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Analog Devices Inc. LTC3805HMSE#PBF
- Part No.:
- LTC3805HMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3805HMSE#PBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:432
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Product details
Overview
LTC3805HMSE#PBF from Analog Devices (formerly Linear Technology) is a current-mode DC/DC controller IC for flyback, boost, and SEPIC converters, designed to drive an external N-channel MOSFET in high-input-voltage applications (e.g., 36V–72V input to 5V/2A output). It features programmable switching frequency (70kHz–700kHz), ±1.5% reference accuracy, 360µA quiescent current, and operates across –40°C to +150°C junction temperature.
For engineers reviewing the LTC3805HMSE#PBF datasheet, LTC3805HMSE#PBF pinout, LTC3805HMSE#PBF application, or LTC3805HMSE#PBF equivalent, key selection considerations include its adjustable slope compensation, RUN pin with precision threshold and hysteresis, soft-start programmability via SSFLT capacitor, overcurrent protection with automatic restart, and compatibility with high-VIN biasing schemes using its internal 9.5V shunt regulator.
Technical Context
The LTC3805HMSE#PBF implements current-mode control using an error amplifier output at ITH to set the peak current comparator threshold, enabling fast line and load transient response. Its oscillator supports resistor-programmed frequency (via FS pin) and external synchronization (SYNC pin), with duty cycle limits of 6% min and 80% max at 200kHz.
It integrates dual protection logic: undervoltage lockout on VCC (turn-on at 8.4V, turn-off at 4.0V) and precision RUN pin control (1.207V turn-on, 1.170V turn-off with 5µA hysteresis current). Fault handling uses the SSFLT pin for both soft-start ramp-up and fault timeout recovery, with internal timers (1.8ms soft-start, 4.5ms timeout) extendable via external capacitor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temperature | –40°C to +150°C junction range - enables use in under-hood automotive and telecom power systems without derating. |
| Reference Voltage Accuracy | ±1.5% over full temp range - ensures stable 5V output regulation even at 150°C junction temperature. |
| Quiescent Current | 360µA normal operation / 40µA micropower startup - minimizes no-load power loss in always-on telecom supplies. |
| Oscillator Frequency Range | 70kHz to 700kHz via single RFS resistor - allows EMI optimization and transformer size reduction across wide input ranges. |
| VCC Shunt Regulator | 9.5V clamp (25mA max sink) - enables direct high-VIN biasing (e.g., 72V input) without external LDO or Zener. |
| Peak Current Sense Threshold | 100mV typical (85–115mV over temp) - sets precise MOSFET current limit independent of duty cycle with slope compensation support. |
| Overcurrent Trip Level | 100mV typical (85–115mV) at OC pin - provides fast short-circuit protection with external resistor programmability. |
| GATE Drive Rise/Fall Time | 30ns each (with 3000pF load) - supports fast-switching MOSFETs for high-efficiency flyback designs. |
Pinout & Package
Package: 10-lead plastic MSOP (MSE), 3mm × 3mm footprint, exposed pad (Pin 11) tied to GND for thermal and electrical performance. Rated θJA = 45°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (1) | Soft-Start & Fault Timeout Control | Capacitor from SSFLT to GND programs both startup ramp time and post-fault retry delay; internal 6µA charge / 2µA discharge currents. |
| ITH (2) | Error Amplifier Output / Compensation Node | Voltage-controlled current comparator threshold; clamped 0.7V–1.9V; connects to RC network for loop stability. |
| FB (3) | Feedback Input | Compares divided output voltage against 0.8V internal reference; sets regulated output voltage (e.g., 5V via 221k/13.7k divider). |
| RUN (4) | Enable/Shutdown Control | Precision UVLO input (1.207V ON / 1.170V OFF); hysteresis set by external divider's Thevenin resistance and 5µA current source. |
| FS (5) | Frequency Set | Resistor to GND sets oscillator frequency per fOSC = 24×10⁹/(RFS − 1500); supports 70–700kHz range. |
| SYNC (6) | External Clock Input | Accepts TTL/CMOS clock; rising edge triggers GATE high; enables synchronized multi-converter systems. |
| ISENSE (7) | Current Sense & Slope Compensation | Monitors MOSFET current via external sense resistor; injects 10µA linear ramp for adjustable slope compensation. |
| OC (8) | Overcurrent Detection | Second current sense input; trips shutdown if voltage exceeds 100mV; threshold adjustable with series resistor. |
