LTC1646
18
1646fa
Table 6. N-Channel Power MOSFET Selection Guide
CURRENT LEVEL (A) PART NUMBER DESCRIPTION MANUFACTURER
0 to 2 MMDF3N02HD Dual N-Channel SO-8 ON Semiconductor
R
DS(ON)
= 0.1Ω
2 to 5 MMSF5N02HD Single N-Channel SO-8 ON Semiconductor
R
DS(ON)
= 0.025Ω
5 to 10 MTB50N06V Single N-Channel DD Pak ON Semiconductor
R
DS(ON)
= 0.028Ω
5 to 10 IRF7413 Single N-Channel SO-8 International Rectifier
R
DS(ON)
= 0.01Ω
5 to 10 Si4410DY Single N-Channel SO-8 Vishay-Siliconix
R
DS(ON)
= 0.01Ω
Table 7. Sense Resistor Selection Guide
CURRENT LIMIT VALUE PART NUMBER DESCRIPTION MANUFACTURER
1A LR120601R055F 0.055Ω, 0.5W, 1% Resistor IRC-TT
WSL1206R055 Vishay-Dale
2A LR120601R028F 0.028Ω, 0.5W, 1% Resistor IRC-TT
WSL1206R028 Vishay-Dale
5A LR120601R011F 0.011Ω, 0.5W, 1% Resistor IRC-TT
WSL2010R011 Vishay-Dale
7.6A WSL2512R007 0.007Ω, 1W, 1% Resistor Vishay-Dale
10A WSL2512R005 0.005Ω, 1W, 1% Resistor Vishay-Dale
PCB Layout Considerations
For proper operation of the LTC1646’s circuit breaker
function, a 4-wire Kelvin connection to the sense resistors
is highly recommended. A recommended PCB layout for
the sense resistor, the power MOSFET, and the GATE drive
components around the LTC1646 is illustrated in
Figure 15. In Hot Swap applications where load currents
can reach 10A, narrow PCB tracks exhibit more resistance
than wider tracks and operate at more elevated tempera-
tures. Since the sheet resistance of 1 ounce copper foil is
approximately 0.5mΩ/
■■, track resistances add up quickly
in high current applications. Thus, to keep PCB track
resistance and temperature rise to a minimum, the sug-
gested 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 1A 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 6 lists some current MOSFET transistors that are
available and Table 7 lists some current sense resistors
that can be used with the LTC1646’s circuit breakers.
Table 8 lists supplier web site addresses for discrete
component mentioned throughout the LTC1646 data sheet.
APPLICATIO S I FOR ATIO
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