Table 13. Watchdog timer

Usage of watchdog timer

Connection of VCW pin

Watchdog timer is not used

Connect to the VO pin

Watchdog timer is used

Connect to an external capacitor Ctw

4.7

Thermal warning and thermal shutdown

To warn the microcontroller about a severe temperature increase, a thermal warning output has been

implemented. If the device detects a junction temperature above Twarn, the advanced thermal warning (TW)

output pin is pulled low while the voltage regulator, and its features remain all active. The TW pin returns to its

high logic level (equal to the VO output value) once the temperature falls below the threshold Twam - Twam_hyst.

Figure 39. Thermal warning diagram

When junction temperature reaches the Tprot thermal shutdown threshold the regulator output is quickly shut-off

through the internal fast output discharge circuit; to be reactivated, junction temperature has to decrease below

Tprot- Tprot_hyst. Being TW an open-drain output an external resistance (RTW) is needed between the TW pin

and the VO pin. The external resistance value can be in a range between 4.7 KΩ and 20 KΩ. Be aware that

the current flowing through the TW pin drawn from VO when the TW pin is pulled low may affect the watchdog

activation/deactivation based on the regulator output current consumption monitoring. Leave floating if not used.

L99VR02J

Thermal warning and thermal shutdown

DS14076 - Rev 1

page 23/38