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Analog Devices Inc. LTC3633AIUFD-2#PBF
- Part No.:
- LTC3633AIUFD-2#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3633AIUFD-2#PBF.pdf
- Description:
- IC REG BUCK ADJ 3A DL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,798
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Product details
Overview
LTC3633AIUFD-2#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic synchronous step-down regulator delivering 3A per channel across a 3.6V–20V input range, featuring current-mode control, 180° phase-shifted operation, and programmable 500kHz–4MHz switching frequency. It serves as a high-efficiency point-of-load power supply for FPGA, ASIC, and DSP core voltage rails in industrial and battery-powered systems.
For engineers reviewing the LTC3633AIUFD-2#PBF datasheet, LTC3633AIUFD-2#PBF pinout, LTC3633AIUFD-2#PBF application, or LTC3633AIUFD-2#PBF equivalent, key selection criteria include its dual 3A output capability, ±8% PGOOD accuracy, 0.6V reference with 0.594V–0.606V tolerance, 20ns minimum on-time, and QFN-28 (4mm × 5mm) thermal performance with θJA = 43°C/W.
Technical Context
The LTC3633AIUFD-2#PBF implements a controlled on-time, current-mode architecture with an internal PLL that locks switching frequency to either an internal oscillator (set by RT resistor) or external clock applied to MODE/SYNC. Its dual channels support independent enable (RUN1/RUN2), tracking/soft-start (TRACKSS1/TRACKSS2), and selectable 0°/180° phase alignment via PHMODE.
Each channel integrates high-side and low-side MOSFETs with 130mΩ/65mΩ RDS(ON), supports VON-referenced on-time scaling (0.6V–6V range), and delivers regulated outputs from 0.6V to 6V using external feedback dividers. Protection includes input overvoltage lockout at 22.5V (rising), overtemperature shutdown, short-circuit limiting (2.6A–4.5A valley current), and 40µs PGOOD filtering.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 20V - supports lithium-ion battery stacks (3S–5S) and standard 12V/5V intermediate bus systems. |
| Output Current per Channel | 3A continuous - enables single-chip dual-rail power for multi-core processors or memory subsystems. |
| Switching Frequency Range | 500kHz to 4MHz - adjustable via RT resistor; allows optimization of inductor size vs. efficiency trade-off. |
| Feedback Reference Voltage | 0.6V ±1% (0.594V–0.606V) - enables precise low-voltage regulation down to 0.6V with minimal dropout error. |
| Minimum On-Time | 20ns at PVIN = 4V - supports high step-down ratios (e.g., 12V→1.2V at 1MHz) without pulse-skipping instability. |
| Phase Shift Control | Selectable 0° or 180° between channels - reduces input/output capacitor RMS current and EMI peak amplitude. |
| Efficiency | Up to 95% - achieved at mid-load with optimized external components; Burst Mode extends light-load efficiency. |
Pinout & Package
Package: 28-lead (4mm × 5mm) plastic QFN with exposed PGND pad (Pin 29), rated for –40°C to +125°C junction temperature and θJA = 43°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PGOOD1 (Pin 1) | Channel 1 power-good status output | Open-drain signal pulled low when VFB1 deviates >±8% from 0.6V; releases at ±5% with 40µs filter - ensures clean system reset sequencing. |
| PHMODE (Pin 2) | Phase select input | Logic-high (INTVCC) forces 180° out-of-phase switching; logic-low forces in-phase operation - directly controls input capacitor stress and EMI profile. |
| RUN1 (Pin 3) | Channel 1 enable input | Active-high enable with 1.22V threshold (rising); <1.01V disables channel - supports sequenced power-up and fault isolation. |
| MODE/SYNC (Pin 4) | Mode select / external sync input | Ground = forced continuous mode; float/INTVCC = Burst Mode; external clock = synchronization - determines light-load efficiency vs. noise trade-off. |
| RT (Pin 5) | Oscillator frequency programming | Resistor-to-SGND sets fSW from 500kHz–4MHz; tied to INTVCC defaults to ~2MHz - enables deterministic frequency planning and EMI band avoidance. |
