Note:

A diode (0.25 V < VF < 0.75 V) connected in series with EN pin is requested only if the regulator is directly

supplied by car battery.

4.5

Reset

The reset circuit supervises the output voltage VO. If the output voltage falls below VO_th then RST is pulled low

with a reaction time Trr. When the output voltage rises above VO_th + VO_th_hyst then RST is pulled high with a

delay time Trd. The delay is generated by an internal circuit. The reset circuit is active when En is high. Being RST

an open-drain output an external resistance (Rrst) is needed between the RST pin and the Vo pin. The external

resistance value can be in a range between 4.7 KΩ and 20 KΩ. Leave the RST pin floating if not used.

Figure 33. Reset timing diagram

4.6

Thermal warning and thermal shutdown

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

implemented (L99VR01J version only). 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 will return to its high logic level (equal to the Vo output value) once the temperature falls below the

threshold Twarn - Twarn_hyst.

Figure 34. Thermal warning diagram

When junction temperature reaches the Tprot_j/s 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_j/s- 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. Leave floating if

not used.

L99VR01

Application information

DS13649 - Rev 4

page 19/40