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Analog Devices Inc. LTC3775IUD#PBF
- Part No.:
- LTC3775IUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3775IUD#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:948
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Product details
Overview
LTC3775IUD#PBF from Analog Devices (formerly Linear Technology) is a high-efficiency, voltage-mode synchronous step-down DC/DC controller driving all-N-channel MOSFETs from 4.5V to 38V input. It delivers precise 0.6V reference accuracy (±0.75%), supports 250kHz–1MHz programmable switching frequency, achieves <30ns minimum on-time for high step-down ratios, and features RDS(ON) or sense-resistor current sensing. It is used in telecom power supplies requiring fast transient response and tight output regulation.
For engineers reviewing the LTC3775IUD#PBF datasheet, LTC3775IUD#PBF pinout, LTC3775IUD#PBF application, or LTC3775IUD#PBF equivalent, key selection criteria include its wide VIN range, line feedforward compensation for fast line transients, cycle-by-cycle peak current limiting, thermally enhanced 3mm × 3mm QFN-16 package with exposed PGND pad, and automotive-grade temperature rating (–40°C to 125°C).
Technical Context
The LTC3775IUD#PBF implements leading-edge modulation voltage mode control with a patented line feedforward circuit that maintains constant modulator gain across input voltage variations, enabling stable loop behavior and fast line transient response. Its error amplifier provides 25MHz gain-bandwidth and ±0.75% reference accuracy over temperature, supporting Type 3 compensation networks for robust phase margin at LC resonance.
It integrates dual high-current gate drivers (TG/BG) with 1.5Ω/1.0Ω pull-down and 2.5Ω/2.5Ω pull-up on-resistances, enabling direct drive of low-Qg N-channel MOSFETs. Cycle-by-cycle current limiting is configurable via ILIMT (100μA sink) and ILIMB (10μA source) pins, supporting both RDS(ON) and discrete sense resistor topologies with independent threshold programming.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4.5V to 38V - supports 12V/24V/28V industrial and telecom inputs without pre-regulation |
| Reference Voltage | 0.6V ±0.75% over temperature - enables accurate output setting down to 0.6V with minimal drift |
| Min On-Time | <30ns - allows >95% step-down ratio (e.g., 24V→1.2V at 500kHz) without pulse skipping |
| Switching Frequency | 250kHz to 1MHz, programmable via FREQ pin resistor - balances efficiency, size, and EMI |
| Shutdown Current | 14μA typical - enables ultra-low-power standby in battery-backed systems |
| Temp Range | –40°C to +125°C junction - qualified for under-hood automotive and industrial environments |
| Package | 16-lead 3mm × 3mm QFN with exposed PGND pad - θJA = 68°C/W, requires PCB thermal pad for thermal reliability |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed PGND pad (Pin 17), rated for –40°C to +125°C operating junction temperature. Exposed pad must be soldered to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ILIMT (Pin 1) | Top-side current limit set point | 100μA internal sink current - sets VIN–SENSE threshold via external resistor to VIN |
| ILIMB (Pin 2) | Bottom-side current limit set point | 10μA internal source current - sets PGND–SW threshold via external resistor to SGND |
| FB (Pin 3) | Error amplifier inverting input | Virtual ground node for feedback divider - connects to VOUT via RA/RB network |
| COMP (Pin 4) | Error amplifier output | Drives line feedforward and PWM comparator - requires RC compensation network to FB |
| SS (Pin 5) | Soft-start control | 1μA internal current source charges external CSS - regulates VFB to SS voltage during ramp-up |
| FREQ (Pin 6) | Oscillator frequency set | Resistor to SGND programs fOSC from 250kHz to 1MHz - sets timing capacitor discharge rate |
| SGND (Pin 7) | Signal ground reference | Kelvin return for FB, SS, COMP, MODE/SYNC - must be isolated from PGND to avoid noise coupling |
| BG (Pin 8) | Bottom gate driver output | Swings PGND to INTVCC - drives gate of synchronous rectifier MOSFET |
| INTVCC (Pin 9) | Internal 5.2V LDO output | Powers gate drivers and logic - requires ≥4.7μF ceramic bypass to PGND |
| SENSE (Pin 10) | Top MOSFET current sense input | Connects to SW node for RDS(ON) sensing or to sense resistor drain - enables lossless current monitoring |
| VIN (Pin 11) | Main input supply | 4.5V–38V input - requires ≥1μF ceramic bypass to PGND near pin |
