Functional description L4925
8/14 Doc ID 1770 Rev 8
3 Functional description
The L4925 is a monolithic integrated voltage regulator, based on the STM modular voltage
regulator approach. Several outstanding features and auxiliary functions are implemented to
meet the requirements of supplying microprocessor systems in automotive applications.
Nevertheless, it is suitable also in other applications where the present functions are
required. The modular approach of this device allows to get easily also other features and
functions when required.
3.1 Voltage regulator
The voltage regulator uses an Isolated Collector Vertical PNP transistor as a regulating
element. With this structure very low dropout voltage at currents up to 500 mA is obtained.
Figure 3. Foldback characteristics of V
O
The dropout operation of the standby regulator is maintained down to 3 V input supply
voltage. The output voltage is regulated up to the transient input supply voltage of 35 V. With
this feature no functional interruption due to overvoltage pulses is generated.
The typical curve showing the standby output voltage as a function of the input supply
voltage is shown in Figure 4.
The current consumption of the device (quiescent current) is less than 250
µA. To reduce
the quiescent current peak in the undervoltage region and to improve the transient response
in this region, the dropout voltage is controlled.
The quiescent current as a function of the supply input voltage is shown in Figure 5.
