ltc4361-1 Linear Technology Corporation, ltc4361-1 Datasheet - Page 11

• Manufacturer Part Number: ltc4361-1
• Description: Overvoltage/overcurrent Protection Controller Features
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
Input Transients
Figure 4 shows a typical setup when an AC wall adaptor
charges a mobile device. The inductor L
lumped equivalent inductance of the cable and the EMI fi lter
found in some wall adaptors. R
resistance of the cable, adaptor output capacitor ESR and
the connector contact resistance.
WALL ADAPTOR
WALL ADAPTOR
AC/DC
+
AC/DC
+
R
IN
R
I
CABLE
CABLE
IN
I
CABLE
CABLE
L
IN
L
IN
IN
IN
is the lumped equivalent
IN
R
SENSE
Figure 4. 20V Hot-Plug into a 10μF Capacitor
IN
SENSE OUT
IN
C
Si1470DH
Figure 5. 20V Hot-Plug into the LTC4361
OUT
LTC4361
represents the
GATE
GND
M1
LOAD
MOBILE
DEVICE
436112 F04a
OUT
C
OUT
LOAD
MOBILE
DEVICE
436112 F05a
L
at IN. If the wall adaptor is powered up fi rst, plugging the
wall adaptor output to IN does the equivalent of applying
a voltage step to this LC circuit. The resultant voltage
overshoot at IN can rise to twice the DC output voltage
of the wall adaptor as shown in Figure 4. Figure 5 shows
the 20V adaptor output applied to the LTC4361. Due to
the low capacitance at the IN pin, the plug-in transient has
been brought down to a manageable level.
IN
and R
IN
form an LC tank circuit with any capacitance
LTC4361-1/LTC4361-2
10V/DIV
20A/DIV
10V/DIV
20A/DIV
1V/DIV
I
I
CABLE
CABLE
V
OUT
V
V
IN
IN
R
L
LOAD = 10Ω, C
R
L
LOAD = 10Ω, C
IN
IN
IN
IN
= 0.7μH
= 150mΩ,
= 0.7μH, R
= 150mΩ,
SENSE
OUT
OUT
5μs/DIV
= 10μF
5μs/DIV
= 10μF
= 25mΩ
436112 F04b
436112 F05b
11
436112f