L6730B datasheet(23/52 Pages) STMICROELECTRONICS

23 / 52 page

L6730 - L6730B

Device description

Doc ID 11938 Rev 3

23/52

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 17 and Figure 18 show

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

rises with a slope of 100 mVµs, emulating the breaking of the high-side MOSFET as an

overvoltage occurs.

Figure 16.

OVP latched

LGate

OSC

L6730B 数据表(PDF) 23 Page - STMicroelectronics