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Analog Devices Inc. LTC3633IUFD#PBF
- Part No.:
- LTC3633IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3633IUFD#PBF.pdf
- Description:
- IC REG BUCK ADJ 3A DL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:708
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Product details
Overview
LTC3633IUFD#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic synchronous step-down regulator delivering up to 3A per channel from 3.6V–15V input, featuring controlled on-time current-mode architecture, 180° phase-shifted operation, and programmable 500kHz–4MHz switching frequency. It integrates two high-efficiency buck regulators with internal MOSFETs, 0.6V reference, and independent RUN/PGOOD pins - deployed in point-of-load power for FPGA, ASIC, and multi-rail embedded systems.
For engineers reviewing the LTC3633IUFD#PBF datasheet, LTC3633IUFD#PBF pinout, LTC3633IUFD#PBF application, or LTC3633IUFD#PBF equivalent, key selection considerations include dual-channel interleaved operation, ±8% PGOOD threshold, 28-pin 4mm × 5mm QFN package with exposed PGND pad, Burst Mode® vs forced continuous mode trade-offs, and VIN overvoltage lockout at 17.5V.
Technical Context
The LTC3633IUFD#PBF implements a constant-frequency, current-mode control loop with internal phase-locked loop (PLL) servoing of on-time to match internal or external clock edges. Each channel uses valley-current sensing via SW–PGND voltage drop and features independent ITH compensation pins for loop stability tuning.
Its dual-channel architecture supports 0° or 180° phase shift via PHMODE pin, enabling interleaved operation that reduces RMS input current and relaxes input capacitor requirements. The device includes integrated 2.5V/10mA LDO (V2P5), 3.3V internal regulator (INTVCC), and separate VIN1/VIN2 inputs allowing asymmetric supply configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 15V - supports dual-cell Li-ion and standard 5V/12V intermediate bus rails. |
| Output Current per Channel | 3A continuous - enables single-chip dual-rail power for processors or memory subsystems. |
| Switching Frequency Range | 500kHz to 4MHz - set by RT resistor; allows optimization between small magnetics (high-f) and efficiency (low-f). |
| Feedback Reference Voltage | 0.6V ±1% - enables precise low-voltage outputs (e.g., 0.9V, 1.2V) with standard resistor dividers. |
| Efficiency | Up to 95% - achieved at mid-load in forced continuous mode with optimized layout and components. |
| Phase Shift Control | 0° or 180° selectable via PHMODE pin - reduces input ripple and eases EMI filtering design. |
| Protection Features | VIN overvoltage lockout (17.5V), thermal shutdown, short-circuit protection, and PGOOD monitoring with 40µs filter. |
Pinout & Package
Package: 28-lead (4mm × 5mm) plastic QFN with exposed PGND pad (Pin 29), rated for –40°C to +125°C operating junction temperature (θJA = 43°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PGOOD1 / PGOOD2 | Open-drain power-good status output | Active-low signal indicating ±8% regulation window violation; releases after return to ±5% with 40µs glitch filter. |
| RUN1 / RUN2 | Channel enable input | High-enable logic: >1.22V activates channel; <1.01V disables with µA-level shutdown current. |
| PHMODE | Phase select control | Ground = in-phase; INTVCC = 180° out-of-phase interleaving - critical for input capacitor sizing. |
| MODE/SYNC | Mode select & sync input | Ground = forced continuous; float/INTVCC = Burst Mode®; external clock = synchronization + forced continuous. |
| RT | Oscillator frequency programming | Resistor-to-SGND sets fSW from 500kHz–4MHz; tied to INTVCC defaults to ~2MHz. |
| VFB1 / VFB2 | Feedback input | Connects to resistor divider; error amplifier compares to 0.6V reference for output regulation. |
| TRACKSS1 / TRACKSS2 | Tracking/soft-start control | Sub-0.6V voltage forces output tracking; internal 1.4µA pull-up enables soft-start with external capacitor. |
| ITH1 / ITH2 | Error amplifier output & compensation | Loop compensation node - connect RC network for stability; tie to INTVCC for internal default. |
| VON1 / VON2 | On-time voltage input | Sets comparator trip point; tying to VOUT makes on-time proportional to output voltage (valid for VOUT < 6V). |
| SW1 / SW2 | Switch node | Drives external inductor; swings from diode-drop below ground to VIN - requires low-inductance layout. |