| SW (Pin 12) | Switch node | Connects to source of top MOSFET - serves as BOOST return and bottom current sense reference |
| TG (Pin 13) | Top gate driver output | Floating driver powered by BOOST - provides true high-side gate drive referenced to SW |
| BOOST (Pin 14) | Top gate charge pump supply | Decoupled to SW via 0.1μF ceramic - forms floating supply for TG driver |
| MODE/SYNC (Pin 15) | Pulse-skipping enable / sync input | 1.2V threshold - low = forced continuous mode; high = pulse-skipping; AC signal = oscillator sync |
| RUN/SHDN (Pin 16) | Enable/shutdown control | 1.22V enable threshold, 0.74V shutdown threshold - includes 1μA pull-up for default turn-on |
| PGND (Exposed Pad) | Power ground return | Return path for BG driver and VIN/INTVCC bypass caps - electrically isolated from SGND |
Key Features
| Feature | Design Value |
|---|---|
| Line feedforward compensation | Maintains constant modulator gain vs. VIN - eliminates need for complex loop re-tuning across input range |
| Programmable soft-start | External CSS capacitor sets linear VOUT ramp time - prevents inrush current and output overshoot |
| Cycle-by-cycle peak current limit | Independent ILIMT/ILIMB pins allow asymmetric top/bottom current thresholds - improves overload protection fidelity |
| Synchronizable oscillator | Accepts external clock on MODE/SYNC pin - enables EMI reduction via frequency dithering or system-level clock alignment |
| Overvoltage protection | Dedicated MAX comparator disables TG and enables BG on >10% VOUT overshoot - protects downstream loads without external components |
| Thermally enhanced QFN | Exposed PGND pad reduces θJA to 68°C/W - sustains full load at 125°C ambient with proper PCB copper area |
Applications
| Telecom Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: 48V backplane-to-3.3V/1.2V conversion in carrier-grade base station power shelves. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating intermediate bus voltages with fast line transient response to handle dynamic load steps. Use Value: 30ns min on-time enables 48V→3.3V conversion at 500kHz without pulse skipping, maintaining low output ripple and predictable EMI profile. | Use Scenario: 24V field power to isolated 5V/3.3V rails in programmable logic controller digital I/O modules. IC Role / Device Role / Timing Role: High-reliability step-down controller with automotive-grade temp rating and robust current limiting for harsh factory environments. Use Value: ±0.75% reference accuracy and line feedforward ensure <±1% output regulation across 24V±20% input variation and full temperature range. |
| Automotive ADAS Camera Module | Point-of-Load Server VRM |
Use Scenario: 12V vehicle battery to 1.8V/1.2V core power for CMOS image sensor and ISP in rear-view camera systems. IC Role / Device Role / Timing Role: Compact, thermally efficient buck controller mounted directly on camera PCB with minimal external components. Use Value: 3mm × 3mm QFN package with exposed PGND pad achieves <15°C/W thermal resistance, enabling 15A operation at 85°C ambient without heatsink. | Use Scenario: 12V intermediate bus to 0.85V CPU core voltage in enterprise server motherboards with strict transient response requirements. IC Role / Device Role / Timing Role: High-bandwidth voltage-mode controller supporting Type 3 compensation for >200kHz crossover and >60° phase margin. Use Value: 25MHz error amplifier GBW and programmable soft-start allow <100μs load-step recovery with <100mV droop at 20A/μs slew rate. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2918GL-Z | Current-mode control, fixed 600kHz fSW, no line feedforward, 4.5V–32V VIN | Lacks line feedforward and programmable frequency - less optimal for wide-VIN telecom apps with fast line transients | Prefer when cost-sensitive designs accept reduced line regulation and fixed frequency constraints |
| TPS53679RSBT | Voltage-mode control, 4.5V–16V VIN, integrated MOSFET drivers only (no external FET support) | Lower VIN max and integrated FETs limit use to sub-12V applications - not suitable for 24V/28V industrial inputs | Choose only for compact 5V/3.3V POL where integrated solution saves board space and thermal design is simplified |
Compared with MP2918GL-Z and TPS53679RSBT, the LTC3775IUD#PBF uniquely combines wide 4.5V–38V input range, programmable 250kHz–1MHz frequency, line feedforward compensation, and external N-FET support - making it the only option among the three qualified for high-ratio, high-input-voltage, automotive-temp applications requiring precise transient performance.
