TLE42694-2 Datasheet, PDF (13/20 Pages) Infineon Technologies AG – Low Dropout Fixed Voltage Regulator

TLE42694-2
4.3
Reset Function
The reset function provides several features:
Block Description and Electrical Characteristics
Output Undervoltage Reset:
An output undervoltage condition is indicated by setting the Reset Output RO to “low”. This signal might be used
to reset a microcontroller during low supply voltage.
Power-On Reset Delay Time:
The power-on reset delay time t_rd allows a microcontoller and oscillator to start up. This delay time is the time frame
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_rd is defined by an external delay capacitor C_D connected to pin D
charged by the delay capacitor charge current I_D,ch starting from V_D = 0 V.
If the application needs a power-on reset delay time t_rd different from the value given in Item 4.3.9, the delay
capacitor’s value can be derived from the specified values in Item 4.3.9 and the desired power-on delay time:
C_D
=
t--_{r--d---,-n---e--w-- × 1,5nF}
t_rd
with
• C_D: capacitance of the delay capacitor to be chosen
• t_rd,new: desired power-on reset delay time
• t_rd: power-on reset delay time specified in this datasheet
For a precise calculation also take the delay capacitor’s tolerance into consideration.
Reset Reaction Time:
The reset reaction time avoids that short undervoltage spikes trigger an unwanted reset “low” signal. The reset
reaction rime t_rr 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 time becomes:
t_rr = t_{rd, int} + t_{rr, d}
with
• t_rr: reset reaction time
• t_rr,int: internal reset reaction time
• t_rr,d: reset discharge
Optional Reset Output Pull-Up Resistor R_RO,ext:
The Reset Output RO is an open collector output with an integrated pull-up resistor. To improve the EMC
behaviour of the component, an external pull-up resistor to the output V_Q can be added. In Table “Electrical
Characteristics Reset Function” on Page 16 a minimum value for the external resistor R_RO,ext is given.
Data Sheet
13
Rev. 1.0, 2012-07-03