TLE7278-2 Datasheet, PDF (8/25 Pages) Infineon Technologies AG – Low Dropout Voltage Regulator

TLE7278-2
Block Description and Electrical Characteristics
5
Block Description and Electrical Characteristics
5.1
Circuit Description
5.1.1 Power On Reset and Reset Output
For an output voltage level V_Q ≥ 1 V the reset output is hold low. When the level of V_Q reaches the reset threshold
V_RT, the signal at RO remains low for the power-up reset delay time t_RD. The reset function and timing is illustrated
in Figure 4. The reset reaction time t_RR avoids wrong triggering caused by short “glitches” on the V_Q-line. In case
of V_Q power down (V_Q < V_RT for t > t_RR) a logic low signal is generated at the pin RO to reset an external micro
controller.
The TLE7278-2GV50 and TLE7278-2EV50 feature an integrated pull-up resistor on the reset output while the
TLE7278-2GV33 and TLE7278-2GV26 have an open drain output requiring an external pull-up resistor. When
connected to a voltage level of V_ext = 5 V, a recommended value for this external resistor is ≥ 5.6 kΩ.
But it’s also possible calculating its value by using the following formula, based on the reset sink current (Example:
external pull-up resistor connected to V_ext = 5 V):
R_extmin = ∆V / I_RO = (V_ext - V_ROmin) / I_RO = (5 V - 0.25 V) / 1.0 mA = 4.75 kΩ
At low output voltage levels V_Q < 1 V the integrated pull-up resistor of the TLE7278-2GV50 is switched off setting
the reset output high ohmic.
V_I
V_{R TI}
V_Q
V_RT
< t_RR
V_RO
t_RD
t_RR
V_ROH
V_ROL
Figure 4 Reset Function and Timing Diagram
Data Sheet
8
t
t
t_RR
t
AET03526NEW.VSD
Rev. 1.2, 2009-04-28