TL331LVDBVR datasheet(20/71 Pages) TI2

20 / 71 page

6.4.2 Power-On-Reset (POR)

The LV family has an internal Power-on-Reset (POR) circuit for known start-up or power-down conditions. While

the power supply (V+) is ramping up or ramping down, the POR circuitry will be activated for up to 30µs after the

minimum supply voltage threshold of 1.5V is crossed, or immediately when the supply voltage drops below 1.5V.

When the supply voltage is equal to or greater than the minimum supply voltage, and after the delay period, the

comparator output reflects the state of the differential input (VID).

The POR circuit will keep the output high impedance (HI-Z) during the POR period (ton).

OH/2

GND

OUT

VCC

GND + 1.5V

GND

Figure 6-1. Power-On-Reset Timing Diagram

Note that it is the nature of an open collector output that the output will rise with the pull-up voltage during the

POR period.

A light pull-up (to V+) or pull-down (to GND) resistor can be used to pre-bias the output condition to prevent the

output from floating.

6.4.3 Inputs

6.4.3.1 Rail to Rail Input

The LV family input voltage range extends from 100mV below GND to 100 mV above V+. The differential input

voltage (VID) can be any voltage within these limits. No phase-inversion of the comparator output will occur when

the input pins exceed V+ or GND.

6.4.3.2 Fault Tolerant Inputs

The LV family inputs are fault tolerant up to 5.5V independent of V+. Fault tolerant is defined as maintaining the

same high input impedance when V+ is unpowered or within the recommended operating ranges.

The fault tolerant inputs can be any value between 0 V and 5.5 V, even while V+ is zero or ramping up or down.

This feature avoids power sequencing issues as long as the input voltage range and supply voltage are within

the specified ranges. This is possible since the inputs are not clamped to V+ and the input current maintains its

value even when a higher voltage is applied to the inputs.

As long as one of the input pins remains within the valid input range, and the supply voltage is valid and not in

POR, the output state will be correct.

The following is a summary of input voltage excursions and their outcomes:

1. When both IN- and IN+ are within the specified input voltage range:

a. If IN- is higher than IN+ and the offset voltage, the output is low.

b. If IN- is lower than IN+ and the offset voltage, the output is high.

2. When IN- is higher than the specified input voltage range and IN+ is within the specified voltage range, the

output is low.

3. When IN+ is higher than the specified input voltage range and IN- is within the specified input voltage range,

the output is high

4. When IN- and IN+ are both outside the specified input voltage range, the output is indeterminate (random).

Do not operate in this region.

Even with the fault tolerant feature, TI strongly recommends keeping the inputs within the specified input voltage

range during normal system operation to maintain datasheet specifications. Operating outside the specified input

range can cause changes in specifications such as propagation delay, which can lead to unpredictable behavior.

TL331LV, TL391LV, LM393LV, LM339LV

SNOSDA4D – JUNE 2020 – REVISED NOVEMBER 2023

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