PM6685TR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
PM6685TR
STMicroelectronics
'PM6685TR' PDF : 52 Pages View PDF
Monitoring and protections
8
Monitoring and protections
PM6685
8.1
Power good signals
The PM6685 provides three independent power good signals: one for each switching
section(PGOOD5/PGOOD3) and the other for the internal linear regulator
LDO3(PGOOD_LDO3).
PGOOD5/PGOOD3 signals are low if the output voltage is out of ±10% of the designed set
point or during the soft-start, the soft end and when the device works in standby and
shutdown mode.
PGOOD_LDO3 signal is low when the output voltage of LDO3 output is lower than its falling
voltage threshold(2.6V typ.). Each power good pin is an open-drain output and can sink
current up to 4mA.
8.2
Thermal protection
The PM6685 has a thermal protection to preserve the device from overheating. The thermal
shutdown occurs when the die temperature goes above +150°C. In this case all internal
circuitry is turned off and the power sections are turned off after the discharge mode.
A power on reset or a toggle on the SHDN pin is necessary to restart the device.
8.3
Overvoltage protection
When the switching output voltage is about 115% of its nominal value, a latched
overvoltage protection occurs. In this case, the synchronous rectifier immediately turns on
while the high-side MOSFET turns off. The output capacitor is rapidly discharged and the
load is preserved from being damaged. The overvoltge protection is also active during the
soft start. Once an overvoltage protection has been detected, a toggle on SHDN, EN3/EN5
pins or a power on reset is necessary to exit from the latched state.
8.4
Undervoltage protection
When the switching output voltage is below 70% of its nominal value, a latched undervoltage
protection occurs. In this case the switching section is immediately disabled and both
switches are open. The controller enters in soft end mode and the output is eventually kept
to ground, turning low side MOSFET on. The undervoltage circuit protection is enabled only
at the end of the soft-start. Once an overvoltage protection has been detected, a toggle on
SHDN, EN5/EN3 pin or a power on reset is necessary to clear the undervoltage fault and
starts with a new soft-start phase.
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