the input voltage range to as high as VCC – 1.5V and as low as 0V. Operation outside of this range can yield

incorrect comparisons.

Below is a list of input voltage situation and the outcomes:

1. When both IN- and IN+ are both within the common mode range:

a. If IN- is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking

current

b. If IN- is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is

not conducting

2. When IN- is higher than common mode and IN+ is within common mode, the output is low and the output

transistor is sinking current

3. 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

4. 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.

7.2.2.2 ESD Protection

The TL331x-Q1 family have dedicated ESD protection on all the pins for improved ESD performance as well as

improved negative input voltage handling. Please see Application Note SNOAA35 for more information.

7.2.2.3 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

exceed 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 7-2 and Figure 7-3 show positive and

negative response times with respect to overdrive voltage.

7.2.2.4 Output and Drive Current

Output current is determined by the load/pull-up resistance and logic/pull-up voltage. The output current

determines the output low voltage (VOL) from the comparator. VOL is proportional to the output current. Use

Output Low Voltage vs. Output Sinking Current at 5V to determine VOL based on the output current.

The output current can also effect the transient response. More is explained in the next section.

7.2.2.5 Response Time

Response time is a function of input over drive. See Application Curves for typical response times. The rise

and fall times can be determined by the load capacitance (CL), load/pullup 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 Output Low Voltage vs. Output Sinking Current at 5V in the

linear region at the desired temperature, or by dividing the VOL by Iout

TL331-Q1, TL331B-Q1, TL391B-Q1

SLVS969H – OCTOBER 2009 – REVISED JANUARY 2025

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