Features Input voltage range from 4.5V to 28V Synchronous dual-channel interleaved switching Forced-PWM or Pulse-skip modes Lossless bottom-side FET current sensing Adaptive duty cycle clamp High current N-channel FET drivers Low shutdown supply current Reference voltage accurate to within ±1.5% Output voltage adjustable down to 0.6V Power Good flag and Chip Enable Under-voltage lockout Over-voltage/Under-voltage protection Soft-start Switching frequency adjustable 200kHz-500kHz TSSOP-28 package Description The LM2657 is an adjustable 200kHz-500kHz dual channel voltage-mode controlled high-speed synchronous buck regulator controller ideally suited for high current applications. The LM2657 requires only N-channel FETs for both the upper and lower positions of each stage. It features line feedforward to improve the response to input transients. At very light loads, the user can choose between the high-efficiency Pulse-skip mode or the constant frequency Forced-PWM mode. Lossless current limiting without the use of external sense resistors is made possible by sensing the voltage drop across the bottom FET. A unique adaptive duty cycle clamping technique is incorporated to significantly reduce peak currents under abnormal load conditions. The two independently programmable outputs switch 180° out of phase (interleaved switching) reducing the input capacitor and filter requirements. The input voltage range is 4.5V to 28V while the output voltages are adjustable down to 0.6V. Standard supervisory and control features include Soft-start, Power Good, output Under-voltage and Over-voltage protection, Under-voltage Lockout, and chip Enable. Applications Low Output Voltage High-Efficiency Buck Regulators

Typical Application click for larger image	Block Diagram click for larger image
Typical Performance click for larger image

Datasheets

Title		Size	Date	Other Language
	LM2657 Dual Synchronous Buck Regulator Controller	982 Kbytes	15-Mar-05

Other Technical Documents

Title		Type	Date
	Reducing Buck Converter Input Capacitance through Multi-Phasing and Clock Synchronization	External Article	2008-01-28
	Robust Controller Design Using Multi-Objective Optimization	External Article	2008-03-10
	Implementing Single-Chip FPGA Power Solutions	Power Designer	2007-03-21

Part Number(s) (NSID)	Top View	Availability	Current Reported Stock	Budgetary Pricing	Pack Size
LM2657MTC/NOPB LM2657MTC RoHS Status	TSSOP	Full production Lead Time: 8 weeks	Distributor Region Qty DIGI-KEY Worldwide 104 MOUSER Worldwide 182 RS COMPONENTS Worldwide 45	$1.75 each at 1K+ pcs	rail of 48
LM2657MTCX/NOPB LM2657MTCX RoHS Status	TSSOP	Full production Lead Time: 6 weeks	Distributor Region Qty AVNET-EM Worldwide 2500 DIGI-KEY Worldwide 0	$1.75 each at 1K+ pcs	reel of 2500

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM2657.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM2657 is located at RoHS Status.

Part Number(s) (NSID)	Weight (milligrams)	Type	Pins	MSL Rating	Peak Reflow	RoHS Status	CAD Symbols	Models	Package Marking Format
LM2657MTC/NOPB LM2657MTC	111.551 112.001	TSSOP	28	3 3	260 235	Detail	Download	N/A	NSUZXYTTE# LM2657 MTC
LM2657MTCX/NOPB LM2657MTCX	111.551 112.001	TSSOP	28	3 3	260 235	Detail	Download	N/A	NSUZXYTTE# LM2657 MTC

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM2657.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM2657 is located at RoHS Status.

Design Tools

Title	Size	Date
Article - Reducing Buck Converter Input Capacitance through Multi-Phasing and Clock Synchronization
Article - Robust Controller Design Using Multi-Objective Optimization

CAD Symbols and Models Download LM2657 CAD Symbols

Models N/A

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM2657MTC	ABCD150	0	42680	0	0	6394000	1	1814314958
LM2657MTCX	ABCD150	0	42680	0	0	6394000	1	1814314958

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

Moisture Sensitivity Level Data for LM2657.

A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

National's certificate of product compliance for LM2657 is located at RoHS Status.