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SIMPLE SWITCHER® DC/DC Converters

Award-winning SIMPLE SWITCHER DC/DC converters deliver robust power supplies with the minimum set of external components. All SIMPLE SWITCHER products work with the enhanced WEBENCH Power Designer end-to-end design and prototyping tools.

LM(2)557x

LM2557x and LM557x High Performance SIMPLE SWITCHER® Regulator Series

The LM557x and LM2557x line of SIMPLE SWITCHER buck regulators feature all of the functions necessary to implement an efficient, high-voltage buck regulator design using minimal external components. The new regulators operate with an input voltage range up to 75V and deliver up to 3A of continuous output current. The patented emulated-current-mode architecture provides superior load transient response in low duty cycle applications that are not addressable by traditional current mode control.

Operating frequency is adjustable from 50 kHz to 1 MHz, providing industry-leading dynamic range. To reduce EMI, a frequency synchronization pin allows multiple ICs from the series to self-synchronize or to synchronize to an external clock. The new regulators guarantee robustness with cycle-by-cycle current limit, short-circuit protection and thermal shut-down.

Features

Wide input voltage ranges from 6V to 75V
Emulated current mode architecture offers superior performance:
- Excellent transient response
- Ultra-short duty cycle
- Reduced noise sensitivity
Adjustable switching frequencies between 50 kHz and 1 MHz

Up to 3A of output current
Self synchronizes when connected to other regulators or an external clock
Adjustable soft-start
Full support with industry leading WEBENCH design tool
Available in TSSOP or thermally enhanced ETSSOP packaging

Product Information

Product ID	V_In(V)	Max V_Out (V)	I_Out (A)	Frequency	Offline Design Spreadsheet	Package
LM25574	6 - 42	39V	0.5	50khz - 1Mhz	Excel file	TSSOP-16
LM5574	6 - 75	70V	0.5	50khz - 500khz		TSSOP-16
LM25575	6 - 42	39V	1.5	50khz - 1Mhz		TSSOP-16EP
LM5575	6 - 75	70V	1.5	50khz - 500khz		TSSOP-16EP
LM25576	6 - 42	39V	3.0	50khz - 1Mhz		TSSOP-20EP
LM5576	6 - 75	70V	3.0	50khz - 500khz		TSSOP-20EP

Design Resources

App Notes

Supplying and Loading of Power Management Circuits Part 2 (EE Times)
Get The Scoop On How To Power Share Between Isolated PoE Channels (EE Times)
Get Negative Auxiliary Output from a Buck Regulator (EE Times)
Critical Layout Tips for Fast Switchers (EE Times)
PD-117 - Overcoming Challenges in Designing Step-Down Regulator Applications with ≥40V Input Voltage
AN-1566 - Techniques for Thermal Analysis of Switching Power Supply Designs
AN-1563 - Quick Start Guide for a 0.5 Amp Buck Regulator Using the LM5574 and LM25574
AN-1571 - Quick Start Guide for a 1.5 Amp Buck Regulator Using the LM5575 and LM25575
AN-1572 - Quick Start Guide for a 3 Amp Buck Regulator Using the LM5576 and LM25576
AN-1568 - LM5574 Evaluation Board
AN-1569 - LM5575 Evaluation Board
AN-1570 - LM5576 Evaluation Board
AN-1577 - LM25574 Evaluation Board
AN-1578 - LM25575 Evaluation Board
AN-1579 - LM25576 Evaluation Board