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9.2.2 Additional Application Information

9.2.2.1 Pull-up Resistor Selection

For the TLV4021 (open-drain output versions of the TLV40x1 family), care should be taken in selecting the

pull-up resistor (RPU) value to ensure proper output voltage levels. First, consider the required output high logic

level requirement of the logic device that is being driven by the comparator when calculating the maximum RPU

value. When in a logic high output state, the output impedance of the comparator is very high but there is a finite

amount of leakage current that needs to be accounted for. Use IO-LKG from the EC Table and the VIH minimum

from the logic device being driven to determine RPU maximum using Equation 4.

(4)

Next, determine the minimum value for RPU by using the VIL maximum from the logic device being driven. In

order for the comparator output to be recognized as a logic low, VIL maximum is used to determine the upper

boundary of the comparator's VOL. VOL maximum for the comparator is available in the EC Table for specific sink

current levels and can also be found from the VOUT versus ISINK curve in the Typical Application curves. A good

design practice is to choose a value for VOL maximum that is 1/2 the value of VIL maximum for the input logic

device. The corresponding sink current and VOL maximum value will be needed to calculate the minimum RPU.

This method will ensure enough noise margin for the logic low level. With VOL maximum determined and the

corresponding ISINK obtained, the minimum RPU value is calculated with Equation 5.

(5)

Since the range of possible RPU values is large, a value between 5 kΩ and 100 kΩ is generally recommended.

A smaller RPU value provides faster output transition time and better noise immunity, while a larger RPU value

consumes less power when in a logic low output state.

9.2.2.2 Input Supply Capacitor

Although an input capacitor is not required for stability, for good analog design practice, connect a 100 nF low

equivalent series resistance (ESR) capacitor from (V+) to (V-).

9.2.2.3 Sense Capacitor

Although not required in most cases, for extremely noisy applications, place a 1 nF to 100 nF bypass capacitor

from the comparator input (IN) to the (V-) for good analog design practice. This capacitor placement reduces

device sensitivity to transients.

9.3 What to Do and What Not to Do

Do connect a 100 nF decoupling capacitor from (V+) to (V-) for best system performance.

If the monitored voltage is noisy, do connect a decoupling capacitor from the comparator input (IN) to (V-).

Don't use resistors for the voltage divider that cause the current through them to be less than 100 times the input

current of the comparator without also accounting for the impact on accuracy.

Don't use a pull-up resistor that is too small because the larger current sunk by the output may exceed the

desired low-level output voltage (VOL).

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TLV4021, TLV4031, TLV4041, TLV4051

SNVSB04C – MARCH 2019 – REVISED DECEMBER 2021

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