PM6686 datasheet(34/50 Pages) STMICROELECTRONICS

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Monitoring and protections

PM6686

34/50

Doc ID 15281 Rev 4

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.

9.1

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).

9.2

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).

9.3

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.

Table 11.

Faults management summary

Fault

Condition

Device reaction

Overvoltage

section1

VOUT>+111%

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).

Overvoltage

section 2

VOUT>+116%

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).

Undervoltage

VOUT<70%

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).

PVCC

undervoltage

PVCC<3,979 V

The controller turns off the switching sections. All faults of switching sections are

cleared. Not latched fault

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