LT3581 LINER [Linear Technology], LT3581 Datasheet - Page 21

• Manufacturer Part Number: LT3581
• Description: 3.3A Boost/Inverting DC/DC Converter with Fault Protection
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
HOT-PLUG
The high inrush current associated with hot-plugging V
can be largely rejected with the use of an external PMOS. A
simple hot-plug controller can be designed by connecting
an external PMOS in series with V
PMOS being driven by the GATE pin of the LT3581. Since
the GATE pin pull-down current is linearly proportional to
the SS voltage, and the SS charge up time is relatively slow,
the GATE pin pull-down current will increase gradually,
thereby turning on the external PMOS slowly. Controlled
in this manner, the PMOS acts as an input current limiter
when V
Likewise, when the PMOS is connected in series with the
output, inrush currents into the output capacitor can be
limited during a hot-plug event. To illustrate this, the circuit
in Figure 18 was re-configured by adding a large 1500µF
IN
hot-plugs or ramps up sharply.
IN
, with the gate of the
IN
capacitor to the output. An 18Ω resistive load was used
and a 2.2µF capacitor was placed on SS. Figure 14 shows
the results of hot-plugging this re-configured circuit. Notice
how the inductor current is well behaved.
Figure 14. Inrush Current Is Well Controlled in Spite Of Hot-
Plugging the Re-configured Boost Converter in Figure 18
10V/DIV
5V/DIV
5A/DIV
1V/DIV
V
OUT
V
SS
IN
I
L
1s/DIV
LT3581
3581 F14

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