Datasheet

LM5069
VIN
GND
GND
LIVE
BACKPLANE
OUT
Q1
PLUG-IN BOARD
R
S
V
SYS
V
OUT
+48V
C
L
Inductive
Load
Q1
SENSE
VIN
UVLO
OVLO
GND
GATE
OUT
PGD
PWR
TIMER
R1
R2
R3
To
Load
LM5069
R
S
CARD EDGE
CONNECTOR
PLUG-IN CARD
V
SYS
GND
LM5069
SNVS452D –SEPTEMBER 2006–REVISED MAY 2013 www.ti.com
Figure 38. Recommended Board Connector Design
System Considerations
A) Continued proper operation of the LM5069 hot swap circuit requires capacitance be present on the supply
side of the connector into which the hot swap circuit is plugged in, as depicted in Figure 23. The capacitor in the
“Live Backplane” section is necessary to absorb the transient generated whenever the hot swap circuit shuts off
the load current. If the capacitance is not present, inductance in the supply lines will generate a voltage transient
at shut-off which can exceed the absolute maximum rating of the LM5069, resulting in its destruction.
B) If the load powered via the LM5069 hot swap circuit has inductive characteristics, a diode is required across
the LM5069’s output. The diode provides a recirculating path for the load’s current when the LM5069 shuts off
that current. Adding the diode prevents possible damage to the LM5069 as the OUT pin will be taken below
ground by the inductive load at shutoff. See Figure 39.
Figure 39. Output Diode Required for Inductive Loads
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