1) Only available for the voltage regulators with RESET function in TLE42xx series, TLE44xx series, TLE46xx series and TLF4949.
2) Only available for the voltage regulators with RESET function in TLE72xx series and TLE7469. The name of this pin can differ from device to device.
3) Not available for TLE4267, TLE4270-2, TLE4271-2, TLE42754, TLE4287, TLE4473, TLE4675 and TLE72xx series.
4) The external pull-up resistor is mandatory for TLE42754, TLE42794, TLE4290, TLE4473, TLE4675, as well as TLE72xx-2GV33/GV26 and TLE7469GV52/GV53, optional for all other voltage regulators with RESET function.
Reset application circuit
|Devices with analog reset|
|Devices with digital reset|
The output undervoltage reset operates by sensing the output voltage V OUT and comparing it to an internal reset threshold voltage V RT. If the output voltage drops below the reset threshold, the reset output is active low as long as the low output state exists. The reset output is typically connected to a microcontroller’s reset pin as shown in the application circuit.
Output undervoltage reset
Most control modules have a microcontroller and an accompanying clock oscillator. When the module is turned on, the clock oscillator requires a period of typically 1 to 10ms to reach a stable frequency. If the microcontroller begins operating before the oscillator is stable, the microcontroller may not initialize correctly. The power-on reset delay prevents a microcontroller from initializing while the oscillator is still stabilizing.
Power-on reset delay
For the Infineon TLE4xxx series and TLF4949 linear voltage regulators, the power-on reset delay time t rd and the reset reaction time t rr are determined by the delay capacitor C D connected to the D pin (see application circuit).
In datasheets, the reset timing is given for a certain capacitor, e.g. 100nF.
Example: TLE4291 reset timing
|Power-on reset delay time||t d,PWR,ON||8||13.5||18||ms||Calculated value;
C D= 100nF
|Internal reset reaction time||t rr,int||-||9.0||15||µs||C D= 0nF|
|Delay capacitor discharge time||t rr,d||-||1.9||3||µs||C D= 100nF|
|Total reset reaction time||t rr,total||-||11.0||18||µs||
In case a power-on reset delay time t rd different from the value specified at C D = 100nF is required, the corresponding value of the delay capacitor can be calculated as follows:
Correspondingly, the reset reaction time t rr can be calculated with the formula:
For the Infineon TLE72xx series linear voltage regulators, the power-on reset delay time t rd is selectable between two predefined values through the configuration at the reset timing selection pin DT/RM/WM (see application circuit).
Example: TLE7279-2 reset timing
|Power-on reset delay time||t rd||12.8||16||19.2||ms||Fast reset timing RM = low|
|25.6||32||38.4||ms||Slow reset timing RM = high|
In some Infineon voltage regulators, the power good/power fail function is implemented. This functionality is similar to the reset function.
In TLE4290, output voltage is supervised through a power good circuit. This function is the same as an analog reset, including delay timing set by a delay capacitance as described above for analog reset timing.
In TLE4285 and TLE4295, output undervoltage is alerted by the power fail (PF) pin. As soon as V Q falls below its power fail switching threshold, its output PF is set to LOW. There is no delay pin available for connecting an external capacitor to set a reaction or delay time.
In the voltage tracker TLE4254, the power good function not only alerts the undervoltage, but also the overvoltage, providing an added safety feature.
Pull-up at reset output RO
The reset output RO is an open collector output requiring a pull-up resistor to a positive voltage rail (e.g. output voltage V Q).
TLE4291 RO internal and external pull-up resistors
In some other regulators, there is no internal pull-up resistor at RO to the output voltage. For those regulators an external pull-up resistor is required. The minimum value of the required external pull-up resistor R RO is given in the datasheet.
Example: TLE42754 RO external pull-up resistor