NCP372 データシートの表示（PDF） - ON Semiconductor
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NCP372 Datasheet PDF : 12 Pages
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NCP372
Operation
The NCP372 provides overvoltage protection for
positive and negative voltages, up to 28 V or down to
−28 V. The negative protection is ensured by an internal
Low RDS(on) NMOS FET. A second internal Low RDS(on)
NMOS FET protects the systems (i.e.: charger) connected
on the Vout pin, against positive overvoltage. At powerup,
with EN pin = low, the output rises ton seconds after the
input overtakes the undervoltage UVLO (Figure 3). The
NCP372 provides a FLAG output, which alerts the system
that a fault has occurred. The FLAG signal rises tstart
seconds after the output signal rises. FLAG pin is an open
drain output.
Undervoltage Lockout (UVLO)
To ensure proper operation under any condition, the
device has a built−in undervoltage lockout (UVLO) circuit.
During Vin positive going slope, the output remains
disconnected from input until Vin voltage is 2.7 V nominal.
The FLAG output remains low as long as Vin does not reach
UVLO threshold. This circuit has a built in hysteresis to
provide noise immunity to transient conditions.
Overvoltage Lockout (OVLO)
To protect connected systems on Vout pin from
overvoltage, the device has a built−in overvoltage lockout
(OVLO) circuit. During overvoltage condition, the output
remains disabled until the input voltage exceeds 6.3 V.
FLAG output remains low until Vin is higher than OVLO.
This circuit has a built in hysteresis to provide noise
immunity to transient conditions.
FLAG Output
The NCP372 provides a FLAG output, which alerts
external systems that a fault has occurred.
This pin goes low as soon the OVLO threshold is
exceeded or when the Vin level is below the UVLO
threshold. When Vin level recovers normal condition,
FLAG goes high, after tstart delay following the output
response. The pin is an open drain output, thus a pullup
resistor (typically 1.0 MW, minimum 10 kW) must be
provided to VCC. The FLAG level always reflects Vin
status, even if the device is turned off (EN = 1).
EN Input
To enable normal operation, the EN pin shall be forced
low or connected to ground. A high level on the pin,
disconnects OUT pin from IN pin. EN does not overdrive
an OVLO or UVLO fault.
Negative Voltage and Reverse Current
The built−in NMOS protects the downstream system
from negative voltages occurring on IN pin down to −28 V.
The same NMOS avoids reverse currents that could
discharge the battery.
When a fault occurs, the output is disconnected from IN
pin and FLAG goes low.
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