| RUN2 (Pin 6) | Channel 2 enable input | Independent enable with same thresholds as RUN1 - allows asymmetric channel activation for dynamic power management. |
| SGND (Pin 7) | Signal ground reference | Low-noise analog ground for feedback, compensation, and RT networks - must be isolated from PGND except at single-point connection. |
| PGOOD2 (Pin 8) | Channel 2 power-good status output | Duplicate functionality of PGOOD1 for second rail - enables independent monitoring of dual output health in safety-critical systems. |
| VFB2 (Pin 9) | Channel 2 feedback input | Connects to resistor divider to set output voltage; referenced to 0.6V internal bandgap - defines regulation accuracy and load transient response. |
| TRACKSS2 (Pin 10) | Channel 2 tracking/soft-start input | Sub-0.6V voltage forces output tracking; internal 1.4µA pull-up enables soft-start with external capacitor - prevents inrush current during power-up. |
| ITH2 (Pin 11) | Channel 2 error amplifier output | Compensation node for loop stability; connect RC network or tie to INTVCC for internal compensation - determines bandwidth and phase margin. |
| VON2 (Pin 12) | Channel 2 on-time voltage reference | Sets comparator trip point; tying to VOUT2 makes on-time proportional to output voltage - maintains constant frequency across VOUT range (0.6V–6V). |
| SW2 (Pins 13,14) | Channel 2 switch node | Drives external inductor; swings from ~–0.3V to PVIN2 - requires low-inductance layout and Kelvin connection to minimize shoot-through risk. |
| PVIN2 (Pins 15,16) | Channel 2 power input | Independent 3.6V–20V supply for high-side/low-side MOSFETs - enables split-input architectures or isolated bias supplies. |
| BOOST2 (Pin 17) | Channel 2 bootstrap supply | Floats above SW2 to drive high-side gate; connects to bootstrap capacitor (+) terminal - critical for proper high-side FET turn-on. |
| INTVCC (Pin 18) | Internal 3.3V regulator output | Powers control circuitry and gate drivers; requires ≥1µF ceramic decoupling to PGND - shuts down when both RUN pins are low. |
| BOOST1 (Pin 19) | Channel 1 bootstrap supply | Duplicate of BOOST2 for first channel - enables independent bootstrap capacitor placement and minimizes cross-talk. |
| SVIN (Pin 20) | Signal input supply | Powers internal LDO for INTVCC; accepts 3.6V–20V - separates control logic supply from power stage inputs for noise immunity. |
| PVIN1 (Pins 21,22) | Channel 1 power input | Independent 3.6V–20V supply for channel 1 MOSFETs - supports asymmetrical input configurations (e.g., different battery cells per channel). |
| SW1 (Pins 23,24) | Channel 1 switch node | Identical function to SW2; drives first external inductor - layout symmetry improves thermal balance and EMI cancellation in out-of-phase mode. |
| VON1 (Pin 25) | Channel 1 on-time voltage reference | Same function as VON2; ties to VOUT1 for VOUT-proportional on-time - ensures consistent frequency behavior across both regulated outputs. |
| ITH1 (Pin 26) | Channel 1 error amplifier output | Duplicate of ITH2 for channel 1 compensation - allows independent loop tuning for mismatched output loads or PCB parasitics. |
| TRACKSS1 (Pin 27) | Channel 1 tracking/soft-start input | Same function as TRACKSS2 - enables coordinated startup of dual rails or staggered sequencing via external RC timing. |
| VFB1 (Pin 28) | Channel 1 feedback input | Primary regulation node for first output; connects to resistor divider - defines DC accuracy and AC response of first power rail. |
| PGND (Pin 29) | Power ground | Exposed pad; must be soldered to PCB ground plane - provides low-impedance return path for high di/dt currents and primary thermal conduction path. |
Key Features
| Feature | Design Value |
|---|---|
| Controlled on-time current-mode architecture | Enables stable high-frequency operation with fast load transient response (<10µs recovery) and inherent cycle-by-cycle current limiting. |
