TLE4275V33_15 Datasheet, PDF (7/12 Pages) Infineon Technologies AG – Stable with ceramic output capacitor

TLE 4275 V33
3.3
Reset Function
Block Description and Electrical Characteristics
The reset function contains serveal features:
Output Undervoltage Reset:
An output undervoltage condition is indicated setting the Reset Output “RO” to low. This signal might be used to
reset a microcontroller during low supply voltage.
In case the battery voltage is already lower than the buffered output voltage V_Q of the voltage regulator, the reset
circuit is supplied from the output “Q”, ensuring a defined reset switching threshold also at V_I = 0 V. The Reset
Output “RO” is held “low” down to an output voltage of V_Q = 1 V, even if the input voltage V_I is 0 V.
Power-On Reset Delay Time:
The power-on reset delay time t_d,PWR-ON allows a microcontoller and oscillator to start up. This delay time is the
time period from exceeding the reset switching threshold V_RT until the reset is released by switching the reset
output “RO” from “low” to “high”. The power-on reset delay time t_d,PWR-ON is defined by an external delay
capacitor C_D connected to pin “D” which is charged up by the delay capacitor charge current I_D,ch starting from
V_D = 0 V.
For easy calculating the power-on reset delay time, a multiplier factor F_d,PWR-ON = t_d,PWR-ON / C_D is specified.
Hence, t_d,PWR-ON becomes:
t_d,PWR-ON = F_d,PWR-ON / C_D .
(1)
For a precise calculation consider also the delay capacitor’s tolerance.
Undervoltage Reset Delay Time:
Unlike the power-on reset delay time, the undervoltage reset delay t_d time considers a short output undervoltage
event where the delay capacitor C_D is assumed to be discharged to V_D = V_DST,lo only before the charging sequence
restarts. Therefore, the undervoltage reset delay time t_d is defined by the delay capacitor charge current I_D,ch
starting from V_D = V_DST,lo and the external delay capacitor C_D.
For easy calculating the undervoltage reset delay time, a multiplier factor F_d = t_d / C_D is specified. Hence, t_d
becomes:
t_d = F_d / C_D .
(2)
For a precise calculation consider also the delay capacitor’s tolerance.
Reset Reaction Time:
The total reset reaction rime t_rr,total considers the internal reaction time t_rr,int and the discharge time t_rr,d defined by
the external delay capacitor C_D (see typical performance graph for details). Hence, the total reset reaction rime
becomes:
t_rr,total = t_rr,int + t_rr,d .
(3)
Reset Output “RO” Low for V_Q ≥ 1 V:
In case of an undervoltage reset condition reset output “RO” is held “low” for V_Q ≥ 1 V, even if the input voltage V_I
is 0 V. This is achieved by supplying the reset circuit from the output capacitor.
Datasheet
7
Rev. 1.1, 2015-01-15