The ISOW7721 has multiple protection features to
create a robust system level solution.
An over-voltage clamp feature
is present on VISOOUT which will clamp the voltage at 6 V, when
VSEL = VISOOUT, or 4 V, when VSEL = GND2, if there is an increase
in voltage seen on VISOOUT. It is recommended that the
VISOOUT stays lower than the over-clamp voltage for device
reliability.
Over-voltage lock out on VDD will occur
when a voltage higher than 7 V is seen. The device will go into a low power
state and the EN pin will go low.
- The device is protected against
output overload and short circuit. Output voltage starts dropping when the power
converter is not able to deliver the current demanded during overload
conditions. For a VISOOUT short-circuit to ground, the duty cycle of
the converter is limited to help protect against any damage.
- Thermal protection is also
integrated to help prevent the device from getting damaged during overload and
short-circuit conditions on the isolated output. Under these conditions, the
device temperature starts to increase. When the temperature goes above 165°C,
thermal shutdown activates and the primary controller turns off which removes
the energy supplied to the VISOOUT load, which causes the device to
cool off. When the junction temperature goes below 150°C, the device starts to
function normally. If an overload or output short-circuit condition prevails,
this protection cycle is repeated. Care should be taken in the design to prevent
the device junction temperatures from reaching such high values.