Obsolete

Product(s)

- Obsolete

Product(s)

RESET CIRCUIT

The block circuit diagram of the reset circuit is shown

in fig. 4. The reset circuit supervises the standby out-

put voltage. The reset threshold of 4.7V is defined

by the internal reference voltage and the standby

output divider.

2

µA

The reaction time of the reset circuit depends on the

The reaction time of the reset circuit increases the

noise immunity. In fact, if the standby output voltage

drops below the reset threshold for a time shorter

occurs. The nominal reset delay is generated for

standby output voltage drops longer than the time

necessary for the complete discharging of the ca-

µs if

shown in fig. 5.

SENSE COMPARATOR

This circuit compares an input signal with an internal

voltage reference of typically 1.23V. The use of an

external voltage divider makes the comparator very

flexible in the application. This function can be used

to supervise the input voltage - either before or after

the protection diode - and to give additional informa-

tion to the microprocessor such as low voltage warn-

ings.

If this feature is not used SI and SO have to con-

nected to GND. In this case the St-by quiescent cur-

rent (14V) increases from 290

µA to 300µA.

Figure 4: Block Diagram of the Reset Circuit.

L4938N - L4938ND - L4938NPD

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