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Table 5. CURRENT LIMIT OPTION REFERENCE VOLTAGE
Current Limit Option
V
[mV]
REFC
Soft Short−Circuit Protection
In case of a short−circuit at the USB cable end or the
portable device USB receptacle it is desired to limit the short
circuit current to prevent a portable device or cable from a
damage. The NCP4371 offers an extended region of output
current limiting down to V
below V
then the HVDCP logic is disabled and D+/−
CC(OFF)
pins are shorted. No further commands from the portable
device are accepted. The only feature enabled is the output
current limiting at the moment. The device stays in the
current limiting mode until V
threshold. The device logic will resume its operation and
goes to a default BC1.2 compatible mode. A new negotiation
between the charger and portable device has to be carried out
in order to enable HVDCP compatibility mode.
Discharge
If voltage level lower than actual V
the discharge circuitry discharges the output capacitors to
reach the new voltage level in a short time. As well, the
discharge circuitry is activated if cable unplug event is
detected. The NCP4371 features two discharge paths. By
default, the discharge is done via built−in regulated current
source at VCC pin. If the VCC pin discharge capability is not
sufficient an external discharge resistor R
C
Discharge Path
out
Figure 20. Dual Discharge Path − Application Idea (USB−Type C Adapter)
A
B
14
17
= 2.2 V. If the V
BUS
BUS
rises back above V
CC
CC(ON)
is requested by PD
BUS
has to be used.
DIS
C
Discharge Path
bus
C
out
www.onsemi.com
NCP4371
C
D
E
22
28
33
The discharge resistor is wired from a positive pole of the
output capacitor to the DISCHARGE pin. The minimum
recommended value of the discharge resistor R
for Class A and 120 W for Class B. The DISCHARGE pin
has an internal protection for a case the user wires the pin
falls
directly to V
BUS
MOSFET at the pin is turned off. It is highly recommended
to use an external discharge resistor always if Class B device
is used. In case of Class A device and C
DISCHARGE pin can be left disconnected.
Dual Discharge Path
The NCP4371 allows to select between a single discharge
path and the dual discharge. By default, if an external
discharge resistor R
of the output capacitor and the DISCHARGE pin, the
NCP4371 recognize it and the internal discharge path via
VCC pin is disabled. Some applications may require even
stronger discharge capability or may need to discharge two
capacitors connected at two different nodes (USB−Type C
output capacitors before and after VBUS switch). The
NCP4371 allows to enable a simultaneous function of
internal discharge via VCC pin and external DISCHARGE
pin. Figure 20 shows an application idea of the dual
discharge paths in the USB−Type C adapter design.
C
bus
12
F
G
38
44
. If this condition is detected the discharge
OUT
is connected between a positive pole
DIS
H
57
is 70 W
DIS
< 1500 mF the
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