TLV4021 datasheet(18/38 Pages) TI

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VIT-

VIT+

VHYS = (VIT+) ± (VIT-)

TLV4021, TLV4031, TLV4041, TLV4051

SNVSB04B – MARCH 2019 – REVISED JUNE 2020

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Device Functional Modes (continued)

The comparator input (IN) is able to swing 5.5 V above (V-) regardless of the device supply voltage. This

includes the instance when no supply voltage is applied to the comparator (VS = 0 V). As a result, the TLV40x1 is

referred to as fault tolerant, meaning it maintains the same high input impedance when VS is unpowered or

ramping up. While not required in most cases, in order to reduce sensitivity to transients and layout parasitics for

extremely noisy applications, place a 1 nF to 100 nF bypass capacitor at the comparator input.

For the TLV40x1Ry comparators, the input bias current is typically 10 pA for input voltages between (V-) and

(V+) and the value typically doubles for every 10°C temperature increase. The comparator input is protected from

voltages below (V-) by an internal diode connected to (V-). As the input voltage goes below (V-), the protection

diode becomes forward biased and begins to conduct causing the input bias current to increase exponentially. A

series resistor is recommended to limit the input current when sources have signal content that is less than (V-).

For the TLV4021S5, the input bias current is limited by the internal resistor divider with typical impedance of 2M

ohms.

7.4.3 Switching Thresholds and Hysteresis (VHYS)

The TLV40x1 transfer curve is shown in Figure 37.

•

VIT+ represents the positive-going input threshold that causes the comparator output to change from a logic

low state to a logic high state.

•

VIT- represents the negative-going input threshold that causes the comparator output to change from a logic

high state to a logic low state.

•

VHYS represents the difference between VIT+ and VIT- and is 20 mV for TLV40x1Ry and 54 mV for

TLV4021S5.

Figure 37. Transfer Curve

VIT+ and VIT- have mV's of variation over temperature. The significant portion of the variation of these parameters

is a result of the internal bandgap voltage from which VIT+ and VIT- are derived. The following hysteresis

histograms demonstrate the performance of the TLV40x1 hysteresis circuitry. Since the bandgap reference is

used to set VIT+ and VIT-, each of these parameters have a tendency to error (track) in the same direction. For

example, if VIT+ has a positive 0.5% error, VIT- would have a tendency to have a similar positive percentage error.

As a result, the variation of hysteresis will never be equal to the difference of the highest VIT+ value of its range

and the lowest VIT- value of its range.

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