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Analog Devices Inc. LTC3634IUFD#PBF
- Part No.:
- LTC3634IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Regulators
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3634IUFD#PBF.pdf
- Description:
- IC REG CONV DDR 2OUT 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,846
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Product details
Overview
LTC3634IUFD#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic synchronous step-down regulator optimized for DDR1/DDR2/DDR3 memory power delivery, providing independent VDDQ (1.8V/3A) and bidirectional VTT (0.9V/±3A) rails from a 3.6V–15V input. It features programmable 500kHz–4MHz switching frequency, 180° out-of-phase operation, ±1.6% VTTR reference accuracy at 0.75V, and integrated 3.3V INTVCC LDO.
For engineers reviewing the LTC3634IUFD#PBF datasheet, LTC3634IUFD#PBF pinout, LTC3634IUFD#PBF application, or LTC3634IUFD#PBF equivalent, key selection criteria include DDR bus termination compliance, dual-channel phase control, VTTR buffer sourcing/sinking capability, and QFN-28 thermal performance in point-of-load designs.
Technical Context
The LTC3634IUFD#PBF implements current-mode control with controlled on-time architecture, enabling stable high-frequency operation (up to 4MHz) and fast transient response for DDR memory loads. Each channel uses valley-current limiting (±3.3A to ±5.5A), internal 0.6V reference (Channel 1) and VDDQIN/2 reference (Channel 2), and independent RUN/PGOOD signaling.
It supports Burst Mode® operation on Channel 1 for light-load efficiency, while Channel 2 operates continuously. Phase shift (90° or 180°) is selected via PHMODE, and external clock synchronization is enabled through MODE/SYNC with PLL locking to SW edge timing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 15V - supports 5V/12V PoL and battery-powered DDR systems without pre-regulation. |
| Output Current per Channel | ±3A - delivers full DDR3 VTT sink/source capability and 3A VDDQ rail with margin. |
| VTTR Accuracy | ±1.6% at 0.75V - ensures precise DDR reference voltage matching JEDEC VTT tolerance requirements. |
| Switching Frequency Range | 500kHz to 4MHz - enables trade-off between small magnetics (high-freq) and peak efficiency (1–2MHz typical). |
| Efficiency | Up to 95% - achieved at 12V input, 1.8V/3A output, reducing thermal load in dense memory modules. |
| Package Thermal Resistance | θJA = 43°C/W (QFN-28) - requires minimal PCB copper for DDR applications operating up to 125°C junction. |
| Protection Features | Input overvoltage lockout (17.5V), overtemperature shutdown, short-circuit protection, and PGOOD with 40µs filtering - ensures robust DDR supply sequencing and fault containment. |
Pinout & Package
The LTC3634IUFD#PBF is housed in a 28-pin 4mm × 5mm plastic QFN package with exposed PGND pad (Pin 29), optimized for thermal dissipation in DDR power applications. Pin numbering follows standard top-view layout with dual-source/dual-sink SW pins and dedicated VTTR/INTVCC/PGOOD outputs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PGOOD1 / PGOOD2 | Open-drain status outputs | Indicate regulation within ±8% window (VFB1 vs 0.6V; VFB2 vs VTTR); 15mV hysteresis prevents noise-induced glitches during DDR load transients. |
| VDDQIN (Pin 10) | External reference input | Sets VTTR = VDDQIN × 0.5; enables tracking of varying DDR supply voltages (e.g., 1.5V DDR3L → 0.75V VTTR). |
| VTTR (Pin 18) | Buffered reference output | Supplies low-noise ±10mA VREF to DDR memory; drives up to 0.01µF capacitive load directly - eliminates need for external op-amp buffer. |
| PHMODE (Pin 2) | Phase select control | Ground = 90° phase shift; INTVCC = 180° phase shift - reduces input RMS current and eases input capacitor sizing in dual-rail DDR designs. |
| MODE/SYNC (Pin 4) | Channel 1 mode control & sync input | Drives external clock → forces continuous mode + PLL-sync; ground = forced continuous; float/INTVCC = Burst Mode® - selectable for efficiency vs ripple trade-off. |
