LTC4360-1 Linear Technology, LTC4360-1 Datasheet - Page 8

• Manufacturer Part Number: LTC4360-1
• Description: Overvoltage Protection Controller
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
LTC4360-1/LTC4360-2
MOSFET Confi gurations and Selection
The LTC4360 can be used with various external MOSFET
confi gurations (see Figure 3). The simplest confi guration is
a single N-channel MOSFET. It has the lowest R
voltage drop and is thus the most power effi cient solution.
When GATE is pulled to ground, the MOSFET can isolate
OUT from a positive voltage at IN up to the BV
MOSFET. However, reverse current can still fl ow from OUT
to IN via the parasitic body diode of the MOSFET.
For near zero reverse leakage current protection when GATE
is pulled to ground, back-to-back N-channel MOSFETs can
be used. Adding an additional P-channel MOSFET controlled
by GATEP (LTC4360-2) provides negative input voltage
protection down to the BV
Another confi guration consists of a P-channel MOSFET
controlled by GATEP and a N-channel MOSFET controlled
by GATE. This provides protection against overvoltage and
negative voltage but not reverse current.
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.
L
at IN. If the wall adaptor is powered up fi rst, plugging the
wall adaptor output to IN does the equivalent of applying
8
IN
and R
WALL ADAPTOR
AC/DC
+
IN
form an LC tank circuit with any capacitance
R
IN
I
CABLE
CABLE
L
IN
DSS
IN
of the P-channel MOSFET.
is the lumped equivalent
IN
Figure 4. 20V Hot-Plug into a 10μF Capacitor
IN
represents the
C
OUT
DS(ON)
DSS
LOAD
MOBILE
DEVICE
of the
436012 F04a
and
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 LTC4360. Due to
the low capacitance at the IN pin, the plug-in transient has
been brought down to a manageable level.
SUPPLY
SUPPLY
SUPPLY
SUPPLY
10V/DIV
20A/DIV
I
CABLE
V
IN
R
LOAD = 10Ω, C
PROTECTION
PROTECTION
Figure 3. MOSFET Confi gurations
IN
NEGATIVE
NEGATIVE
VOLTAGE
VOLTAGE
GATEP
GATEP
= 150mΩ, L
M2
M2
OUT
IN
IN
IN
IN
IN
= 0.7μH
5μs/DIV
= 10μF
OVERVOLTAGE
OVERVOLTAGE
PROTECTION
OVERVOLTAGE, REVERSE
OVERVOLTAGE, REVERSE
PROTECTION
CURRENT PROTECTION
CURRENT PROTECTION
GATE
GATE
GATE
GATE
M1
M1
M1
M1
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436012 F04b
M3
M3
436012 F03
OUT
OUT
OUT
OUT
436012f