8.2.3 Detailed Design Procedure

The TLV841SADL01 can monitor any voltage above 0.505V using an external voltage divider. This device has

a negative going input threshold voltage of 0.505V; however, the design needs to assert a reset when VDD

drops below 2.90V. By using a resistor divider (R1 = 47.5 kΩ, R2 = 10kΩ) the negative going threshold voltage

becomes 2.90V. The device's positive going voltage threshold is VIT- + VHYS. The typical VHYS is 25mV. This in

combination with the resistor divider makes the design's positive going threshold voltage equal to 3.05V. If VDD

falls below 2.90V, RESET will assert. If VDD rises above 3.05V, RESET will deassert. See Figure 8-2 for a timing

diagram detailing the voltage levels and reset assertion/deassertion conditions.

RESET

tD-HL

SENSE

tD

VIT–

2.90V

3.3V

VIT–

VHYS = 3.05V

Push-button input

tD-HL

tD

Figure 8-2. Design 1 Timing Diagram

This design will also enter a reset condition when the "push-button input" is asserted. The push-button is tied

to ground and when pressed will drop the SENSE voltage to 0V, making the device assert a reset. As a good

analog practice, a 0.1 µF capacitor was also placed on VDD.

The desired reset timing conditions are sense propagation delay time (tP_HL of 25 μs (how long it takes to assert

RESET) and a reset delay time of 40 μs (how long it takes to deassert RESET). Figure 8-3 and Figure 8-4 are

the results of the described application where the measured propagation delay and reset delay time are shown

respectively.

For the requirement of a maximum output current, an external pull-up resistor needs to be selected so that the

current through the external pull-up resistor exceeds no more than 150 µA. When the reset output is low, the

voltage drop across the external pull-up resistor is equal to VDD. Ohm’s law is used to calculate the minimum

resistor value. The resistor needs to be greater than 22kΩ in order to pull less than 150 µA in the reset asserted

low condition. A resistor value of 30.1kΩ was selected to accomplish this.

Note that this design does not account for tolerances.

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TLV841

SLVSFO5E – APRIL 2020 – REVISED FEBRUARY 2026

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