PM6686 STMicroelectronics, PM6686 Datasheet - Page 34

• Manufacturer Part Number: PM6686
• Description: Dual Step-down Controller With Adjustable Voltages, Adjustable Ldo And Auxiliary Charge Pump Controller For Notebook
• Manufacturer: STMicroelectronics

Monitoring and protections
9
9.1
9.2
9.3
Table 11.
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Undervoltage
undervoltage
Overvoltage
Overvoltage
section 2
section1
PVCC
Fault
Monitoring and protections
The PM6686 controls its switching output to prevent any damage or uncontrolled working
condition.
The device offers also PGOOD signals to monitor the state of each switching output voltage.
PGOOD is an open drain output: it is pulled low if the output voltage is below the 90% or
above the OVP threshold. of the nominal value.
Overvoltage protection
PM6686 provides a latched overvoltage protection (OVP). If the output voltage rises above
the +111% typ. for section 1 and above the +116% typ. for the section 2, a latched OVP
protection is activated. The controller tries to pull down the output voltage down to 0 V,
working in PWM. The current is limited by the negative current limit. The low-side MOSFET
is kept on when the output voltage is about 0 V. This management avoids high negative
undervoltage of the output rail that may damage the load.
The protection is latched and this fault is cleared toggling cleared by toggling EN or by
driving PVCC<3.979V and then PVCC>4.025V (PVCC Power On Reset).
Undervoltage protection
If during regulation the output voltage droops under the 70% of the nominal value, an
undervoltage latched fault is detected. The controller performs a soft-end procedure (see
“soft-start and soft-end” paragraph). The undervoltage fault is cleared by toggling EN or by
driving PVCC<3.979V and then PVCC>4.025V (PVCC power on reset).
PVCC monitor
The device monitors the driver supply voltage at PVCC pin. The switching sections can start
operating only if the voltage at PVCC pin is above 4,025 V typ. If PVCC falls below 3,979 V
typ., both the switching sections are turned off until the PVCC voltage goes over 4,025 V typ.
Faults management summary
PVCC<3,979 V
V
V
V
OUT
OUT
Condition
OUT
>+111%
>+116%
<70%
Negative current limit protection activated. Low-side MOSFET is turned on when
the output voltage is about 0 V. Latched fault, cleared by toggling EN or by driving
PVCC<3.979V and then PVCC>4.025V (PVCC POR).
Negative current limit protection activated. Low-side MOSFET is turned on when
the output voltage is about 0 V. Latched fault, cleared by toggling EN or by driving
PVCC<3.979V and then PVCC>4.025V (PVCC POR).
The controller performs a soft-end. Latched fault cleared by toggling EN or by
driving PVCC<3.979V and then PVCC>4.025V (PVCC POR).
The controller turns off the switching sections. All faults of switching sections are
cleared. Not latched fault
Doc ID 15281 Rev 4
Device reaction
PM6686