LTC3728L/LX

PRODUCTION

Dual, 550kHz, 2-Phase Synchronous Regulators

Part Models: 17
1ku List Price: Starting From $5.18

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Part Details

Dual, 180° Phased Controllers Reduce Required
Input Capacitance and Power Supply Induced Noise
OPTI-LOOP^® Compensation Minimizes C_OUT
±1% Output Voltage Accuracy (LTC3728LC)
Power Good Output Voltage Indicator
Phase-Lockable Fixed Frequency 250kHz to 550kHz
Dual N-Channel MOSFET Synchronous Drive
Wide V_IN 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 I_Q: 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/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 V_OUT 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.


	V_in Range	V_ref 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

Applications

Notebook and Palmtop Computers
Telecom Systems
Portable Instruments
Battery-Operated Digital Devices
DC Power Distribution Systems

Part Models: 17
1ku List Price: Starting From $5.18

Documentation

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. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC3728LCGN#PBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LCGN#TRPBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LCUH#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LCUH#TRPBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LEGN#PBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LEGN#TRPBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LEUH#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LEUH#TRPBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LIGN#PBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LIGN#TRPBF	28-Lead SSOP (Narrow 0.15 Inch)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LIUH#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LIUH#TRPBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LIUH-1#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LXCUH#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LXCUH#TRPBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LZEUH#PBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys
LTC3728LZEUH#TRPBF	32-Lead QFN (5mm x 5mm x 0.75mm w/ EP)	Material Declaration Reliablity Data	Ultra Librarian SamacSys

Part Models	Product Lifecycle	PCN

Oct 3, 2024 - 24_0235 (QSOP/SSOP PKG) Migrating Bottom Trace Code Marking to Top Side Laser Marking
		PCN24_0235_Form Material_Report Other Delta Qualification Matrix
LTC3728LCGN#PBF	PRODUCTION
LTC3728LCGN#TRPBF	PRODUCTION
LTC3728LEGN#PBF	PRODUCTION
LTC3728LEGN#TRPBF	PRODUCTION
LTC3728LIGN#PBF	PRODUCTION
LTC3728LIGN#TRPBF	PRODUCTION
Aug 10, 2022 - 22_0177 Laser Top Mark Conversion for QSOP20_24_28 Assembled in ADPG [PNG] and UTL
		PCN22_0177_Form Material_Report Delta Qualification Matrix
LTC3728LCGN#PBF	PRODUCTION
LTC3728LCGN#TRPBF	PRODUCTION
LTC3728LEGN#PBF	PRODUCTION
LTC3728LEGN#TRPBF	PRODUCTION
LTC3728LIGN#PBF	PRODUCTION
LTC3728LIGN#TRPBF	PRODUCTION
Apr 17, 2025 - 25_0043 Change of Gold to Copper Wire and BOM (Automotive)
		PCN25_0043_Form Material_Report Delta Qualification Matrix Qualification Results Summary
LTC3728LCUH#PBF	PRODUCTION
LTC3728LCUH#TRPBF	PRODUCTION
LTC3728LIUH#PBF	PRODUCTION
LTC3728LIUH#TRPBF	PRODUCTION
LTC3728LXCUH#PBF	PRODUCTION
LTC3728LXCUH#TRPBF	PRODUCTION
LTC3728LZEUH#PBF	PRODUCTION
LTC3728LZEUH#TRPBF	PRODUCTION
Feb 14, 2025 - 25_0017 Bond Wire Change from Gold to Copper
		PCN25_0017_Form Material_Report Qualification Results Summary
LTC3728LIUH-1#PBF	PRODUCTION

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

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Silicon Oscillators 2
LTC6908		Resistor Set SOT-23 Oscillator with Spread Spectrum Modulation
LTC6909	PRODUCTION	1 to 8 Output, Multiphase Silicon Oscillator with Spread Spectrum Modulation

Parts	Product Life Cycle	Description
LTC3850	PRODUCTION	Dual, 2-Phase Synchronous Step-Down Switching Controller

Tools & Simulations

LTspice

Models for the following parts are available in LTspice:

LTC3728
LTC3728L

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.

Evaluation Kits

LTC3728LEUH Demo Board | Dual Output, 5V to 24VIN, 5VOUT1 @ 4A, 3.3VOUT2 @ 5A

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Product Details

Demonstration circuit 392 is a dual output, step-down, synchronous buck converter featuring either the 150kHz to 300kHz LTC1628EUH controller (DC392A-A), the 250kHz to 550kHz LTC3728EUH (DC392A-B) or 250kHz to 550kHz LTC3728LUH (DC392A-C). It operates with an input voltage range of 7V to 24V and provides 3.3V @ 5A and 5V @ 4A at its output. The LTC3728L has a lower maximum input voltage than the LTC3728 (28V vs. 36V) and thus is more cost effective.

Resources

DC392A - Demo Manual
9/24/2009

DC392A - Schematic
9/24/2009

DC392A - Design File
9/24/2009

LTC3728LXCUH Demo Board | 2-Phase, 4.5V ≤ VIN ≤ 13.2V, VOUT1 = 2.5V @ 5A, VOUT2 = 3.3V @ 5A

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Product Details

Demonstration circuit 899 is a high efficiency supply featuring the dual-output, 2-phase synchronous buck regulator LTC3728LX (not tested cold and 1.5% accurate VREF). The input voltage range of the demo board is from 4.5V to 13.2V, though the LTC3728LX controller can take up to 30V (max) Vin. The outputs are 2.5V@5A and 3.3V@5A.

Resources

DC899A - Schematic
9/24/2009

DC899A - Demo Manual
9/24/2009

DC899A - Design File
9/24/2009

LTC3728LCUH Demo Board | 4.5V ≤ VIN ≤ 13.2V, VOUT1 = 2V @ 10A, VOUT2 = 1.8V @ 10A

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Product Details

Demonstration circuit 898 is a high current density supply featuring the dual-output, 2-phase synchronous buck regulator LTC3728L. The input voltage of the demo board is designed from 4.5V to 13.2V, though the LTC3728L controller can take up to 30V (max) V_IN. There are two assemblies of the demo board, DC898A-A and DC898A-B. DC898A-A is a cost effective design with 2.0V/10A and 1.8V/10A outputs. DC898A-B is a high current design with 1.5V/15A and 1.2V/15A outputs.