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Analog Devices Inc. LTC3805IDD#PBF
- Part No.:
- LTC3805IDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LTC3805IDD#PBF.pdf
- Description:
- IC REG CTRLR FLYBACK 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,447
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Product details
Overview
LTC3805IDD#PBF from Analog Devices (formerly Linear Technology) is a current-mode DC/DC controller IC designed specifically for flyback, boost, and SEPIC converters, driving 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 +125°C junction temperature.
For engineers reviewing the LTC3805IDD#PBF datasheet, LTC3805IDD#PBF pinout, LTC3805IDD#PBF application, or LTC3805IDD#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 dual-package compatibility (10-lead DFN).
Technical Context
The LTC3805IDD#PBF implements peak-current-mode control using an internal error amplifier (gm = 333 µA/V), ITH-based PWM modulation, and a programmable oscillator synchronized via SYNC pin. Its current comparator trips when ISENSE voltage exceeds a threshold set by ITH voltage, enabling fast line/load transient response.
It integrates a 9.5V internal shunt regulator on VCC (sinking up to 25mA), supports micropower startup (40µA), and uses dual undervoltage lockout thresholds: VTURNON = 8.4V / VTURNOFF = 4.0V on VCC and VRUNON = 1.207V / VRUNOFF = 1.170V on RUN - both with user-adjustable hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology Support | Flyback, boost, SEPIC - no internal power switch; requires external N-MOSFET and transformer/inductor. |
| Switching Frequency | 70kHz to 700kHz, set by single resistor on FS pin; synchronizable to external clock via SYNC pin. |
| Reference Accuracy | ±1.5% over –40°C to +125°C (I-grade), enabling stable 5V/2A output regulation in telecom and automotive supplies. |
| Quiescent Current | 360µA normal operation; 40µA micropower startup - critical for low-noise, high-efficiency biasing schemes. |
| VCC Shunt Regulator | 9.5V clamping (8.9V–9.9V range), sinking up to 25mA - allows direct high-VIN powering via series resistor. |
| Overcurrent Protection | Programmable OC threshold (85–115mV); automatic fault timeout (~4.5ms internal) and restart via SSFLT capacitor. |
| Soft-Start Control | Externally programmable via SSFLT capacitor; also defines fault timeout duration - enables controlled ramp-up and recovery. |
Pinout & Package
Package: 10-lead (3mm × 3mm) plastic DFN with exposed pad (Pin 11 = GND), rated for –40°C to +125°C operating junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SSFLT (Pin 1) | Soft-Start & Fault Timeout | Capacitor to GND sets soft-start ramp time and fault recovery delay; internal 6µA charge / 2µA discharge currents. |
| ITH (Pin 2) | Error Amplifier Output | Compensation node (0.7V–1.9V clamped); sets current comparator threshold - primary loop control point. |
| FB (Pin 3) | Feedback Input | Monitors output divider; regulates VOUT by servoing FB to 0.800V reference (±1.5% over temp). |
| RUN (Pin 4) | Enable Control | Precision UVLO input (1.170V–1.207V threshold); hysteresis set by external divider's Thevenin resistance. |
| FS (Pin 5) | Frequency Set | Resistor to GND programs fOSC = 24×10⁹/(RFS − 1500); supports 70kHz–700kHz range. |
| SYNC (Pin 6) | External Clock Input | Rising-edge triggered; overrides internal oscillator - enables multi-phase or noise-sensitive synchronization. |
| ISENSE (Pin 7) | Current Sense & Slope Comp | Measures MOSFET current; injects 10µA linear ramp for slope compensation - prevents subharmonic oscillation. |
| OC (Pin 8) | Overcurrent Detection | Secondary current sense path; trips at 85–115mV - independent of ITH, enabling robust short-circuit protection. |
| VCC (Pin 9) | Supply Input | Powered via internal 9.5V shunt regulator; bypass with ≥1µF ceramic cap adjacent to exposed GND pad. |
| GATE (Pin 10) | MOSFET Driver Output | Push-pull gate driver (30ns rise/fall into 3000pF); swings GND to VCC - drives N-channel MOSFET directly. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Frequency Range | 70kHz–700kHz via single RFS resistor - enables EMI optimization and magnetics size reduction. |
| Programmable Slope Compensation | 10µA linear current ramp from ISENSE pin - eliminates need for external ramp generator in high-duty-cycle designs. |
| Precision RUN Pin Threshold | 1.207V turn-on / 1.170V turn-off with 5µA hysteresis current - enables clean, noise-immune enable/disable sequencing. |
| Low Quiescent Current | 40µA micropower startup - supports trickle-charge biasing from output rail without compromising efficiency. |
| Automatic Fault Recovery | SSFLT capacitor controls both soft-start and fault timeout - eliminates need for external reset circuitry. |
Applications
| Telecom Power Supplies | Automotive 42V/12V Systems |
|---|---|
|
Use Scenario: 36V–72V input telecom rectifier supplying isolated 5V/2A for base station control logic. IC Role / Device Role / Timing Role: Flyback controller managing primary-side switching, feedback regulation, and overcurrent shutdown. Use Value: ±1.5% reference accuracy ensures stable 5V rail under wide input variation; 125°C rating supports chassis-mount thermal environments. |
Use Scenario: Non-isolated flyback converter in commercial vehicle ECU, stepping 42V battery down to 5V for microcontroller supply. IC Role / Device Role / Timing Role: High-voltage DC/DC controller with RUN pin sequencing for ignition-synchronized power-up. Use Value: Adjustable frequency avoids AM band interference; micropower startup enables cold-cranking operation below 6V battery. |
| Isolated Industrial Equipment | High-Voltage Test & Measurement |
|