Availability
LTC3775IUD#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLC I/O modules, automotive ADAS camera systems, and point-of-load server VRMs requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3775IUD#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC3775IUD#PBF belongs to ADI's high-efficiency power management controller product line, designed specifically for demanding synchronous buck applications in telecom infrastructure, industrial automation, and automotive electronics where wide input range, precision regulation, and thermal robustness are critical.
FAQ
What is the maximum input voltage supported by the LTC3775IUD#PBF?
The LTC3775IUD#PBF supports an absolute maximum input voltage of 40V on the VIN pin, with recommended operating range from 4.5V to 38V. This wide range enables direct use with 24V and 28V industrial buses and 48V telecom systems with appropriate derating. Operation above 38V risks exceeding specified electrical characteristics and thermal limits, even if within absolute maximum ratings.
How does the LTC3775IUD#PBF achieve fast line transient response?
The LTC3775IUD#PBF achieves fast line transient response primarily through its patented line feedforward compensation circuit, which dynamically adjusts the PWM modulator gain to maintain constant loop gain across input voltage variations. Combined with a high-bandwidth 25MHz error amplifier and low 30ns minimum on-time, this architecture reduces line-induced output deviation to <1% under 10V/μs input steps - verified in typical application circuits at 500kHz switching frequency.
Can the LTC3775IUD#PBF operate with only RDS(ON) current sensing, or is a sense resistor required?
The LTC3775IUD#PBF supports both RDS(ON) current sensing (via SENSE pin connected to SW node) and discrete sense resistor sensing (via SENSE pin connected to resistor drain). RDS(ON) sensing maximizes efficiency by eliminating sense resistor losses, while the sense resistor option provides higher current limit accuracy - especially useful in high-precision overcurrent protection applications. No external components are required for basic RDS(ON) operation.
What is the purpose of the exposed pad (Pin 17) on the LTC3775IUD#PBF QFN package?
The exposed pad (Pin 17) on the LTC3775IUD#PBF QFN package is electrically connected to PGND and serves two critical functions: (1) it provides the primary thermal path to the PCB, reducing θJA from >100°C/W to 68°C/W when properly soldered; and (2) it acts as the low-impedance return path for the BG gate driver and high-current VIN/INTVCC bypass capacitors. Failure to solder this pad results in severe thermal derating and potential functional instability.
Does the LTC3775IUD#PBF support synchronization to an external clock, and how is it implemented?
Yes, the LTC3775IUD#PBF supports external clock synchronization via the MODE/SYNC pin (Pin 15). When an external logic-level clock signal (CMOS/TTL compatible) is applied to this pin, the internal oscillator locks to the external frequency within ±20% of its free-running value. The pin also serves dual function: DC voltage <1.2V forces continuous conduction mode, while >1.2V enables pulse-skipping - allowing single-pin configuration of both sync and operating mode.
LTC3775IUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 38V
- Frequency - Switching:
- 250kHz ~ 1MHz
- Duty Cycle (Max):
- 90%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC3775IUD#PBF FAQ
1.How can I place an order for LTC3775IUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3775IUD#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 LTC3775IUD#PBF reliable?
The price and inventory of LTC3775IUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3775IUD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3775IUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3775IUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3775IUD#PBF?
LTC3775IUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3775IUD#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 LTC3775IUD#PBF?
For technical support, including LTC3775IUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3775IUD#PBF requirements.
6.How does Aetrix verify that LTC3775IUD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3775IUD#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 LTC3775IUD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3775IUD#PBF?
All LTC3775IUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3775IUD#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 LTC3775IUD#PBF part is unused and in its original packaging.
Return procedure for LTC3775IUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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