L4925(2000) データシートの表示（PDF） - STMicroelectronics

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L4925
(Rev.:2000)

VERY LOW DROP VOLTAGE REGULATOR

STMicroelectronics 

L4925

RESET CIRCUIT

The block circuit diagram of the reset circuit is

shown in Figure 3. The reset circuit supervises

the output voltage. The reset threshold of 4.5V is

defined with the internal reference voltage and

standby output divider.

The reset pulse delay time tRD, is defined with the

charge time of an external capacitor CT:

tRD=CT2µxA2V

The reaction time of the reset circuit originates

from the discharge time limitation of the reset ca-

pacitor CT and it is proportional to the value of CT.

The reaction time of the reset circuit increases the

noise immunity.Standby output voltage drops be-

low the reset threshold only a bit longer than the

reaction time results in a shorter reset delay time.

The nominal reset delay time will be generated for

standby output voltage drops longer than approxi-

mately 50µs. The typical reset output waveforms

are shown in Figure 4.

Figure 3

Figure 4

5/8

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