L9001 datasheet(7/38 Pages) STMICROELECTRONICS

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DS12089 Rev 2

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L9001

General description

1.4

Supervision and diagnosis

In addition to the described protection features of current limitation and output voltage

monitor, the device provides additional supervision and diagnosis functions: VS UV/OV,

over temperature, watchdog and latch mode.

VS input voltage is monitored and if an undervoltage or overvoltage is detected with respect

to the specified thresholds, the device enters a so called safe state in which output voltages

are switched off.

The device internal temperature is also monitored: when temperature increases over the

specified threshold, the TWN output is asserted low and, if the temperature increases above

a shutdown threshold, the device enters safe state.

The device also has a charge pump block which is used to ensure proper regulators

functionality inside spec limits; undervoltage on CP also triggers device safe state.

The device integrates a watchdog functional block which constantly monitors the status of

the microcontroller's oscillator. This is done by checking the synchronization of the

microcontroller with an internal time signal whose period is configured by applying a specific

capacitor at the input pin WDT. If the microcontroller signal, which is transmitted to the

watchdog via the pin WDI, is not serving the watchdog correctly, the output pin WDO is

asserted low for the specified time.

L9001 provides a feature, called latch state, that disables the system in case a systematic

fault is repetitively detected on the charge pump structure, watchdog or in case of repetitive

thermal events. The separated fail counters and detection mechanism are explained in the

dedicated sections of this document.

1.5

Low power mode

For low power applications L9001 provides a Low Power mode feature which drastically

reduces the device power consumption while the attached loads are still supplied via bypass

LDOs. This mode can be entered with STBY input pin to high level as described in the

dedicated section of this document. Load current is monitored in this mode and main

regulators are automatically reenabled if needed.

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