Datasheet

PM6644 Device description
Doc ID 023203 Rev 1 19/35
2.1.6 Soft-start and soft-end
The switching section has an EN pin. A non-programmable soft-start procedure takes place
when the EN pin rises above 2.1 V.
To prevent high input inrush currents, the current limit is increased from 25% to 100% of the
current limit threshold with steps of 25%.
The procedure is not programmable and ends typically in 2.8 ms. The overvoltage protection
is always active while the undervoltage protection is enabled at the end of the 2.8 ms.
Driving one EN pin below 1.8 V makes the section perform a soft-end: gate driving signals
are pulled low and the output is discharged through an internal MOSFET with R
DS(on)
of
50 Ω typ.
2.1.7 Monitoring
The PM6644 controls its switching output to prevent any damage or uncontrolled working
condition.
2.1.8 Overvoltage protection
The PM6644 provides a latched overvoltage protection (OVP). If the output voltage rises
above 120% of the nominal value, a latched OVP protection is activated. The controller turns
on the low-side MOSFET keeping the output voltage at 0 V.
The protection is latched and this fault is cleared by cycling VCC < 2.1 V and then > 3 V.
2.1.9 Undervoltage protection
If, during regulation, the output voltage drops under 62% of the nominal value, an
undervoltage latched fault is detected. The controller performs a soft-end procedure (see
Section 2.1.6 ). The undervoltage fault is reset by toggling the EN pin or by cycling VCC <
2.1 V and then > 3 V.
2.1.10 VCC undervoltage
The device monitors the voltage at the VCC pin. The switching section can start operating
only if the voltage at the PVCC pin is above 3 V. If PVCC falls below 2.1 V, the switching
section is turned off until PVCC voltage goes over 3 V.
Table 8. Fault management summary
Fault Condition Device behavior
Overvoltage V
OUT
> +120%
The low-side MOSFET is turned on keeping the
output voltage at 0 V. Latched fault, cleared
toggling EN or cycling VCC < 2.1 V and then > 3
V.
Undervoltage V
OUT
< 62%
The controller performs a soft-end. Latched fault
cleared toggling EN or cycling VCC < 2.1 V and
then > 3 V.
VCC undervoltage V
CC
< 2.1 V
The controller turns off the switching section until
PVCC voltage goes over 3 V. Not latched fault.