8.3.2 Reset During Power Up and Power Down

The TLV803 output is valid when VDD is greater than 1.1 V. When VDD is less than 1.1 V, the output transistor

turns off and becomes high impedance. The voltage on the RESET pin rises to the voltage level connected to

the pull-up resistor. Figure 8-2 shows a typical waveform for power-up, assuming the RESET pin has a pull-up

resistor connected to the VDD pin.

RESET

V

DD

t

d

V

+V

IT

HYS

-

1.1V

ValidOutput

Figure 8-2. Power-Up Response

8.3.3 Bidirectional Reset Pins

Some microcontrollers have bidirectional reset pins that act as both inputs and outputs. In a situation where the

TLV803 is pulling the RESET line low while the microcontroller is trying the force the RESET line high, a series

resistor should be placed between the output of the TLV803 and the RESET pin of the microcontroller to protect

against excessive current flow. Figure 8-3 shows the connection of the TLV803 to a microcontroller using a

series resistor to drive a bidirectional RESET line.

100kW

TLV803S

V

DD

3.3V

RESET

GND

47kW RST

Microprocessor

V

CC

Figure 8-3. Connection To Bidirectional Reset Pin

8.4 Device Functional Modes

8.4.1 Normal Operation (VDD > Power-Up Reset Voltage)

When the voltage on VDD is greater than 1.1 V, the RESET signal asserts when VDD is less than VIT– and

deasserts when VDD is greater thanVIT–.

8.4.2 Power On Reset (VDD < Power-Up Reset Voltage)

When the voltage on VDD is lower than the required voltage to internally pull the asserted output to GND

(power-up reset voltage), both outputs are in a high-impedance state.

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TLV803, TLV853, TLV863

SBVS157E – APRIL 2011 – REVISED DECEMBER 2020

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