PM6681A STMicroelectronics, PM6681A Datasheet - Page 29

• Manufacturer Part Number: PM6681A
• Description: Dual synchronous step down controller with adjustable LDO
• Manufacturer: STMicroelectronics

PM6681A
8
8.1
8.2
8.3
8.4
Monitoring and protections
Power Good signals
The PM6681A provides three independent Power Good signals: one for each switching
section (PGOOD1/PGOOD2).
PGOOD1/PGOOD2 signals are low if the output voltage is out of ± 10 % of the designed set
point or during the soft-start, standby and shutdown mode.
Thermal protection
The PM6681A 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.
Overvoltage protection
When the switching output voltage goes over the OVP threshold (about 116 % of its nominal
value), the low side MOSFET turns on. The LS MOSFET is kept on until the output voltage
returns under the OVP threshold.
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, EN1/EN2 pin or a power on reset is necessary to clear the
undervoltage fault and starts with a new soft-start phase.
Table 10.
Undervoltage
Overvoltage
protection
protection
shutdown
Thermal
Mode
Protections and operatives modes
OUT1/OUT2 > 115 % of
the nominal value
OUT1/OUT2 < 70 % of the
nominal value
T
J
> +150 °C
Conditions
LGATE1/LGATE2 pin is forced high until the output
voltage is over the OVP threshold, LDO5 remains
active.
LGATE1/LGATE2 is forced high after the soft-end
mode, LDO5 remains active. Exit by a power on reset
or toggling SHDN or EN1/EN2
All circuitry off. Exit by a POR on VIN or toggling
SHDN.
Description
Monitoring and protections
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