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Analog Devices Inc. LTC3805EMSE-5#PBF
- Part No.:
- LTC3805EMSE-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3805EMSE-5#PBF.pdf
- Description:
- IC REG CTRLR MULT TOP 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,245
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Product details
Overview
LTC3805EMSE-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 - used in automotive auxiliary power supplies and isolated telecom housekeeping rails.
For engineers reviewing the LTC3805EMSE-5#PBF datasheet, LTC3805EMSE-5#PBF pinout, LTC3805EMSE-5#PBF application, or LTC3805EMSE-5#PBF equivalent, key selection considerations include its 10-lead MSOP package, 4.5V VCC undervoltage lockout, 100mV current sense threshold, RUN pin with 1.207V turn-on threshold and user-adjustable hysteresis, and compatibility with high-side gate drive in non-isolated boost or isolated flyback configurations.
Technical Context
The LTC3805EMSE-5#PBF implements peak current-mode control using an internal error amplifier with transconductance of 333µA/V, ITH pin clamped between 0.7V and 1.9V for loop compensation, and a dedicated current comparator that trips when ISENSE exceeds a voltage proportional to ITH. Slope compensation is provided by a programmable 10µA ramp injected at ISENSE, enabling stable operation across wide duty cycles.
It integrates dual shutdown mechanisms: VCC UVLO (4.5V turn-on / 4.0V turn-off) and precision RUN pin control (1.207V turn-on / 1.170V turn-off), with 5µA hysteresis current enabling user-defined input voltage hysteresis. Fault handling uses SSFLT pin-based soft-start (1.8ms internal, extendable with capacitor) and fault timeout (4.5ms internal, restart on SSFLT discharge to 0.7V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no built-in power switch; requires external N-MOSFET and transformer/inductor. |
| Output Voltage Accuracy | ±1.5% - achieved via 0.800V internal reference (E-grade, 0°C–85°C) and FB pin feedback loop. |
| Switching Frequency Range | 70kHz to 700kHz - set by single resistor from FS to GND; synchronizable to external clock via SYNC pin. |
| VCC Operating Range | 4.7V to 8.8V from low-impedance source, or up to 25mA current-fed via internal 9.5V shunt regulator. |
| Quiescent Current | 360µA normal operation; 40µA micropower startup - enables low-noise, low-power auxiliary rail design. |
| Current Sense Threshold | 100mV typical - sets peak switch current limit; adjustable via OC pin resistor for overload protection. |
| Undervoltage Lockout | VCC: 4.5V turn-on / 4.0V turn-off; RUN: 1.207V turn-on / 1.170V turn-off - ensures clean enable/disable sequencing. |
Pinout & Package
Package: 10-lead plastic MSOP (MSE), exposed pad (Pin 11) connected to GND for thermal and electrical performance. Pin pitch: 0.5mm. Body dimensions: 3mm × 3mm × 1.1mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-start & fault timeout timing node | Capacitor to GND sets soft-start ramp time and post-fault restart delay; internal 6µA charge / 2µA discharge currents. |
| ITH (2) | Error amplifier output / compensation point | Voltage-controlled PWM threshold (0.7V–1.9V range); connects to RC network for loop stability tuning. |
| FB (3) | Feedback input | Monitors output voltage divider; regulates to 0.800V reference; 20nA input bias enables high-resistor dividers. |
| RUN (4) | Enable/disable control input | 1.207V turn-on threshold with 5µA hysteresis current; supports VIN-referenced sequencing or external logic control. |
| FS (5) | Frequency set input | Resistor to GND programs oscillator frequency per fOSC = 24×10⁹/(RFS − 1500) Hz. |
| SYNC (6) | External clock synchronization input | Accepts 2.9V+ rising-edge-triggered clock; overrides internal oscillator for EMI reduction or multi-phase sync. |
| ISENSE (7) | Current sensing & slope compensation injection | Measures MOSFET source voltage; injects 10µA linear ramp for duty-cycle-dependent slope compensation. |
| OC (8) | Overcurrent fault detection input | Trips shutdown if voltage exceeds ~100mV; external resistor adjusts trip level independently of ISENSE path. |
| VCC (9) | Supply input | Powered from 4.7–8.8V low-Z source or high-VIN via series resistor + internal 9.5V/25mA shunt regulator. |
