Output voltage monitor and protections
Figure 22. Output voltage protections and typical principle connections
L6713A
+5VSB
(OUTEN = 0)
Preliminary OVP
VSEN Monitored
(OUTEN = 1)
Programmable OVP
VSEN Monitored
+12V
VCC
V
cc
UVLO
UVLO
VCC
VCCDR1
VCCDR2
VCCDR3
Preliminary OVP Enabled
VSEN Monitored
OVP
No Protection
Provided
17.3
Over voltage and programmable OVP
Once VCC crosses the turn-ON threshold and the device is enabled (OUTEN = 1), L6713A
provides an Over Voltage Protection: when the voltage sensed by VSEN overcomes the
OVP threshold, the controller permanently switches on all the low-side MOSFETs and
switches OFF all the high-side MOSFETs in order to protect the load. The OSC/ FAULT pin
is driven high (5V) and power supply or OUTEN pin cycling is required to restart
operations.The OVP Threshold varies according to the operative mode selected (See
Table 11).
The OVP threshold can be also programmed through the OVP pin: leaving the pin floating, it
is internally pulled-up and the OVP threshold is set according to Table 11. Connecting the
OVP pin to SGND through a resistor ROVP, the OVP threshold becomes the voltage present
at the pin. Since the OVP pin sources a constant IOVP=12.5µA current(See Table 4), the
programmed voltage becomes:
OVPTH
OVPTH = ROVP ⋅ 12.5µA
Filter OVP pin with 100pF(max) vs. SGND.
⇒
ROVP = -------------------
12.5µA
17.4
PGOOD (only for AMD mode)
It is an open-drain signal set free after the soft-start sequence has finished. It is pulled low
when the output voltage drops below -300mV of the programmed voltage.
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HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
