LTC1644IGN datasheet(22/24 Pages) LINER

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LTC1644

1644f

APPLICATIO S I FOR ATIO

Table 7. Manufacturers’ Web Site

MANUFACTURER

WEB SITE

International Rectifier

www.irf.com

ON Semiconductor

www.onsemi.com

IRC-TT

www.irctt.com

Vishay-Dale

www.vishay.com

Vishay-Siliconix

www.vishay.com

Diodes, Inc.

www.diodes.com

Obtaining Information on Specific Parts

For more information regarding or to request a copy of the

CompactPCI specification, contact the PCI Industrial Com-

puter Manufacturers Group at:

PCI Industrial Computer Manufacturers Group

Wakefield, MA 01880 USA

Phone: 01 (617) 224-1100

Web Site: http://www.picmg.com

TransZorb SMAJ12CA and diodes BAV99 are supplied by:

Diodes, Incorporated

Westlake Village, CA 91362 USA

Phone: 01 (805) 446-4800

Web Site: http://www.vishay-liteon.com or

http://www.diodes.com

Transistors MMBT2222A and TVS 1PMT5.0AT3 are

supplied by:

Semiconductor Components Industries, LLC

Phoenix, AZ 85008 USA

Phone: 01 (602) 244-6600

Web Site: http://www.onsemi.com

PCB Layout Considerations

For proper operation of the LTC1644’s circuit breaker

operation, 4-wire Kelvin-sense connections between the

sense resistor and the LTC1644’s 5VIN and 5VSENSE pins

and 3VIN and 3VSENSE pins are strongly recommended.

The PCB layout should be balanced and symmetrical to

minimize wiring errors. In addition, the PCB layout for the

sense resistors and the power MOSFETs should include

good thermal management techniques for optimal device

power dissipation.

A recommended PCB layout for the sense resistor, the

power MOSFET and the GATE drive components around

the LTC1644 is illustrated in Figure 18. In Hot Swap

applications where load currents can be 10A, narrow PCB

tracks exhibit more resistance than wider tracks and

operate at more elevated temperatures. Since the sheet

resistance of 1 ounce copper foil is approximately

0.45m

Ω/s

s, track resistances add up quickly in high

current applications. Thus, to keep PCB track resistance

and temperature rise to a minimum, the suggested trace

width in these applications for 1 ounce copper foil is 0.03"

for each ampere of DC current.

In the majority of applications, it will be necessary to use

plated-through vias to make circuit connections from

component layers to power and ground layers internal to

the PC board. For 1 ounce copper foil plating, a general rule

is 1 ampere of DC current per via, making sure the via is

properly dimensioned so that solder completely fills any

void. For other plating thicknesses, check with your PCB

fabrication facility.

Power MOSFET and Sense Resistor Selection

Table 8 lists some current sense resistors that can be used

the LTC1644’s circuit breakers and Table 9 list some

power MOSFET transistors that are available. Table 7 lists

supplier web site addresses for discrete component men-

tioned throughout the LTC1644 data sheet.

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