l6730cqtr STMicroelectronics, l6730cqtr Datasheet - Page 21

• Manufacturer Part Number: l6730cqtr
• Description: Adjustable Step-down Controller With Synchronous Rectification
• Manufacturer: STMicroelectronics

L6730C - L6730D
Figure 13. OVP latched
Figure 14. OVP with sink enabled: the low-side MOSFET is turned-on in advance.
It must be taken into account that there is an electrical network between the output terminal and
the FB pin and therefore the voltage at this pin is not a perfect replica of the output voltage. If
the converter can sink current, in the most of cases the low-side will be turned-on before the
output voltage exceeds the over-voltage threshold, because the error amplifier will throw off
balance in advance. Even if the device doesn’t report an over-voltage, the behaviour is the
same, because the low-side is turned-on immediately. Instead, if the sink-mode is disabled, the
low-side will be turned-on only when the over-voltage-protection (OVP) operates and not
before, because the current can’t be reversed. In this case a delay between the output voltage
rising and the FB voltage rising can appear and the OVP can operate on late. The following two
figures show an over-voltage event in case of sink enabled and disabled. The output voltage
rises with a slope of 100mV/µs, emulating in this way the breaking of the high-side MOSFET as
an over-voltage cause.
109%
V
LGate
V
FB
OUT
Device description
LGate
OSC
FB
21/50