LTC3634 - 15V Dual 3A Monolithic Step-Down Regulator for DDR Power
Features
- 3.6V to 15V Input Voltage Range
- ±3A Output Current per Channel
- Up to 95% Efficiency
- Selectable 90°/180° Phase Shift Between Channels
- Adjustable Switching Frequency: 500kHz to 4MHz
- VTTR = VDDQ/2 = VTT Reference
- ±1.6% Accurate VTTR at 0.75V
- Optimal VOUT Range: 0.6V to 3V
- ±10mA Buffered Output Supplies VREF Reference Voltage
- Current Mode Operation for Excellent Line and Load Transient Response
- External Clock Synchronization
- Short-Circuit Protected
- Input Overvoltage and Overtemperature Protection
- Power Good Status Outputs
- Available in (4mm × 5mm) QFN-28 and Thermally Enhanced 28-Lead TSSOP Packages
Typical Application
Description
The LTC®3634 is a high efficiency, dual-channel monolithic synchronous step-down regulator which provides power supply and bus termination rails for DDR1, DDR2, and DDR3 SDRAM controllers. The operating input voltage range is 3.6V to 15V, making it suitable for point-of-load power supply applications from a 5V or 12V input, as well as various battery powered systems.
The VTT regulated output voltage is equal to VDDQIN• 0.5. An on-chip buffer capable of driving a 10mA load provides a low noise reference output (VTTR) also equal to VDDQIN• 0.5.
The operating frequency is programmable and synchronizable from 500kHz to 4MHz with an external resistor. The two channels can operate 180° out-of-phase, which relaxes the requirements for input and output capacitance. The unique controlled on-time architecture is ideal for powering DDR applications from a 12V supply at high switching frequencies, allowing the use of smaller external components.
The LTC3634 is offered in both 28-pin 4mm × 5mm QFN and 28-pin exposed pad TSSOP packages.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LTC3634EFE#PBF | TSSOP-28 | FE | E | 05-08-1663 (EB) | Yes |
| LTC3634EFE#TRPBF | TSSOP-28 | FE | E | 05-08-1663 (EB) | Yes |
| LTC3634EUFD#PBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LTC3634EUFD#TRPBF | 4x5 QFN-28 | UFD | E | 05-08-1712 | Yes |
| LTC3634HFE#PBF | TSSOP-28 | FE | H | 05-08-1663 (EB) | Yes |
| LTC3634HFE#TRPBF | TSSOP-28 | FE | H | 05-08-1663 (EB) | Yes |
| LTC3634HUFD#PBF | 4x5 QFN-28 | UFD | H | 05-08-1712 | Yes |
| LTC3634HUFD#TRPBF | 4x5 QFN-28 | UFD | H | 05-08-1712 | Yes |
| LTC3634IFE#PBF | TSSOP-28 | FE | I | 05-08-1663 (EB) | Yes |
| LTC3634IFE#TRPBF | TSSOP-28 | FE | I | 05-08-1663 (EB) | Yes |
| LTC3634IUFD#PBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | Yes |
| LTC3634IUFD#TRPBF | 4x5 QFN-28 | UFD | I | 05-08-1712 | Yes |
| LTC3634MPFE#PBF | TSSOP-28 | FE | MP | 05-08-1663 (EB) | Yes |
| LTC3634MPFE#TRPBF | TSSOP-28 | FE | MP | 05-08-1663 (EB) | Yes |
| LTC3634MPUFD#PBF | 4x5 QFN-28 | UFD | MP | 05-08-1712 | Yes |
| LTC3634MPUFD#TRPBF | 4x5 QFN-28 | UFD | MP | 05-08-1712 | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LTC3634EFE#PBF | TSSOP-28 | E | $6.29 | $4.40 | Yes | |
| LTC3634EFE#TRPBF | TSSOP-28 | E | $4.46 | Yes | ||
| LTC3634EUFD#PBF | 4x5 QFN-28 | E | $6.07 | $4.25 | Yes | |
| LTC3634EUFD#TRPBF | 4x5 QFN-28 | E | $4.31 | Yes | ||
| LTC3634HFE#PBF | TSSOP-28 | H | $7.34 | $5.14 | Yes | |
| LTC3634HFE#TRPBF | TSSOP-28 | H | $5.20 | Yes | ||
| LTC3634HUFD#PBF | 4x5 QFN-28 | H | $7.10 | $4.97 | Yes | |
| LTC3634HUFD#TRPBF | 4x5 QFN-28 | H | $5.03 | Yes | ||
| LTC3634IFE#PBF | TSSOP-28 | I | $6.99 | $4.89 | Yes | |
| LTC3634IFE#TRPBF | TSSOP-28 | I | $4.95 | Yes | ||
| LTC3634IUFD#PBF | 4x5 QFN-28 | I | $6.74 | $4.72 | Yes | |
| LTC3634IUFD#TRPBF | 4x5 QFN-28 | I | $4.78 | Yes | ||
| LTC3634MPFE#PBF | TSSOP-28 | MP | $18.86 | $13.20 | Yes | |
| LTC3634MPFE#TRPBF | TSSOP-28 | MP | $13.26 | Yes | ||
| LTC3634MPUFD#PBF | 4x5 QFN-28 | MP | $18.22 | $12.75 | Yes | |
| LTC3634MPUFD#TRPBF | 4x5 QFN-28 | MP | $12.81 | Yes | ||
| Buy Now • Request Samples | ||||||
Demo Boards
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC1708A | LTC3634EUFD Demo Board (QFN) | VIN= 3.6V to 15V, VOUT1 =1.5V/1.8V/2.5V@±3A, VOUT2 = 0.5VIN (VTT)@±3A, VOUT3 = 0.5VIN (VTTR)@±10mA | $150.00 | |
| DC1839A | LTC3634EFE Demo Board (TSSOP) | VIN= 3.6V to 15V, VOUT1 =1.5V/1.8V/2.5V @ ±3A, VOUT2 =0.5VIN (VTT) @ ±3A, VOUT3 = 0.5VIN (VTTR) @ ±10mA | $150.00 | |
| Buy Now | |||
Applications
- DDR Memory Power Supplies
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Design Tools
LTspice
LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice
Models for the following parts are available in LTspice:
LTC3634
LTpowerCAD
The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD
Design tools for the following parts are available in LTpowerCAD:
LTC3634
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
