LTC3728L - Dual, 550kHz, 2-Phase Synchronous Regulators
Features
- Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise - OPTI-LOOP® Compensation Minimizes COUT
- ±1% Output Voltage Accuracy (LTC3728LC)
- Power Good Output Voltage Indicator
- Phase-Lockable Fixed Frequency 250kHz to 550kHz
- Dual N-Channel MOSFET Synchronous Drive
- Wide VIN Range: 4.5V to 28V Operation
- Very Low Dropout Operation: 99% Duty Cycle
- Adjustable Soft-Start Current Ramping
- Foldback Output Current Limiting
- Latched Short-Circuit Shutdown with Defeat Option
- Output Overvoltage Protection
- Low Shutdown IQ: 20µA
- 5V and 3.3V Standby Regulators
- 3 Selectable Operating Modes: Constant Frequency, Burst Mode® Operation and PWM
- 5mm x 5mm QFN and 28-Lead Narrow SSOP Packages
AEC-Q100 data available for specific packages
Typical Application
Description
The LTC3728L/LTC3728LX are dual high performance step-down switching regulator controllers that drive all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phase lockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase.
OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference and power good output indicator are compatible with future microprocessor generations, and a wide 4.5V to 28V (30V maximum) input supply range encompasses all battery chemistries.
A RUN/SS pin for each controller provides both soft-start and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3728L/LTC3728LX include a power good output pin that indicates when both outputs are within 7.5% of their designed set point.
| Vin Range | Vref Accy | Current Limit Latch Off | 3.3V LDO Available | |
|---|---|---|---|---|
| LTC3728 | 3.5V to 36V | +/-1% | Yes | |
| LTC3728L | 4.5V to 28V | +/-1% | Yes | Yes |
| LTC3728LX | 4.5V to 28V | +/- 1.5% | Yes | Yes |
| LTC3728L-1 | 4.5V to 28V | +/- 1.5% | Foldback only | Yes |
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 |
|---|---|---|---|---|---|
| LTC3728LCGN#PBF | SSOP-28 | GN | C | 05-08-1641 (GN28) | Yes |
| LTC3728LCGN#TRPBF | SSOP-28 | GN | C | 05-08-1641 (GN28) | Yes |
| LTC3728LCUH#PBF | 5x5 QFN-32 | UH | C | 05-08-1693 | Yes |
| LTC3728LCUH#TRPBF | 5x5 QFN-32 | UH | C | 05-08-1693 | Yes |
| LTC3728LEGN#PBF | SSOP-28 | GN | E | 05-08-1641 (GN28) | Yes |
| LTC3728LEGN#TRPBF | SSOP-28 | GN | E | 05-08-1641 (GN28) | Yes |
| LTC3728LEUH#PBF | 5x5 QFN-32 | UH | E | 05-08-1693 | Yes |
| LTC3728LEUH#TRPBF | 5x5 QFN-32 | UH | E | 05-08-1693 | Yes |
| LTC3728LIGN#PBF | SSOP-28 | GN | I | 05-08-1641 (GN28) | Yes |
| LTC3728LIGN#TRPBF | SSOP-28 | GN | I | 05-08-1641 (GN28) | Yes |
| LTC3728LIUH-1#PBF | 5x5 QFN-32 | UH | I | 05-08-1693 | Yes |
| LTC3728LIUH#PBF | 5x5 QFN-32 | UH | I | 05-08-1693 | Yes |
| LTC3728LIUH#TRPBF | 5x5 QFN-32 | UH | I | 05-08-1693 | Yes |
| LTC3728LXCUH#PBF | 5x5 QFN-32 | UH | C | 05-08-1693 | Yes |
| LTC3728LXCUH#TRPBF | 5x5 QFN-32 | UH | C | 05-08-1693 | Yes |
| LTC3728LZEUH#PBF | 5x5 QFN-32 | UH | E | 05-08-1693 | Yes |
| LTC3728LZEUH#TRPBF | 5x5 QFN-32 | UH | E | 05-08-1693 | 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 | |
|---|---|---|---|---|---|---|
| LTC3728LCGN#PBF | SSOP-28 | C | $6.25 | $4.40 | Yes | |
| LTC3728LCGN#TRPBF | SSOP-28 | C | $4.50 | Yes | ||
| LTC3728LCUH#PBF | 5x5 QFN-32 | C | $6.52 | $4.55 | Yes | |
| LTC3728LCUH#TRPBF | 5x5 QFN-32 | C | $4.65 | Yes | ||
| LTC3728LEGN#PBF | SSOP-28 | E | $6.61 | $4.65 | Yes | |
| LTC3728LEGN#TRPBF | SSOP-28 | E | $4.75 | Yes | ||
| LTC3728LEUH#PBF | 5x5 QFN-32 | E | $6.88 | $4.80 | Yes | |
| LTC3728LEUH#TRPBF | 5x5 QFN-32 | E | $4.90 | Yes | ||
| LTC3728LIGN#PBF | SSOP-28 | I | $8.10 | $5.25 | Yes | |
| LTC3728LIGN#TRPBF | SSOP-28 | I | $5.31 | Yes | ||
| LTC3728LIUH-1#PBF | 5x5 QFN-32 | I | $7.06 | $4.94 | Yes | |
| LTC3728LIUH#PBF | 5x5 QFN-32 | I | $8.10 | $5.25 | Yes | |
| LTC3728LIUH#TRPBF | 5x5 QFN-32 | I | $5.31 | Yes | ||
| LTC3728LXCUH#PBF | 5x5 QFN-32 | C | $6.16 | $4.30 | Yes | |
| LTC3728LXCUH#TRPBF | 5x5 QFN-32 | C | $4.40 | Yes | ||
| LTC3728LZEUH#PBF | 5x5 QFN-32 | E | $6.20 | $4.34 | Yes | |
| LTC3728LZEUH#TRPBF | 5x5 QFN-32 | E | $4.40 | 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 |
|---|---|---|---|
| DC392A-C | LTC3728LEUH Demo Board | Dual Output, 5V to 24Vin, 5Vout1 @ 4A, 3.3Vout2 @ 5A | $125.00 | |
| DC898A-A | LTC3728LCUH Demo Board | 4.5V ≤ VIN ≤ 13.2V, Vout1 = 2V @ 10A, Vout2 = 1.8V@ 10A | Contact Factory | |
| DC898A-B | LTC3728LCUH Demo Board | 4.5V ≤ VIN ≤ 13.2V, Vout1 = 1.5V @ 15A , Vout2 = 1.2V @15A | Contact Factory | |
| DC899A | LTC3728LXCUH Demo Board | 2-Phase, 4.5V ≤ VIN ≤ 13.2V, Vout1 = 2.5V @ 5A, Vout2 = 3.3V @ 5A | Contact Factory | |
| Buy Now | |||
Designed for Automotive and Transportation Applications
AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LTC3728LIGN#PBF | SSOP-28 | I | $8.10 | $5.25 | Yes | |
| LTC3728LIGN#TRPBF | SSOP-28 | I | $5.31 | Yes | ||
| LTC3728LIUH-1#PBF | 5x5 QFN-32 | I | $7.06 | $4.94 | Yes | |
| LTC3728LIUH#PBF | 5x5 QFN-32 | I | $8.10 | $5.25 | Yes | |
| LTC3728LIUH#TRPBF | 5x5 QFN-32 | I | $5.31 | Yes | ||
| Buy Now • Request Samples | ||||||
Applications
- Notebook and Palmtop Computers
- Telecom Systems
- Portable Instruments
- Battery-Operated Digital Devices
- DC Power Distribution Systems
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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:
LTC3728
LTC3728L
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.