| 180° phase-shifted dual-channel operation | Reduces input capacitor RMS current by up to 30% and lowers peak EMI emissions compared to in-phase switching. |
| Burst Mode® vs. forced continuous mode selection | Extends light-load efficiency to >85% at 10mA while maintaining low output ripple in forced mode for noise-sensitive applications. |
| 0.6V ±1% internal reference with ±0.002%/V line regulation | Ensures <±1% total output error over full input range and temperature, critical for precision core voltage regulation. |
| Integrated 130mΩ/65mΩ MOSFETs with 20ns min on-time | Eliminates external power switches and enables compact 12V→1.2V conversion at 2MHz without duty-cycle limitation. |
| Independent RUN, TRACKSS, and VON inputs per channel | Supports flexible power sequencing, output voltage tracking, and adaptive on-time scaling for varying VOUT requirements. |
Applications
| Industrial PLC I/O Modules | FPGA Core & Auxiliary Power |
|---|---|
Use Scenario: Providing tightly regulated 1.2V core and 2.5V auxiliary rails in space-constrained programmable logic controller backplanes. IC Role / Device Role / Timing Role: Dual-channel synchronous buck regulator delivering 3A each with independent soft-start and tracking to meet FPGA configuration sequencing requirements. Use Value: Eliminates need for two discrete regulators; 180° phase shift cuts input capacitance by 40% and reduces thermal hotspots in sealed enclosures. |
Use Scenario: Powering Xilinx Artix-7 or Intel Cyclone V FPGA banks requiring simultaneous 1.0V core, 1.8V transceiver, and 3.3V I/O rails. IC Role / Device Role / Timing Role: Monolithic dual-buck IC with TRACKSS inputs enabling precise voltage ramp coordination during configuration and reconfiguration events. Use Value: Achieves <±1% output accuracy across –40°C to +85°C ambient, meeting FPGA vendor VCCINT tolerance specs without external calibration. |
| Battery-Powered Test Equipment | Medical Imaging Sensor Subsystems |
Use Scenario: Generating 3.3V and 5V rails from a 3S Li-ion battery (9V–12.6V) in handheld oscilloscopes and multimeters. IC Role / Device Role / Timing Role: High-efficiency dual buck converter operating across full battery discharge curve with Burst Mode extending runtime at standby. Use Value: 95% peak efficiency at 2A load and <500µA quiescent current in sleep mode extend battery life beyond 8 hours per charge. |
Use Scenario: Supplying low-noise 1.8V and 3.3V rails to CMOS image sensor arrays and ADC front-ends in portable ultrasound probes. IC Role / Device Role / Timing Role: Dual regulator with forced continuous mode option and tight PGOOD window (±5%) ensuring clean power delivery during critical acquisition windows. Use Value: <10mVpp output ripple in forced mode meets medical-grade SNR requirements; independent RUN pins allow sensor-specific power gating. |
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 |
|---|---|---|---|
| MP8852GQ-Z from Monolithic Power Systems | Single-channel 6A output vs. dual 3A; fixed 500kHz frequency; no phase-shift or external sync capability. | Requires two ICs for dual-rail designs; lacks TRACKSS and independent RUN control. | Choose when only one high-current rail is needed and board area permits dual IC placement. |
| TPS544B25RJER from Texas Instruments | Dual 4A/channel; supports PMBus interface; 400kHz–2.2MHz frequency; no integrated VON scaling or Burst Mode. | Offers digital telemetry and margining but higher quiescent current (1.2mA vs. 13mA active, 500µA sleep). | Prefer when system-level power monitoring, fault logging, or remote voltage adjustment is required. |
Compared with MP8852GQ-Z and TPS544B25RJER, the LTC3633AIUFD-2#PBF uniquely combines dual 3A outputs, 180° phase shifting, VON-referenced on-time scaling, and sub-500µA Burst Mode current - making it optimal for compact, high-efficiency, analog-controlled dual-rail systems where digital interface overhead is undesirable.
