LTC4232-1
14
42321fb
For more information www.linear.com/LTC4232-1
applicaTions inForMaTion
The values for overvoltage, undervoltage and power good
thresholds using the resistive dividers on the UV, OV and
FB pins match the requirements of turn-on at 9.88V and
turn-off at 15.2V.
The final schematic in Figure 6 results in very few external
components. The pull-up resistor, R7, connects to the PG
pin while the 20k (R
MON
) converts the I
MON
current to a
voltage at a ratio:
V
IMON
= 20[µA/A] • 20k • I
OUT
= 0.4[V/A] • I
OUT
In addition there is a 1µF bypass (C1) on the INTV
CC
pin.
Layout Considerations
In Hot Swap applications where load currents can be 5A,
narrow PCB tracks exhibit more resistance than wider tracks
and operate at elevated temperatures. The minimum trace
width for 1oz copper foil is 0.02" per amp to make sure
the trace stays at a reasonable temperature. Using 0.03"
per amp or wider is recommended. Note that 1oz copper
Figure 7. Recommended Layout
42321 F07
HEAT SINK
VIA TO
SINK
GND
C
OUTV
DD
exhibits a sheet resistance of about 0.5mΩ/square. Small
resistances add up quickly in high current applications.
There are two V
DD
pins on opposite sides of the package
that connect to the sense resistor and MOSFET. The PCB
layout should be balanced and symmetrical to each V
DD
pin to balance current in the MOSFET bond wires. Figure 7
shows a recommended layout for the LTC4232-1.
Although the MOSFET is self protected from overtem
-
perature, it is recommended to solder the backside of the
package to a copper trace to provide a good heat sink.
Note that the backside is connected to the SENSE pin and
cannot be soldered to the ground plane. During normal loads
the power dissipated in the MOSFET is as high as 1.9W.
A
10mm
×
10mm area of 1oz copper should be sufficient.
This area of copper can be divided in many layers.
It is also important to put C1, the bypass capacitor for
the INTV
CC
pin as close as possible between the INTV
CC
and GND.
