LTC1646
U
W U U
APPLICATIO S I FOR ATIO
PCB Layout Considerations
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
thePCboard.For1ouncecopperfoilplating,ageneralrule
is 1A of DC current per via, making sure the via is properly
dimensioned so that solder completely fills any void. For
otherplatingthicknesses, checkwithyourPCBfabrication
facility.
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
thesenseresistor, thepowerMOSFET, andtheGATEdrive
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
approximately0.5mΩ/■,trackresistancesaddupquickly
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.
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
componentmentionedthroughouttheLTC1646datasheet.
Table 6. N-Channel Power MOSFET Selection Guide
CURRENT LEVEL (A)
PART NUMBER
DESCRIPTION
Dual N-Channel SO-8
= 0.1Ω
MANUFACTURER
0 to 2
MMDF3N02HD
ON Semiconductor
R
DS(ON)
2 to 5
MMSF5N02HD
MTB50N06V
IRF7413
Single N-Channel SO-8
= 0.025Ω
ON Semiconductor
ON Semiconductor
International Rectifier
Vishay-Siliconix
R
DS(ON)
5 to 10
5 to 10
5 to 10
Single N-Channel DD Pak
= 0.028Ω
R
DS(ON)
Single N-Channel SO-8
= 0.01Ω
R
DS(ON)
Si4410DY
Single N-Channel SO-8
= 0.01Ω
R
DS(ON)
Table 7. Sense Resistor Selection Guide
CURRENT LIMIT VALUE
PART NUMBER
DESCRIPTION
MANUFACTURER
1A
LR120601R055F
WSL1206R055
0.055Ω, 0.5W, 1% Resistor
IRC-TT
Vishay-Dale
2A
5A
LR120601R028F
WSL1206R028
0.028Ω, 0.5W, 1% Resistor
0.011Ω, 0.5W, 1% Resistor
IRC-TT
Vishay-Dale
LR120601R011F
WSL2010R011
IRC-TT
Vishay-Dale
7.6A
10A
WSL2512R007
WSL2512R005
0.007Ω, 1W, 1% Resistor
0.005Ω, 1W, 1% Resistor
Vishay-Dale
Vishay-Dale
1646fa
18
Linear [ Linear ]
