L4995 STMICROELECTRONICS [STMicroelectronics], L4995 Datasheet - Page 17

• Manufacturer Part Number: L4995
• Description: 5V, 500mA low drop voltage regulator
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

L4995
3.2
Reset
The reset circuit supervises the output voltage Vo. The Vo_th reset threshold is defined with
the in-ternal reference voltage and a resistor output divider. If the output voltage becomes
lower than Vo_th then Res goes low with a reaction time trr. The reset low signal is
guaranteed for an output voltage Vo greater than 1V.
When the output voltage becomes higher than Vo_th then Res goes high with a delay trd.
This delay is obtained by an internal oscillator.
The oscillator period is given by:
where:
trd is given by:
Reset is active when En is high.
Figure 28. Reset timing diagram
Tosc = [(Vrhth-Vrlth) x Ctr] / Icr + [(Vrhth-Vrlth) x Ctr] / Idr
Icr:
Idr:
Vrhth, Vrlth:
Ctr:
trd = (Vrhth x Ctr)/Icr + 3 x Tosc
Wi
Wi
Vo
Vo
Res
Res
Vcr
Vcr
< trr
< trr
is an internally generated charge current
is an internally generated discharge current
are two voltages defined with the output voltage and a resistor output
divider
is an external capacitance.
trr
trr
Tosc
Tosc
trd
trd
Application information
Vrhth
Vrhth
Vrlth
Vrlth
Vout_th
Vout_th
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