TLV1861DBVR datasheet(21/42 Pages) TI

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7.1.1.3 Overdrive Voltage

The overdrive voltage, VOD, is the amount of input voltage beyond the reference voltage (and not the total input

peak-to-peak voltage). The overdrive voltage is 100mV as shown in the Figure 7-1 example. The overdrive

voltage can influence the propagation delay (tp). The smaller the overdrive voltage, the longer the propagation

delay, particularly when <100mV. If the fastest speeds are desired, it is recommended to apply the highest

amount of overdrive possible.

The risetime (tr) and falltime (tf) is the time from the 20% and 80% points of the output waveform.

7.1.2 Hysteresis

The basic comparator configuration may produce a noisy "chatter" output if the applied differential input voltage

is near the comparator's offset voltage. This usually occurs when the input signal is moving very slowly across

the switching threshold of the comparator. This problem can be prevented by adding external hysteresis to the

comparator.

Since the TLV185x and TLV186x devices only have a minimal amount of internal hysteresis of 2.7mV, external

hysteresis can be applied in the form of a positive feedback loop that adjusts the trip point of the comparator

depending on its current output state.

The hysteresis transfer curve is shown in Figure 7-2. This curve is a function of three components: VTH, VOS,

and VHYST:

• VTH is the actual set voltage or threshold trip voltage.

• VOS is the internal offset voltage between VIN+ and VIN–. This voltage is added to VTH to form the actual trip

point at which the comparator must respond to change output states.

• VHYST is the hysteresis (or trip window) that is designed to reduce comparator sensitivity to noise.

VTH + VOS ± (VHYST / 2)

VTH + VOS + (VHYST / 2)

VTH + VOS

Figure 7-2. Hysteresis Transfer Curve

For more information, please see Application Note SBOA219 "Comparator with and without hysteresis circuit".

7.1.2.1 Inverting Comparator With Hysteresis

The inverting comparator with hysteresis requires a three-resistor network that is referenced to the comparator

supply voltage (VCC), as shown in Figure 7-3.

1 0Ÿ

+VCC

+5 V

VIN

1 0Ÿ

5 V

0 V

VA2

VA1

1.67 V

3.33 V

VIN

Figure 7-3. TLV185x in an Inverting Configuration With Hysteresis

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TLV1851, TLV1861, TLV1852, TLV1862, TLV1854, TLV1864

SNOSDE7B – DECEMBER 2022 – REVISED SEPTEMBER 2024

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