| GATE (10) | N-MOSFET gate driver output | Push-pull driver (30ns rise/fall into 3000pF); swings rail-to-rail between GND and VCC; 1A peak sink/source. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable soft-start with fault timeout | Single external capacitor on SSFLT controls both startup ramp and post-fault holdoff - eliminates need for separate timers. |
| Adjustable slope compensation | 10µA linear current ramp from ISENSE pin enables precise duty-cycle-dependent compensation without extra op-amps. |
| Dual independent shutdown inputs | VCC UVLO and RUN pin thresholds operate independently - allows flexible power sequencing and system-level enable control. |
| Low quiescent current micropower mode | 40µA startup current enables direct connection to battery-backed rails without significant drain during standby. |
| High-side gate drive capability | GATE pin drives N-MOSFET source-connected high-side switch in boost/SEPIC - no bootstrap capacitor required. |
Applications
| Automotive Auxiliary Power | Telecom Housekeeping Supply |
|---|---|
Use Scenario: Generating isolated 5V/3.3V rails from 12V vehicle battery for infotainment MCU, CAN transceivers, and sensor interfaces. IC Role / Device Role / Timing Role: Primary controller for flyback converter; regulates output via optocoupler feedback; provides precise enable sequencing via RUN pin tied to ignition signal. Use Value: ±1.5% regulation accuracy maintains MCU brown-out immunity; 4.5V VCC UVLO prevents erratic operation during cold-crank transients. |
Use Scenario: Providing bias power to control circuitry in 48V telecom rectifiers and PoE midspans where primary output is 54V. IC Role / Device Role / Timing Role: Boost controller generating 12V from 5V standby rail; synchronized to system clock via SYNC pin to reduce conducted EMI. Use Value: 70–700kHz frequency adjustability enables optimal magnetics selection for space-constrained modules; 100mV current sense minimizes power loss in sense resistor. |
| Isolated Industrial Sensors | Power over Ethernet (PoE) PD Interface |
Use Scenario: Powering isolated analog front-ends and ADCs in hazardous-area field transmitters with galvanic separation. IC Role / Device Role / Timing Role: Flyback controller with transformer-coupled feedback; RUN pin configured for remote enable/disable via 24V control line. Use Value: Adjustable RUN hysteresis prevents chatter during noisy industrial bus transitions; SSFLT capacitor enables controlled power-up of isolated domains. |
Use Scenario: Generating 3.3V/5V auxiliary rails in PoE-powered devices (e.g., IP cameras, VoIP phones) after 802.3af/at classification. IC Role / Device Role / Timing Role: SEPIC controller accepting wide input (37–57V) and delivering regulated output; OC pin protects against shorted secondary windings. Use Value: Internal 9.5V VCC shunt allows direct bias from PoE input without external LDO; 360µA quiescent current meets IEEE 802.3bt no-load efficiency requirements. |
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 |
|---|---|---|---|
| LT3751IMSE#PBF | Higher VCC rating (up to 100V), integrated high-voltage bias supply, fixed 100kHz frequency; no SYNC or programmable slope compensation. | Targeted at flyback LED drivers and high-input-voltage industrial converters; lacks soft-start programmability and RUN hysteresis control. | Select LT3751IMSE#PBF only when >60V input is required and fixed frequency suffices; LTC3805EMSE-5#PBF preferred for flexible low-voltage bias and precise sequencing. |
| UCC28086D | Fixed 1MHz frequency, no SSFLT pin, no RUN pin, lower VCC range (8V–15V), no internal shunt regulator - requires external bias supply. | Designed for cost-sensitive AC/DC PFC + LLC combos; lacks autonomous fault recovery and programmable UVLO hysteresis. | UCC28086D suits high-frequency, high-efficiency offline designs with dedicated bias; LTC3805EMSE-5#PBF better fits low-voltage, isolated, or battery-backed systems needing robust sequencing. |
Compared with LT3751IMSE#PBF and UCC28086D, the LTC3805EMSE-5#PBF uniquely combines wide-frequency adjustability, dual independent enable inputs, integrated soft-start/fault timeout timing, and high-voltage bias capability in a compact MSOP - making it optimal for space-constrained, multi-rail embedded power systems requiring design flexibility and reliability.