| VCC (9) | Supply Input | Internally clamped to 9.5V; accepts up to 25mA sink; bypassed with ≥1µF ceramic cap adjacent to GND. |
| GATE (10) | MOSFET Gate Driver Output | Push-pull driver swinging GND to VCC; 30ns rise/fall into 3000pF; drives N-channel MOSFET gate directly. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable Frequency with Single Resistor | Enables EMI compliance tuning and transformer optimization without changing layout or components. |
| Adjustable Slope Compensation via ISENSE Pin | 10µA linear current ramp supports stable current-mode operation at high duty cycles (>50%) in flyback topologies. |
| Two-Stage Protection Logic (VCC + RUN) | Independent UVLO thresholds prevent erratic startup during brownout or slow-rising input rails in automotive systems. |
| Integrated Soft-Start and Fault Timeout on One Pin | SSFLT capacitor simultaneously controls output voltage ramp rate and auto-retry interval after overcurrent faults. |
| High-VIN Bias Capability via Internal Shunt Regulator | Eliminates need for external bias supply or LDO when VIN exceeds 9.5V - simplifies 48V telecom and 42V automotive designs. |
| ±1.5% Reference Accuracy Over Full Temp Range | Ensures tight output regulation without external trimming, critical for industrial and automotive power rail stability. |
Applications
| Telecom Power Supplies | 42V Automotive Power Supplies |
|---|---|
|
Use Scenario: 36V–72V input telecom rectifier powering 5V/2A base station subsystems with strict efficiency and reliability requirements. IC Role / Device Role / Timing Role: Primary-side flyback controller managing MOSFET switching, output regulation, and fault recovery without optocoupler feedback. Use Value: Internal 9.5V shunt regulator enables direct high-VIN biasing; ±1.5% reference ensures stable 5V rail across temperature; 360µA IQ minimizes standby loss. |
Use Scenario: Under-hood 42V battery-powered infotainment or ADAS module requiring isolated 5V/1.5A supply with extended temperature operation. IC Role / Device Role / Timing Role: High-temp-rated flyback controller providing isolated DC/DC conversion with robust overcurrent and thermal fault management. Use Value: H-grade (–40°C to +150°C) operation eliminates derating; RUN pin hysteresis prevents cycling during cold-crank transients; SSFLT capacitor enables controlled restart after load dump. |
| Isolated Industrial Equipment | Nonisolated Flyback Converters |
|
Use Scenario: Isolated 24V-to-5V/1A converter for PLC I/O modules where galvanic separation and EMC immunity are mandatory. IC Role / Device Role / Timing Role: Primary-side controller implementing current-mode regulation with synchronous rectification support and precise timing control. Use Value: Adjustable slope compensation stabilizes operation across wide input/output ratios; SYNC pin enables noise-free interleaving with other power stages. |
Use Scenario: Cost-sensitive nonisolated flyback (e.g., 36V–72V to 5V/2A) for LED drivers or auxiliary rails where transformer isolation is unnecessary. IC Role / Device Role / Timing Role: Compact, low-pin-count controller driving N-MOSFET with integrated gate driver and protection logic. Use Value: 10-lead MSOP package saves board space; programmable frequency avoids audible noise; low 40µA micropower start-up enables energy harvesting compatibility. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28C43DR | Fixed 100kHz frequency; no SYNC or slope compensation; lower IQ (1.5mA); 0°C–70°C only | Limited to fixed-frequency, lower-temp consumer/industrial apps; lacks programmability for EMI-sensitive designs | Choose UCC28C43DR only for cost-driven, non-automotive applications where frequency flexibility and high-temp operation are not required. |
| MAX17595ATP+T | Wider VIN range (4.5V–60V); integrated gate driver; no internal shunt regulator; requires external bias | Better suited for mid-range inputs; cannot directly replace LTC3805HMSE#PBF in >60V bias scenarios without redesign | Select MAX17595ATP+T when input is ≤60V and board space permits external bias circuitry; avoid for 72V telecom inputs. |
Compared with UCC28C43DR and MAX17595ATP+T, the LTC3805HMSE#PBF uniquely combines high-temperature rating (–40°C to +150°C), internal 9.5V shunt regulator for >60V biasing, and fully programmable slope compensation - making it the only option qualified for ruggedized telecom and under-hood automotive flyback controllers.
