L6730B datasheet(23/52 Pages) STMICROELECTRONICS

23 / 52 page

L6730 - L6730B

Device description

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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 does not report an overvoltage event, the behavior 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 overvoltage protection (OVP) operates and not before because the

current can not be reversed. In this case, a delay between the output voltage rising and FB

voltage rising can appear and the OVP can turn on late. Figure 16.and Figure 17.show an

overvoltage event in the cases of the sink being enabled or disabled. The output voltage rises

with a slope of 100mV

µs, emulating the breaking of the high-side MOSFET as an overvoltage

occurs.

Figure 16. OVP with sink enabled: the low-side MOSFET is turned-on in advance.

Figure 17. OVP with sink disabled: delay on the OVP operation.

VOUT

109%

VFB

LGate

126%

VOUT

VFB

LGate

L6730B 数据表(PDF) 23 Page - STMicroelectronics