LTC4244IGN#PBF Linear Technology, LTC4244IGN#PBF Datasheet - Page 16

• Manufacturer Part Number: LTC4244IGN#PBF
• Description: IC CTRLR HOTSWAP PCI 20-SSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4244IGN#PBF

• Applications: CompactPCI™
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 5V, ±12V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.154", 3.91mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC4244/LTC4244-1
immediately to its I
current limit for more than 25 s, all of the supplies will be
latched off. The 25 s prevents quick current spikes—for
example, from a fan turning on—from causing false trips
of the circuit breaker.
After power-up, the 5V and 3.3V supplies are protected
from short circuits by dual-level circuit breakers. In the
event that either supply’s current exceeds the nominal
current limit, an internal timer is started. If the supply is
still overcurrent after 25 s, the circuit breaker trips and all
the supplies are turned off (Figure 5). An analog current
limit loop prevents the supply current from exceeding 3
the nominal current limit in the event of a short circuit
(Figure 6). The LTC4244 will stay in the latched off state
until the OFF/ON pin is cycled high then low or the 12V
power supply is cycled low then high.
The current limit and the foldback current level for the 5V
and 3.3V outputs are both a function of the external sense
16
5V
IN
100mV/DIV
– 5V
20V/DIV
10V/DIV
20V/DIV
5V/DIV
TIMER
FAULT
5V
SENSE
GATE
OUT
Figure 5. Overcurrent Fault on 5V Output
U
LIMIT
value. If that supply remains in
U
10 s/DIV
W
U
4244 F05
IN
resistor. As shown in Figure 1, a sense resistor is con-
nected between 5V
the 3.3V supply, a sense resistor is connected between
3.3V
foldback current levels are given by Equations 6 and 7:
where n V
The current limit for the internal 12V switch is set at
850mA folding back to 360mA and the –12V switch at
610mA folding back to 225mA.
3V
IN
500mV/DIV
I
I
– 3V
LIMIT VOUT
FOLDBACK VOUT
IN
20V/DIV
3.3V
20V/DIV
5V/DIV
5V/DIV
TIMER
FAULT
SENSE
GATE
and 3.3V
OUT
(
n
Figure 6. Short-Circuit Fault on 3.3V Output
OUT
(
n
= 5V
)
SENSE
OUT
R
IN
)
SENSE VOUT
and 5V
. The typical current limit and the
or 3.3V
51
R
SENSE VOUT
mV
(
n
16
SENSE
mV
OUT
(
n
10 s/DIV
)
.
for the 5V supply. For
)
42441f
4244 F06
(6)
(7)