Features • Two synchronous buck regulators • 180° out of phase operation • 200kHz fixed nominal frequency: LM5642 • 375kHz fixed nominal frequency: LM5642X • Synchronizable switching frequency from 150kHz to 250kHz for the LM5642 and 200kHz to 500kHz for the LM5642X • 4.5V to 36V input range • 50µA Shutdown current • Adjustable output from 1.3V to 90% of Vin • 0.04% (typical) line and load regulation accuracy • Current mode control with or without a sense resistor • Independent enable/soft-start pins allow simple sequential startup configuration. • Configurable for single output parallel operation. (See ) • Adjustable cycle-by-cycle current limit • Input under-voltage lockout • Output over-voltage latch protection • Output under-voltage protection with delay • Thermal shutdown • Self discharge of output capacitors when the regulator is OFF • TSSOP and eTSSOP (Exposed PAD) packages Description The LM5642 series consists of two current mode synchronous buck regulator controllers operating 180° out of phase with each other at a normal switching frequency of 200kHz for the LM5642 and at 375kHz for the LM5642X. Out of phase operation reduces the input RMS ripple current, thereby significantly reducing the required input capacitance. The switching frequency can be synchronized to an external clock between 150kHz and 250kHz for the LM5642 and between 200 kHz and 500 kHz for the LM5642X. The two switching regulator outputs can also be paralleled to operate as a dual-phase, single output regulator. The output of each channel can be independently adjusted from 1.3V to 90% of Vin. An internal 5V rail is also available externally for driving bootstrap circuitry. Current-mode feedback control assures excellent line and load regulation and wide loop bandwidth for excellent response to fast load transients. Current is sensed across either the Vds of the top FET or across an external current-sense resistor connected in series with the drain of the top FET. The LM5642 features analog soft-start circuitry that is independent of the output load and output capacitance making the soft-start behavior more predictable and controllable than traditional soft-start circuits. Over-voltage protection is available for both outputs. A UV-Delay pin is also available to allow delayed shut off time for the IC during an output under-voltage event. Applications • Embedded Computer Systems • Navigation Systems • Telecom Systems • Set-Top Boxes • WebPAD • Point Of Load Power Architectures

Also Recommended LM2647 Dual Synchronous Buck Controller With Output Voltages As Low As 0.6V LM5642X▲ 200-500 KHz Osc Switch Frequencies LM2633▲ Dual Sync Buck + LDO Controller. Perfect For FPGAs And Similar Devices LM2642▲ Pin Compatible Except That SYNC Is Replaced By PGOOD, And Has 300 KHz Fixed Frequency LM2648▲ Triple / Quad Channel Syncronous Buck Controller MY BRIEFCASE                                       Click any "Briefcase" icon to add an item

Typical Application *click for larger image	Block Diagram click for larger image
Typical Performance *click for larger image Ch.2 Efficiency at 3.3Vout

Datasheet

Title		Size	Date	Other Language
	LM5642/LM5642X High Voltage, Dual Synchronous Buck Converter with Oscillator Synchronization	793 Kbytes	20-Jun-07

Featured Application Notes

Title		Size	Date	Other Language
	AN-1292: Application Note 1292 LM5642 Evaluation Board	2111 Kbytes	2-Sep-03

More Application Notes

Title		Size	Date	Other Language
	AN-1984: Application Note 1984 LM57 Temperature Switch vs Thermistors	210 Kbytes	28-Jul-09

Design Tools

Title	Size	Date
Mathcad Design Tools
Power Reference Design Library
Article - Reducing Buck Converter Input Capacitance through Multi-Phasing and Clock Synchronization

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM5642MH	ABCD150	0	34175	0	0	4234000	1	1201409060
LM5642MHX	ABCD150	0	34175	0	0	4234000	1	1201409060
LM5642MTC	ABCD150	0	34175	0	0	4234000	1	1201409060
LM5642MTCX	ABCD150	0	34175	0	0	4234000	1	1201409060

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.

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