Dual, 2-Phase Synchronous Step-Down Switching Controller
Features and Benefits
- Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
- OPTI-LOOP® Compensation Minimizes COUT
- ±1.5% Output Voltage Accuracy
- Power Good Output Voltage Indicator
- Phase-Lockable Fixed Frequency 250kHz to 550kHz
- Over Current Latch-off Disabled
- Wide VIN Range: 4.5V to 28V (35V for LTC3728LI-1) Operation
- Very Low Dropout Operation: 99% Duty Cycle
- Adjustable Soft-Start Current Ramping
- Foldback Output Current Limiting
- 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 × 5mm QFN and 28-Lead Narrow SSOP Packages
The LTC3728L-1 is a dual high performance step-down switching regulator controller that drives 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. The LTC3728L-1 is identical to the LTC3728L except that the LTC3728L-1 lacks the over current latch-off feature.
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/35V for LTC3728LI-1) input supply range encompasses all battery chemistries.
A RUN/SS pin for each controller provides soft-start. Current foldback limits MOSFET dissipation during shortcircuit conditions. The FCB mode pin can select among Burst Mode operation, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3728L-1 includes 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|
- Notebook and Palmtop Computers
- Telecom Systems
- Portable Instruments
- Battery-Operated Digital Devices
- DC Power Distribution Systems
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.