| ITH1 / ITH2 (Pins 26, 11) | Error amplifier compensation nodes | Interface with RC networks to stabilize loop response; critical for maintaining <1% VDDQ/VTT deviation during 0→3A DDR load steps. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-channel DDR-specific regulation | Independent VDDQ (0.6–3V) and VTT (bidirectional ±3A) outputs with matched references - meets JEDEC DDR1/2/3 termination and supply specs. |
| Controlled on-time architecture | Enables stable 12V-to-0.9V conversion at 2MHz+ with minimal external components - avoids sub-harmonic instability common in fixed-frequency current-mode controllers. |
| VTTR buffered reference | ±10mA drive capability with <0.01µF capacitive load support - eliminates external buffer IC and reduces BOM count in DDR memory subsystems. |
| 180° interleaved switching | Halves input ripple current magnitude and reduces required VIN bulk capacitance by ~30% - improves power integrity in space-constrained DIMM or SoC modules. |
| Integrated 3.3V INTVCC LDO | Self-powered gate drivers and logic; shuts down when both RUN pins are low - simplifies bias supply design and reduces standby current to 15µA. |
Applications
| DDR3 Memory Power Supply | DDR2 Termination System |
|---|---|
|
Use Scenario: Powering DDR3 SDRAM on server memory modules requiring strict VDDQ (1.5V) and VTT (0.75V) rails with fast load-step response. IC Role / Device Role / Timing Role: Dual-output regulator delivering regulated VDDQ and bidirectional VTT with synchronized soft-start and PGOOD sequencing. Use Value: ±1.6% VTTR accuracy and 180° phase shift ensure JEDEC-compliant termination voltage stability during burst-mode memory access. |
Use Scenario: Providing VTT termination for DDR2 graphics memory interfaces where VDDQ = 1.8V and VTT = 0.9V must track tightly. IC Role / Device Role / Timing Role: Generates VTT = VDDQIN × 0.5 using internal resistor divider and buffered VTTR output. Use Value: Eliminates external resistive divider and op-amp buffer, reducing layout area and improving noise immunity on high-speed memory buses. |
| Industrial Embedded DDR Controller | Battery-Powered DDR1 Module |
|
Use Scenario: Powering DDR controller in industrial PLC with wide input range (5V–12V) and extended temperature requirement (–40°C to 125°C). IC Role / Device Role / Timing Role: High-efficiency dual buck regulator with overvoltage/overtemperature protection and robust PGOOD signaling. Use Value: 95% peak efficiency and 43°C/W θJA enable fanless operation in sealed enclosures under full DDR load. |
Use Scenario: DDR1 memory subsystem in portable medical device powered by 2-cell Li-ion (6V–8.4V nominal). IC Role / Device Role / Timing Role: Single-chip solution for VDDQ (2.5V) and VTT (1.25V) with Burst Mode® for >85% efficiency at 10mA standby. Use Value: 15µA shutdown current and programmable 500kHz–4MHz frequency extend battery life while supporting dynamic frequency scaling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel DDR power supply applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS51220RGER | Single-channel VDDQ + VTT controller; no integrated VTTR buffer; requires external reference for VTT. | Limited to simpler DDR2/DDR3 implementations without stringent VTTR noise requirements. | Choose when cost sensitivity outweighs VTTR buffer integration and dual-channel independence. |
| ISL95831IRZ | Triple-output (VDDQ/VTT/VREF); higher quiescent current (2.5mA vs 1.3mA); TSSOP-32 package only. | Supports DDR3L/DDR4 with adaptive VTT and additional VREF rail - broader but less thermally efficient. | Prefer for DDR4 migration paths or when VREF rail generation is mandatory alongside VDDQ/VTT. |
Compared with TPS51220RGER and ISL95831IRZ, the LTC3634IUFD#PBF uniquely integrates a ±10mA VTTR buffer, supports true dual independent regulation with 180° interleaving in a thermally optimized QFN, and delivers tighter VTTR accuracy - making it optimal for space-constrained, high-reliability DDR2/DDR3 memory power where reference integrity is critical.
