LM339ADE4 datasheet(25/51 Pages) TI

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The following list describes the outcomes of some input voltage situations.

• When both IN– and IN+ are both within the common-mode range:

– If IN– is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking current

– If IN– is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is

not conducting

• When IN– is higher than common mode and IN+ is within common mode, the output is low and the output

transistor is sinking current

• When IN+ is higher than common mode and IN– is within common mode, the output is high impedance and

the output transistor is not conducting

• When IN– and IN+ are both higher than common mode, see Section 2 of Application Design Guidelines for

LM339, LM393, TL331 Family Comparators Including the New B-versions

9.2.2.2 Minimum Overdrive Voltage

Overdrive voltage is the differential voltage produced between the positive and negative inputs of the comparator

over the offset voltage (VIO). To make an accurate comparison, the overdrive voltage (VOD) must be higher than

the input offset voltage (VIO). Overdrive voltage can also determine the response time of the comparator, with

the response time decreasing with increasing overdrive. Figure 9-2 and Figure 9-3 show positive and negative

response times with respect to overdrive voltage.

9.2.2.3 Output and Drive Current

Output current is determined by the load and pullup resistance and logic and pullup voltage. The output current

produces a low-level output voltage (VOL) from the comparator, where VOL is proportional to the output current.

The output current can also effect the transient response.

9.2.2.4 Response Time

Response time is a function of input over-drive. See the Section 7.19 graphs for typical response times. The rise

and fall times can be determined by the load capacitance (CL), load/pull-up resistance (RPULLUP) and equivalent

collector-emitter resistance (RCE).

• The rise time (τR) is approximately τR~ RPULLUP × CL

• The fall time (τF) is approximately τF ~ RCE × CL

– RCE can be determined by taking the slope of Figure 7-35 in its linear region at the desired temperature, or

by dividing the VOL by IOUT

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LM139, LM239, LM339, LM339B, LM139A, LM239A

LM339A, LM2901B, LM2901, LM2901AV, LM2901V

SLCS006X – OCTOBER 1979 – REVISED OCTOBER 2023

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