burst-mode transitions during sleep states. Use Value: ±1.5% H-grade accuracy maintains MCU brownout immunity at 150°C; 40µA micropower startup sustains memory retention during cranking. |
Use Scenario: 48V telecom rectifier-derived 12V/5V housekeeping supply powering management ASICs and fans. IC Role / Device Role / Timing Role: Boost controller driving discrete N-MOSFET; synchronized to system clock to minimize conducted EMI in dense backplane layouts. Use Value: 70–700kHz frequency adjustability enables optimal core loss vs. size trade-off; 100mV ISENSE threshold reduces heat in high-current sense resistors. |
| Isolated Industrial Sensor Interface | Power over Ethernet (PoE) Midspan Bias Supply |
|
Use Scenario: 24V industrial bus-powered isolated 3.3V supply for analog sensor front-ends in hazardous areas. IC Role / Device Role / Timing Role: SEPIC controller providing non-inverting buck-boost conversion with inherent input-output isolation via coupled inductor. Use Value: Adjustable slope compensation ensures stability across wide input range (18–36V); RUN pin hysteresis prevents nuisance shutdown during line dips. |
Use Scenario: Auxiliary 12V bias supply derived from PoE PSE output for midspan PD classification circuitry. IC Role / Device Role / Timing Role: Flyback controller operating from 44–57V PoE input; OC pin configured for fast short-circuit shutdown to protect upstream PSE. Use Value: Dual overcurrent paths (ISENSE + OC) enable fast fault response (<1µs) while maintaining regulation accuracy; SSFLT capacitor sets safe retry interval after cable fault. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode flyback/boost/SEPIC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3805IMSE-5#PBF | Same architecture and pinout; rated for –40°C to 125°C (I-grade) instead of –40°C to 150°C (H-grade). | Lower max junction temperature rating - suitable for cabin-mounted telecom or industrial modules but not under-hood automotive. | Select when ambient temperature stays below 125°C and cost sensitivity outweighs extended thermal margin. |
| LT3751EMSE#PBF | Higher integration: includes high-side gate driver, 75V VCC rating, and programmable soft-start; different pinout and control architecture. | Targeted at active clamp forward and resonant topologies; lacks native SEPIC support and has higher BOM count for basic flyback. | Choose for 75V-input systems requiring integrated gate drive, but expect layout redesign and revalidation due to non-pin-compatible interface. |
Compared with LTC3805IMSE-5#PBF, the LTC3805HMSE-5#PBF adds guaranteed operation up to 150°C junction temperature - critical for engine bay placement - while retaining identical electrical specs and pinout. Versus LT3751EMSE#PBF, it offers lower system cost and simpler biasing for standard flyback/boost, but requires external MOSFET and lacks high-voltage input capability.
Availability
LTC3805HMSE-5#PBF is available at Aetrix Electronics and suitable for automotive auxiliary power supplies, telecom housekeeping converters, isolated industrial sensor interfaces, and Power over Ethernet midspan bias supplies requiring stable component supply across extended temperature ranges.
Supply support for LTC3805HMSE-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 portfolio. Linear's legacy emphasizes precision, reliability, and ruggedized operation in demanding environments.
The LTC3805 family was designed specifically for flexible, high-efficiency DC/DC conversion in flyback, boost, and SEPIC topologies - targeting automotive, telecom, and industrial applications where external MOSFET control, wide input range, and thermal resilience are essential.
FAQ
What is the maximum junction temperature specification for the LTC3805HMSE-5#PBF?
The LTC3805HMSE-5#PBF is specified for continuous operation from –40°C to 150°C junction temperature. This H-grade rating is explicitly guaranteed per the datasheet's Electrical Characteristics table and Typical Performance plots, making it suitable for under-hood automotive and high-ambient industrial deployments where thermal derating is critical. The LTC3805HMSE-5#PBF achieves this through process and test validation, not just characterization.
How does the LTC3805HMSE-5#PBF implement slope compensation, and is it required for all applications?
The LTC3805HMSE-5#PBF injects a 10µA linear current ramp from the ISENSE pin, which develops slope compensation voltage across an external resistor. This feature is required for stable operation in flyback or boost topologies operating above 50% duty cycle to prevent subharmonic oscillation. The LTC3805HMSE-5#PBF datasheet confirms this ramp begins at 6% duty cycle and peaks at 80%, and its use is validated in the Typical Application circuits.
Can the LTC3805HMSE-5#PBF be powered directly from a 24V automotive rail?
Yes - the LTC3805HMSE-5#PBF can be powered from a 24V rail using a series resistor into the VCC pin. Its internal 9.5V shunt regulator sinks up to 25mA, limiting VCC to ~9.5V. For example, a 620Ω resistor drops ~14.5V at 23.4mA, keeping dissipation within safe limits. This method avoids needing a separate LDO and is confirmed in the "Powering the LTC3805-5" section of the datasheet.
What is the function of the OC pin versus the ISENSE pin on the LTC3805HMSE-5#PBF?
The ISENSE pin monitors MOSFET current for primary regulation and implements slope compensation, with a typical 100mV threshold. The OC pin provides independent overcurrent protection: it triggers immediate shutdown if voltage exceeds 85–115mV, bypassing the regulation loop. This dual-path architecture ensures fast fault response without compromising steady-state accuracy - a key distinction documented in the "Overcurrent Protection" section of the LTC3805HMSE-5#PBF datasheet.
Does the LTC3805HMSE-5#PBF support synchronization to an external clock, and what are the requirements?
Yes - the LTC3805HMSE-5#PBF supports synchronization via the SYNC pin, which accepts a rising-edge clock signal between 70kHz and 700kHz. The minimum amplitude is 2.9V, and the pulse width is flexible. Synchronization aligns the GATE switching edge to the external clock, reducing beat frequencies and enabling multi-phase interleaving - confirmed in the "Setting the Oscillator Frequency" section and Absolute Maximum Ratings table of the datasheet.
LTC3805HMSE-5#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) 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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LTC3805HMSE-5#PBF FAQ
1.How can I place an order for LTC3805HMSE-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805HMSE-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 LTC3805HMSE-5#PBF reliable?
The price and inventory of LTC3805HMSE-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 LTC3805HMSE-5#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805HMSE-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805HMSE-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805HMSE-5#PBF?
LTC3805HMSE-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805HMSE-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 LTC3805HMSE-5#PBF?
For technical support, including LTC3805HMSE-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805HMSE-5#PBF requirements.
6.How does Aetrix verify that LTC3805HMSE-5#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805HMSE-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 LTC3805HMSE-5#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805HMSE-5#PBF?
All LTC3805HMSE-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805HMSE-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 LTC3805HMSE-5#PBF part is unused and in its original packaging.
Return procedure for LTC3805HMSE-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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