Keeping A Low Signal At Reset Output For Voltages Below 1.1; Measurements Of Switching Power With A Tps2051; An Additional Resistor Ensures A Valid Reset Down To 0 V - Texas Instruments TPS3801 Application Report

Applications
Figure 19. Measurements of Switching Power With A TPS2051
5.3 Keeping a Low Signal at Reset Output for Voltages Below 1.1 V
The reset output is defined for supply voltages above 1.1 V. Below this voltage,
a low level at RESET cannot be assured, because the internal transistors need
a certain voltage level to pull down the output to ground. When the supply voltage
is below this voltage level, the reset input of the connected device is floating and
this state should be avoided. Although most microcontrollers and DSPs do not
work at voltages below 1.1 V, there are systems, that requires a correct reset
signal down to 0 V.
To solve this problem, a pulldown resistor of 100 kΩ is placed between the reset
output and ground. The disadvantage of this solution is a steady current flow
during inactive state. At a supply voltage of 2.5 V, a current of 25 µA has to be
taken into the account.
Figure 20. An Additional Resistor Ensures a Valid Reset Down to 0 V
SLVA075
16
V DD RESET
V in
TPS3801J25
GND
100 nF
V DD
RESET
DSP
100 kΩ
GND