Availability
LTC3805HMSE#PBF is available at Aetrix Electronics and suitable for telecom power supplies, 42V automotive power supplies, and isolated industrial equipment requiring stable component supply across extended temperature and high-reliability environments.
Supply support for LTC3805HMSE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LTC3805 product line was designed specifically for high-efficiency, high-input-voltage flyback, boost, and SEPIC DC/DC converters requiring precision regulation, robust fault protection, and flexible biasing - targeting telecom, automotive, and industrial power systems.
FAQ
What is the maximum input voltage the LTC3805HMSE#PBF can support?
The LTC3805HMSE#PBF itself has no intrinsic VIN limit - its pins are isolated from primary-side voltages. Input voltage is constrained only by external components: the MOSFET's BVDSS rating, transformer insulation, and output capacitor voltage rating. In the documented 36V–72V to 5V/2A application, the LTC3805HMSE#PBF is powered via its internal 9.5V shunt regulator from VIN through a resistor, confirming safe operation with 72V input.
How does the RUN pin function on the LTC3805HMSE#PBF?
The RUN pin on the LTC3805HMSE#PBF provides precision enable/disable control with 1.207V turn-on and 1.170V turn-off thresholds, plus 5µA hysteresis current that interacts with the external voltage divider's Thevenin resistance. This allows programmable input voltage activation windows and prevents oscillation during slow-rising or noisy supply rails - critical for automotive cold-crank and telecom brownout resilience.
Can the LTC3805HMSE#PBF be synchronized to an external clock?
Yes, the LTC3805HMSE#PBF supports external synchronization via the SYNC pin (Pin 6). A rising edge on SYNC forces the oscillator to begin a new switching cycle - i.e., drives GATE high - allowing precise phase alignment with other converters or noise-sensitive system clocks. The external clock frequency must fall within 70kHz–700kHz, matching the device's programmable oscillator range.
What is the purpose of the SSFLT pin on the LTC3805HMSE#PBF?
The SSFLT pin (Pin 1) on the LTC3805HMSE#PBF serves dual functions: it controls soft-start duration via a capacitor charging at 6µA, and it manages fault timeout recovery via the same capacitor discharging at 2µA after overcurrent events. When CSS is added, soft-start completes when SSFLT reaches ~2.25V; after fault, restart occurs when SSFLT falls to ~0.7V - enabling one-component control of both startup behavior and fault recovery timing.
Does the LTC3805HMSE#PBF require an external current sense resistor?
Yes, the LTC3805HMSE#PBF requires two external current sense resistors: one (RSENSE) between the MOSFET source and GND for primary-side current sensing at ISENSE (Pin 7), and another (ROC) in series with the OC pin (Pin 8) to program overcurrent trip level. Both resistors interface directly with the controller's internal comparators and are essential for peak current mode control and short-circuit protection.
LTC3805HMSE#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-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Flyback
- 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#PBF FAQ
1.How can I place an order for LTC3805HMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805HMSE#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#PBF reliable?
The price and inventory of LTC3805HMSE#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#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805HMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805HMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805HMSE#PBF?
LTC3805HMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805HMSE#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#PBF?
For technical support, including LTC3805HMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805HMSE#PBF requirements.
6.How does Aetrix verify that LTC3805HMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805HMSE#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#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805HMSE#PBF?
All LTC3805HMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805HMSE#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#PBF part is unused and in its original packaging.
Return procedure for LTC3805HMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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