Availability
LTC3634IUFD#PBF is available at Aetrix Electronics and suitable for DDR memory power supplies, industrial embedded controllers, and battery-powered memory modules requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across –40°C to 125°C.
Supply support for LTC3634IUFD#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. Linear's legacy emphasizes precision, efficiency, and reliability in power conversion ICs.
The LTC3634IUFD#PBF belongs to Linear's DDR-specific power management product line, engineered to replace discrete multi-IC solutions with monolithic, JEDEC-compliant regulators for memory subsystems in servers, networking, and industrial computing.
FAQ
What is the maximum supported input voltage for the LTC3634IUFD#PBF?
The LTC3634IUFD#PBF has an absolute maximum input rating of 16V, with transient overvoltage lockout activating at 17.5V (rising) and releasing at 16.5V (falling). Its specified operating input range is 3.6V to 15V, making it compatible with standard 5V, 12V, and multi-cell battery inputs. Operation above 15V violates the recommended conditions and risks permanent damage.
How does the VTTR output function in the LTC3634IUFD#PBF?
The VTTR output of the LTC3634IUFD#PBF is a buffered reference equal to VDDQIN × 0.5, accurate to ±1.6% at 0.75V. It sources/sinks up to ±10mA and drives capacitive loads ≤0.01µF directly. This output serves as the error amplifier reference for Channel 2 (VTT), eliminating external components and ensuring tight tracking between VDDQ and VTT rails required by DDR standards.
Can the LTC3634IUFD#PBF operate with only one channel enabled?
Yes, the LTC3634IUFD#PBF supports independent channel control: RUN1 enables/disables Channel 1 (VDDQ), and RUN2 controls Channel 2 (VTT). Either channel can be disabled while the other remains active. When both RUN pins are pulled low, the device enters shutdown with IQ ≤15µA, and INTVCC is disabled. This allows flexible power sequencing in DDR systems with partial memory activation.
What is the purpose of the PHMODE pin on the LTC3634IUFD#PBF?
The PHMODE pin on the LTC3634IUFD#PBF selects inter-channel phase relationship: grounding it configures 90° phase shift, while tying it to INTVCC sets 180° out-of-phase operation. This reduces input RMS current and relaxes input capacitor requirements. The 180° mode is especially valuable in high-current DDR applications where minimizing input ripple and EMI is critical for system-level signal integrity.
Does the LTC3634IUFD#PBF support external clock synchronization?
Yes, the LTC3634IUFD#PBF supports external clock synchronization via the MODE/SYNC pin. Applying a clean CMOS clock signal (500kHz–4MHz) to this pin engages an internal PLL that locks the bottom MOSFET turn-on edge to the rising edge of the external clock. Channel 1 automatically switches to forced continuous mode during sync, while Channel 2 remains continuously operational - enabling deterministic timing in synchronized multi-rail systems.
LTC3634IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Converter, DDR
- Voltage - Input:
- 1.4V ~ 15V
- Number of Outputs:
- 2
- Voltage - Output:
- 0.6V ~ 3V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3634IUFD#PBF FAQ
1.How can I place an order for LTC3634IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3634IUFD#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 LTC3634IUFD#PBF reliable?
The price and inventory of LTC3634IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3634IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3634IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3634IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3634IUFD#PBF?
LTC3634IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3634IUFD#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 LTC3634IUFD#PBF?
For technical support, including LTC3634IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3634IUFD#PBF requirements.
6.How does Aetrix verify that LTC3634IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3634IUFD#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 LTC3634IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3634IUFD#PBF?
All LTC3634IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3634IUFD#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 LTC3634IUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3634IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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