Availability
LTC3633AIUFD-2#PBF is available at Aetrix Electronics and suitable for industrial PLCs, FPGA power supplies, battery-powered test equipment, medical imaging subsystems, and distributed power architectures requiring stable component supply and long-term manufacturability.
Supply support for LTC3633AIUFD-2#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, documentation, and manufacturing continuity for the LTC portfolio.
The LTC3633A series was designed specifically for high-density, high-efficiency dual-output point-of-load regulation in space-constrained industrial, medical, and test equipment applications - emphasizing thermal robustness, analog control flexibility, and seamless integration with legacy linear regulator footprints.
FAQ
What is the maximum input voltage rating for the LTC3633AIUFD-2#PBF?
The LTC3633AIUFD-2#PBF has an absolute maximum PVIN rating of 20V, with overvoltage protection triggering at 22.5V (rising) and releasing at 21.5V (falling). This protects internal MOSFETs during transient spikes while maintaining operation across the full 3.6V–20V nominal input range specified for reliable performance in 12V and multi-cell battery systems.
Does the LTC3633AIUFD-2#PBF support output voltage tracking between its two channels?
Yes, the LTC3633AIUFD-2#PBF supports precise output voltage tracking via dedicated TRACKSS1 and TRACKSS2 pins. Applying a shared ramp voltage below 0.6V to both pins forces each channel's FB input to servo to that voltage, enabling matched rise/fall times and eliminating sequencing mismatches - critical for FPGA and processor core/I/O rail coordination.
How does the PHMODE pin affect EMI performance in the LTC3633AIUFD-2#PBF?
The PHMODE pin directly controls EMI by selecting 0° (in-phase) or 180° (out-of-phase) switching between channels. When set to 180°, input capacitor ripple current cancels partially, reducing peak amplitude by up to 6dB and spreading spectral energy - verified in conducted EMI tests per CISPR 22 Class B limits with minimal additional filtering.
Can the LTC3633AIUFD-2#PBF operate with only one channel enabled?
Yes, the LTC3633AIUFD-2#PBF supports independent channel operation: pulling RUN1 low disables Channel 1 while Channel 2 remains fully functional with full 3A capability, and vice versa. This enables dynamic power scaling in systems where load demand varies significantly between rails, improving overall system efficiency without hardware modification.
What is the thermal resistance (θJA) of the LTC3633AIUFD-2#PBF in its QFN-28 package?
The LTC3633AIUFD-2#PBF in the 4mm × 5mm QFN-28 package has a measured θJA of 43°C/W under standard JEDEC 2-layer board conditions (2 oz copper, 2 in² exposed pad). This value assumes the exposed PGND pad (Pin 29) is fully soldered to a solid thermal plane - achieving this layout is mandatory to sustain 3A per channel continuously at +85°C ambient.
LTC3633AIUFD-2#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):
- 20V
- Voltage - Output (Min/Fixed):
- 0.6V
- Voltage - Output (Max):
- 6V
- 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)
LTC3633AIUFD-2#PBF FAQ
1.How can I place an order for LTC3633AIUFD-2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3633AIUFD-2#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 LTC3633AIUFD-2#PBF reliable?
The price and inventory of LTC3633AIUFD-2#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3633AIUFD-2#PBF is usually 5 days.
3.What payment methods are accepted for LTC3633AIUFD-2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3633AIUFD-2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3633AIUFD-2#PBF?
LTC3633AIUFD-2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3633AIUFD-2#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 LTC3633AIUFD-2#PBF?
For technical support, including LTC3633AIUFD-2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3633AIUFD-2#PBF requirements.
6.How does Aetrix verify that LTC3633AIUFD-2#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3633AIUFD-2#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 LTC3633AIUFD-2#PBF meets industry standards.
7.What is the process for return or replacement of LTC3633AIUFD-2#PBF?
All LTC3633AIUFD-2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3633AIUFD-2#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 LTC3633AIUFD-2#PBF part is unused and in its original packaging.
Return procedure for LTC3633AIUFD-2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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