Use Scenario: Isolated 24V-to-15V/1A supply for analog sensor front-end in factory automation PLC modules. IC Role / Device Role / Timing Role: Primary-side controller implementing optocoupler-free regulation via auxiliary winding feedback. Use Value: Programmable slope compensation stabilizes operation at >50% duty cycle; SSFLT capacitor enables inrush-limited start-up. |
Use Scenario: Bias supply for high-voltage probe amplifiers requiring ultra-low noise and precise 12V/500mA output. IC Role / Device Role / Timing Role: Low-quiescent-current flyback controller powering sensitive analog stages from 60V intermediate rail. Use Value: 360µA operating current minimizes self-heating drift; SYNC pin allows clock alignment to main system ADC sampling. |
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 1MHz frequency; no SYNC or slope compensation; 1.5% reference but only rated to 105°C. | Lacks programmable frequency and soft-start timing control - less flexible for EMI-sensitive or thermally constrained layouts. | Choose UCC28C43DR only if fixed-frequency operation and lower cost outweigh need for thermal margin and design flexibility. |
| MAX17595ATP+ | Integrated 1.2A MOSFET driver; supports wider VIN (4.5V–60V); includes built-in soft-start timer (no SSFLT cap required). | Higher integration reduces BOM count but limits max input voltage vs. LTC3805IDD#PBF's 72V+ capability via external components. | Choose MAX17595ATP+ for compact 12V–48V systems where layout space is critical and 72V+ input is unnecessary. |
Compared with UCC28C43DR and MAX17595ATP+, the LTC3805IDD#PBF offers superior thermal range (–40°C to +125°C), full programmability (frequency, slope comp, soft-start, OC threshold), and higher input voltage scalability - making it optimal for ruggedized telecom and industrial flyback designs.
Availability
LTC3805IDD#PBF is available at Aetrix Electronics and suitable for telecom power supplies, automotive 42V/12V systems, and isolated industrial equipment requiring stable component supply across extended temperature ranges.
Supply support for LTC3805IDD#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 with rigorous reliability testing and long-term product support.
The LTC3805IDD#PBF belongs to Linear's legacy high-voltage current-mode controller family, engineered for robust flyback, boost, and SEPIC topologies in demanding telecom, automotive, and industrial power applications.
FAQ
What is the maximum input voltage supported by the LTC3805IDD#PBF?
The LTC3805IDD#PBF itself has no intrinsic input voltage limit - its pins are isolated from VIN/VOUT. The practical maximum input is determined by external components: MOSFET BVDSS, transformer insulation, and input capacitor voltage rating. In typical 36V–72V applications, the LTC3805IDD#PBF is powered via its internal 9.5V shunt regulator from VIN through a series resistor.
How does the RUN pin function on the LTC3805IDD#PBF?
The RUN pin on the LTC3805IDD#PBF provides precision enable/disable control with 1.207V turn-on and 1.170V turn-off thresholds, plus 5µA hysteresis current. When used with an external resistor divider from VIN, it enables clean power sequencing - for example, delaying LTC3805IDD#PBF startup until input voltage stabilizes above 36V in telecom systems.
Can the LTC3805IDD#PBF be synchronized to an external clock?
Yes, the LTC3805IDD#PBF supports external synchronization via its SYNC pin (Pin 6). A rising edge on SYNC forces the start of a new switching cycle - i.e., GATE goes high - allowing noise-sensitive applications to align switching with system clocks or avoid specific EMI bands. The SYNC signal must be 2.9V minimum amplitude and operate between 70kHz and 700kHz.
What is the purpose of the SSFLT pin on the LTC3805IDD#PBF?
The SSFLT pin (Pin 1) on the LTC3805IDD#PBF serves dual functions: it controls soft-start timing via an external capacitor that charges at 6µA, and it defines fault timeout duration by discharging at 2µA after overcurrent events. This eliminates need for separate timers - one capacitor manages both startup ramp and automatic restart behavior in the LTC3805IDD#PBF.
Does the LTC3805IDD#PBF include integrated slope compensation?
Yes, the LTC3805IDD#PBF provides integrated slope compensation via a 10µA linear current ramp injected from the ISENSE pin (Pin 7). This ramp develops voltage across an optional external resistor, compensating for subharmonic oscillation in continuous-conduction-mode flyback designs - eliminating external ramp generators while maintaining stability at high duty cycles.
LTC3805IDD#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-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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LTC3805IDD#PBF FAQ
1.How can I place an order for LTC3805IDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3805IDD#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#PBF reliable?
The price and inventory of LTC3805IDD#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#PBF is usually 5 days.
3.What payment methods are accepted for LTC3805IDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3805IDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3805IDD#PBF?
LTC3805IDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3805IDD#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#PBF?
For technical support, including LTC3805IDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3805IDD#PBF requirements.
6.How does Aetrix verify that LTC3805IDD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3805IDD#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#PBF meets industry standards.
7.What is the process for return or replacement of LTC3805IDD#PBF?
All LTC3805IDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3805IDD#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#PBF part is unused and in its original packaging.
Return procedure for LTC3805IDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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