LTC4219 LINER [Linear Technology], LTC4219 Datasheet - Page 14

• Manufacturer Part Number: LTC4219
• Description: 5A Integrated Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
LTC4219
The power good threshold using the internal resistive
divider on the FB pin matches the 10.5V requirement.
The fi nal schematic in Figure 5 results in very few external
components. The pull-up resistors, R1 and R3, connect
to the FLT and PG pins while the 20k (R2) converts the
I
In addition there is a 0.1μF bypass (C1) on the INTV
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
exhibits a sheet resistance of about 0.5mΩ/square. Small
resistances add up quickly in high current applications.
There are two V
that connect to the sense resistor and MOSFET. The PCB
layout should be balanced and symmetrical to each V
pin to balance current in the MOSFET bond wires. Figure 6
shows a recommended layout for the LTC4219.
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 can-
not be soldered to the ground plane. During normal loads
14
MON
V
IMON
current to a voltage at a ratio:
= 20 µA/A
⎡ ⎣
DD
pins on opposite sides of the package
5V
⎤ ⎦ • 20k •I
OUT
= 0.4 V/A
⎡ ⎣
Figure 7. 5V, 5A Card Resident Application
5V
⎤ ⎦ •I
R1
10k
C
0.1μF
T
OUT
CC
V
EN1
EN2
FLT
TIMER
INTV
DD
pin.
DD
CC
LTC4219DHC-5
GND
the power dissipated in the package is as high as 1.9W. A
10mm × 10mm area of 1oz copper should be suffi cient.
This area of copper can be divided in many layers.
It is also important to put C1, the bypass capacitor for
the INTV
and GND.
Additional Applications
The LTC4219 has a wide operating range from 2.9V to 15V.
The PG threshold is set with an internal resistive divider.
All other functions are independent of supply voltage.
Figure 7 shows a 5V application with a PG threshold of
4.35V.
In addition to Hot Swap applications, the LTC4219 also
functions as a backplane resident switch for removable
load cards (see the Typical Application section).
I
OUT
MON
PG
CC
5V
R2
10k
R
20k
pin as close as possible between the INTV
V
+
DD
MON
Figure 6. Recommended Layout
C
100μF
L
ADC
V
5V
5A
OUT
4219 F07
HEAT SINK
C
VIA TO
SINK
GND
OUT
4217 F06
4219f
CC