| VIN1 / VIN2 | Power input per channel | Independent inputs allow different supply sources (e.g., 12V for one rail, 5V for another). |
| BOOST1 / BOOST2 | Floating gate driver supply | Bootstrap connection for high-side MOSFET drive; swing range ≈ INTVCC to VIN + INTVCC. |
| INTVCC | Internal 3.3V regulator output | Powers internal logic and drivers; disabled when both RUN pins are low; requires ≥1µF ceramic bypass. |
| V2P5 | 2.5V auxiliary LDO output | 10mA capable; bypass with ≥1µF ceramic; tie to INTVCC if unused. |
| SGND | Signal ground reference | Low-noise analog ground for feedback, compensation, and RT networks - separate from PGND. |
| PGND | Power ground (exposed pad) | Must be soldered to PCB plane for thermal dissipation and low-impedance return path for input/output capacitors. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-channel interleaved buck regulation | Enables 180° phase shift to halve effective input ripple current and reduce required bulk capacitance. |
| Controlled on-time current-mode architecture | Delivers fast transient response and stable operation across wide duty-cycle range (e.g., 5% at 2.25MHz). |
| User-selectable Burst Mode® or forced continuous operation | Extends light-load efficiency without sacrificing regulation accuracy or requiring external circuitry. |
| Integrated 2.5V/10mA LDO (V2P5) and 3.3V regulator (INTVCC) | Eliminates need for external bias supplies while supporting independent channel enable and sequencing. |
| Independent tracking, soft-start, and PGOOD per channel | Supports complex power sequencing in multi-rail systems (e.g., FPGA core/I/O voltage ramp control). |
| VIN overvoltage lockout and thermal protection | Automatically suspends switching at 17.5V VIN and resumes at 16.5V - protects internal MOSFETs during transients. |
Applications
| Telecom Line Cards | Industrial PLC Modules |
|---|---|
Use Scenario: Powering FPGA, DSP, and interface ICs on dense line cards with strict thermal and space constraints. IC Role / Device Role / Timing Role: Dual-rail point-of-load regulator providing 1.2V/3A and 3.3V/3A from 12V backplane. Use Value: Interleaved 180° operation reduces input capacitor count by 30–50% versus single-channel solutions, easing board area and cost. |
Use Scenario: Supplying isolated I/O modules and microcontroller subsystems in factory automation controllers. IC Role / Device Role / Timing Role: Primary DC-DC converter generating 5V and 2.5V rails from 24V industrial supply with robust overvoltage protection. Use Value: VIN OVLO (17.5V) prevents damage during 24V supply transients; PGOOD signals enable safe system reset sequencing. |
| Test & Measurement Equipment | Medical Imaging Subsystems |
Use Scenario: Providing ultra-low-noise, tightly regulated supplies for ADCs, DACs, and RF front-ends in bench instruments. IC Role / Device Role / Timing Role: Dual-channel buck supplying 1.8V analog and 3.3V digital rails with independent soft-start and tracking. Use Value: Independent TRACKSS pins enable synchronized ramp-up of analog/digital domains, minimizing startup glitches and measurement errors. |
Use Scenario: Powering image sensor arrays and real-time processing units in portable ultrasound or X-ray modules. IC Role / Device Role / Timing Role: High-reliability dual-buck delivering 1.1V/3A and 1.8V/3A from battery or adapter input with thermal fault reporting. Use Value: Overtemperature protection and PGOOD status support fail-safe shutdown in safety-critical diagnostic hardware. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MPQ4436-AEC1 from Monolithic Power Systems | Automotive-grade AEC-Q100 qualified; fixed 2.2MHz fSW; no external RT programming or phase shift control. | Targeted at automotive infotainment and ADAS; lacks independent tracking/soft-start per channel. | Select when AEC-Q100 compliance is mandatory and 180° interleaving is not required. |
| TPS544B25 from Texas Instruments | Single-channel 4A buck with PMBus interface; supports AVS and dynamic voltage scaling; no dual-channel integration. | Used where digital control and telemetry are needed; requires two devices for dual-rail implementation. | Select when system-level telemetry, margining, or adaptive voltage scaling outweighs integration benefits. |
Compared with MPQ4436-AEC1 and TPS544B25, the LTC3633IUFD#PBF uniquely delivers true dual-channel integration with user-programmable frequency, 180° phase control, and per-channel sequencing - reducing BOM count and PCB area in space-constrained industrial and test equipment.
