NCL30082
www.onsemi.com
30
CS Pin Short Circuit Protection
Normally, if the CS pin or the sense resistor is shorted to
ground, the Driver will not be able to turn off, leading to
potential damage of the power supply. To avoid this, the
versions A, B, B1, B2, B3 and D feature a circuit to protect
the power supply against a short circuit of the CS pin. When
the MOSFET is on, if the CS voltage stays below VCS(low)
after the adaptive blanking timer has elapsed, the controller
shuts down and will attempt to restart on the next VCC
hiccup. In the NCL30082B1, this protection is disabled.
+
−
CS
Q_drv
CS_short
S
R
Q
UVLO
BO_NOK
Adaptative
Blanking Time
Figure 69. CS Pin Short Circuit Protection Schematic
Q
V
CS(low)
V
VIN
Fault Management
OFF Mode
The circuit turns off whenever a major condition prevents
it from operating:
• Incorrect feeding of the circuit: “UVLO high”. The
UVLO signal becomes high when V
CC
drops below
V
CC(off)
and remains high until V
CC
exceeds V
CC(on)
.
• OTP
• V
CC
OVP
• OVP2 (additional OVP provided by SD pin)
• Output diode short circuit protection: “WOD_SCP
high”
• Output / Auxiliary winding Short circuit protection:
“Aux_SCP high”
• Die over temperature (TSD)
• Brown−Out: “BO_NOK” high
• Pin CS short circuited to GND: “CS_short high”
In this mode, the DRV pulses are stopped. The VCC
voltage decrease through the controller own consumption
(I
CC1
).
For the output diode short circuit protection, the CS pin
short circuit protection, the output / aux. winding short
circuit protection and the OVP2, the controller waits 4
seconds (auto−recovery timer) and then initiates a startup
sequence (V
CC
≥ V
CC(on)
) before re−starting switching.
Latch Mode
This mode is activated by the output diode short−circuit
protection (WOD_SCP), the OTP and the Aux−SCP in
version A only.
In this mode, the DRV pulses are stopped and the
controller is latched. There are hiccups on V
CC
.
The circuit un−latches when V
CC
< V
CC(reset)
.
