LTC4218CDHC-12#PBF Linear Technology, LTC4218CDHC-12#PBF Datasheet - Page 13

• Manufacturer Part Number: LTC4218CDHC-12#PBF
• Description: IC CTLR HOT SWAP 16-DFN
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4218CDHC-12#PBF

• Applications: ATCA, MicroTCA™
• Internal Switch(s): No
• Voltage - Supply: 2.9 V ~ 26.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-WFDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
In this same fi gure the OV threshold is lowered from
15.05V to 13.5V. Decreasing the OV threshold requires
adding a resistor between V
be calculated as follows:
Use the equation for R
FB thresholds. Likewise, use the equation for R
decreasing the UV and FB thresholds.
Design Example
Consider the following design example (Figure 5): V
12V, I
V
gers an automatic restart of the power up sequence.
The selection of the sense resistor, (R
overcurrent threshold of 15mV:
OVOFF
R
R
18k • 15.05
S
SHUNT2
MAX
1.235
= 15mV/I
= 15.05V, V
= 7.5A. I
=
R
⎛
⎜
⎝
MAX
( )
IN
(
(
13.5 – 1.235
15.05 – 13.5
V
INRUSH
PWRGD
( )
= 15mV/7.5A = 0.002Ω
• V
TH
OLD
SHUNT1
12V
= 1A, C
= 10.5V. A current limit fault trig-
⎛
⎜
⎜
⎜
⎝
DD
(
V
(
)
)
for increasing the OV and
NEW
V
and OV. This resistor can
⎞
⎟ = 1.736M
⎠
L
OLD
= 330μF , V
– V
– V
OV TH
NEW
Figure 5. 6A, 12V Card Resident Application
S
), is set by the
( )
UVON
0.1μF
)
C
0.1μF
T
)
C1
SHUNT2
⎞
⎟
⎟
⎟
⎠
=
= 9.88V,
2mΩ
R
IN
S
SENSE
V
UV
FLT
TIMER
INTV
SENSE
for
DD
=
CC
LTC4218DHC-12
+
–
10Ω
Si7108DN
R1
GATE
GND
The MOSFET should be sized to handle the power dissi-
pation during the inrush charging of the output capacitor
C
the principal:
Thus:
Calculate the time it takes to charge up C
The inrush current is set to 1A using C
The average power dissipated in the MOSFET:
The SOA (safe operating area) curves of candidate MOS-
FETs must be evaluated to ensure that the heat capacity
of the package can stand 6W for 4ms. The SOA curves of
the Vishay Siliconix Si7108DN provide 1.5A at 10V (15W)
for 100ms, satisfying the requirement.
Q1
OUT
E
E
P
C
t
C
C
CHARGUP
DISS
SOURCE
GATE
. The method used to determine the power in Q1 is
= Energy in C
= ½ CV
I
MON
PG
= E
= C
12V
C
L
2
=
/t
R2
10k
R3
20k
I
CHARGUP
= ½ (330μF)(12)
C
I
GATE(UP)
I
INRUSH
INRUSH
L
• V
R
1k
L
GATE
C
0.01μF
+
GATE
= Energy in Q1
IN
ADC
= 0.024J/4ms = 6W
=
= 330µF
C
330μF
L
330µF • 12V
V
12V
6A
4218 F05
OUT
1A
2
= 0.024J
24µA
1A
GATE
= 4ms
LTC4218
≅ 0.01µF
OUT
:
:
13
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