Availability
LTC3633IUFD#PBF is available at Aetrix Electronics and suitable for telecom infrastructure, industrial automation, and medical imaging systems requiring stable component supply, extended temperature operation (–40°C to +125°C), and long-term production continuity.
Supply support for LTC3633IUFD#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 power management portfolio with rigorous qualification and long-term support.
The LTC3633IUFD#PBF belongs to Linear's monolithic synchronous buck regulator family, designed specifically for high-density, multi-rail point-of-load applications demanding efficiency, precision, and reliability in harsh environments.
FAQ
What is the operating temperature range for the LTC3633IUFD#PBF?
The LTC3633IUFD#PBF is specified for –40°C to +125°C junction temperature operation and is qualified for industrial applications. Its UFD QFN package has θJA = 43°C/W, and thermal performance depends on PCB copper area and airflow. Derating curves in the datasheet confirm full electrical specifications across this range, unlike the E-grade version which is only guaranteed to 85°C.
How does the LTC3633IUFD#PBF achieve 180° phase shift between channels?
The LTC3633IUFD#PBF achieves 180° phase shift by asserting a logic high on the PHMODE pin (tied to INTVCC), which configures the internal timing logic to align the falling edge of SW2 with the falling edge of SW1. This interleaving reduces input RMS current and eases input capacitor selection - confirmed in the datasheet's "Out-Of-Phase Operation" section and typical application schematics.
Can the LTC3633IUFD#PBF operate with different input voltages on VIN1 and VIN2?
Yes, the LTC3633IUFD#PBF supports independent input supplies: VIN1 powers Channel 1's MOSFETs and INTVCC LDO, while VIN2 powers Channel 2's MOSFETs only. This allows asymmetric configurations - for example, 12V on VIN1 and 5V on VIN2 - provided each stays within 3.6V–15V and meets minimum dropout requirements for the desired output voltages.
What is the purpose of the V2P5 pin on the LTC3633IUFD#PBF?
The V2P5 pin on the LTC3633IUFD#PBF provides a regulated 2.5V output capable of sourcing up to 10mA. It is intended for biasing external circuitry such as level shifters, ADC references, or optocouplers. When unused, it must be tied to INTVCC per the datasheet to disable the LDO and avoid floating node issues.
Does the LTC3633IUFD#PBF support external frequency synchronization?
Yes, the LTC3633IUFD#PBF supports external synchronization via the MODE/SYNC pin. Applying a clean CMOS clock signal (500kHz–4MHz) to this pin locks the internal PLL to the external source, forcing forced continuous mode and eliminating beat frequencies. The datasheet specifies SYNC VIH ≥ 0.95V and confirms synchronization behavior in the "OPERATION" section and typical performance plots.
LTC3633IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 15V
- Voltage - Output (Min/Fixed):
- 0.6V
- Voltage - Output (Max):
- 14.7V
- Current - Output:
- 3A
- Frequency - Switching:
- 500kHz ~ 4MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3633IUFD#PBF FAQ
1.How can I place an order for LTC3633IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3633IUFD#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 LTC3633IUFD#PBF reliable?
The price and inventory of LTC3633IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3633IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3633IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3633IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3633IUFD#PBF?
LTC3633IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3633IUFD#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 LTC3633IUFD#PBF?
For technical support, including LTC3633IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3633IUFD#PBF requirements.
6.How does Aetrix verify that LTC3633IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3633IUFD#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 LTC3633IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3633IUFD#PBF?
All LTC3633IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3633IUFD#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 LTC3633IUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3633IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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