LTC4244-1_15 Datasheet, PDF (15/28 Pages) Linear Technology – Rugged, CompactPCI Bus Hot Swap Controllers

LTC4244/LTC4244-1
APPLICATIO S I FOR ATIO
Table 1. t_TIMER vs C_TIMER
C_TIMER (±10%)
0.1µF
0.22µF
0.33µF
0.47µF
0.68µF
0.82µF
t_TIMER(MIN)
35ms
77ms
115ms
164ms
238ms
287ms
t_TIMER(MAX)
74ms
162ms
243ms
346ms
500ms
603ms
The TIMER pin is immediately pulled low when the BD_SEL#
pin signal goes high.
Thermal Shutdown
The internal switches for the 12V and –12V supplies are
protected by a thermal shutdown circuit. When the junc-
tion temperature of the die reaches 150°C, all switches will
be latched off and the FAULT pin will be pulled low.
Short-Circuit Protection
During a normal power-up sequence, if the TIMER pin is
done ramping and any supply is still in current limit all of
the pass transistors will be immediately turned off and
FAULT will be pulled low as shown in Figure 4.
In order to prevent excessive power dissipation in the pass
transistors and prevent voltage spikes on the supplies
during short-circuit conditions, the current limit on each
supply is designed to be a function of the output voltage.
As the output voltage drops, the current limit decreases.
Unlike a traditional circuit breaker function where large
currents can flow before the breaker trips, the current
foldback feature guarantees that the supply current will be
kept at a safe level.
If either the 12V or –12V supply exceeds current limit
after power-up, the shorted supply’s current will drop
TIMER
10V/DIV
GATE
10V/DIV
3.3V_OUT
10V/DIV
BD_SEL#
10V/DIV
HEALTHY#
10V/DIV
LCL_PCI_RST#
10V/DIV
FAULT
10V/DIV
5V_OUT
10V/DIV
12V_OUT
10V/DIV
V_EEOUT
10V/DIV
20ms/DIV
4244 F04
Figure 4. Power-Up Into a Short on a 3.3V Output
42441f
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