TLV431ACLP datasheet(22/54 Pages) TI

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The more overdrive voltage provided, the faster the TLV431 will respond. This can be seen in Figure 8-3 and

Figure 8-4 where it displays the output responses to various input voltages.

For applications where TLV431 is being used as a comparator, it is best to set the trip point to greater than the

positive expected error (that is, +1.0% for the A version). For fast response, setting the trip point to > 10% of the

internal Vref should suffice.

For minimal voltage drop or difference from Vin to the ref pin, TI recommends using an input resistor < 10kΩ to

provide Iref.

8.2.1.2.3 Output Voltage and Logic Input Level

For the TLV431 to properly be used as a comparator, the logic output must be readable by the receiving logic

device. This is accomplished by knowing the input high and low level threshold voltage levels, typically denoted

by VIH and VIL.

As seen in Figure 8-3, TLV431's output low level voltage in open-loop/comparator mode is approximately 1V,

which is sufficient for some 3.3V supplied logic. However, this does not work for 2.5V or 1.8V supplied logic. To

accommodate this a resistive divider can be tied to the output to attenuate the output voltage to a voltage legible

to the receiving low voltage logic device.

TLV431's output high voltage is approximately Vsup due to TLV431 being open-collector. If Vsup is much higher

than the receiving logic's maximum input voltage tolerance, the output must be attenuated to accommodate the

outgoing logic's reliability.

When using a resistive divider on the output, be sure to make the sum of the resistive divider (R1 and R2 in

Figure 8-2) is much greater than Rsup to not interfere with TLV431's ability to pull close to Vsup when turning off.

8.2.1.2.3.1 Input Resistance

TLV431 requires an input resistance in this application to source the reference current (Iref) needed from this

device to be in the proper operating regions while turning on. The actual voltage seen at the ref pin will be Vref =

Vin – Iref × Rin. Because the Iref can be as high as 0.5µA, TI recommends using a resistance small enough that

will mitigate the error that Iref creates from Vin.

8.2.1.3 Application Curves

Figure 8-3. Output Response with Small Overdrive

Voltages

Figure 8-4. Output Response with Large Overdrive

Voltage

TLV431, TLV431A, TLV431B

SLVS139Z – JULY 1996 – REVISED JUNE 2024

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