datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

L4938N View Datasheet(PDF) - STMicroelectronics

Part Name
Description
View to exact match
L4938N
STMICROELECTRONICS
STMicroelectronics STMICROELECTRONICS
L4938N Datasheet PDF : 12 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
L4938N - L4938ND - L4938NPD
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.
occurs. The nominal reset delay is generated for
standby output voltage drops longer than the time
necessary for the complete discharging of the ca-
pacitor CT. This time is typically equal to 50µs if
CT = 100nF. The typical reset output waveforms are
shown in fig. 5.
The reset pulse delay time tRD, is defined by the SENSE COMPARATOR
charge time of an external capacitor CT :
This circuit compares an input signal with an internal
tRD =
CT x 2V
2µA
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
) The reaction time of the reset circuit depends on the
t(s discharge time limitation of the reset capacitor CT
c and is proportional to the value of CT.
u The reaction time of the reset circuit increases the
d noise immunity. In fact, if the standby output voltage
ro ) drops below the reset threshold for a time shorter
P t(s than the reaction time tRR, no reset output variation
OObbssoolleettee PPrroodduucctt((ss)) -- OObbssoolleettee Produc Figure 4: Block Diagram of the Reset Circuit.
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 290µA to 300µA.
7/12
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]