Availability
LTC3805EMSE-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 powered device (PD) designs requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3805EMSE-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 product support, datasheets, and application engineering for legacy Linear parts including the LTC3805 family.
The LTC3805 series is part of Linear's high-performance analog power controller portfolio, designed specifically for flexible, efficient, and robust DC/DC conversion in isolated and non-isolated topologies where precision regulation, low quiescent current, and programmable protection are critical.
FAQ
What is the maximum duty cycle supported by the LTC3805EMSE-5#PBF?
The LTC3805EMSE-5#PBF supports a maximum switch-on duty cycle of 95% at 200kHz. This enables high step-up ratios in boost and SEPIC configurations and accommodates wide input voltage ranges in flyback designs. Duty cycle is internally limited to prevent instability and ensure reliable current-mode operation across all operating conditions.
Can the LTC3805EMSE-5#PBF be powered directly from a 24V input?
Yes - the LTC3805EMSE-5#PBF can be powered from a 24V input using a series resistor into the VCC pin. Its internal 9.5V shunt regulator sinks up to 25mA, allowing safe operation as long as power dissipation in the resistor stays within limits. The LTC3805EMSE-5#PBF datasheet provides design equations and layout guidance for this configuration.
Does the LTC3805EMSE-5#PBF require an external current sense resistor?
Yes - the LTC3805EMSE-5#PBF requires an external current sense resistor connected between the MOSFET source and ground (or low-side switch node). The ISENSE pin monitors voltage across this resistor to implement peak current-mode control, while the OC pin uses the same node (optionally with a series resistor) for overcurrent protection.
What is the purpose of the SSFLT pin on the LTC3805EMSE-5#PBF?
The SSFLT pin on the LTC3805EMSE-5#PBF serves dual functions: it controls soft-start timing via an external capacitor that charges at 6µA, and it implements fault timeout by discharging at 2µA after overcurrent events. When SSFLT reaches ~2.25V, regulation begins; when it falls to ~0.7V after a fault, the LTC3805EMSE-5#PBF attempts automatic restart.
How does the RUN pin hysteresis work on the LTC3805EMSE-5#PBF?
The RUN pin on the LTC3805EMSE-5#PBF 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, allowing users to program additional hysteresis by selecting R1/R2 values - enabling precise control of input voltage window for reliable system enable/disable behavior.
LTC3805EMSE-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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LTC3805EMSE-5#PBF FAQ
1.How can I place an order for LTC3805EMSE-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805EMSE-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 LTC3805EMSE-5#PBF reliable?
The price and inventory of LTC3805EMSE-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 LTC3805EMSE-5#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805EMSE-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805EMSE-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805EMSE-5#PBF?
LTC3805EMSE-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805EMSE-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 LTC3805EMSE-5#PBF?
For technical support, including LTC3805EMSE-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805EMSE-5#PBF requirements.
6.How does Aetrix verify that LTC3805EMSE-5#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805EMSE-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 LTC3805EMSE-5#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805EMSE-5#PBF?
All LTC3805EMSE-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805EMSE-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 LTC3805EMSE-5#PBF part is unused and in its original packaging.
Return procedure for LTC3805EMSE-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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