LTC4242IUHF#PBF Linear Technology, LTC4242IUHF#PBF Datasheet - Page 18

• Manufacturer Part Number: LTC4242IUHF#PBF
• Description: IC CTRLR HOTSWAP DUAL-SLOT 38QFN
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4242IUHF#PBF

• Applications: General Purpose, PCI Express
• Internal Switch(s): No
• Voltage - Supply: 2.7 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 38-WFQFN, Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4242
APPLICATIO S I FOR ATIO
Yet another mode of operation is the Force ON with cur-
rent limit mode. To enter this mode, pull both FON and
EN high. In this mode of operation, the ACLs are enabled
with the 20µs fi lter time disabled. The fault latch of the
AUX supply can be latched if the AUX’s I
AUXFAULT indicates whether the AUX channel FET is on
or off. To enter normal operation, pull FON and EN low
and recycle the ON and AUXON pins.
PCB Layout Considerations
For proper operation of the LTC4242’s circuit breaker,
a Kelvin connection to the sense resistors is required.
The Kelvin sense PCB layout traces should be minimum
length, closed together, 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
12V sense resistor and the power MOSFET is illustrated
in Figure 12.
18
Figure 12. Recommended Layout for Power MOSFET, Sense Resistor and GATE Components for the 12V Rail
U
U
12V
12V
GND
IN1
ON 1OZ Cu FOIL C1
0.03" PER AMPERE
TRACK WIDTH W:
CURRENT FLOW
*ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE!
TO LOAD
W
W
W
CBAUX
RESISTOR
is exceeded.
SENSE
U
LTC4242G*
12V
GATE1
CURRENT FLOW
TO SOURCE
In Hot Swap applications where load currents can be 10A,
narrow PCB tracks exhibit more resistance than wider
tracks and hence, operate at higher temperatures. Since
the sheet resistance of 1oz copper foil is approximately
0.5mΩ/square, track resistances and voltage drops add
up quickly in high current applications. Thus, to keep PCB
track resistance, voltage drop and temperature rise to a
minimum, the suggested trace width in these applica-
tions for 1oz 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 circuitry connections from
components layers to power and ground layers internal
to the PCB. For 1oz copper foil plating, a general rule is
1A of DC current per via making sure the via is properly
dimensioned so that solder completely fi lls any void.
Check with your PCB fabrication facility for via current
specifi cations.
R
R5
POWER PAK
G1
SO-8
C
G1
•
•
CURRENT FLOW
TO LOAD
VIA PATH
TO GND
VIA TO
GND PLANE
W
12V
4242 F12
GND
12V
OUT1
4242f