I'm currently using TLV3604 and I'm curious about Input common mode voltage.
https://www.ti.com/document-viewer/lit/html/SSZT114
Here, Input common mode voltage is the intersection of the two inputs.
However, datasheet does not define common mode voltage separately, and it assumes V_ee + 0.3.
What exactly does common mode voltage mean in TLV3604 datasheet?
Hello Shin,
"Common mode" is a legacy holdover from Op-amps and should not really be used in relation to comparators. Very rarely are comparator inputs held at a "common" voltage.
Comparator inputs tend to be at widely different voltages. The correct term should be "Input Voltage Range". The limit is PER INPUT and NOT the average of the inputs.
For the TLV360x, the input is Rail to Rail so the input range extends from 200mV below Vee to 200mV above Vcci.
The following text is from the LM339 family appnote, section 3.5:
Application Design Guidelines for LM339, LM393, TL331 Family Comparators
3.5 Input Voltage Range vs. Common Mode Voltage Range
"The phrases Common Mode Voltage Range and Input Voltage Range tend to be used interchangeably, but
there is an important difference when discussing comparators. The common definition of Common Mode Voltage
(CMVR or CMR) is the average of the inverting (-IN) and non-inverting (+IN) input voltages. This definition
is acceptable for operational amplifiers where the inputs are kept to less than a millivolt of each other due
to negative feedback, but comparator inputs are rarely kept at the same potential and can see several volts
of differential voltage under normal operation. If the average value is used, there can be an instance where
one input voltage slightly exceeds the input range specification, and the average of the two inputs can still
reside within the input range, even though that one input is violating the input range. The average gives a false
impression of meeting the input voltage range requirement."
Note
The input voltage limits must be considered per input and NOT the average of the two input voltages.
If, for example, the calculated input voltage limit is 3.5 V, then neither input can exceed 3.5 V.
Sorry chi,
I'm using 5V power
In tlv3604 datasheet Fig. 6-21, propagation delay changes according to overdrive voltage
I want to know if this graph changes according to threshold level
Hi Shin,
The graph doesn't change necessarily but depending where you set the threshold level and how high your input signal goes above the threshold level, the prop delay will change accordingly to overdrive. “Input Overdrive” is defined as the additional input signal amplitude relative to the reference level.
